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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.

An internal HTS effort identified a novel PDE2 inhibitor series that was subsequently optimized for improved PDE2 activity and off-target selectivity. The optimized lead, compound 4, improved cognitive performance in a rodent novel object recognition task as well as a non-human primate object retrieval task. In addition, co-crystallization studies of close analog of 4 in the PDE2 active site revealed unique binding interactions influencing the high PDE isoform selectivity.

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.

The IC50 of a beta-secretase (BACE-1) lead compound was improved ∼200-fold from 11 μM to 55 nM through the addition of a single methyl group. Computational chemistry, small molecule NMR, and protein crystallography capabilities were used to compare the solution conformation of the ligand under varying pH conditions to its conformation when bound in the active site. Chemical modification then explored available binding pockets adjacent to the ligand. A strategically placed methyl group not only maintained the required pKa of the piperidine nitrogen and filled a small hydrophobic pocket, but more importantly, stabilized the conformation best suited for optimized binding to the receptor.

A new vinylamine equivalent, N-vinyloxazolone 3, has been prepared in three steps and shown to undergo Heck arylation with a variety of substrates. The Heck adducts thus obtained are then converted in one step and high yield to phenethylamine hydrochlorides. As a general synthetic method for preparation of substituted phenethylamines, use of this new reagent is shown to be superior to N-vinylphthalimide in number of steps, regiospecificity, and chemical yield

A new vinylamine equivalent, N-vinyloxazolone 3, has been prepared in three steps and shown to undergo Heck arylation with a variety of substrates. The Heck adducts thus obtained are then converted in one step and high yield to phenethylamine hydrochlorides. As a general synthetic method for preparation of substituted phenethylamines, use of this new reagent is shown to be superior to N-vinylphthalimide in number of steps, regiospecificity, and chemical yield

Two complementary methods for the preparation of α-substituted 1,2-benzenedimethanamines have been described. The N-substituted benzamide approach can be useful when the N-substituent on the phthalazinone is large; however, it does not have the versatility of the phthalazinone approach. In reducing the phthalazines with borane, a novel cleavage of a N-N bond has been encountered