COMPOUND LIBRARIES OF 2H-SPIRO (ISOQUINOLINE-1 , 4 -PIPERIDINE) DERIVATIVES AND RELATED COMPOUNDS FOR TARGETTING COMPOUNDS CAPABLE OF BINDING TO THE G-PROTEIN
RECEPTOR
Introduction
5 Background
The present invention relates to compounds capable of binding to G-protein coupled receptors. In particular, a library of compounds is provided for use in screening 10 programmes against GPCR targets as well as the individual compounds for use in hit to lead and lead optimisation projects and similar stages in the drug discovery process.
The method also provides methods for making compounds and 15 libraries.
As part of the process of discovering drugs or agrochemicals it is customary to screen libraries of compounds against biological targets to discover Hits'
20 which are then further developed into ^Leads' and subsequently drugs or agrochemicals by using the techniques of medicinal chemistry. Accordingly the success or not of a drug or agrochemical discovery project is critically dependent on the quality of the hit and this
25 in turn is dictated by the quality of the screening library.
Technological advances have enabled screening on a very large scale and the screening of hundreds of thousands of 30 compounds at the start of a discovery program is routine. This, however, does entail a significant cost. The hits obtained from such screening efforts are not all of the best quality and often take a large .amount of subsequent time and effort in order to get a good lead. It has been
estimated that only about 25% of projects actually get to the lead optimisation stage and part of the reason for this is the intractability of hits from high throughput screening.
Screening libraries are commonly collections of compounds from several sources. As a result, they typically contain compounds synthesised as a part of previous projects in the history of a company. With regard to drug discovery, these collections will be drug-like but are likely to be limited in scope and will be directed to certain areas of a particular project. It has been the common practice of many pharmaceutical companies in recent times to augment the collections by purchasing either single compounds from vendors or by contracting the synthesis of combinatorial libraries of compounds. The singly purchased compounds may have been selected to fill in areas of compound space poorly represented in the compound collections. Combinatorial libraries are typically synthesised around well-performing chemistries with some design based on producing ^diversity' in compound space.
A complementary approach, and one that is increasingly preferred, is to screen focused libraries against the target of choice. Focused libraries are becoming of increasing importance in their ability to generate hits capable of rapid expansion in many areas including GPCRs . Such libraries are slightly more expensive to prepare but have attributes of reliability, reproducibility and provide a considerably higher hit rate: typically 10-100 fold and above compared with random screening. They are, however, very difficult to design and their efficiency relates directly to the amount of effort that has gone into the design. Using focused libraries, it is usually
possible to get a number of hits in the low micromolar and below range. As there is a defined set of compounds there is the potential to observe indications of SAR in a chemical series and progress the chemistry efficiently.
G-protein-coupled receptors (GPCRs) are very important in the regulation of numerous body processes and a significant proportion of all drugs work by interaction with these receptors. There are several hundred known, many of which are orphans - those receptors that have no established ligands. They fall into a class of 7- transmembrane receptors and there is only one X-ray structure known that of the bovine rhodopsin receptor, and this is at a resolution of 2.8 Angstroms and is thus not suitable for accurate modelling work. In addition, the rhodopsin receptor is somewhat unusual in its interactions with its ligand and is not used as a drug target. Nevertheless the overall three dimensional arrangement can be deduced from the X-ray and is in accordance with previous work based upon bacteriorhodopsin receptor which is not G-protein-coupled.
GPCRs are most often characterised by sequence homology as being comprised of several sub-families. Most attention currently is directed towards Family A receptors as being the most tractable class historically and also the one with the most potential targets .
Family A comprises about 300 receptors that are potential drug targets, approximately half of which have known ligands and the rest, the so-called orphan receptors. The group of druggable receptors is composed essentially of two types: those whose natural ligand interacts wholly within the transmembrane domain, such as the aminergic,
nucleotide-like, prostaglandin receptors, etc. and those peptide liganded receptors, which have a large part of their interactions in the extracellular region and which may insert a peptide loop or tail into the transmembrane region to effect signal transduction. Examples of this class are angiotensin, cholecystokinin and opioid receptors . Irrespective of the mode of action of the natural ligand or the GPCR family, the vast majority of drug molecules interact in the all-helical domain of the transmembrane region with exceptions being those mimics of glutamate at the metabotropic glutamate receptor and some peptide therapeutics administered parenterally. In looking for lead molecules for an unexplored or orphan GPCR it therefore makes sense to concentrate on interactions in the transmembrane domain.
The focused library provided herein is designed to interact with a range of the family A receptors. Each library is a defined set of compounds that will enhance the probability of finding a small molecule that will interact with one or more type of GPCR receptor.
For example, focused libraries can be provided having compounds which will interact with aminergic GPCRs, and peptidic GPCRs requiring an obligatory positive charge in ligands, or other types or groups of GPCRs.
Focused libraries according to this invention can provide hit rates of 1-13% or more for the requisite predicted GPCRs from both amine- and peptide-liganded classes and with agonists and antagonists .
Summary of Invention
We provide herein a "focused" library of compounds which will provide "leads" for ligands which bind to Family A G- Protein coupled receptors .
In the context of the present invention, "library" means a group of compounds which are structurally related by virtue of a core chemical structure (or "scaffold") but which differ from each other by virtue of permutation of specific substituent groups attached to the scaffold.
Generally speaking such a library will consist of or comprise a number of compounds, e.g. as many as about 100, 1000,2000, 3000 or indeed 10,000 compounds. The number of compounds should be sufficient to provide an adequate diversity of related compounds without being so large as to be unduly complex/expensive to produce.
In the context of the present invention the terms "permitted substituents" and analogous terms are used to refer to defined chemical groups that may be attached to a "scaffold" to provide permutations of the chemical structure of related compounds.
Where the chemical formulae of permitted substituents are shown in this description and claims, the substituent may appear in the compound exactly as shown (i.e. simply covalently bonded to the scaffold) or may be a derivative of the shown chemical formula of the substituent by virtue of use of a reactive group to couple the substituent to the scaffold.
It will be appreciated that the total number of permutations created by the permitted substituents may be a very large number, far greater in magnitude than the actual number of compounds in an actual library. In other words, the number of possible compounds for any "virtual" library may well greatly exceed the number of synthesised compounds making up an embodiment of the "real" library. The invention is intended to encompass libraries having all, and a number, which is less than all, of the permitted substitutions represented by compounds therein.
It will be appreciated that some specific combinations of permitted substituents may be more or less difficult to synthesise and/or use in a focused library of the invention. This does not detract from the generality of applicability of the invention as described herein. It is to be expected that real libraries will be synthesised from a selected group of permutations/combinations of permitted substituents, taking into consideration factors affecting the intended purpose of the library and its cost and complexity of synthesis .
Even if theoretically permitted, it is currently considered unlikely that any compound would be prepared for inclusion in a focused library if it had either or both of the following properties
(1) molecular weight >700
(2) log p <-3 or >9 (an index of lipophilicity as calculated using commercially available
"Chemenlighten 2.8" and "Biobyte" software for the log p calculation) .
The present invention provides a novel focused library of compounds . Most of the compounds defined by the permitted substitutions on the scaffolds are also novel compounds per se and the invention is intended to encompass each individual novel compound. Any known compound having a structural formula identical to any one of the compounds covered by the formulae of scaffolds and permitted substitutions described herein is hereby explicitly disclaimed per se.
Library 3
Library 3 is a library consisting of four scaffolds and is designed to pick up interactions with receptors for a subset of peptidic receptors, namely those with recognition sites for amide and acidic ligands centred on transmembrane helices (TM) 3 and TM6, although similar interactions are also found in lipid-type and ADP/ATP/UDP- types of receptors .
The general mode of interaction of peptide liganded receptors is considered to be a primary interaction with the extracellular loop regions followed by a secondary interaction brought about by the insertion of a C-terminal tail or a loop into a consensus binding region defined by the top halves of TM2-7. It is this secondary interaction which promotes signal transduction and which is the target for the vast majority of drugs which interact with this type of receptor. Accordingly, a subset of peptide liganded receptors contain a combination of residues which pick up C-terminal carboxylate interactions. In another group similar residues are able to interact with amide and urea functionalities on drugs. The molecules in library 3 are designed to act as probes for both these type of interactions which are found in such receptors as angiotensin II, bombesin, some chemokines, growth hormone secretagogue receptor and melanocortin receptors.
In addition to the acid-amide interactions described above, the templates used in this library are designed to pick up extra interactions with areas recognising electron-rich rings and benzhydryl ^rabbit ears' type of interactions . The spatial arrangements between these functions have been captured in two ways . One is
illustrated in series of spiro-fused piperidines; examples are MK499 (K-channel blocker) , LU 28-179 (s2 ligand) and ibutamoren (growth hormone secretagogue) . The other is found in such ligands as devazepide and sertindole amongst others
The invention provides a compound library, library 3, comprising or consisting of a set of structurally related compounds based on scaffolds of general formulae PS203, PS204, PS205 and PS144.
PS144 wherein in compounds of formula PS203 n may be 1 or 2 and m may be 2 or 3 ; the permitted substituents for RI are derived from List 1; and the permitted substituents for R2 are derived from List 3 and List 4
in compounds of formula PS204, the permitted substituents for RI are derived from List 5; and the permitted substituents for R2 are derived from List 6 and List 7;
in compounds of formula PS205, the permitted substituents for RI are derived from List 8; and the permitted substituents for R2 are derived from List 9 and 10;
in compounds of formula PS144, the permitted substituents of RI are derived from List 11; the permitted substituents for R2 are derived from List
12 ; and the permitted substituents for R3 are derived from List 14 and List 15; and Y may be C or N.
Novelty of Compounds of Library 3
PS203
Substitution of the following groups at X is known where * = point of attachment.
PS204
There are no known compounds .
PS205
Substitution of the following group at Y is known where * = point of attachment .
There are no known compounds ,
Methods for Preparing Compounds of Library 3
Compounds of Library 3 (SFG03) can be produced according to the following reaction schemes :
Method of Preparing Compounds of Formula PS203
PS 203
(CH2)n (CH2)m
An appropriately substituted tryptamine derivative (1) selected from List 1 is reacted with an appropriately substituted nitrogen heterocycle (2) selected from List 2 (n = 1 or 2 and m = 2 or 3) to give spiro compounds (3) .
The spiro compounds are then acylated by reacting (3) with cylic anhydrides selected from List 3 to give PS203 compounds (4) with R2 = -(C)nCOOH (where n = 2 or 3) or by reacting with isocyanates selected from List 4 to give PS203 compounds (5) with R2 = optionally substituted alkyl, aryl or heteroaryl.
To a solution of (3) (0.12mmol) in DMF (0.7ml, 0.16M) with triethylamine (6eq. , 0.1ml) was added a solution of anhydride or isocyanate (0.24mmol) in DMF (0.5ml, 0.48M) and the suspension shaken at room temperature for 16h. The reactions were quenched by addition of DMF:H20, 1:1 (0.5ml) and the crude products purified by prep HPLC.
Examples of Compounds having- Formula PS203
3,3-Dimethyl-5-oxo-5- (1' ,4' ,5' ,6' -tetrahydro-lH- spiro[2,3,4, 9-tetrahydro-lH-beta-carboline] -1,4 ' - piperidine) pentanoic acid.
Yield; 54.3mg, HPLC; RT 2.10 mins (100%); MS (AP; [M+H] +) m/z: 384.3.
N- (3-methoxyphenyl) -l'^'fS'-β1 -tetrahydro-lH- spiro [2,3,4, 9-tetrahydro-lH-beta-carboline-l,4 ' - piperidine] -1-carboxamide.
Yield; 54.1mg, HPLC; RT 3.20 mins (100%) ; MS (AP; [M+H] m/z: 391.3.
Method for Preparing Compounds of Formula PS204
PS 204
An appropriately substituted tryptophol derivative (6) selected from List 5 is reacted with 4-piperidone monohydrate hydrochloride to give the spiro compounds (7) . The spiro compounds are then acylated by reacting with a cylic anhydride selected from list 6 to give PS204 compounds (9) with R = -(C)
nCOOH (where n = 2 or 3) or by reacting with isocyanates selected from list 7 to give PS204 compounds (8) with R = optionally substituted alkyl, aryl or heteroaryl .
To a solution of (7) (0.12mmol) in DMSO (0.75ml, 0.16M) with triethylamine (3eq., 0.05ml) was added a solution of anhydride or isocyanate (0.24mmol) in DMSO (0.5ml, 0.48M) and the suspension shaken at room temperature for 16h. The reactions were quenched by addition of DMSO:H0, 1:1 (0.5ml) and the crude products purified by prep HPLC.
Examples of Compounds of Formula PS204
N- (2,3-dihydro-l,4-benzodioxin-6-yl) - ' , 5 ' -dihydro-lH, l'H- spiro [6-methoxy-l,3,4, 9-tetrahydropyrano{3,4-b}indole- 1,4 ' -piperidine] -1-carboxamide.
Yield; 56.0mg HPLC; RT 3.34 mins (100%); MS (AP; [M+H] +) m/z: 450.4.
2- (41 ,5' -dihydro-lH,l'H-spiro[6-methoxy-l,3,4,9- tetrahydropyrano{3,4 b}indole-l, 4' -piperidine] -1- ylcarbonyl) cyclobutanecarboxylic acid.
Yield; 53.3mg, HPLC; RT 2.10 mins (100%); MS (AP; [M+H] +) m/z: 399.4.
Method of Preparing Compounds of Formula PS205 PS 205
(14) (13)
An appropriately substituted phenylacetonitrile (10) selected from List 8 was reacted with an N protected 4- piperidone. The resultant spiropiperidine structure (11) was deprotected to give the amines (12) . These spiro compounds are then acylated by reacting with a cylic anhydride selected from list 9 to give PS204 compounds (13) with R2 = -(C)nCOOH (where n = 2 or 3) or by reacting with isocyanates selected from list 10 to give PS205 compounds (14) with R2 = optionally substituted alkyl, aryl or heteroaryl.
To a solution of (12) (0.12mmol) in DMSO (0.75ml, 0.16M) with triethylamine (3eq., 0.05ml) was added a solution of anhydride or isocyanate (0.24mmol) in DMSO (0.5ml, 0.48M) and the suspension shaken at room temperature for 16h. The reaction was quenched by addition of DMSO:H20, 1:1 (0.5ml) and the crude product purified by prep HPLC.
Examples of Compounds of Formula PS205
6,7-Dimethoxy-3-oxo-3 ,4-dihydro-2H-spiro [isoquinoline-
1,4 ' -piperidine] -1' -carboxylic acid (2,5-dimethoxy- phenyl) -amide.
Yield; 33.0mg, HPLC; RT 2.98 mins (91%); MS (AP; [M+H]
+) m/z: 456.5.
[2-oxo-2-(3-oxo-3,4-dihydro-l'H,2H-spiro[3,4- dihydrobenzo [f] isoquinolin-2 (IH) -one-1, ' -piperidin] -1' - yl) ethoxy] acetic acid.
Yield; 32.9mg, HPLC; RT 1.95 mins (100%); MS (AP; [M+H] m/z: 383.3.
Method of Preparing Compounds of Formula PS144 PS 144
(22) (21) v '
The benzhydryl amines (16) can be prepared from an appropriately substituted cyano heterocycle (15) (List 11) by reaction with an alkyl lithium or Grignard reagent (List 12) . An amide (18) is formed from the reaction of an N-BOC protected amino acid (17) (List 13) and subsequent cyclisation provides the bicyclic heterocycle structure (19) . Removal of the protecting group to give (20) allows subsequent derivitisation to be carried out by acylating with a cylic anhydride selected from list 15 to give PS144 compounds (22) with R3 = -(C)nCOOH (where n = 1 or 2) or by reacting with isocyanates selected from list 14 to give PS144 compounds (21) with R3 = optionally substituted alkyl , aryl or heteroaryl .
To a solution of (20) (0.12mmol) in DMF (0.75ml), 0.16M) with triethylamine (3eq., 0.05ml) was added a solution of anhydride or isocyanate (0.24mmol) in DMF (0.5ml), 0.48M)
and the suspension shaken at room temperature for 16h. The reactions were quenched by addition of DMF:H20, 1:1 (0.5ml)) and the crude products purified by prep HPLC.
Examples of Compounds of Formula PS144
2- [1- ( -Fluoro- henyl) -imidazo [l,5-a]pyridin-3-yl] - pyrrolidine-1-carboxylic acid (4-trifluoromethoxy-phenyl) - amide.
Yield; 62.5mg, HPLC; RT 4.15 mins (100%); MS (AP; [M+H] +) m/z: 485.3.
2,3,4,5-Tetrachloro-6-{4- [1- (4-fluoro-phenyl) -imidazo [1, 5- a]pyridin-3-yl] -piperidine-l-carbonyl}-benzoic acid.
Yield; 49.8mg, HPLC; RT 2.95 mins (100%) ; MS (AP; [M+H] +) m/z: 582.2.
3,3-Dimethyl-5-oxo-5- [2- (1-phenyl-imidazo [l,5-a]pyridin-3- yl) -pyrrolidin-1-yl] -pentanoic acid.
Yield; 49.7mg, HPLC; RT 2.51 mins (100%); MS (AP; [M+H]+) m/z: 406.3.
4- [1- (4-Fluoro-phenyl) -imidazo [l,5-a]pyridin-3-yl] - piperidine-1-carboxylic acid (4-trifluoromethoxy-phenyl) - amide.
Yield; 49.8mg, HPLC; RT 4.16 mins (100%); MS (AP; [M+H]+) m/z: 498.8.
4-{3- [1- (4-Fluoro-phenyl) -imidazo [l,5-a]pyridin-3-yl] iperidin-1-yl} -4-oxo-2,3-diphenyl-but-2-enoic acid.
Yield; 51.7mg, HPLC; RT 2.96 mins (100%); MS (AP; [M+H] +) m/z: 546.4.
3- (1-Phenyl-imidazo [l,5-a]pyridin-3-yl) -piperidine-1- carboxylic acid (1-phenyl-ethyl) -amide.
Yield; 54.0mg, HPLC; RT 3.91 mins (100%); MS (AP; [M+H] m/z: 425.
Analytical HPLC conditions Mobile phase. 0.2% TFA/water, ACN Flow rate 25 ml/min. Gradient: 85/15 H20 + 0.2% for 1.5 min.
TFA / ACN
5/95 in 9.5 min. for 1.5 min.
85/15 in 0.5 min.
Detector: ELS. (approx. 1.5ml/min flow split to Sedex 55 ELSD)
Gas (Nitrogen) 2.0 bar
Nebulizer 40°C Column: Waters SymmetryPrep ™ 19mm x 150m x 7mm C18
The permitted substituents for compounds of Library 3 (SFG03) can be derived from the following lists:
List 1
List 3
List 8
List 10
List 11
List 13
List 14
List 15