WO2001058861A1

WO2001058861A1 - Process for making and using isocyanide resins

Info

Publication number: WO2001058861A1
Application number: PCT/US2001/004219
Authority: WO
Inventors: Jian Chen
Original assignee: The Procter & Gamble Company
Priority date: 2000-02-09
Filing date: 2001-02-08
Publication date: 2001-08-16
Also published as: AU2001234975A1

Abstract

A process for making isocyanide resin from amino acid resin comprising the steps: (a) formylation of an amino acid resin, and (b) dehydration of the formylated resin.

Description

PROCESS FOR MAKING AND USING ISOCYANIDE RESINS

FIELD OF THE INVENTION The subject invention involves a process for making isocyanide resins from amino acid resins, and uses thereof.

CROSS REFERENCE This application claims priority under Title 35, United States Code 119(e) from Provisional Application Serial No. 60/181,266, filed February 9, 2000. BACKGROUND

Multi-component condensation reactions, such as the Passerini and Ugi reactions, have become important synthetic approaches for high throughput combinatorial synthesis of small organic molecules. Many pharmaceutically important scaffolds can be constructed using these reactions. In spite of remarkable achievements of the two aforementioned reactions, their practice is still restrained by the malodor and the commercial availability of isocyanide reagents. Previous accounts of studies recently addressed this problem by immobilizing isocyanide functionality to solid supports; see (a) Zhang et al, Tetrahedron Lett., Vol. 37 (1996), pp. 751-754; (b) Short et al.,

Tetrahedron Lett.. Vol. 38 (1997), pp. 6653-6679; (c) Hulme et al, Tetrahedron Lett., Vol. 39 (1998), pp. 7227-7230. A variety of pharmaceutically important compounds, such as gamma- lactams, iminohydantoins, benzodiazepins, and diketopiperazines can be synthesized using resin bound isocyanides. The previous reported isocyanide resins have been prepared only from linear C3 to C14 amino acid attached and aniline-attached solid supports. The conversion of a-amino acid resins to corresponding isocyanide resins has not been reported, even though the starting resins are readily available from commercial sources.

SUMMARY OF THE INVENTION The subject invention involves a process for making isocyanide resin from amino acid resin comprising the following steps: (a) formylation of an amino acid resin of structure 1 to produce resin 2:

1 2 wherein R is selected from the group consisting of hydrogen, alkyl, aryl, and heterocyclyl;

(b) dehydration of resin 2 to produce isocycanide resin 3:

DETAILED DESCRIPTION OF THE INVENTION As used herein unless specified otherwise, "alkyl" means a hydrocarbon chain which is branched, linear or cyclic, saturated or unsaturated (but not aromatic), substituted or unsubstituted. The term "alkyl" may be used alone or as part of another word where it may be shortened to "alk" (e.g., in alkoxy, alkylacyl). Preferred linear alkyl have from one to about twenty carbon atoms, more preferably from one to about ten carbon atoms, more preferably still from one to about six carbon atoms, still more preferably from one to about four carbon atoms; most preferred are methyl or ethyl. Preferred cyclic and branched alkyl have from three to about twenty carbon atoms, more preferably from three to about ten carbon atoms, more preferably still from three to about seven carbon atoms, still more preferably from three to about five carbon atoms. Preferred cyclic alkyl have one hydrocarbon ring, but may have two, three, or more, fused or spirocycle hydrocarbon rings. Preferred alkyl are unsaturated with from one to about three double or triple bonds, preferably double bonds; more preferably they are mono-unsaturated with one double bond. Still more preferred alkyl are saturated. Saturated alkyl are referred to herein as "alkanyl". Alkyl unsaturated only with one or more double bonds (no triple bonds) are referred to herein as "alkenyl". Preferred substituents of alkyl include halo, alkyl, aryl, heterocyclyl, hydroxy, alkoxy, aryloxy, thio, alkylthio, arylthio, amino, alkylamino, arylamino, amide, alkylamide, arylamide, formyl, alkylacyl, arylacyl, carboxy and its alkyl and aryl esters and amides, nitro, and cyano. Also, unsubstituted alkyl are preferred.

As used herein, "heteroatom" means a nitrogen, oxygen, or sulfur atom. As used herein, "alkylene" means an alkyl which connects two other moieties, "heteroalkylene" means an alkylene having one or more heteroatoms in the connecting chain.

As used herein unless specified otherwise, "aryl" means an aromatic hydrocarbon ring (or fused rings) which is substituted or unsubstituted. The term "aryl" may be used alone or as part of another word (e.g., in aryloxy, arylacyl). Preferred aryl have from six to about fourteen, preferably to about ten, carbon atoms in the aromatic ring(s), and a total of from about six to about twenty, preferably to about twelve, carbon atoms. Preferred aryl is phenyl or naphthyl; most preferred is phenyl. Preferred substituents of aryl include halo, alkyl, aryl, heterocyclyl, hydroxy, alkoxy, aryloxy, thio, alkylthio, arylthio, amino, alkylamino, arylamino, amide, alkylamide, arylamide, formyl, alkylacyl, arylacyl, carboxy and its alkyl and aryl esters and amides, nitro, and cyano. Also, unsubstituted aryl are preferred.

As used herein unless specified otherwise, "heterocyclyl" means a saturated, unsaturated or aromatic cyclic hydrocarbon ring (or fused rings) with one or more heteroatoms in the hydrocarbon ring(s). Preferred heterocyclyls have from one to about six heteroatoms in the ring(s), more preferably one or two or three heteroatoms in the ring(s). Preferred heterocyclyls have from three to about fourteen, preferably to about ten, carbon plus heteroatoms in the ring(s), more preferably from three to about seven, more preferably still five or six, carbon plus heteroatoms in the rings(s); and a total of from three to about twenty carbon plus heteroatoms, more preferably from three to about ten, more preferably still five or six, carbon plus heteroatoms. Preferred heterocyclyls have one ring, but may have two, three, or more, fused or spirocycle rings. More preferred heterocyclyl rings include those which are one ring with 5 or 6 carbon plus heteroatoms in the ring with no more than three ring heteroatoms, no more than two of which are O and S. Still more preferred are such 5- or 6-ring atom heterocyclyls with one or two ring atoms being O or S and the others being C; or with one, two or three ring atoms being N and the others being C. Such preferred 5- or 6-ring atom heterocyclyls are preferably saturated, unsaturated with one or two double bonds, or aromatic. Such preferred 5- or 6-ring atom heterocyclyls are preferably a single ring; or fused with a 3- to 6-ring atom hydrocarbon ring which is saturated, unsaturated with one double bond, or aromatic (phenyl); or fused with another such 5- or 6-ring atom heterocyclic ring. Heterocyclyls are unsubstituted or substituted. Preferred heterocyclyl substituents are the same as for alkyl.

As used herein unless specified otherwise, "heteroaryl" means an aromatic heterocyclyl. The first step of the subject invention process for making isocyanide resin is the formylation of amino acid resin 1 as follows:

1 2

The formylating reagent is preferably formic acid in the presence of diisopropyl carbodiimide. The reaction is preferably carried out at a temperature of from about 0°C to about room temperature over a period of from about 1-4 hours.

Formylated resin 2 is dehydrated to isocyanide resin 3 using POCl_β/diisopropylethylamine

(DIPEA) as follows:

The dehydration reaction is preferably carried out at a temperature of from about 0°C to about room temperature over a period of from about 3-8 hours.

The above process is generally quantitative and produces resins of light yellow color that are stable for months when stored refrigerated. Side chain protections typically used in the above processes, such as Boc, t-Bu, O-t-Bu, Tos, O-Bzl, and 2,2,4,6,7-pentamethyl-dihydrobenzofuran- sulfonyl (Pbf) are preserved during this conversion. The amino acid resin starting material is preferably a commercially-available α-amino acid resin. Non-limiting examples of commercially-available α-amino acid resins useful as starting materials for the subject process include Fmoc-Phe-Wang, Fmoc-Lys(Boc)-Wang, Fmoc-Tyr(tBu)- Wang, Fmoc-Asp(OtBu)-OH, Fmoc-Glu(OtBu)-OH, Fmoc-Arg(Pbf)-Merrifield, Boc-Phe- Merrifield, Boc-Ser(OBzl)-Merrifield, Boc-Met-Merrifield, Boc-His(Tos)-Merrifield, Boc- Thr(OBzl)-Merrifield, Boc-Ala-Merrifield resins.

In the above schemes, R is selected from hydrogen, alkyl, aryl, and heterocyclyl. Preferred R is unsubstituted or substituted alkyl, preferably having from 1 to about 8 carbon atoms, more preferably from 1 to about 4 carbon atoms. Preferred substituents of such alkyl include unsubstituted and substituted hydroxy, amino, thio, and phenyl. Preferred examples of R include tBu-OCOCH₂-, tBu-OCOCH₂CH₂-, Pbf-NH(C=NH)NHCH₂CH₂CH₂-, PhCH₂-, PhCH₂OCH₂-,

CH SCH₂CH₂-, CH₃_₅ / fBuOPhCH₂-, Boc-NHCH₂CH₂CH2CH₂-. The following is a non-limiting example of the preparation of an isocyanide resin according to the subject invention.

A deprotected amino acid resin ester is swelled in anhydrous dichloromethane (DCM). Under the ice cooling, formic acid (8 eq) is added, followed by diisopropylcarbodiimide (DIC) (8 eq). The suspension is stirred at 0°C for half hour, then for 1 1/2 h at room temperature. The resin is washed and dried to a constant weight. The formylated amino acid resin is suspended in anhydrous CH2CI2. Under ice cooling and Argon protection, diisopropylethylamine (DIPEA) (15 eq) is cannulated, followed by POCI3 (5eq). The suspension is stirred at 0°C for 5 h, and then for 1 h at ambient room temperature. The resin is then washed with CH2CI2 in ether, then dried in a vacuum to a constant weight. The disappearance of formyl CO (-1740 cm^"') and the emergence of NC (~ 2150 cm"') absorption in IR spectra confirms the conversion.

The isocyanide resins made according to the subject invention process are useful for making a variety of compounds which use an isocyanide reactant. Such compounds include, but are not limited to, dipeptides, γ-lactams, iminohydantoins, benzodiazepins, diketopiperazines. The isocyanide resins made according to the subject invention process are particularly useful for making combinatorial libraries of the above compounds.

The following scheme depicts a Ugi three component condensation (3CC) reaction using an isocyanide resin:

4

An aldehyde R2CHO (8 eq) is pre-mixed with a secondary amine RβRβ'NH (8 eq) in

CHCl /MeOH/trimethylorthoformate (TMOF) along with acetic acid. This solution is then agitated with an isocyanide resin 3 at about room temperature until the reaction is complete. The progress of the reaction can be followed by the disappearance of NC absorption in IR spectra. The reaction is generally complete in about 4 hours. The resin is washed, dried and treated with about 20% trifluoroacetic acid (TFA) in DCM to provide crude product after evaporating solvent. Purified product 4 is obtained using HPLC purification.

The subject resins are reliable isocyanide resources for Ugi 3CC reactions. The reactions on these resins tolerate a wide range of amines and aldehydes. Aliphatic aldehydes tend to provide products with higher yield and purity. Aromatic aldehydes, which are problematic in other Ugi condensation reactions, perform satisfactorily with these resins.

The following is a non-limiting example of a Ugi 3CC reaction. The aldehyde (8 eq), secondary amine (8 eq), and HOAc (4 eq) are mixed in CHCl_β/MeOH/TMOF (1/1/1 , v/v/v) for 1 h. The mixture is then added to the isocyanide resin. The suspension is agitated at ambient temperature overnight. The resin is washed with MeOH, DMF, MeOH, CH2CI2, MeOH, then dried. If Wang resin is used, the product is released from the solid support by treating the resin with 20% TFA/CH2CI2 (2 x 20 min) at room temperature. If Merrifϊeld resin is used, the product is cyclizatively cleaved or released as a methyl amide using MeNH2/THF.

Non-limiting examples of compounds made according to the above scheme and example using corresponding aldehydes, secondary amines, and isocyanide resins include 3a - 3i:

3g 3h 3i While particular embodiments of the subject invention have been described, it will be obvious to those skilled in the arts that various changes and modifications of the subject invention can be made without departing from the spirit and scope of the invention. It is intended to cover, in the appended claims, all such modifications that are within the scope of this invention.

Claims

WHAT IS CLAIMED IS:

1. N process for making isocyanide resin from amino acid resin comprising the following steps:

(a) formylation of an amino acid resin of structure 1 to produce formylated resin 2:

1 2 characterized in that R is selected from the group consisting of hydrogen, alkyl, aryl, and heterocyclyl;

(b) dehydration of resin 2 to produce isocyanide resin 3:

2 3

2. The process of Claim 1 characterized in that step (b) is carried out with reagents comprising POCI3 and diisopropylethylamine.

3. The process according to any of the preceding claims characterized in that step (a) is carried out with reagents comprising formic acid and diisopropylcarbodiimide.

4. The process according to any of the preceding claims characterized in that step (b) is carried out at a temperature of from 0°C to room temperature over a period of from 3 to 8 hours.

5. The process according to any of the preceding claims characterized in that step (a) is carried out at temperature of 0°C to room temperature over a period of from 1 to 4 hours.

6. The process according to any of the preceding claims characterized in that step (b) is carried out at temperature of 0°C for 5 h, then at room temperature for 1 h.

7. The process according to any of the preceding claims characterized in that step (a) is carried out at a temperature of 0°C for Vi h, then at room temperature for 1 ^lΛ h.

8. The process according to any of the preceding claims characterized in that R is alkyl having from 1 to 8 carbon atoms, unsubstituted or substituted.

9. The process of Claim 8 characterized in that substituents of the alkyl R are selected from the group consisting of unsubstituted and substituted hydroxy, thio, amino, and phenyl.

10. Use of an isocyanide resin made according to any of the preceding claims in a Ugi three component condensation reaction.