Synthesis and determination of absolute configuration of a non-peptidic αvß6 integrin antagonist for the treatment of idiopathic pulmonary fibrosis.

A diastereoselective synthesis of (S)-3-(3-(3,5-dimethyl-1H-pyrazol-1-yl)phenyl)-4-((R)-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-yl)butanoic acid (1), a potential therapeutic agent for the treatment of Idiopathic Pulmonary Fibrosis, which is currently undergoing Phase I clinical trials is reported. The key steps in the synthesis involved alkylation of 2-methylnaphthyridine with (R)-N-Boc-3-(iodomethyl)-pyrrolidine, and an asymmetric Rh-catalysed addition of an arylboronic acid to a 4-(N-pyrrolidinyl)crotonate ester. The overall yield of the seven linear step synthesis was 8% and the product was obtained in >99.5% ee proceeding with 80% de. The absolute configuration of 1 was established by an alternative asymmetric synthesis involving alkylation of an arylacetic acid using Evans oxazolidinone chemistry, acylation using the resulting 2-arylsuccinic acid, and reduction. The absolute configuration of the benzylic asymmetric centre was established as (S).

Discovery and Development of Highly Potent and Orally Bioavailable Nonpeptidic αvß6 Integrin Inhibitors.

A series of 3-aryl((S)-3-fluoropyrrolidin-1-yl)butanoic acids were developed as potent orally bioavailable αvß6 integrin inhibitors. Starting from a zwitterionic peptidomimetic series optimized for inhaled administration, the balancing of potency and passive permeability to achieve suitable oral agents through modification and exploration of aryl substituents and pKa of the central cyclic amine is described. (S)-4-((S)-3-Fluoro-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-yl)-3-(3-(2-methoxyethoxy)phenyl)butanoic acid was found to have highly desirable oral pharmacokinetic profiles in rat, dog, and minipig, with low to moderate clearance (26%, 7%, and 18% liver blood flow, respectively), moderate volumes of distribution (3.6, 1.4, and 0.9 L/kg, respectively), high to complete oral bioavailabilities, high αvß6 integrin potency of pIC50 of 8.0, and high solubility in physiological media (>2 mg/mL). Equating to the estimated human dose range of 10-75 mg b.i.d. to achieve 90% αvß6 target engagement at Cmin, it was selected for further investigation as a potential therapeutic agent for the treatment of idiopathic pulmonary fibrosis.

Synthesis and pharmacological investigation of azaphthalazinone human histamine H(1) receptor antagonists.

5-Aza, 6-aza, 7-aza and 8-aza-phthalazinone, and 5,8-diazaphthalazinone templates were synthesised by stereoselective routes starting from the appropriate pyridine/pyrazine dicarboxylic acids by activation with CDI, reaction with 4-chlorophenyl acetate ester enolate to give a ß-ketoester, which was hydrolysed, and decarboxylated. The resulting ketone was condensed with hydrazine to form the azaphthalazinone core. The azaphthalazinone cores were alkylated with N-Boc-D-prolinol at N-2 by Mitsunobu reaction, de-protected, and then alkylated at the pyrrolidine nitrogen to provide the target H(1) receptor antagonists. All four mono-azaphthalazinone series had higher affinity (pK(i)) for the human H(1) receptor than azelastine, but were not as potent as the parent non-aza phthalazinone. The 5,8-diazaphthalazinone was equipotent with azelastine. The least potent series were the 7-azaphthalazinones, whereas the 5-azaphthalazinones were the most lipophilic. The more hydrophilic series were the 8-aza series. Replacement of the N-methyl substituent on the pyrrolidine with the n-butyl group caused an increase in potency (pA(2)) and a corresponding increase in lipophilicity. Introduction of a ß-ether oxygen in the n-butyl analogues (2-methoxyethyl group) decreased the H(1) pA(2) slightly, and increased the selectivity against hERG. The duration of action in vitro was longer in the 6-azaphthalazinone series. The more potent and selective 6-azaphthalazinone core was used to append an H(3) receptor antagonist fragment, and to convert the series into the long acting single-ligand, dual H(1) H(3) receptor antagonist 44. The pharmacological profile of 44 was very similar to our intranasal clinical candidate 1.

Discovery of ( S)-3-(3-(3,5-Dimethyl-1 H-pyrazol-1-yl)phenyl)-4-(( R)-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-yl)butanoic Acid, a Nonpeptidic αvß6 Integrin Inhibitor for the Inhaled Treatment of Idiopathic Pulmonary Fibrosis.

A series of 3-aryl(pyrrolidin-1-yl)butanoic acids were synthesized using a diastereoselective route, via a rhodium catalyzed asymmetric 1,4-addition of arylboronic acids in the presence of ( R)-BINAP to a crotonate ester to provide the ( S) absolute configuration for the major product. A variety of aryl substituents including morpholine, pyrazole, triazole, imidazole, and cyclic ether were screened in cell adhesion assays for affinity against αvß1, αvß3, αvß5, αvß6, and αvß8 integrins. Numerous analogs with high affinity and selectivity for the αvß6 integrin were identified. The analog ( S)-3-(3-(3,5-dimethyl-1 H-pyrazol-1-yl)phenyl)-4-(( R)-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-yl)butanoic acid hydrochloride salt was found to have very high affinity for αvß6 integrin in a radioligand binding assay (p Ki = 11), a long dissociation half-life (7 h), very high solubility in saline at pH 7 (>71 mg/mL), and pharmacokinetic properties commensurate with inhaled dosing by nebulization. It was selected for further clinical investigation as a potential therapeutic agent for the treatment of idiopathic pulmonary fibrosis.

Synthesis and structure-activity relationships of indazole arylsulfonamides as allosteric CC-chemokine receptor 4 (CCR4) antagonists.

A series of indazole arylsulfonamides were synthesized and examined as human CCR4 antagonists. Methoxy- or hydroxyl-containing groups were the more potent indazole C4 substituents. Only small groups were tolerated at C5, C6, or C7, with the C6 analogues being preferred. The most potent N3-substituent was 5-chlorothiophene-2-sulfonamide. N1 meta-substituted benzyl groups possessing an α-amino-3-[(methylamino)acyl]-group were the most potent N1-substituents. Strongly basic amino groups had low oral absorption in vivo. Less basic analogues, such as morpholines, had good oral absorption; however, they also had high clearance. The most potent compound with high absorption in two species was analogue 6 (GSK2239633A), which was selected for further development. Aryl sulfonamide antagonists bind to CCR4 at an intracellular allosteric site denoted site II. X-ray diffraction studies on two indazole sulfonamide fragments suggested the presence of an important intramolecular interaction in the active conformation.

Synthesis of arrays using low molecular weight MPEG-assisted Mitsunobu reaction.

Triphenylphosphine tagged with a short poly-(ethyleneglycol)-ω-monomethyl ether chain (light MPEG, 10−16 ethylenoxy units, (M)TPP-G2) and an MPEG-tagged version of diethyl azodicarboxylate ((M)DEAD) have been used to prepare a 20 member library of esters, ethers, and sulfonamides, with cLogP's in the range of 1.4−5.7 on a 0.1 mmol scale. Removal of MPEG-tagged side products was achieved by MPEG-assisted solid-phase extraction (MSPE) on prepacked silica columns to give the products in good yield and high purity.

The discovery of phthalazinone-based human H1 and H3 single-ligand antagonists suitable for intranasal administration for the treatment of allergic rhinitis.

A series of potent phthalazinone-based human H(1) and H(3) bivalent histamine receptor antagonists, suitable for intranasal administration for the potential treatment of allergic rhinitis, were identified. Blockade of H(3) receptors is thought to improve efficacy on nasal congestion, a symptom of allergic rhinitis that is currently not treated by current antihistamines. Two analogues (56a and 56b) had slightly lower H(1) potency (pA(2) 9.1 and 8.9, respectively, vs 9.7 for the clinical gold-standard azelastine, and H(3) potency (pK(i) 9.6 and 9.5, respectively, vs 6.8 for azelastine). Compound 56a had longer duration of action than azelastine, low brain penetration, and low oral bioavailability, which coupled with the predicted low clinical dose, should limit the potential of engaging CNS-related side-effects associated with H(1) or H(3) antagonism.

Low molecular weight MPEG-assisted organic synthesis.

A toolkit of low molecular weight MPEG-supported coupling agents ((M)IIDQ, (M)EDCI), reagents for the Mitsunobu reaction ((M)DEAD, (M)TPP), an alternative to diazomethane, and scavengers can be used in the solution-phase synthesis of amides, esters and ureas and are easily removed after use by solid-phase extraction (MSPE) using normal silica.

Short and novel stereospecific synthesis of trisubstituted 2,5-diketopiperazines.

Novel syntheses of chiral trisubstituted 2,5-diketopiperazines using multicomponent Ugi reactions were developed.