WO2007069924A1 - Deazapurine analogs of 4'-aza-l-nucleosides - Google Patents

Abstract

The invention relates to compounds of the formula (I), which are L-enantiomeric forms of nucleoside analogues, and to pharmaceutical compositions containing the compounds, methods of treating certain diseases, including cancer, bacterial infection, parasitic infection, and T-cell mediated diseases, using the compounds, processes for preparing the compounds, and intermediates useful in the preparation of the compounds.

Description

DEAZAPURINE ANALOGS OF 4'-AZA-L-NUCLEOSIDES

TECHNICAL FIELD

This invention relates to certain L-enantiomeric forms of nucleoside analogues, the use of these compounds as pharmaceuticals, pharmaceutical compositions containing the compounds, methods of treating certain diseases using the compounds, processes for preparing the compounds, and intermediates useful in the preparation of the compounds.

BACKGROUND Recent research in the area of purine nucleoside phosphorylase (PNP), methylthioadenosine phosphorylase (MTAP) and 5'-methylthioadenosine nucleosidase (MTAN) and nucleoside hydrolase inhibitors has resulted in the design and synthesis of a class of compounds known as the Immucillins, some of which are potent inhibitors of one or more of the above enzymes, lmmucillins are nucleoside analogues where the sugar has been replaced with an imino sugar moiety.

PNP catalyses the phosphorolytic cleavage of the ribo- and deoxyribonucleosides of guanine and hypoxanthine to give the corresponding sugar-1 -phosphate and guanine or hypoxanthine.

Humans deficient in PNP suffer a specific T-cell immunodeficiency due to an accumulation of dGTP and its toxicity to stimulated T lymphocytes. Because of this, inhibitors against PNP are immunosuppressive, and are active against T-cell malignancies.

US 5,985,848, US 6,066,722 and US 6,228,741 describe compounds that are inhibitors of PNP and purine phosphoribosyltransferases (PPRT). The compounds are useful in treating parasitic infections, T-cell malignancies, autoimmune diseases and inflammatory disorders. They are also useful for immunosupression in organ transplantation.

US 6,693,193 describes a process for preparing certain PNP inhibitor compounds, providing another useful route to the synthesis of this class of compounds. US 7,109,331 discloses further compounds that are inhibitors of PNP and PPRT.

The imino sugar part of the inhibitor compounds referred to above (generally known as Immucillins) has the nitrogen atom located between C-1 and C-4 so as to form 1 ,4-dideoxy-

1 ,4-imino-D-ribitol compounds. The location of the nitrogen atom in the ribitol ring may be important for binding to enzymes. In addition, the location of the link between the imino sugar moiety and the nucleoside base analogue may be critical for enzyme inhibitory activity. The compounds described above have that link at C-1 of the imino sugar ring.

More recently, another related class of nucleoside phosphorylase and nucleosidase inhibitor compounds (known as the DAD-Me-lmmucillins) has been developed. The location of the nitrogen atom in the imino sugar ring of this class of compounds is varied and where the imino sugar moiety is linked to the nucleoside base analogue via a methylene bridge. The DAD-Me-lmmucillins are described in US 10/524,995.

Some of the lmmucillins have also been identified as inhibitors of MTAP and MTAN. These are the subject of US 7,098,334.

MTAP and MTAN function in the polyamine biosynthesis pathway, in purine salvage in mammals, and in the quorum sensing pathways in bacteria. MTAP catalyses the reversible phosphorolysis of MTA to adenine and 5-methylthio-α-D-ribose-1-phosphate (MTR-1 P). MTAN catalyses the reversible hydrolysis of MTA to adenine and 5-methylthio-α-D-ribose, and of S-adenosyl-L-homocysteine (SAH), to adenine and S-ribosyl-homocysteine (SRH). The adenine formed is subsequently recycled and converted into nucleotides. Essentially, the only source of free adenine in the human cell is a result of the action of these enzymes. The MTR-1 P is subsequently converted into methionine by successive enzymatic actions.

MTA is a by-product of the reaction involving the transfer of an aminopropyl group from decarboxylated S-adenosylmethionine to putrescine during the formation of spermidine. The reaction is catalyzed by spermidine synthase. Likewise, spermine synthase catalyses the conversion of spermidine to spermine, with concomitant production of MTA as a by-product. The spermidine synthase is very sensitive to product inhibition by accumulation of MTA. Therefore, inhibition of MTAP or MTAN severely limits the polyamine biosynthesis and the salvage pathway for adenine in the cells.

Likewise, MTA is the by-product of the bacterial synthesis of acylated homoserine lactones from S-adenosylmethionine (SAM) and acyl-acyl carrier proteins in which the subsequent lactonization causes release of MTA and the acylated homoserine lactone. The acylated homoserine lactone is a bacterial quorum sensing molecule in bacteria that is involved in bacterial virulence against human tissues. The homoserine lactone pathway will suffer feedback inhibition by the accumulation of MTA. MTAP deficiency due to a genetic deletion has been reported with many malignancies. The loss of MTAP enzyme function in these cells is known to be due to homozygous deletions on chromosome 9 of the closely linked MTAP and p16/MTS1 tumour suppressor gene. As absence of p16/MTS1 is probably responsible for the tumour, the lack of MTAP activity is a consequence of the genetic deletion and is not causative for the cancer. However, the absence of MTAP alters the purine metabolism in these cells so that they are mainly dependent on the cfe novo pathway for their supply of purines.

MTA has been shown to induce apoptosis in dividing cancer cells, but to have the opposite, anti-apoptotic effect on dividing normal cells such as hepatocytes (E. Ansorena et al., Hepatology, 2002, 35: 274-280). Administration of MTA in circumstances where its degradation by MTAP is inhibited by an MTAP inhibitor will lead to greater circulatory and tissue levels of MTA and consequently an enhanced effect in the treatment of cancer.

MTAP and MTAN inhibitors may therefore be used in the treatment of diseases such as cancer, bacterial infections or protozoal parasitic infections, where it is desirable to inhibit MTAP or MTAN. Such treatments are described in US 7,098,334 and 10/524,995.

The lmmucillins and DAD-Me-lmmucillins are also useful as inhibitors of nucleoside hydrolases. These enzymes catalyse the hydrolysis of nucleosides. They are not found in mammals, but are required for nucleoside salvage in some protozoan parasites. Certain protozoan parasites use nucleoside phosphorylases instead of or as well as nucleoside hydrolases for this purpose. Inhibitors of nucleoside hydrolases and phosphorylases can be expected to interfere with the metabolism of the parasite and therefore be usefully employed against protozoan parasites.

The lmmucillins and the DAD-Me lmmucillins therefore represent two classes of compounds which are inhibitors of PNP, MTAP, MTAN and/or nucleoside hydrolases. Initially, work in this area of drug design focused on the synthesis of these compounds in their natural enantiomeric forms. Thus, to date, all of the active inhibitor compounds have incorporated the D-enantiomeric form of the imino sugar moiety. It was thought that the D-form of the sugar was necessary in order for the compounds to exhibit the requisite inhibitory activity.

The X-ray crystal structures of two of the inhibitor compounds (Immucillin-H and Immucillin- G) bound to bovine PNP have been described (G. A. Kicksa, P. C. Tyler, G. B. Evans, R. H.

Furneaux, W. Shi, A. Fedorov, A. Lewandowicz, S. M. Cahill, S. C. Almo and V. L. Schramm,

Biochemistry, (2002) 41 , 14489). Complexes of these inhibitors with PNP have favourable hydrogen bonds to almost every hydrogen bond donor-acceptor site in the complex. Even a slight structural change can disrupt this favourable hydrogen bonding pattern.

All indications have suggested that the D-form of the imino sugar is the preferable form for designing and synthesising suitable inhibitor compounds. Not only does the D-form correspond to the naturally occurring sugar form, but it has been demonstrated that the binding of the inhibitors is acutely sensitive to structural modifications (see for example the effect of structural modification of D-lmmucillin-H on the inhibition of human and Plasmodium falciparum purine nucleoside phosphorylases in A. Lewandowicz, E.A.T. Ringia, L.-M. Ting, K. Kim, P.C. Tyler, G.B. Evans, O.V. Zubkova, S. Mee, G.F. Painter, D.H. Lenz, R.H. Furneaux and V. L. Schramm, J. Biol Chem., 280 (2005) 30320-30328).

However, despite all the evidence pointing to the D-enantiomeric forms as being suitable inhibitor compounds, it has now surprisingly been found that the L-enantiomeric forms of the lmmucillins are also inhibitors of PNP MTAP, MTAN, and/or nucleoside hydrolases.

It is therefore an object of the present invention to provide novel inhibitors of PNP, MTAP, MTAN, and/or nucleoside hydrolases, or to at least provide a useful choice.

STATEMENTS OF INVENTION

In a first aspect the invention provides a compound of formula (I):

(I)

where:

A is CH, N or CF;

B is OH, NH₂, NHR, H or halogen; D is OH, NH₂, NHR, H, halogen or SCH₃;

R is an optionally substituted alkyl, aralkyl or aryl group;

X and Y are independently selected from H, OH or halogen except that when one of X and Y is OH or halogen, the other is H; and

Z is H, OH, halogen, SQ, OQ, or Q, where Q is an optionally substituted alkyl, aralkyl or aryl group;

or a tautomer thereof; or a pharmaceutically acceptable salt thereof; or an ester thereof; or a prodrug thereof.

Preferably when either of B or D is NHR, then R is C_1-C₄ alkyl.

It is preferred that any halogen is selected from chlorine and fluorine.

Q may be substituted with one or more substituents selected from OH, halogen (particularly fluorine or chlorine), methoxy, amino, or carboxy.

Preferably Z is OH, SQ, OQ, Q or H. Preferably Q is C₁-C₅ alkyl or phenyl, optionally substituted with one or more substituents selected from OH, halogen, methoxy, amino, or carboxy. Where Q is substituted with one or more halogen, the halogen(s) are preferably selected from fluorine and chlorine.

Preferably D is H. Alternatively, when D is not H, B is OH.

Preferred compounds are those where B is OH, D is H, OH or NH₂, X is OH or H and Y is H. It is further preferred that Z is OH, H or alkylthio, especially methylthio. Particularly preferred compounds include those where Z is OH.

Other preferred compounds are those where B is NH₂, D is H, X is OH and Y is H. It is further preferred that for these compounds Z is SQ.

Where R is an optionally substituted alkyl, aralkyl or aryl group, R is preferably substituted with one or more substituents selected from OH or halogen, especially fluorine or chlorine. Particularly preferred compounds of the invention include:

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1-(9-Deazaadenin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eAyfΛro-pentitol; (1 R)-1-(9-Dea2aadenin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-ethylthio-L-ribitol;

(1R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(2-fluoroethylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(2-hydroxyethylthio)-L-ribitol; (1 R)-1 -(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-propylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-isopropylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-butylthio-L-ribitol;

(1 R)-1 -(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-phenylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-fluorophenylthio)-L-ribitol; (1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-chlorophenylthio)-L-ribitol;

(1R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-chlorophenylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-methylphenylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-methylphenylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-benzylthio-L-ribitol; (1 R)-1-(9-Deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 R)-1 -(9-Deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-arabinitol;

(1S)-1-(9-Deazaguanin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eAyf/7ro-pentitol;

(1 R)-1-(9-Deazaguanin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1 -(9-Deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol; (1 R)-1 -(9-Deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 R)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-arabinitol;

(1S)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eAyif/?ro-pentitol;

(1 R)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1 -(9-Deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol; (1 R)-1-(9-Deaza-8-fluorohypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 R)- 1-(9-Deazaxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1S)-1-(9-Deazaxanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eA3^/7ro-pentitol;

(1 R)-1-(9-Deazaxanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(9-Deazaxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol; (1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1 -(8-Aza-9-deazaadenin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eryf/7ro-pentitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol; (1 R)-1 -(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-ethylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-propylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-isopropylthio-L-ribitol; (1 R)-1 -(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-butylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-phenylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4~imino-5-(4-fluorophenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-chlorophenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-chlorophenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-methylphenylthio)-L- ribitol; (1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-methylphenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-benzylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1-(8-Aza-9-deazaguanin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-e/y#?ro-pentitol; (1 R)-1-(8-Aza-9-deazaguanin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(8-Aza-9-deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1 -(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-erj^/7ro-pentitol;

(1 R)-1-(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol; (1 R)-1-(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(8-Aza-9-xanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1-(8-Aza-9-xanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-ery#?ro-pentitol;

(1 R)-1-(8-Aza-9-xanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(8-Aza-9-xanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol; or (1S)-1-(9-deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol.

According to another aspect of the invention, there is provided a pharmaceutical composition comprising a pharmaceutically effective amount of a compound of the first aspect of the invention.

Preferably the pharmaceutical composition comprises one of the above preferred compounds of the invention. In another aspect of the invention there is provided a method of treating or preventing diseases or conditions in which it is desirable to inhibit PNP comprising administering a pharmaceutically effective amount of a compound of formula (I) to a patient requiring treatment. The diseases or conditions include cancer, bacterial and parasitic infections, and T-cell mediated diseases such as psoriasis, lupus, arthritis and other autoimmune diseases. This aspect of the invention also includes use of the compounds for immunosuppression for organ transplantation. Preferably the compound is one of the above preferred compounds of the invention.

The parasitic infections include those caused by protozoan parasites such as those of the genera Giardia, Trichomonas, Leishmania, Trypanosoma, Crithidia, Herpetomonas, Leptomonas, Histomonas, Eimeria, lsopora and Plasmodium. The method can be advantageously applied with any parasite containing one or more nucleoside hydrolases or phosphorylases inhibited by a compound of the invention when administered in an amount providing an effective concentration of the compound at the location of the enzyme. In order to effectively control a parasite infection in a host, it may be necessary to inhibit both the target enzyme of the parasite and the host, in which case it will be advantageous that the compound chosen has inhibitory potency against both the parasite and host enzyme.

In another aspect, the invention provides a method of treating or preventing diseases or conditions in which it is desirable to inhibit MTAP comprising administering a pharmaceutically effective amount of a compound of formula (I) to a patient requiring treatment. The diseases include cancer, for example prostate and head and neck tumours.

In another aspect, the invention provides a method of treating or preventing diseases or conditions in which it is desirable to inhibit MTAN comprising administering a pharmaceutically effective amount of a compound of formula (I) to a patient requiring treatment. The diseases include bacterial infections.

In another aspect the invention provides the use of a compound of formula (I) for the manufacture of a medicament for treating one or more of these diseases or conditions.

In still a further aspect of the invention there is provided a method of preparing a compound of formula (I). In still a further aspect of the invention there is provided an intermediate useful in the preparation of a compound of formula (I).

DETAILED DESCRIPTION Definitions

The term "alkyl" is intended to include both straight- and branched-chain alkyl groups. The same terminology applies to the non-aromatic moiety of an aralkyl radical. Examples of alkyl groups include: methyl group, ethyl group, n-propyl group, /so-propyl group, /7-butyl group, /so-butyl group, sec-butyl group, f-butyl group, n-pentyl group, 1,1-dimethylpropyl group, 1 ,2- dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, 2-ethylpropyl group, n- hexyl group and 1-methyl-2-ethylpropyl group.

The term "aryl" means an aromatic radical having 6 to 18 carbon atoms and includes heteroaromatic radicals. Examples include monocyclic groups, as well as fused groups such as bicyclic groups and tricyclic groups. Some examples include phenyl group, indenyl group, 1-naphthyl group, 2-naphthyl group, azulenyl group, heptalenyl group, biphenyl group, indacenyl group, acenaphthyl group, fluorenyl group, phenalenyl group, phenanthrenyl group, anthracenyl group, cyclopentacyclooctenyl group, and benzocyclooctenyl group, pyridyl group, pyrrolyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazolyl group, tetrazolyl group, benzotriazolyl group, pyrazolyl group, imidazolyl group, benzimidazolyl group, indolyl group, isoindolyl group, indolizinyl group, purinyl group, indazolyl group, furyl group, pyranyl group, benzofuryl group, isobenzofuryl group, thienyl group, thiazolyl group, isothiazolyl group, benzothiazolyl group, oxazolyl group, and isoxazolyl group.

The term "halogen" includes fluorine, chlorine, bromine and iodine.

The compounds are useful for the treatment of certain diseases and disorders in humans and other animals. Thus, the term "patient" as used herein includes both human and other animal patients.

The term "prodrug" as used herein means a pharmacologically acceptable derivative of the compound of formula (I) or formula (II), such that an in vivo biotransformation of the derivative gives the compound as defined in formula (I) or formula (II). Prodrugs of compounds of formula (I) or formula (II) may be prepared by modifying functional groups present in the compounds in such a way that the modifications are cleaved in vivo to give the parent compound. The term "pharmaceutically acceptable salts" is intended to apply to non-toxic salts derived from inorganic or organic acids, including, for example, the following acid salts: acetate, adipate, alginate, aspartate, benzoate, benzenesulfonate, bisulfate, butyrate, citrate, camphorate, camphorsulfonate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptanoate, glycerophosphate, glycolate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, 2- hydroxyethanesulfonate, lactate, maleate, malonate, methanesulfonate, 2- naphthalenesulfonate, nicotinate, nitrate, oxalate, palmoate, pectinate, persulfate, 3- phenylpropionate, phosphate, picrate, pivalate, propionate, p-toluenesulfonate, salicylate, succinate, sulfate, tartrate, thiocyanate, and undecanoate.

As used herein, the term "protecting group" means a group that selectively protects an organic functional group, temporarily masking the chemistry of that functional group and allowing other sites in the molecule to be manipulated without affecting the functional group. Suitable protecting groups are known to those skilled in the art and are described, for example, in Protective Groups in Organic Synthesis (3^rd Ed.), T. W. Greene and P. G. M. Wuts, John Wiley & Sons lnc (1999).

Description of the Inhibitor Compounds

It is well known that chiral components of natural products occur predominantly in one of their enantiomeric forms. For sugars, these are the L- and D-modifications. Since enzymes work together with their substrates like a lock and key, one enantiomer, typically the naturally occurring species, is usually a better "fit" than the other. In the case of sugars, the D-form is naturally occurring, so work in this area of synthetic drug design has, in the past, been restricted to the investigation of D-sugars.

In light of this, it is surprising and unexpected that the compounds of the invention are inhibitors of PNP, MTAP, MTAN and/or nucleoside hydrolases, as the imino sugar moiety in these compounds is the L-enantiomeric form. It was previously thought that the D- enantiomer, being the naturally occurring form, would be preferable for designing and synthesising suitable inhibitor compounds. In addition, it has been demonstrated that the D- enantiomers bind to the PNP enzyme with a number of favourable hydrogen bond contacts.

The compounds of the invention therefore represent a new class of inhibitors of PNP, MTAP, MTAN, and/or nucleoside hydrolases. As such, they are useful in treating diseases and conditions such as cancer, bacterial infections, parasitic infections, T-cell mediated diseases and other autoimmune diseases, and for immunosuppression for organ transplantation. Cancer means any type of cancer, including, but not limited to, cancers of the head, neck, bladder, bowel, skin, brain, CNS, breast, cervix, kidney, larynx, liver, oesophagus, ovaries, pancreas, prostate, lung, stomach, testes, thyroid, uterus, as well as melanoma, leukaemia, lymphoma, osteosarcoma, Hodgkin's disease, glioma, sarcoma and colorectal, endocrine, gastrointestinal cancers.

General Aspects

The compounds of the invention are useful in both free base form and in the form of salts.

It will be appreciated that the representation of a compound of formula (I), where B and/or D is a hydroxy group, is of the enol-type tautomeric form of a corresponding amide, and this will largely exist in the amide form. The use of the enol-type tautomeric representation is simply to allow fewer structural formulae to represent the compounds of the invention.

Similarly, it will be appreciated that the representation of a compound of formula (I), where B and/or D is a thiol group, is of the thioenol-type tautomeric form of a corresponding thioamide, and this will largely exist in the thioamide form. The use of the thioenol-type tautomeric representation is simply to allow fewer structural formulae to represent the compounds of the invention.

The active compounds may be administered to a patient by a variety of routes, including orally, parenterally, by inhalation spray, topically, rectally, nasally, buccally or via an implanted reservoir. The amount of compound to be administered will vary widely according to the nature of the patient and the nature and extent of the disorder to be treated. Typically the dosage for an adult human will be in the range less than 1 to 1000 milligrams, preferably 0.1 to 100 milligrams. The specific dosage required for any particular patient will depend upon a variety of factors, including the patient's age, body weight, general health, sex, etc.

For oral administration the compounds can be formulated into solid or liquid preparations, for example tablets, capsules, powders, solutions, suspensions and dispersions. Such preparations are well known in the art as are other oral dosage regimes not listed here. In the tablet form the compounds may be tableted with conventional tablet bases such as lactose, sucrose and corn starch, together with a binder, a disintegration agent and a lubricant. The binder may be, for example, corn starch or gelatin, the disintegrating agent may be potato starch or alginic acid, and the lubricant may be magnesium stearate. For oral administration in the form of capsules, diluents such as lactose and dried cornstarch may be employed. Other components such as colourings, sweeteners or flavourings may be added.

When aqueous suspensions are required for oral use, the active ingredient may be combined with carriers such as water and ethanol, and emulsifying agents, suspending agents and/or surfactants may be used. Colourings, sweeteners or flavourings may also be added.

The compounds may also be administered by injection in a physiologically acceptable diluent such as water or saline. The diluent may comprise one or more other ingredients such as ethanol, propylene glycol, an oil or a pharmaceutically acceptable surfactant.

The compounds may also be administered topically. Carriers for topical administration of the compounds include mineral oil, liquid petrolatum, white petrolatum, propylene glycol, polyoxyethylene, polyoxypropylene compound, emulsifying wax and water. The compounds may be present as ingredients in lotions or creams, for topical administration to skin or mucous membranes. Such creams may contain the active compounds suspended or dissolved in one or more pharmaceutically acceptable carriers. Suitable carriers include mineral oil, sorbitan monostearate, polysorbate 60, cetyl ester wax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol and water.

The compounds may further be administered by means of sustained release systems. For example, they may be incorporated into a slowly dissolving tablet or capsule.

Synthesis of the Inhibitor Compounds As the skilled person will realise, the compounds of the invention may be synthesised using similar methods to those used for the synthesis of the corresponding D-enantiomers.

(1) Direct Synthetic Route

The first synthetic strategy for the synthesis of the compounds of the invention involves a direct route. The various direct methods described below are suitable for preparing the compounds, as was the case for the D-enantiomers.

Method (A): (4-hydroxypyrrolo[3,2-d]pyrimidines and access to 5'-deoxy-, 5'-deoxy-5'- halogeno-, 5'-ether and 5'-thio-analogues) Rreacting a compound of formula (II)

(H) [wherein Z¹ is a hydrogen or halogen atom, a group of formula SQ or OQ, or a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group and Q is an optionally substituted alkyl, aralkyl or aryl group] (typically 11 is a tert-butyldimethylsilyloxy, trityloxy or similar group)

sequentially with N-chlorosuccinimide then a sterically hindered base (such as lithium tetramethylpiperadide) to form an imine, then with the anion of acetonitrile (typically made by treatment of acetonitrile with n-butyllithium) followed by di-tert-butyl dicarbonate. This generates a compound of formula (III)

[wherein Z¹ is as defined for formula (II) where first shown above]

which is then elaborated following the approach used to prepare 9-deazainosine [Lim et al., J. Org. Chem., 48 (1983) 780] in which a compound of formula (III) is condensed with (Me₂N)₂CHOBu* and hydrolyzed under weakly acidic conditions to a compound of formula

(IV) [wherein Z' is as defined for formula (II) where first shown above]

which is then sequentially condensed with a simple ester of glycine (e.g. ethyl glycinate) under mildly basic conditions, cyclized by reaction with a simple ester of chloroformic acid (e.g. benzyl chloroformate or methyl chloroformate) and then deprotected on the pyrrole nitrogen by hydrogenolysis in the presence of a noble metal catalyst (e.g. Pd/C) in the case of a benzyl group or under mildly basic conditions in the case of a simple alkyl group such as a methyl group, to give a compound of formula (V)

(V)

[wherein Z' is as defined for formula (II) where first shown above, and R is an alkyl group] (typically R is a methyl or ethyl group)

which is then condensed with formamidine acetate to give a compound of formula (Vl)

(Vl)

[wherein Z' is as defined for formula (II) where first shown above]

which is then fully deprotected under acidic conditions, e.g. by treatment with trifluoroacetic acid.

A method for the synthesis of a compound of formula (II) wherein Z' is a tert- butyldimethylsilyloxy group is detailed the Examples herein. Compounds of formula (ii) can alternatively be synthesized by standard protecting group methodology applied to 1 ,4- dideoxy-1 ,4-imino-L-ribitol which can be synthesized (a) from D-mannose as in G. W. J. Fleet, J. C. Son, D. St. C. Green, I. C. di BeIIo and B. Winchester, Synthesis from D- Mannose of 1 ,4-Dideoxy-1 ,4-imino-L-ribitol and of the α-Mannosidase Inhibitor 1 ,4-Dideoxy- 1 ,4-imino-D-talitol, Tetrahedron, 44 (1988) 2649.; or (b) from L-gulonolactone using the methodology for the D-enantiomer from D-gulonolactone as in G. W. J. Fleet and J. C. Son, Polyhydroxylated Pyrrolidines from Sugar Lactones: Synthesis of 1 ,4-Dideoxy-1,4-imino-D- glucitol from D-Galactonolactone and Syntheses of 1 ,4-Dideoxy-1 ,4-imino-D-allitol, 1 ,4- Dideoxy-1 ,4-imino-D-ribitol and (2S,3R,4S)-3,4-Dihydroxyproline from D-Gulonolactone, Tetrahedron 44 (1988) 2637.

A compound of formula (II) [wherein Z' is a halogen atom], can be prepared from a compound of formula (II) [wherein Z¹ is a hydroxy group], by selective N-alkyl- or aralkyl- oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trifluoroacetic anhydride and a base) to give a compound of formula (VII):

(VII)

[wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl- carbonyl group and Z' is a hydroxy group]

which is then either:

(i) 5-O-sulfonylated (typically with p-toluenesulfonyl chloride, methanesulfonyl chloride or trifluoromethanesulfonic anhydride and a base) to give a compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z¹ is an optionally substituted alkyl- or aryl- sulfonyloxy group], then subjected to a sulfonate displacement reaction with a reagent capable of providing a nucleophilic source of halide ion (typically sodium, lithium or a tetraalkylammonium fluoride, chloride, bromide, or iodide); or (ii) subjected to a reagent system capable of directly replacing a primary hydroxy group with a halogen atom, for example as in the Mitsunobu reaction (e.g. using triphenylphosphine, diethyl azodicarboxylate and a nucleophilic source of halide ion as above), by reaction with diethylaminosulfur trifluoride (DAST), or by reaction with methyltriphenoxyphosphonium iodide in dimethylformamide [see e.g. Stoeckler et al,

Cancer Res., 46 (1986) 1774] or by reaction with thionyl chloride or bromide in a polar solvent such as hexamethylphosphoramide [Kitagawa and lchino, Tetrahedron Lett, (1971) 87];

to give a compound of formula (VIl) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z¹ is a halogen atom], which is then selectively N-deprotected by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use.

A compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z" is a hydroxy group] can also be prepared from a compound of formula (II) [wherein Z¹ is a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group], by N-alkyl- or aralkyl-carboxylation or N-acylation as above, then selective 5-O-deprotection by acid-catalyzed hydrolysis or alcoholysis, catalytic hydrogenolysis, or treatment with a source of fluoride ion (eg tetrabutylammonium fluoride) as required for the 5-O-protecting group in use.

The compound of formula (II) [wherein Z¹ is a hydrogen atom] can be prepared from either:

(i) a 5-hydroxy compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z¹ is a hydroxy group], by formation and radical deoxygenation of a 5-O-thioacyl derivative; or

(ii) a 5-deoxy-5-halogeno-compound of formula (VII) [wherein Z' is a chlorine, bromine or iodine atom] by reduction, either using a hydride reagent such as tributyltin hydride under free radical conditions, or by catalytic hydrogenolysis, typically with hydrogen over a palladium catalyst;

followed by selective N-deprotection by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use. A compound of formula (II) [wherein Z' is an optionally substituted alkylthio, aralkylthio or arylthio group] can be prepared by reaction of a 5-deoxy-5-halogeno or a 5-O-sulfonate derivative of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z¹ is a halogen atom or an optionally substftuted alkyl- or aryl-sulfonyloxy group] mentioned above, with an alkali metal or tetraalkylammonium salt of the corresponding optionally substituted alkylthiol, aralkylthiol or arylthiol followed by selective N-deprotection by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use [see e.g. Montgomery et al., J. Med. Chem., 17 (1974) 1197].

The compound of formula (II) [wherein Z' is a group of formula OQ, and Q is an optionally substituted alkyl, aralkyl or aryl group] can be prepared from a 5-hydroxy compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is a hydroxy group], by

(i) reaction with an alkyl or aralkyl halide in the presence of a base (e.g. methyl iodide and sodium hydride, or benzyl bromide and sodium hydride, in tetrahydrofuran as solvent); or

(ii) sequential conversion to a 5-O-sulfonate derivative (as above) and reaction with an alkali metal or tetraalkylammonium salt of the desired phenol;

followed by selective N-deprotection by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use.

It will be appreciated that the conversions above are conventional reactions employed in carbohydrate chemistry. Many alternative reagents and reaction conditions can be employed that will effect these conversions, and references to many of these can be found in the Specialist Periodical Reports "Carbohydrate Chemistry", Volumes 1 - 28, published by the Royal Society of Chemistry, particularly in the chapters on Halogeno-sugars, Amino-sugars, Thio-sugars, Esters, Deoxy-sugars, and Nucleosides.

Method (B): (2-amino-4-hydroxypyrrolo[3,2-d]pyrimidines)

Reacting a compound of formula (V) [wherein Z' is as defined for formula (II) where first shown above, and R is an alkyl group] with benzoyl isothiocyanate then methyl iodide in the presence of a base (e.g. DBU or DBN) following the approach used to prepare 9- deazaguanosine and its derivatives [see e.g. Montgomery et al., J. Med. Chem., 36 (1993) 55, Lim et al., J. Org. Chem., 48 (1983) 780, and references therein] to give a compound of formula (VIII)

(VIII)

[wherein Z" is a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group, a hydrogen or halogen atom, SQ, OQ or Q wherein Q is an optionally substituted alkyl, aralkyl or aryl group and R is an alkyl group] (typically Z¹, when a protected hydroxy group, is a tert-butyldimethylsilyloxy, trityloxy or similar group, and R is a methyl or ethyl group)

which is then cyclized in the presence of ammonia to give a separable mixture of compounds of formula (IX)

(IX)

[wherein D is an amino or methylthio group, and Z¹ and R are as defined for formula (VIlI) where first shown above, or Z¹ is a hydroxy group] (where for example a tert- butyldimethylsilyloxy group has been cleaved under the reaction conditions)

and the product of formula (IX) [wherein D is an amino or methylthio group] is fully deprotected under acidic conditions by the procedures set out in Method (A).

Method (C): (4-aminopyrrolo[3,2-d]pyrimidines) Reacting a compound of formula (IV) [wherein Z' is as defined for formula (II) where first shown above] with aminoacetonitrile under mildly basic conditions, cyclization of the product by reaction with a simple ester of chloroformic acid (typically benzyl chloroformate or methyl chloroformate) to give a compound of formula (X)

[wherein Z¹ is a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group, a hydrogen or halogen atom, SQ or OQ wherein Q is an optionally substituted alkyl, aralkyl or aryl group and R is an aralkyl or alkyl group] (typically Z', when a protected hydroxy group, is a tert-butyldimethylsilyloxy, trityloxy or similar group, and R is a benzyl or methyl group)

which is then deprotected on the pyrrole nitrogen by hydrogenolysis in the presence of a noble metal catalyst (e.g. Pd/C) in the case of a benzyl group or under mildly basic conditions in the case of a simple alkyl group such as a methyl group, and processed as described above for the transformation (V) → (Vl) → (I) or (V) → (VIII) → (IX) → (I). This method follows the approach used to prepare 9-deazaadenosine and its analogues [Lim and

Klein, Tetrahedron Lett, 22 (1981) 25, and Xiang et al., Nucleosides Nucleotides 15 (1996) 1821]

Method (D): (7~hydroxypyrazolo[4,3-d]pyrimidines - Daves' methodology) Reacting a compound of formula (II) [as defined where first shown above] sequentially with Λ/-chlorosuccinimide and a hindered base (such as lithium tetramethylpiperidide) to form an imine, then condensing this with the anion produced by abstraction of the bromine or iodine atom from a compound of formula (XIa) or (XIb)

(XIa) (XIb)

[wherein R³ is a bromine or iodine atom and R⁴ is a tetrahydropyran-2-yl group]

typically using butyllithium or magnesium, to give a product which is then fully deprotected under acidic conditions (as in Method (A)). The condensation reaction can be usefully catalyzed by Lewis acids, preferably boron trifluoride diethyl etherate, titanium tetrachloride or stannic chloride as described for the D-enantiomers in Evans et al, J. Org. Chem., 69 (2004) 2217-2200. Methods for preparing compounds of formula (XIa) and (XIb) and mixtures thereof are described in Zhang and Daves, J. Org. Chem., 57 (1992) 4690, Stone et al., J. Org. Chem., 44 (1979) 505, and references therein.

It will be appreciated that while the tetrahydropyran-2-yl group is favoured as the protecting group for this reaction, other 0,N-protecting groups can be used, and that this method will also be applicable to the synthesis of analogous pyrazolo[4,3-d]pyrimidines bearing substituents at position-5 and/or -7 of the pyrazolo[4,3-d]pyrimidine ring independently chosen from a hydroxy group, an amino, alkylamino, or aralkylamino group or a hydrogen atom using analogues of compounds of formula (XIa) and (XIb) in which the ionizable hydrogen atoms of any hydroxy or amino groups have been replaced by a suitable protecting groups.

Method (E): (7-hydroxypyrazolo[4,3-d]pyrimidines - the Kalvoda method) Reacting a compound of formula (II) [as defined where first shown above] sequentially with N-chlorosuccinimide and a hindered base (such as lithium tetramethylpiperadide) to form an imine, then with a combination of trimethylsilyl cyanide and a Lewis acid (typically boron trifluoride diethyl etherate) followed by acid catalyzed hydrolysis to give a compound of formula (XII)

(XII) [wherein Z' is a hydrogen or halogen atom, a hydroxy group, or a group of formula SQ, OQ or Q where Q is an optionally substituted alkyl, aralkyl or aryl group]

which is then converted by sequential selective N-protection (typically with trifluoroacetic anhydride, di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base), and O-protection with an acyl chloride or anhydride and a base (typically acetic anhydride or benzoyl chloride in pyridine) to a suitably protected derivative of formula (XIII)

(XIII)

[wherein R¹ is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl- carbonyl group, Z¹ is a hydrogen or a halogen atom, a group of formula SQ, OQ or Q where Q is an optionally substituted alkyl, aralkyl or aryl group, or a group of formula R²O, and R² is an alkylcarbonyl or optionally substituted arylcarbonyl group]

(typically R¹ will be a trifluoroacetyl, tert-butoxycarbonyl or benzyloxycarbonyl group, and R² will be an acetyl or benzoyl group).

The carboxylic acid moiety in the resulting compound of formula (XIII) is then transformed into a pyrazolo[4,3-d]pyrimidin-7-one-3-yl moiety following the method described by Kalvoda [Collect. Czech. Chem. Commun., 43 (1978) 1431], by the following sequence of reactions:

(i) chlorination of the carboxylic acid moiety to form an acyl chloride, typically with thionyl chloride with a catalytic amount of dimethylformamide in an inert solvent;

(ii) use of the resulting acyl chloride to acylate hydrogen cyanide in the presence of tert- butoxycarbonyltriphenylphosphorane (i.6.Ph₃P=CHCO₂Bu¹) to give a 3-cyano-2- propenoate derivative; (iii) cycloaddition of this with diazoacetonitrile (which can be prepared from aminoacetonitrile hydrochloride and sodium nitrite) with concomitant elimination of hydrogen cyanide to give a pyrazole derivative;

(iv) acid-catalyzed hydrolysis of the tert-butyl ester in this pyrazole derivative to its equivalent carboxylic acid;

(v) Curtius reaction, typically with phenylphosphoryl azide and 2,2,2-trichloroethanol in the presence of triethylamine, which converts the carboxylic acid moiety into a 2,2,2- trichloroethoxycarbonylamino group (i.e. the product is a carbamate);

(vi) reductive cleavage of this trichloroethyl carbamate, typically with zinc dust in methanol containing ammonium chloride;

(vii) condensation of the resulting ethyl 3-amino-5-substituted-pyrazole-2-carboxylate with formamidine acetate to give a compound of formula (XIV)

(XIV)

[wherein R¹ is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl- carbonyl group, Z' is a hydrogen or a halogen atom, SQ, OQ or Q where Q is an optionally substituted alkyl, aralkyl or aryl group, or a group of formula R²O, and R² is an alkylcarbonyl or optionally substituted arylcarbonyl group, A is a nitrogen atom, B is a hydroxy group and D is a hydrogen atom]

which is then N- and O-deprotected by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the O- and N-protecting groups in use. Method (F): (7-amino- and 7-hydroxy-pyrazolo[4,3-d]pyrimidines - the Buchanan method and the Evans' modification)

Reacting a compound of formula (II) [as defined where first shown above] sequentially with N-chlorosuccinimide and a hindered base (such as lithium tetramethylpiperadide) to form an imine, which is then transformed into either a 7-amino- or a 7-hydroxy-pyrazolo[4,3- d]pyrimidine derivative following the approach used to prepare formycin and its analogues by

Buchanan and co-workers [J. Chem. Soc, Perkin Trans. I (1991) 1077 and references therein], as adapted by Evans et al [J. Med. Chem., 46 (2003) 155] for the synthesis of 8- aza-lmmucillin, by the following sequence of reactions:

(i) addition of lithiated 3,3-diethoxy-1-propyne to the imine, typically at 10-15 ⁰C in diethyl ether;

(ii) N-protection, preferably with 2,2,2-trichloroethyl chloroformate, but alternatively with trifluoroacetic anhydride, di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base;

(iii) mild acid hydrolysis to remove the acid sensitive O-protecting groups and convert the diethyl acetal moiety into an aldehydic moiety, preferably using a mixture of glacial acetic acid and 10% aqueous hydrochloric acid;

(iv) condensation with hydrazine to convert the 3-substituted prop-2-ynal derivative into a 3-substituted pyrazole derivative;

(v) acylation, typically with acetic anhydride or benzoyl chloride in pyridine;

(vi) nitration, typically with ammonium nitrate, trifluoroacetic anhydride and trifluoroacetic acid, to produce to a 3-substituted 1 ,4-dinitopyrazole;

(vii) reaction with a reagent capable of delivering cyanide ion, typically with potassium cyanide in a mixture of ethanol and ethyl acetate to cause a cine-substitution of one of the two nitro-groups;

(viii) reduction of the residual nitro-group, typically with zinc in acetic acid, with simultaneous removal of the N-(2,2,2-trichloroethyl chloroformyl) group where that is present; (ix) optional removal of the acetate protecting groups (as some of the reagents required for later steps result in their partial loss), typically by deacetylation under Zemplen conditions;

(x) reprotection of the iminoribitol nitrogen, typically as the f-butyl carbamate using tert- butoxycarbonic anhydride; and

(xi) either condensation with formamidine acetate, typically in refluxing ethanol, then treatment with dilute hydrochloric acid to give a compound of formula (i) [wherein A is N, B is an amino group and D is a hydrogen atom and X₁ Y and Z are as first herein defined] as the hydrochloride salt;

(xii) or hydrolysis of the nitrile function to an amide, typically with by treatment with hydrogen peroxide and potassium carbonate in dimethylsufoxide; and condensation with formamidine acetate, typically in refluxing ethanol, then treatment with dilute hydrochloric acid to give a compound of formula (i) [wherein A is N, B is a hydroxy group and D is a hydrogen atom and X, Y and Z are as first herein defined] as the hydrochloride salt.

Method (G): (2'-deoxy-analogues)

Effecting the overall 2'-deoxygenation of a compound of formula (I) [wherein X and Z are hydroxy groups, Y is a hydrogen atom, and A, B and D are as defined where this formula is first shown above] through sequential:

(i) selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trifluoroacetic anhydride and a base) of the 1 ,4-dideoxy-1 ,4-iminoribitol moiety in such a compound of formula (I); and

(ii) 3',5'-O-protection of the resulting product by reaction with 1 ,3-dichloro-i , 1,3,3- tetraisopropyldisiloxane and a base to give a compound of formula (XV):

[wherein R¹ is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, R² is either the same as R¹ or is a hydrogen atom, and A, B and D are as defined for formula (I) where first shown above]

(iii) 2'-O-thioacylation of the resulting compound of formula (XV) (typically with phenoxythionocarbonyl chloride and a base; or sodium hydride, carbon disulfide and methyl iodide);

(iv) Barton radical deoxygenation (typically with tributyltin hydride and a radical initiator);

(v) cleavage of the silyl protecting group by a reagent capable of acting as a source of fluoride ion, e.g. tetrabutylammonium fluoride in tetrahydrofuran or ammonium fluoride in methanol; and

(vi) cleavage of the residual N- and O-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use.

Reagents and reaction conditions suitable for conducting the key steps in this transformation can be found in Robins et al., J. Am. Chem. Soc, 105 (1983) 4059; Solan and Rosowsky, Nucleosides Nucleotides 8 (1989) 1369; and Upadhya et al., Nucleic Acid Res., 14(1986) 1747.

It will be appreciated that a compound of formula (I) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing alkyl- or aralkyl-oxycarbonylation or acylation during step (i), or thioacylation during step (ii), depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali- catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry in the imino-ribitol moiety, and can be removed during the final deprotection step(s). If desired, this approach can be applied to a compound of formula (XV) [as defined above, but additionally bearing N-protecting groups on the pyrazolo- or pyrrolo-pyrimidine moiety]. Methods suitable for preparing such N-protected compounds can be found in Ciszewski et al., Nucleosides Nucleotides 12 (1993) 487; and Kambhampati et al.,

Nucleosides and Nucleotides 5 (1986) 539, as can methods to effect their 2'- deoxygenation, and conditions suitable for N-deprotection.

Method (H): (2'-epi-analogues) Effecting the overall C-2' epimerization of a compound of formula (I), by oxidizing and then reducing a compound of formula (XV) [as defined where first shown above] to give compound of formula (XVI):

[wherein R¹, R², A, B and D are as defined for formula (XV) where first shown above]

which may be present in a mixture with the starting alcohol of formula (XV), and then fully deprotecting this compound of formula (XVI) as set out in steps (v) and (vi) of Method (G).

Reagents and reaction conditions suitable for conducting the key steps in this transformation can be found in Robins et al., Tetrahedron 53 (1997) 447.

Method (I): (2'-deoxy-2'-halogeno- and 2^!-deoxy-2'-epi-2'-halogeno-analogues)

Reacting a compound of formula (XV) or (XVI) [as defined where first shown above] by the methods set out in Method (A) for the preparation of a compound of formula (II) [wherein Z' is a halogen atom] which involve either (i) 2'-O-sulfonylation and sulfonate displacement with a halide ion; or

(ii) direct replacement of the 2'-hydroxy group with a halogen atom, e.g by the Mitsunobu reaction or reaction with diethylaminosulfur trifluoride (DAST)

to give a compound of inverted stereochemistry at C-2', which is then fully deprotected as set out in steps (v) and (vi) of Method (G).

It will be appreciated that a compound of formula (XV) or (XVI) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing sulfonylation during step (i), depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-sulfonate substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry in the iminoribitol moiety, and can be removed during the final deprotection step(s).

If desired, this approach can be applied to a compound of formula (XV) or (XVI) [as defined above, but additionally bearing N-protecting groups on the pyrazolo- or pyrrolo- pyrimidine moiety]. Methods suitable for preparing such N-protected compounds can be found in Ciszewski et al., Nucleosides Nucleotides 12 (1993) 487; and Kambhampati et al., Nucleosides and Nucleotides 5 (1986) 539, as can methods to effect 2'-O-triflate formation and displacement by halide ion with inversion, and conditions suitable for N- deprotection.

Method (J): (5-cfeoxy-, 5'-deoxy-5'-halogeno-, 5'-ether and 5'-thio-analogues) By applying the procedures described in Method (A) for converting a compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z¹ is a hydroxy group] into a compound of formula (II) [wherein Z¹ is a halogen or hydrogen atom or SQ or OQ where Q is an optionally substituted alkyl, aralkyl or aryl group alkylthio group of one to five carbon atoms] to a compound of formula (XVII):

(XVII)

[wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl- carbonyl group, 11 is a hydroxy group, and A, B and D are as defined for formula (I) where first shown above]

which is then fully deprotected under acidic conditions, e.g. by treatment with aqueous trifluoroacetic acid.

Such a compound of formula (XVII) can be prepared from a compound of formula (I) [wherein X and Z are both hydroxy groups, Y is a hydrogen atom and A, B, and D have the meanings defined for formula (I) where first shown above] in the following two reaction steps, which may be applied in either order:

(i) selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trifluoroacetic anhydride and a base) of the 1 ,4-dideoxy-1 ,4-iminoribitol moiety; and

(ii) 2',3'-0-isopropylidenation, which may be effected with a variety of reagents, e.g. acetone and anhydrous copper sulfate with or without added sulfuric acid; acetone and sulfuric acid; 2,2-dimethoxypropane and an acid catalyst; or 2-methoxypropene and an acid catalyst.

It will be appreciated that such a compound of formula (I) or formula (XVII) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing sulfonylation, thioacylation, acylation or aralkyl-oxycarbonylation, depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali- catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry in the iminoribitol moiety, and can be removed during the final deprotection step(s). Method (K): (2- and 4-aminopyrrolo[3,2-d]pyrimidine and 5- and 7-aminopyrazolo[4,3- djpyrimidine analogues)

Chlorinating a compound of formula (XVIII)

(XVIII)

[wherein

R¹ is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group,

R² is an alkylcarbonyl or optionally substituted arylcarbonyl group,

X and Y are independently chosen from a hydrogen or halogen atom, or a group of formula R²O, except that when one of X or Y is a halogen atom or a group of formula R²O, the other is a hydrogen atom,

Z' is a group of formula R²O or, when X is a group of formula R²O, Z" is a hydrogen or halogen atom, a group of formula R²O or of formula OQ or SQ wherein Q is an optionally substituted alkyl, aralkyl or an aryl group,

A is a nitrogen atom or a methine group, and

one of B or D is a hydroxy group, and the other is a chlorine, bromine or hydrogen atom]

with a chlorinating reagent, and then displacing the chlorine atom with a nitrogen nucleophile by one of the following methods:

(i) ammoniolysis, typically using liquid ammonia, concentrated aqueous ammonia, or a solution of ammonia in an alcohol such as methanol; or (ii) conversion first to a triazole derivative, by addition of -4-chlorophenyl phosphorodichloridate to a solution of the chloride and 1 ,2,4-triazole in pyridine, and alkaline hydrolysis of both the tetrazole moiety and the ester protecting groups with ammonium hydroxide;

(iii) reaction with a source of azide ion, e.g. an alkali metal azide or tetraalkylammonium azide, and reduction of the resulting product, typically by catalytic hydrogenation; or

(iv) reaction with an alkylamine or aralkylamine, such as methylamine or benzylamine in methanol.

These conditions are sufficiently basic that O-ester groups will generally be cleaved but any residual O- or N-protecting groups can then be removed by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use.

Suitable chlorinating agents are thionyl chloride - dimethylformamide complex [Ikehara and Uno, Chem. Pharm. Bull., 13 (1965) 221], triphenylphosphine in carbon tetrachloride and dichloromethane with or without added 1 ,8-diazabicyclo[5.4.0]undec-7-ene (DBU) [De Napoli et al., J. Chem. Soα, Perkin Trans.1 (1995) 15 and references therein], phosphoryl chloride [Imai, Chem. Pharm. Bull., 12 (1964) 1030], or phenylphosphoryl chloride and sodium hydride.

Suitable conditions for such an ammoniolysis or a reaction with an alkylamine can be found in Ikehara and Uno, Chem. Pharm. Bull., 13 (1965) 221 ; Robins and Tripp, Biochemistry 12 (1973) 2179; Marumoto et al., Chem. Pharm. Bull., 23 (1975) 759; and Hutchinson et al., J. Med. Chem., 33 (1990) 1919].

Suitable conditions for conversion of such a chloride to an amine via a tetrazole derivative can be found in Lin et al., Tetrahedron 51 (1995) 1055.

Suitable conditions for reaction with azide ion followed by reduction can be found in Marumoto et al., Chem. Pharm. Bull., 23 (1975) 759.

Such a compound of formula (XVIII) can be prepared from a compound of formula (I) by selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation of the 1 ,4-dideoxy-1 ,4- iminoribitol moiety and then O-acylation (typically with acetic anhydride or benzoyl chloride in pyridine). It will be appreciated that such a compound of formula (I) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing alkyl- or aralkyl-oxycarbonylation or acylation depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry, and can be removed during the final deprotection step(s).

The above chlorination - amination - deprotection sequence can also be applied to a compound of formula (XVII) [wherein B is a hydroxy group, D is a hydrogen atom, Z¹ is a hydrogen or halogen atom, or a group of formula R²O, R² is a trialkylsilyloxy or alkyldiarylsilyloxy group, or an optionally substituted triarylmethoxy, alkylcarbonyl or arylcarbonyl group, R and A are as defined for formula (XVII) where first shown above]. Suitable conditions for conducting this reaction sequence can be found in lkehara et al., Chem. Pharm. Bull., 12 (1964) 267.

Method (L): (2,4-dihydroxypyrrolo[3,2-d]pyήmidine and 5, 7-dihydroxypyrazolo[4,3- djpyrimidine analogues) Oxidation of either:

(i) a compound of formula (XVIII) [wherein R² is a hydrogen atom; X and Y are independently chosen from a hydrogen or halogen atom, or a hydroxy group, except that when one of X or Y is a halogen atom or a hydroxy group, the other is a hydrogen atom; T is a hydroxy group or, when X is a hydroxy group, Z¹ is a hydrogen or halogen atom, a hydroxy group, or OQ; Q is an optionally substituted alkyl, aralkyl or aryl group; B is a hydroxy group or an amino group; D is a hydrogen atom; and R¹ and A are as defined for formula (XVIII) where first shown above] with bromine in water; or

(ii) a compound of formula (XVIII) [wherein Z' is a hydrogen or a halogen atom, or a group of formula R²O, or OQ; Q is an optionally substituted alkyl, aralkyl or aryl group; B is a hydroxy group or an amino group, D is a hydrogen atom and R¹, R², X, Y and A are as defined for formula (XVIII) where first shown above], with bromine or potassium permanganate in water or in an aqueous solvent mixture containing an inert, water-miscible solvent to improve the solubility of the substrate, to give a related compound of formula (XVIII) [but wherein B and D are now hydroxy groups]; and then

removal of any O- and N-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use.

Such a compound of formula (XVIII) required for step (i) above can be prepared from a compound of formula (I) [wherein Z is Z', and X, Y, Z, A, B and D are as defined for the required compound of formula (XVIII)] by selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trifluoroacetic anhydride and a base) of the 1 ,4-dideoxy- 1 ,4-iminoribitol moiety. This can then be converted to the corresponding compound of formula (XVIII) required for step (ii) above by O-acylation (typically with acetic anhydride or benzoyl chloride in pyridine). It will be appreciated that such a compound of formula (I) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing alkyl- or aralkyl- oxycarbonylation or acylation depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry, and can be removed during the final deprotection step(s).

Method (WI): (4-amino-2-chloropyrrolo[3,2-d]pyrimidine and 7-amino-5-chloropyrazolo[4,3- djpyrimidine analogues) Chlorinating a compound of formula (XVIII) [wherein B and D are hydroxy groups and R¹, R², X, Y, Z' and A are as defined for formula (XVIII) where first shown above] to give a corresponding dichloro-derivative of formula (XVIII) [wherein B and D are chlorine atoms], typically with neat phosphorous oxychloride, and then displacing the more reactive chloro- substituent selectively by ammoniolysis, typically using anhydrous liquid ammonia in a pressure bomb or methanolic ammonia, which simultaneously cleaves the O-ester protecting groups. The residual N-protecting group is then removed by acid-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use, to give a compound of formula (I) [wherein B is an amino-group and D is a chlorine atom].

The above dichloro-derivative of formula (XVIII) can be converted into a compound of formula (I) [wherein B and D are chlorine atoms] by removal of the O- and N-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis as required for the protecting groups in use. It will be appreciated that one of the chlorine atoms in the aforementioned compound of formula (XVIII) or of formula (I) is quite reactive and that conditions chosen for deprotection must be mild enough that they limit unwanted reactions involving this atom.

Suitable reaction conditions for the key steps in this method can be found in Upadhya et al., Nucleic Acid Res., 14 (1986) 1747 and Kitagawa et al., J. Med. Chem., 16 (1973) 1381.

Method (N): (2-chloro-4-hydroxypyrrolo[3,2-d]pyrimidine and 5-chloro-7- hydroxypyrazolo[4,3-d]pyrimidine analogues from dichloro-compounds) Hydrolysis of a compound of formula (XVIII) [wherein B and D are chlorine atoms] available as an intermediate from the first reaction of Method (M)₁ typically with aqueous potassium hydroxide or sodium carbonate, in the presence of an inert, water-miscible solvent such as dioxane to enhance solubility as required, followed by removal of the residual N-protecting group by acid-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use, to give a compound of formula (I) [wherein B is a hydroxy group and D is a chlorine atom].

Method (O): (2-chloro-4-hydroxypyrrolo[3,2-d]pyrimidine and 5-chloro-7- hydroxypyrazolo[4,3-d]pyrimidine analogues from aminochloro-compounds) Deamination of a compound of formula (XVIII) [wherein B is an amino group, D is a chlorine atom, R¹ is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl- carbonyl group, R² is a hydrogen atom, Z' = Z and X, Y, Z and A are as defined for formula (I) where first shown above], available as an intermediate following the chlorination and ammonyolysis reactions of Method (M), by reaction with nitrosyl chloride, followed by removal of the protecting groups as set out in Method (M) . Typical reaction conditions can be found in Sanghvi et al., Nucleosides Nucleotides 10 (1991) 1417.

Method (P): (4-halogenopyrrolo[3,2-d]pyrimidine and 7-halogenopyrazolo[4,3-d]pyrimidine analogues) Reacting a compound of formula (XVIII) [wherein R¹ is tert-butoxycarbonyl group, B is a hydroxy group, D is a hydrogen atom and R², X, Y, Z" and A are as defined for formula (XVIII) where first shown above] by a method used to prepare halogeno-formycin analogues [Watanabe et al., J. Antibiotic, Ser. A 19 (1966) 93] which involves sequential treatment with:

(i) phosphorous pentasulfide by heating in pyridine and water under reflux to give a mercapto-derivative; (ii) methyl iodide to give a methylthio-derivative;

(iii) a base in a simple alcohol or an aqueous solution of a simple alcohol, e.g. sodium methoxide in methanol, to remove the O-protecting groups; and

(iv) chlorine, bromine or iodine in absolute methanol to give a halogeno-derivative

which is then N-deprotected by reaction with aqueous acid, typically a concentrated trifluoroacetic acid solution.

Method (Q): (pyrrolo[3,2-d]pyrimidine and pyrazolo[4,3-d]pyrimidine analogues) Hydrogenolytic cleavage of the chloride intermediate resulting from the chlorination reaction used as the first reaction in Method (K), or the chloride intermediate resulting from the chlorination reaction step (iv) in Method (P), or the compound of formula (I) produced by Method (P)₁ typically using hydrogen over palladium on charcoal as the catalyst, optionally with magnesium oxide present to neutralize released acid, followed by cleavage of any residual O- or N-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis as required for the protecting groups in use.

Method (R): (N-alkylated 4-aminopyrrolo[3,2-d]pyrimidine and 7-aminopyrazolo[4,3- d]pyrimidine analogues)

Heating an O-deprotected methylthio-derivative produced by step (iii) of Method (P) with an amine, e.g. methylamine, in absolute methanol in a sealed tube or bomb, and then removing the N-protecting group by reaction with aqueous acid, typically a concentrated trifluoroacetic acid solution. This method has been used to prepare N-alkylated-formycin analogues [Watanabe et al., J. Antibiotic, Ser. A 19 (1966) 93]; or

reacting a compound of formula (I) [wherein either B or D is an amino group] with 1 ,2- bis[(dimethylamino)rnethylene]hydrazine and trimethylsilyl chloride in toluene to convert the amino group into a 1 ,3,4-triazole group, hydrolysis to cleave the O-silyl groups (e.g. with acetic acid in aqueous acetonitrile), and displacement of the 1 ,3,4-triazole group with an alkylamine in a polar solvent (e.g. water or aqueous pyridine). This method has been used to prepare N,N-dimethyl-formycin A [Miles et al., J. Am. Chem. Soc, 117 (1995) 5951]; or

subjecting a compound of formula (I) [wherein either B or D is an amino group] to an exchange reaction by heating it with an excess of an alkylamine. This method has been used to prepare N-alkyl-formycin A derivatives [Hecht et a!., J. Biol. Chem., 250 (1975) 7343].

Method (S): (2~chloro-4-hydroxypyrrolo[3,2-d]pyrimidine and 5-chloro-7-hydroxypyrazolo[4,3- djpyrimidine analogues)

Selective chlorination of dihydroxy compound of formula (XVIII) [wherein B and D are hydroxy groups, and R¹, R², X, Y, Z¹ and A are as defined for formula (XVIII) where first shown above], taking advantage of the greater reactivity of the 4-hydroxy group on a 2,4- dihydroxypyrrolo[3,2-d]pyrimidine derivative and the 7-hydroxy group on a 5,7- dihydroxypyrazolo[4,3-d]pyrimidine derivative, followed by removal of protecting groups, using the methods set out in Method (M).

Method (T): (2-halogeno-, 4-halogeno- and 2,4-dihalogeno-pyrrolo[3,2-d]pyrimidine and 5- halogeno-, 7-halogeno-, and 5, 7~dihalogeno-pyrazolo[4,3-d]pyrimidine analogues) Diazotization of a compound of formula (XVIII) [wherein one of B or D is an amino group, and the other is independently chosen from an amino group, or a halogeno or hydrogen atom, and R¹ , R² , X, Y, Z" and A are as defined for formula (XVIII) where first shown above] and subsequent reaction using one of the following procedures:

(i) with nitrous acid (made in situ from sodium nitrite) in the presence of a source of halide ion. For replacement of an amino-group with a fluorine atom, a concentrated aqueous solution of fluoroboric acid [Gerster and Robins, J. Org. Chem., 31 (1966) 3258; Montgomery and Hewson, J. Org. Chem., 33 (1968) 432] or hydrogen fluoride and pyridine at low temperature (e.g. -25 to -30 ⁰C) [Secrist et al., J. Med. Chem., 29 (1986) 2069] can serve both as the mineral acid and the fluoride ion source; or

(ii) with an alkyl nitrite, typically tert-butyl or n-butyl nitrite, in a non-aqueous solvent in the presence of a source of halide ion. For replacement of an amino-group with a chlorine atom, a combination of chlorine and cuprous chloride, or antimony trichloride can be used in chloroform as solvent [Niiya et al, J. Med. Chem., 35

(1992) 4557 and references therein]; or

(iii) with an alkyl nitrite, typically tert-butyl or n-butyl nitrite, in a non-aqueous solvent coupled with photohalogenation. For replacement of an amino group with a chlorine, bromine or iodine atom, carbon tetrachloride, bromoform, or diiodomethane have been used as reagent and solvent and an incandescent light source (e.g. a 200 W bulb) has been used to effect photohalogenation [Ford et al., J. Med. Chem., 38 (1995) 1189; Driscoll et al., J. Med. Chem., 39 (1996) 1619; and references therein];

to give a corresponding compound of formula (XVIII) [wherein B is a halogen atom and D is either a halogen atom or an amino group], followed by removal of the protecting groups as set out in Method (M).

The same transformations can be effected for a corresponding starting compound of formula (XVIII) [wherein one of B or D is an amino group, and the other is a hydroxy group] if the hydroxy group is first converted to a thiol group [Gerster and Robins, J. Org. Chem., 31 (1966) 3258]. This conversion can be effected by reaction with phosphorous pentasulfide by heating in pyridine and water under reflux (see Method (P)).

Method (U): (4-iodo-pyrazolo[3,2-d]pyrimidine and 7-iodopyrazolo[4,3-d]pyrimidine analogues)

Treatment of corresponding chloro-analogue of formula (I) [wherein B is a chlorine atom] with concentrated aqueous hydroiodic acid, following the method of Gerster et al., J. Org. Chem., 28 (1963) 945.

Method (V): (5'-deoxy-5'-halogeno- and 5'-thio-analogues)

By reacting a compound of formula (XVIII) [wherein R² is a hydrogen atom; X and Y are independently chosen from a hydrogen or halogen atom, or a hydroxy group, except that when one of X or Y is a halogen atom or a hydroxy group, the other is a hydrogen atom; Z' is a hydroxy group; and R¹, A, B and D are as defined for formula (XVIII) where first shown above] with either

(i) a trisubstituted phosphine and a disulfide, e.g. tributylphosphine and diphenyl disulfide; or

(ii) a trisubstituted phosphine (e.g. triphenylphosphine) and carbon tetrabromide; or

(iii) thionyl chloride or bromide;

and then removal of the N-protecting group by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting group in use. Conditions suitable for conducting such selective replacements of a 5'-hydroxy group with a thio group or a halogen atom can be found in Chern et al., J. Med. Chem., 36 (1993) 1024; and Chu et al., Nucleoside Nucleotides 5 (1986) 185.

In addition, the above and other methods for the synthesis of compounds of formula (I) have been exemplified for the synthesis of the enantiomers of compounds of formula (I) as detailed in the review article by Evans, Aust. J. Chem., 57 (2004) 837-854 and references therein, which are incorporated herein by reference.

(2) Convergent Synthetic Route

An alternate route to the compounds of the invention involves a convergent route, rather than a linear one. This can have the advantage of providing higher yields of the compounds of formula (I). Such a convergent route has been described for the D-enantiomers in Evans et al., J. Org. Chem., 66 (2001) 5723-5730.

The/donvergent process comprises the step of reacting a compound of the formula (II)

(H)

where Z is a hydrogen or halogen atom, a group of formula SQ, OQ or Q, or a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triaryimethoxy group and Q is an optionally substituted alkyl, aralkyl or aryl group, sequentially with a halogenating agent, such as N- chlorosuccinimide, and a sterically hindered base, to form an imine. The imine thus prepared is then condensed with an anion produced by abstraction of the bromine or iodine atom from a compound of the formula (XIX):

(XIX) wherein R⁵ is a bromine or iodine atom, R⁶ is an N-protecting group, B' and D' are independently selected from H, OR⁷ and N(R⁸)₂, and R⁷ and R⁸ are O- and N- protecting groups respectively, to form a compound of formula (XX):

R⁹

(XX)

wherein R⁹ is a hydrogen atom, Z' is as defined above for compounds of formula (II) and R⁶, B' and D' are as defined above for compounds of formula (XIX).

This is followed by optionally converting the compound of formula (XX) to a compound of formula (XX) wherein Z', R⁶, B' and D' are as defined above but R⁹ is alkoxycarbonyl or aralkoxycarbonyl, or optionally, where Z' in the compound of formula (XX) is trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy, converting the compound of formula (XX) to a compound of formula (XX) wherein R⁶, R⁹, B' and D¹ are as defined above but Z' is OH; and

The above steps are then followed by N- and O-deprotecting the compound of formula (XX) by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the O- and N-protecting groups in use, to produce a compound of the formula (I) as defined above.

If desired, the compound of formula (I) thus prepared may be converted into a pharmaceutically acceptable salt, ester or prodrug thereof, using methods known in the art.

Particularly suitable as N-protecting groups R⁶ in the compound of formula (XIX) include alkoxymethyl groups such as benzyloxymethyl, silyl groups such as tert-butyldimethylsilyl, and arylmethyl groups such as benzyl.

Suitable O-protecting groups R⁷ in the compound of formula (XIX) include alkyl or arylmethyl groups such as methyl, terf-butyl or benzyl. Particularly suitable as N-protecting groups R⁸ in the compound of formula (XIX) are arylmethyl groups such as benzyl, or the two R⁸ groups may together form the 2,4-hexadien- 2,5-yl group.

The compounds of formula (XIX) defined above may be prepared by known methods. In particular, unprotected deazapurines can be converted by conventional methods into their protected forms (XIX). Alternatively, known 5-nitro-6-methylpyrimidine derivatives can first be converted into suitably protected intermediates, and then cyclized to the corresponding deazapurines, for example by reaction with tert-butoxy-bis(dimethylamino)methane, and then N-protected.

Suitable reagents for halogenation of a compound of formula (II) include chlorinating or brominating agents, and these include Λ/-chloro- and bromoamides, chlorine and bromine, preferably /V-chlorosuccinimide. Halogenation is conveniently carried out at ambient temperatures in an alkane as solvent, preferably hexane, more preferably pentane. Where the halogenation reagent is Λ/-chlorosuccinimide, the succimide byproduct and any excess reagent can be removed by filtration. An excess of the halogenation reagent can be employed, though it is preferable to use close to equimolar quantity.

Suitable sterically hindered bases that can be used to form the imine by dehalogenation include alkali metal salts of bulky alcohols or amines, such as potassium terf-butoxide, lithium diisopropylamide or preferably lithium tetramethylpiperadide. An excess of base can be employed, though it is preferable to use close to an equimolar quantity. Preferably the amount of base used is determined experimentally as just sufficient to result in complete reaction of the compound of formula (XIX), and this can be judged by thin layer chromatography.

The imine formed by halogenation and dehydrohalogenation of a compound of formula (II) is more stable when kept at room temperature or below, but does not readily condense with the anion produced by abstraction of bromine or iodine from a compound of formula (XIX) at temperatures below -40 ⁰C. The anion can be prepared at temperatures of -35 to -75 ⁰C, but the temperature of the reaction medium should be in the range of -20 to +10 ⁰C to effect the condensation reaction. The anion is unstable at temperatures above +10 ⁰C, and is preferably kept at temperatures below 0 ⁰C, more preferably at or below -10 ⁰C. The anion can be more stable in diethyl ether solution, and this is the preferred solvent. Compounds of formula (XIX) and the anions formed from them can have limited solubility in diethyl ether, however, so that addition of a further solvent to assist with solubility is sometimes necessary. In this case the favoured solvent is anisole, so that the favoured reaction medium is a mixture of diethyl ether and anisole, the proportions being chosen to optimize solubility and stability of the reactants. An excess of either the anion or the imine can be employed, though it is preferable to use close to equimolar quantities of these reactants. As a small portion of the anion can be quenched by proton abstraction reactions or be subject to degradation reactions at the temperatures required to effect coupling, it is sometimes preferable to use a small excess of the anion, up to 2 equivalents, preferably up to 1.2 equivalents.

Examples of preferred reagents for performing the abstraction of the bromine or iodine atom from the compound of formula (XIX) are butyllithium or magnesium, and other suitable reagents will be apparent to those skilled in the art.

The above condensation reaction can be usefully catalyzed by Lewis acids, preferably boron trifluoride diethyl etherate, titanium tetrachloride or stannic chloride as described for the D- enantiomers in Evans et al, J. Org. Chem., 69 (2004) 2217-2200.

The above condensation reaction produces a compound of the formula (XX) as defined above.

In some instances, in order to facilitate purification, a derivative of formula (XX) wherein Z is a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group (such as trityloxy (ie unsubstituted triphenylmethoxy) or 4-mono or 4,4'-dimethoxytrityloxy) and R⁹ is a hydrogen atom can be further converted into a derivative of formula (XX) wherein Z' is a hydroxy group and R⁹ is a hydrogen atom. For example, in the case wherein Z' is a trialkylsilyloxy or alkyldiarylsilyloxy group, preferably a te/Y-butyldimethylsilyloxy group, this can be achieved by treatment with tetrabutylammonium fluoride in tetrahydrofuran followed by chromatography.

Furthermore, in some instances, in order to facilitate purification, a derivative of formula (XX) wherein R⁹ is a hydrogen atom can be further converted into a derivative of formula (XX) wherein R⁹ is an alkoxycarbonyl or aralkyloxycarbonyl group, preferably a terf-butoxycarbonyl group, for example by treatment with di-tert-butyl dicarbonate in methylene chloride followed by chromatography.

The compound of formula (XX) (either prepared directly from the condensation reaction or from subsequent conversion to another compound of formula (XX) as described immediately above) is then N- and O-deprotected by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the O- and N-protecting groups in use, to produce a compound of the formula (I) as defined above.

Where R⁶ is a trialkylsilyl (preferably a terf-butyldimethylsilyl), alkyldiarylsilyl or 2- trimethylsilylethoxymethyl group, this group can be removed with a source of fluoride, such as tetrabutylammonium fluoride or hydrogen fluoride pyridine complex, in a solvent such as tetrahydrofuran.

Where B' is a benzyloxy group, and/or R⁶ is a benzyloxymethyl group, and/or R⁸ is a benzyl or p-methoxybenzyl group, and/or R⁹ is an aralkyloxycarbonyl (preferably a benzyloxycarbonyl) group, deprotection can be effected by hydrogenolysis over a metal catalyst. A suitable catalyst is palladium on charcoal, and suitable solvents are ethyl acetate, ethanol and methanol.

Where R⁶ is a benzyloxymethyl group it can be removed by treatment with a strong acid, such as concentrated hydrochloric acid, the excess acid being removed by evaporation, suitably under reduced pressure. Alternatively it can be removed by hydrogenolysis over a metal catalyst. A suitable catalyst is palladium on charcoal, and suitable solvents are ethyl acetate, ethanol and methanol. Intermediates in these process are compounds wherein R⁶ is a hydroxymethyl group. This group can resist further reaction under the above conditions but can readily be removed by alkali treatment. Suitable alkaline conditions are ammonia or an alkylamine (such as triethylamine) in water or alcohol solution at room temperature or up to 100 ⁰C. The aforementioned hydrogenolysis can be conducted under alkaline conditions to effect full deprotection.

Where B' is a methoxy, te/if-butoxy or benzyloxy group, and/or Z' is a trialkylsilyloxy (preferably a te/f-butyldimethylsilyloxy) or alkyldiarylsilyloxy group, and/or R⁶ is a trialkylsilyl (preferably a te/if-butyldimethylsilyl), alkyldiarylsilyl, 2-trimethylsilylethoxymethyl or benzyloxymethyl group, and/or R⁹ is an alkoxycarbonyl or aralkyloxycarbonyl group, especially a tert-butoxycarbonyl group, deprotection can be effected by treatment with aqueous, alcoholic or concentrated acid. Suitable acids are hydrochloric or trifluoroacetic acids. The reaction can be conducted in the range 20 - 120 ⁰C, preferably in concentrated aqueous hydrochloric acid under reflux. EXAMPLES

The following examples further illustrate the invention. It is to be appreciated that the invention is not limited to the examples.

General

Imidazole was recrystallised from CH₂CI₂. All other reagents were used as supplied; anhydrous solvents were obtained commercially. Air sensitive reactions were carried out under argon unless otherwise stated. Organic solutions were dried over MgSO₄ and the solvents were evaporated under reduced pressure. Chromatography solvents were distilled prior to use. Thin layer chromatography (t.l.c.) was performed on glass or aluminium sheets coated with 60 F₂₅₄ silica. Organic compounds were visualised under uv light or by use of a spray or dip of cerium(IV) sulfate (0.2%, w/v) and ammonium molybdate (5%) in sulfuric acid (2M), one of I₂ (0.2%) and Kl (7%) in H₂SO₄ (M) or , for nitrogen-containing compounds, p- (Λ/,Λ/-dimethylamino)benzaldehyde (1%) in HCI (37%)-MeOH, 1 :3 (100 ml) (Erlich reagent). Flash column chromatography was performed on Sorbsil C60 40/60 silica, Scharlau or Merck silica gel 60 (40-60 μm). Melting points were recorded on a Kofler hot block or a Reichert hot stage microscope and are uncorrected. Optical rotations were recorded on a Perkin-Elmer 241 polarimeter with a path length of 1 dm and are in units of 10^"1deg cm² g^'1; concentrations are in g/100 ml.

NMR spectra were recorded on a Bruker AC300E or Bruker DPX 400 spectrometer. ¹H spectra at 300 or 400 MHz were measured in CDCI₃, CD₃OD or CD₃CN (internal reference Me₄Si, δ 0), and ¹³C spectra at 75.5 or 100.6 MHz in CDCI₃ (reference, solvent centre line, δ 77.0), CD₃OD (reference, solvent centre line δ 49.0) or CD₃CN (reference, solvent centre line δ 118.7, CN). Assignments of ¹H and ¹³C resonances were based on 2D (¹H-¹H DQF-COSY, ¹H-¹³C HSQC) spectra, and DEPT experiments gave unambiguous data on the numbers of protons bonded to each carbon atom. The assignments of the ¹³C resonances were consistent with the multiplicities observed. Coupling constants (J) are quoted in Hz. Infrared spectra were recorded on a Perkin-Elmer 1750 IR Fourier Transform, or Perkin-Elmer Paragon 1000 spectrophotometer using thin films on NaCI plates (thin film). Only characteristic absorptions are quoted. Electrospray ionisation (ES) low resolution mass spectra {m/z) were measured on a Micromass BioQ N-ZS mass spectrometer. For high resolution mass spectra (HRMS), ES data were collected on a Waters 2790-Micromass LCT mass spectrometer operated at a resolution of 5000 full width half height. Positive ion electrospray ionisation (ES+) spectra were calibrated relative to PEG with tetraoctylammonium bromide as the internal lock mass. Negative ion ES spectra were calibrated relative to poly-DL-alanine with Leu-enkephalin as the internal lock mass. Chemical ionization (Cl, NH₃) HRMS were recorded on a Micromass 500 OAT spectrometer. Positive ion fast atom bombardment (FAB+) HRMS were measured on a VG 7070 instrument in a glycerol matrix, and positive ion electron impact (El+) HRMS were measured on a VG 70SE instrument. Microanalyses were carried out by the Campbell Microanalytical Laboratory, University of Otago or in the Department of Chemistry, University of Oxford.

Scheme 1

HO

5-O-fe/t-Butyldimethylsilyl-2,3-O-isopropylidene-D-lyxono-1,4-lactone (2) The isopropylidene lactone 1 (Fleet et al., J. Chem. Soc, Perkin Trans. 1, (1989) 665-666) (3.84 g, 20.4 mmol), derived from the unsubstituted lactone (Behling et al., Tetrahedron, 49 (1993) 3359-3368) was added to a solution of fe/f-butyldimethylsilyl chloride (4.61 g, 30.6 mmol) and imidazole (2.78 g, 30.6 mmol) in DMF (25 ml). The solution was stirred at 20 ⁰C under an atmosphere of nitrogen. After 4 h, t.l.c. analysis (EtOAc - cyclohexane, 1 : 1) indicated complete conversion of starting material (R_f 0.12) into a major product (R_f 0.52). The reaction mixture was concentrated and coevaporated with toluene. The residue was then purified by flash chromatography (EtOAc - cyclohexane, 1 : 2) to give the fully protected lactone 2 (5.69 g, 91%) as a white crystalline solid, mp 90-91 ⁰C, [α]^² + 54.9 (c, 1.03,

CHCI₃); μ_max (thin film) 1773 (C=O); NMR δ_H (400 MHz; CDCI₃) 0.10 (6 H, s, SiMe₂), 0.91 (9 H, s, Si'Bu), 1.40, 1.47 [2x3 H, 2s, C(CHs)₂], 3.94 (1 H, dd, J_5,4 6.5, J₅., 10.4, H-5), 3.99 (1 H, dd, J₅.,₄ 6.1 , H-5'), 4.53 (1 H, m, H-4), 4.82 (2 H, m, H-2,3); δ_c (100.6 MHz; CDCI₃) - 5.5, - 5.4

[Si(CHa)₂], 18.3 [C(CH₃)₃], 25.8 [C(CHa)₃], 25.9 [C(CH₃J₂], 26.8 [2xC(CH₃)₂], 60.9 (C-5), 75.7 (C-3), 76.0 (C-2), 79.4 (C-4), 114.1 [S(CHs)₂], 173.7 (C-1); HRMS (Cl+) m/z 303.1625; Ci₄H₂₇O₅Si [(M+H)⁺] requires 303.1628. (Found: C, 55.7; H, 8.2%; C₁₄H₂₆O₅Si requires C₁ 55.6; H, 8.7%).

5-O-terf-Butyldϊmethylsilyl-2,3-O-isopropylidene-D-lyxitol (3)

Lithium borohydride (4 ml, 2M in THF, 8 mmol) was added dropwise to a stirred solution of the TBDMS ether 2 (1.21 g, 4.00 mmol) in THF (4 ml) and the stirring was continued at - 30 ⁰C under an atmosphere of nitrogen. After 5 h, t.l.c. analysis (EtOAc - cyclohexane, 1 : 1) showed residual starting material as well as a major product (R_f 0.35). More lithium borohydride (2 ml, 2M in THF 4 mmol) was added and the mixture was left stirring at - 30 ⁰C for a further 2 h. The reaction mixture was then allowed to assume room temperature. After a further 16 h, t.l.c. analysis (EtOAc - cyclohexane, 1 : 2) indicated most of the starting material had reacted. A solution of aqueous ammonium chloride (4 ml, saturated) was then added dropwise to the reaction mixture which was partitioned between EtOAc (20 ml) and brine (20 ml). The organic layer was then collected, washed with water (3 x 10 ml) and dried. The solvent was removed and the residue was crystallized from THF to afford the diol 3 (910 mg,

75%), mp 67-68 ⁰C, [α]^³ - 9.2 (c, 0.08, CHCI₃); μ_maχ (thin film) 3400 (broad, O-H); NMR δ_H

(400 MHz; CDCI₃) 0.08 (6 H, s, SiMe₂), 0.91 (9 H, s, Sϊ^*Bu), 1.38, 1.50 [2x3 H, 2s, C(CHs)₂], 2.78-2.91 (2 H, br s, OH), 3.63 (1 H, dd, J_5,5. 10.0, J_5,4 6.8, H-5), 3.73 (1 H, dd, J_SA 6.2, H-5'), 3.77-3.82 (3 H, m, H-1 ,1',4), 4.82 (2 H, m, H-2,3); δ_c (100.6 MHz; CDCI₃) - 5.5, - 5.4 [Si(CHg)₂], 18.3 [C(CH₃)₃], 25.0 [C(CH₃)₂], 25.8 [C(CH₃)₃], 27.1 [C(CH₃)₂], 61.4 (C-1), 64.6 (C- 5), 69.2 (C-4), 75.7, 77.3 (C-2, C-3), 110.4 [C(CH₃)₂]; HRMS (ES-) m/z 305.1796; C₁₄H₂₉O₅Si ([M-HD requires 305.1784. (Found: C, 54.75; H, 10.0; C₁₄H₃₀O₅Si requires C, 54.9; H, 9.9%).

5-O-te/t-Butyldimethylsilyl-2,3-O-isopropylidene-1,4-di-O-methanesulfonyl-D-lyxitol (4)

A solution of the diol 3 (2.40 g, 8.16 mmol) in CH₂CI₂ (3.5 ml) was added dropwise to a mixture of 4-(Λ/,/V-dimethylamino)pyridine (0.50 g, 4.08 mmol) and methanesulfonic anhydride (6.36 g, 36.5 mmol) in dry pyridine (13 ml) at 0 ⁰C under an atmosphere of nitrogen. The reaction mixture was stirred for 30 min at 0 ⁰C, then at 20 ⁰C for 18 h, after which time t.l.c. analysis (EtOAc - cyclohexane, 1 : 1) indicated the presence of a major product (R_f 0.54). The reaction mixture was then diluted with CH₂CI₂ (100 ml) and aqueous HCI (0.1 M, 50 ml) was added dropwise. The organic layer was washed with aqueous NaHCO₃ (50 ml, saturated), water (50 ml), dried and evaporated. The residue was purified by flash chromatography (EtOAc - cyclohexane, 1 : 4) to give the dimesylate 4 (3.17 g, 88%) as a colourless oil, [α]_p + 5.0 (C, 0.14, CHCI₃); μ_max (thin film) 1360, 1178 (S=O); NMR δ_H (400 MHz; CD₃CN) 0.12 (6 H, s, SiMe₂), 0.92 (9 H, s, Si*Bu), 1.37, 1.49 [2x3 H, 2s, C(CH₃)J, 3.09, 3.14 (2x3 H, 2s, 2SO₂Me), 3.86 (1 H, dd, J₅,₅. 11.4, J_5|4 5.3, H-5), 3.93 (1 H, dd, J₅.₄ 5.3, H-5'), 4.33-4.39 (2 H, m, H-1 ,1¹), 4.42-4.46 (1 H, m, H-2), 4.47 (1 H, dd, J₃,₂ 6.1 , J₃,₄ 9.7, H-3), 4.72 (1 H, dt, J_4,3 9.7, H-4); δ_c (100.6 MHz; CD₃CN) - 6.0 [Si(CH₃)₂], 18.3 IC(CHa)₃], 25.1 [C(CH₃)₂], 25.6 [C(CH₃)₃], 26.9 [C(CH₃)₂], 37.0, 38.8 (2xSO₂Me), 63.4 (C-5), 69.2 (C-1), 74.7 (C-2), 75.5 (C-3), 80.1 (C- 4), 109.6 [C(CHs)₂]; HRMS (ES+) m/z 463.1490; C₁₆H₃₅O₉S₂Si (M+H)⁺ requires 463.1492. (Found C, 41.6; H, 7.4; C₁₆H₃₄O₉S₂Si requires C, 41.5; H, 7.4%).

i-Azido-δ-O-te/t-butyldimethylsilyl-i-deoxy^^-O-isopropylidene^-O-methanesulfonyl- D-lyxitol (4) and 1,4-diazido-5-O-te/t-butyldimethylsilyl-1,4-dideoxy-2,3-O- isopropylidene-L-ribitol (5)

Sodium azide (0.133 g, 2.04 mmol) was added to a solution of the dimesylate 4 (0.942 g, 2.04 mmol) in DMF (5 ml) and the reaction mixture stirred at 100 ⁰C under an atmosphere of nitrogen. The formation of the monoazide 5 (R_f 0.58, EtOAc - cyclohexane, 1 : 2) after 20 min was indicated by t.l.c, but much of the starting material 4 (R_f 0.27) remained. After 1 h, a minor second product (6) (R_f 0.74) started to form. The mixture was stirred at 100 ⁰C for another hour, allowed to cool to room temperature and the solvent was removed. The resulting yellow oil was purified by flash chromatography (EtOAc - cyclohexane, 1 : 4) to give the azido mesylate 5 (0.35 g, 42%), [a];,⁵ + 27.7 (c, 1.43, CHCI₃); μ_max (thin film) 2104 (N₃), 1358, 1174 (S=O); NMR δ_H (400 MHz; CDCI₃) 0.09, 0.10 (2^χ3H, 2s, SiMe₂), 0.90 (9 H, s, Si^fBu), 1.40, 1.53 [2x3 H₁ 2s, C(CH₃)₂], 3.12 (3 H, s, SO₂Me), 3.42 (1 H, dd, J₁,,. 12.8, J_1i2 3.6, H-1), 3.50 (1 H, dd, J₁.₂ 7.6, H-1¹), 3.82 (1 H, dd, J_5,5. 11.2, J_5,4 6.4, H-5), 3.93 (1 H, dd, J₅.₄ 4.8, H-5'), 4.31 (1 H, m, H-2), 4.36 (1 H, dd, J_3,4 13.2, J_3,2 6.0, H-3), 4.73 (1 H, ddd, H-4); δ_c (100.6 MHz; CDCI₃) - 5.6 [Si(CHs)₂], 18.2 [C(CH₃)₃], 25.4 [C(CHs)₂], 25.8 [C(CHs)₃], 27.6 [C(CHa)₂], 38.7 (SO₂Me), 51.0 (C-1), 63.3 (C-5), 75.8 (C-3), 76.1 (C-2), 79.4 (C-4), 109.2 [C(CHs)₂]; HRMS (Cl+) m/z 427.2052; C₁₅H₃₅N₄O₆SSi ([M+NH₄]⁺) requires 427.2047. (Found: C, 44.35; H, 7.4; N, 10.1; C₁₅H₃₁N₃O₆SSi requires C, 44.0; H, 7.6; N, 10.3%).

This was followed by the 6/s-azide (6), (0.11 g, 15%), [α]£ + 87.1 (c, 0.56, CHCI₃); μ_max

(thin film) 2102 (N₃); NMR δ_H (400 MHz; CD₃CN) 0.15, 0.16 (2^χ3H, 2s, SiMe₂), 0.94 (9 H, s, Siteu), 1.33, 1.46 [2x3 H, 2s, C(CHs)₂], 3.47 (2 H, d, J_1|2 13.2, H-1 ,1'), 3.53 (1 H, m, H-4), 3.84

(1 H, dd, J₅,₅. 10.8, J₅,₄ 6.0, H-5), 4.06 (1 H, dd, J₅.₄ 2.8, H-5¹), 4.11 (1 H, dd, J_3,2 6.4, J_3,4 11.6,

H-3), 4.35 (1 H, dd, H-2); δ_c (100.6 MHz; CDCI₃) - 6.0 [Si(CH₃)₂], 18.2 [C(CH₃)₃], 25.0

[C(CHs)₂], 25.5 [C(CHs)₃], 25.7 [C(CHs)₂], 51.0 (C-1), 61.0 (C-4), 64.5 (C-5), 74.4 (C-3), 76.7

(C-2), 109.4 [C(CHa)₂]; (ES+) m/z 329 ([M-N₂+H]⁺), (75%), 301 ([M-2N₂+H]⁺), (20%). The starting dimesylate (10) (0.317 g, 34%) was also recovered from the reaction. 5-O-terf-ButyldimethylsιϊyM ,4-dideoxy-1 ,4-imino-2,3-O-isopropylidene-L-ribitol (7)

The azidomesylate 5 (0.34 g, 0.84 mmol) in 1 ,4-dioxane (10 ml) was stirred at 20 ⁰C under an atmosphere of hydrogen in the presence of palladium black (0.07 g) and sodium acetate (0.07g, 0.825 mmol) for 3 days after which time t.l.c. analysis (EtOAc - cyclohexane, 1 : 1) indicated complete conversion of starting material (Rf 0.35) to a major product (R_f 0.17). The suspension was then filtered through Celite^®, and the 1 ,4-dioxane removed. The resulting yellow oil was dissolved in CH₂CI₂ (20 ml) and washed with water (3 x 20 ml), dried and the solvent was removed to afford the protected L-iminoribitol 7 (0.224 g, 94%) as a yellow oil,

[α]^⁵ - 15.5 (c, 0.56, CHCI₃)L Mmax (thin film) 3332 (sharp, N-H); NMR δ_H (400 MHz; CDCI₃)

0.02, 0.03 (6 H, 2s, SiMe₂), 0.91 (9 H, s, SilBu), 1.34, 1.48 (2x3 H, 2s, [C(CH₃)₂], 2.54 (1 H, br s, NH), 3.02 (2 H, d, J_1|2 2.7, H-1 ,1¹), 3.23 (1 H, dt, J₄,5, Λs_' 5.4, H-4), 3.56 (1 H, dd, J₅,₅. 10.4 J_5ι4 5.8, H-5), 3.65 (1 H, dd, H-5'), 4.65 (1 H, d, J_3,2 5.8, H-3), 4.70 (1 H, dt, H-2); δ_c (100.6 MHz, CDCI₃) - 5.5 [Si(CH₃)₂], 18.1 [C(CH₃)₃J, 24.1 [C(CH₃)₂], 25.9 [C(CH₃)₃], 26.4 [C(CH₃)₂], 53.4 (C-1), 63.8 (C-5), 66.3 (C-4), 82.2 (C-2), 83.4 (C-3), 110.9 [C(CHa)₂]; HRMS (ES+) m/z 288.1995; C₁₄H₃₀NO₃Si ([M+Hf) requires 288.1995.

Scheme 2

(1 R)-Λ -(9-Deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol hydrochloride [(+)- 10.HCI]

The L-iminoribitol derivative 7 (500 mg) was converted to the imine 8 (186 mg, 39%) and hence to L-lmmucillin-H [(+)-10.HCI] (75 mg, 29%), [α]^,⁵ + 51.5 (c 0.8, H₂O) as was described for the analogues of the D-series (G. B. Evans, R. H. Furneaux, G. J. Gainsford, V. L. Schramm and P. C. Tyler, Tetrahedron, 2000, 56, 3053-3062; G. B. Evans, R. H. Furneaux, T. Hutchison, H. S. Kezar, P. E. Morris, Jr., V. L. Schramm and P. C. Tyler, J. Org. Chem., 2001, 66, 5723-5730). The enantiomeric products (+)- and (-)- 10.HCI gave ¹H and ¹³C NMR spectra with corresponding chemical shifts within 0.1 and 0.01 ppm of each other and ³JH,H values within 0.2 Hz. The specific rotation of the D-enantiomer was found in the present work to be - 53.6 (c 2.7, H₂O). Biological Data

Kinetic studies of the interactions between compounds (+)-10.HCI and (-)-10.HCI and human, plasmodial and bovine PNPases were carried out according to published methods (R. W. Miles, P. C. Tyler, R. H. Fumeaux, C. K. Bagdassarian, and V. L. Schramm, Biochemistry, 1998, 37, 8615-8621 ; G. B. Evans, R. H. Furneaux, A. Lewandowicz, V. L. Schramm and P. C. Tyler, J. Med. Chem. 2003, 46, 3412-3423) and the results are given in Table 1. The inhibition constants K₁ are the dissociation constants for the enzyme-inhibitor complex measured from initial reaction rates. For many, but not all, of the applicants' previously described inhibitor compounds, a slow-onset of inhibition then occurs consequent upon a time dependent conformational change in the enzyme that leads to tighter binding characterised by the constant K^* (J. F. Morrison and C. T. Walsh, Adv, Enzymol. Relat Areas MoI. Biol., 1988, 61, 201-310).

Table 1 Kinetic data for the inhibition of human, plasmodial and bovine PNPs by (-)-10.HCI and (+)-10.HCI

The L-enantiomer (+)-10.HCI is revealed to be a slow onset tight binding inhibitor of the PNPs of human, bovine and Plasmodium falciparum (the protozoan parasite responsible for malaria) origins. It shows surprising potency in the above assays.

Although the invention has been described by way of example, it should be appreciated that variations or modifications may be made without departing from the scope of the invention. Furthermore, when known equivalents exist to specific features, such equivalents are incorporated as if specifically referred to in the specification.

INDUSTRIAL APPLICABILITY

The invention relates to compounds which are the L-enantiomeric forms of nucleoside analogues. These compounds are expected to be useful as pharmaceuticals in the treatment of certain diseases such as cancer, bacterial infection, parasitic infection, and T- cell mediated diseases.

Claims

1. A compound of formula (I):

(I)

where:

A is CH or N;

B is OH, NH₂, NHR, H or halogen;

D is OH, NH₂, NHR₁ H₁ halogen or SCH₃;

R is an optionally substituted alkyl, aralkyl or aryl group;

X and Y are independently selected from H, OH or halogen except that when one of X and Y is OH or halogen, the other is H; and

Z is H, OH, halogen, SQ, OQ, or Q, where Q is an optionally substituted alkyl, aralkyl or aryl group;

or a tautomer thereof; or a pharmaceutically acceptable salt thereof, or an ester thereof; or a prodrug thereof.

2. A compound as claimed in claim 1 where either of B or D is- NHR, and R is C_1-C₄ alkyl.

3. A compound as claimed in claim 1 where any halogen is selected from chlorine and fluorine.

4. A compound as claimed in any one of claims 1 to 3 where Z is OH, SQ, OQ, Q or H.

5. A compound as claimed in claim 4 where, when Z is SQ, OQ or Q, Q is substituted with one or more substituents selected from OH, halogen, methoxy, amino, or carboxy.

6. A compound as claimed in claim 4 or claim 5 where the halogen is fluorine or chlorine.

7. A compound as claimed in claim 4 where, when Z is SQ, OQ or Q, Q is C₁-C₅ alkyl or phenyl, optionally substituted with one or more substituents selected from OH, halogen, methoxy, amino, or carboxy.

8. A compound as claimed in claim 7 where Q is substituted with one or more substituents selected from fluorine and chlorine.

9. A compound as claimed in any one of claims 1 to 8 where D is H.

10. A compound as claimed in any one of claims 1 to 8 where D is not H and B is OH.

11. A compound as claimed in claim 1 where B is OH, D is H, OH or NH₂, X is OH or H and Y is H.

12. A compound as claimed in claim 11 where Z is OH, H or alkylthio.

13. A compound as claimed in claim 12 where Z is methylthio.

14. A compound as claimed in claim 12 where Z is OH.

15. A compound as claimed in claim 1 where B is NH₂, D is H, X is OH and Y is H.

16. A compound as claimed in any one of claims 1 to 13 or 15 where Z is SQ.

17. A compound as claimed in any one of claims 1 to 16 where, when B or D is NHR, R is substituted with one or more substituents selected from OH or halogen,

18. A compound as claimed in any one of claims 1 to 17 where, when B or D is NHR, R is substituted with one or more substituents selected from fluorine or chlorine.

19. A compound as claimed in claim 1 , selected from:

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1 -(9-Deazaadenin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-ery^ro-pentitol; (1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy~L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-ethylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(2-fluoroethylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(2-hydroxyethylthio)-L-ribitol; (1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-propylthio-L-ribitol;

(1R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-isopropylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-butylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-phenylthio-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-fluorophenylthio)-L-ribitol; (1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-chlorophenylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-chlorophenylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-methylphenylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-methylphenylthio)-L-ribitol;

(1 R)-1-(9-Deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-benzylthio-L-ribitol; (1 R)-1-(9-Deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 R)-1 -(9-Deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-arabinitol;

(1S)-1-(9-Deazaguanin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-e/yf/7ro-pentitol;

(1 R)-1-(9-Deazaguanin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(9-Deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol; (1 R)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 R)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-arabinitol;

(1S)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eAyf/?ro-pentitol;

(1 R)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(9-Deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol; (1 R)-1-(9-Deaza-8-fluorohypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 R)- 1 -(9-Deazaxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1 -(9-Deazaxanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eAyf/?ro-pentitol; (1 R)-1-(9-Deazaxanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(9-Deazaxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1S)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-eryf/jro-pentitol; (1 R)-1 -(8-Aza-9-deazaadenin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1 -(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-ethylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-propylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-isopropylthio-L-ribitol; (1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-butylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-phenylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-fluorophenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-chlorophenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-chlorophenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(3-methylphenylthio)-L- ribitol; (1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-(4-methylphenylthio)-L- ribitol;

(1 R)-1-(8-Aza-9-deazaadenin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-benzylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazaguanin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1S)-1-(8-Aza-9-deazaguanin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-e/>f/7ro-pentitol; (1 R)-1-(8-Aza-9-deazaguanin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1 -(8-Aza-9-deazaguanin-9-y))-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1-(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-er/f/jro-pentitol;

(1 R)-1-(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol; (1 R)-1-(8-Aza-9-deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol;

(1 R)-1-(8-Aza-9-xanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol;

(1 S)-1 -(8-Aza-9-xanthin-9-yl)-1 ,4-imino-1 ,2,4-trideoxy-L-e/yf/7ro-pentitol;

(1 R)-1-(8-Aza-9-xanthin-9-yl)-1 ,4-imino-1 ,4,5-trideoxy-L-ribitol;

(1 R)-1-(8-Aza-9-xanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-5-methylthio-L-ribitol; or (1S)-1-(9-deazahypoxanthin-9-yl)-1 ,4-dideoxy-1 ,4-imino-L-ribitol.

20. A pharmaceutical composition comprising a pharmaceutically effective amount^' of a compound as claimed in any one of claims 1 to 19.

21. A pharmaceutical composition as claimed in claim 20 where the compound is a compound as claimed in claim 19.

22. A method of treating or preventing a disease or condition in which it is desirable to inhibit PNP comprising administering a pharmaceutically effective amount of a compound as claimed in any one of claims 1 to 19 to a patient requiring treatment.

23. A method as claimed in claim 22 where the disease or condition is cancer, a bacterial infection, a parasitic infection, or a T-cell mediated disease

24. A method as claimed in claim 23 where the T-cell mediated disease is psoriasis, lupus, arthritis or another autoimmune disease.

25. A method as claimed in claim 23 where the parasitic infection is an infection caused by a protozoan parasite.

26. A method as claimed in claim 25 where the protozoan parasite is a parasite of the genera Giardia, Trichomonas, Leishmania, Trypanosoma, Crithidia, Herpetomonas, Leptomonas, Histomonas, Eimeria, lsopora or Plasmodium, or by any parasite containing one or more nucleoside hydrolases or phosphorylases inhibited by a compound of claim 1.

27. A method of immunosuppression in a patient who has undergone organ transplantation comprising administering a pharmaceutically effective amount of a compound as claimed in any one of claims 1 to 19 to the patient.

28. A method of treating or preventing a disease or condition in which it is desirable to inhibit MTAP comprising administering a pharmaceutically effective amount of a compound as claimed in any one of claims 1 to 19 to a patient requiring treatment.

29. A method as claimed in claim 28 where the disease is cancer.

30. A method as claimed in claim 29 where the cancer is prostate cancer or head or neck tumours.

31. A method of treating or preventing a disease or condition in which it is desirable to inhibit MTAN comprising administering a pharmaceutically effective amount of a compound as claimed in any one of claims 1 to 19 to a patient requiring treatment.

32. A method as claimed in claim 31 where the disease is a bacterial infection.

33. A method as claimed in any one of claims 22 to 32 where the compound is a compound as claimed in claim 19.

34. The use of a compound as claimed in any one of claims 1 to 19 for the manufacture of a medicament for treating or preventing a disease or condition in which it is desirable to inhibit PNP.

35. The use as claimed in claim 34 where the disease or condition is cancer, a bacterial infection, a parasitic infection, or a T-cell mediated disease

36. The use as claimed in claim 35 where the T-cell mediated disease is psoriasis, lupus, arthritis or another autoimmune disease.

37. The use as claimed in claim 35 where the parasitic infection is an infection caused by a protozoan parasite.

38. The use as claimed in claim 37 where the protozoan parasite is a parasite of the genera Giardia, Trichomonas, Leishmania, Trypanosoma, Crithidia, Herpetomonas,

Leptomonas, Histomonas, Eimeria, lsopora or Plasmodium, or by any parasite containing one or more nucleoside hydrolases or phosphorylases inhibited by a compound of claim 1.

39. The use of a compound as claimed in any one of claims 1 to 19 for the manufacture of a medicament for immunosuppression in a patient who has undergone organ transplantation.

40. The use of a compound as claimed in any one of claims 1 to 19 for the manufacture of a medicament for treating or preventing a disease or condition in which it is desirable to inhibit MTAP.

41. The use as claimed in claim 40 where the disease is cancer.

42. The use as claimed in claim 41 where the cancer is prostate cancer or head or neck tumours.

43. The use of a compound as claimed in any one of claims 1 to 19 for the manufacture of a medicament for treating or preventing a disease or condition in which it is desirable to inhibit MTAN.

44. The use as claimed in claim 43 where the disease is a bacterial infection.

45. A method of preparing a compound of any one of claims 1 to 19.

46. An intermediate useful in the preparation of a compound of any one of claims 1 to 19.