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[Image: see text] A novel series of tricyclic tetrahydroquinolines were identified as potent and selective CRTh2 receptor antagonists. The agonism and antagonism switch was achieved through structure-based drug design (SBDD) using a CRTh2 receptor homologue model. The challenge of very low exposures in pharmacokinetic studies was overcome by exhaustive medicinal chemistry lead optimization through focused SAR studies on the tricyclic core. Further optimization resulted in the identification of the preclinical candidate 4-(cyclopropyl((3aS,9R,9aR)-7-fluoro-4-(4-(trifluoromethoxy)benzoyl)-2,3,3a,4,9,9a-hexahydro-1H-cyclopenta[b]quinolin-9-yl)amino)-4-oxobutanoic acid (15c, MK-8318) with potent and selective CRTh2 antagonist activity and a favorable PK profile suitable for once daily oral dosing for potential treatment of asthma.

With the goal of identifying inhibitors of hepatitis C virus (HCV) NS3/4a protease that are potent against a wide range of genotypes and clinically relevant mutant viruses, several subseries of macrocycles were investigated based on observations made during the discovery of MK-5172. Quinazolinone-containing macrocycles were identified as promising leads, and optimization for superior cross-genotype and mutant enzyme potency as well as rat liver and plasma concentrations following oral dosing, led to the development of MK-2748. Additional investigation of a series of bis-macrocycles containing a fused 18- and 15-membered ring system were also optimized for the same properties, leading to the discovery of MK-6325. Both compounds display the broad genotype and mutant potency necessary for clinical development as next-generation HCV NS3/4a protease inhibitors.

A series of macrocyclic compounds containing a cyclic constraint in the P2–P4 linker region have been discovered and shown to exhibit excellent HCV NS3/4a genotype 3a and genotype 1b R155 K, A156T, A156 V, and D168 V mutant activity while maintaining high rat liver exposure. The effect of the constraint is most dramatic against gt 1b A156 mutants where ∼20-fold improvements in potency are achieved by introduction of a variety of ring systems into the P2–P4 linker.

The discovery of MK-1220 is reported along with the development of a series of HCV NS3/4A protease inhibitors containing a P2 to P4 macrocyclic constraint with improved preclinical pharmacokinetics. Optimization of the P2 heterocycle substitution pattern as well as the P3 amino acid led to compounds with greatly improved plasma exposure following oral dosing in both rats and dogs while maintaining excellent enzyme potency and cellular activity. These studies led to the identification of MK-1220.

A new class of HCV NS3/4a protease inhibitors which contain a P2 to P4 macrocyclic constraint was designed using a molecular-modeling derived strategy. Exploration of the P2 heterocyclic region, the P2 to P4 linker, and the P1 side chain of this class of compounds via a modular synthetic strategy allowed for the optimization of enzyme potency, cellular activity, and rat liver exposure following oral dosing. These studies led to the identification of clinical candidate 35b (vaniprevir, MK-7009), which is active against both the genotype 1 and genotype 2 NS3/4a protease enzymes and has good plasma exposure and excellent liver exposure in multiple species.

Development of a series of highly kinome-selective spleen tyrosine kinase (Syk) inhibitors with favorable druglike properties is described. Early leads were discovered through X-ray crystallographic analysis, and a systematic survey of cores within a selected chemical space focused on ligand binding efficiency. Attenuation of hERG ion channel activity inherent within the initial chemotype was guided through modulation of physicochemical properties including log D, PSA, and pKa. PSA proved most effective for prospective compound design. Further profiling of an advanced compound revealed bacterial mutagenicity in the Ames test using TA97a Salmonella strain, and subsequent study demonstrated that this mutagenicity was pervasive throughout the series. Identification of intercalation as a likely mechanism for the mutagenicity-enabled modification of the core scaffold. Implementation of a DNA binding assay as a prescreen and models in DNA allowed resolution of the mutagenicity risk, affording molecules with favorable potency, selectivity, pharmacokinetic, and off-target profiles.

An efficient synthesis of 3-amino-1,4-benzodiazepin-2-ones utilizing triisopropylbenzenesulfonyl azide (trisyl azide) for the direct azidation of 1,4-benzodiazepin-2-ones is described.

3-Bromophenol and 3-Bromothiophenol are converted into the title compounds by proton abstraction followed by halogen-metal exchange with tert-butyllithium. The resulting dianions are then trapped on carbon with various electrophiles.

The key feature in the synthesis of topically-active carbonic hydrase inhibitor MK-0507 (13b) is a Ritter reaction that exhibits an unexpected tendency to proceed with retention of chirality. This phenomenon was further studied on model compounds free from potential diastereomeric effects. A mechanism involving transannular stabilization of the sp 2 -hybridized center by sulfone oxygen is proposed with the net result of double inversion. A second key feature in the preferred sequence to MK-0507 involves the classic problem of how to maximize substitution over elimination.This problem manifests itself in the stereospecific alkylation of 2-mercaptothiophene with derivatized methyl (R)-3-hydroxybutyrate and is compounded by a subsequent Michael reaction leading to a loss of product chirality.Results are presented that eliminate this problem.

Spiro isochromane-1 -ones 1 were treated with lithium aluminum hydride or Grignard reagents to afford diol intermediates 2, which cyclize in 85% phosphoric acid at 100 o C to spiro isochromanes 3 in 72-94% isolated yields

An efficient synthesis of 3-amino-1,4-benzodiazepin-2-ones utilizing triisopropylbenzenesulfonyl azide (trisyl azide) for the direct azidation of 1,4-benzodiazepin-2-ones is described.

A novel series of annulated tricyclic compounds was synthesized and evaluated as NMDA/NR2B antagonists. Structure-activity development was directed towards in vitro optimization of NR2B activity and selectivity over the hERG K(+) channel. Preferred compounds were subsequently evaluated for selectivity in an alpha(1)-adrenergic receptor binding counter-screen and a cell-based assay of NR2B activity.

Molecular modeling of inhibitor bound full length HCV NS3/4A protease structures proved to be a valuable tool in the design of a new series of potent NS3 protease inhibitors. Optimization of initial compounds provided 25a. The in vitro activity and selectivity as well as the rat pharmacokinetic profile of 25a compare favorably with the data for other NS3/4A protease inhibitors currently in clinical development for the treatment of HCV.

The discovery of a novel series of NR2B subtype selective N-methyl-d-aspartate (NMDA) antagonists is reported. Initial optimization of a high-throughput screening lead afforded an aminopyridine derivative 13 with significant NR2B antagonist potency but limited selectivity over hERG-channel and other off-target activities. Further structure−activity studies on the aminoheterocycle moiety and optimization of the carbamate led to the highly potent 2-aminopyrimidine derivative 20j with a significantly improved off-target activity profile and oral bioavailability in multiple species coupled with good brain penetration. Compound 20j demonstrated efficacy in in vivo rodent models of antinociception, allodynia, and Parkinson's disease.

The synthesis of the first high specific activity S-35-labeled hERG radioligand, [(35)S]MK-0499, for use in HTS assays of drug candidates for hERG interaction is described. The radioligand is prepared by [(35)S]sulfonylation of a high diastereomeric excess (de) aniline precursor prepared from unlabeled MK-0499.

A new series of benzodiazepine-containing γ-secretase inhibitors with potential use in the treatment of Alzheimer's disease is disclosed. Structure–activity relationships of the pendant hydrocinnamate side-chain which led to the preparation of highly potent inhibitors are described.

Novel 5-cyclopropyl-1,4-benzodiazepin-2-ones having various N-l substituents were identified as potent and selective blockers of the slowly activating cardiac delayed rectifier potassium current (I(Ks)). Compound 11 is the most potent I(Ks) channel blocker reported to date.

Novel potent and selective diarylimidazole inhibitors of p38 MAP (mitogen-activated protein) kinase are described which have activity in both cell-based assays of tumor necrosis factor-alpha (TNF-alpha) release and an animal model of rheumatoid arthritis. The SAR leading to the development of selectivity against c-Raf and JNK2alpha1 kinases is presented, with key features being substitution of the 4-aryl ring with m-trifluoromethyl and substitution of the 5-heteroaryl ring with a 2-amino substituent. Cell-based activity was significantly enhanced by incorporation of a 4-piperidinyl moiety at the 2-position of the imidazole which also enhanced aqueous solubility. In general, oral bioavailability of this class of compounds was found to be poor unless the imidazole was methylated on nitrogen. This work led to identification of 48, a potent (p38 MAP kinase inhibition IC50 0.24 nM) and selective p38 MAP kinase inhibitor which inhibits lipopolysaccharide-stimulated release of TNF-alpha from human blood with an IC50 2.2 nM, shows good oral bioavailability in rat and rhesus monkey, and demonstrates significant improvement in measures of disease progression in a rat adjuvant-induced arthritis model.

Time-dependent inhibitors of the enzyme human leukocyte elastase have been developed based on the cephem nucleus. A series of cephalosporin tert-butyl esters has been examined, and the activity of these compounds has been found to be very sensitive to C-7 substituents, with small, alpha-oriented, electron-withdrawing groups showing greatest activity. Additionally, the oxidation state of the sulfur atom has been found to play a role in potency, with sulfones showing considerably greater activity than the corresponding sulfides or beta-sulfoxides. The alpha-sulfoxides were inactive.

Spiro isochromane-1 -ones 1 were treated with lithium aluminum hydride or Grignard reagents to afford diol intermediates 2, which cyclize in 85% phosphoric acid at 100 o C to spiro isochromanes 3 in 72-94% isolated yields