Paul D. O’Shea

Selective monolithiation of 2,5-dibromopyridine with butyllithium

Abstract Selective monolithiation of 2,5-dibromopyridine at either the 2-position or the 5-position is reported. Solvent and concentration strongly influence the selectivity. Coordinating solvents and higher concentration favor the 5-position while non-coordinating solvents and lower concentration favor the 2-position.

Preparative Scale Synthesis of the Biaryl Core of Anacetrapib via a Ruthenium-Catalyzed Direct Arylation Reaction: Unexpected Effect of Solvent Impurity on the Arylation Reaction†

In this report, we disclose our findings regarding the remarkable effect of a low-level impurity found in the solvent used for a ruthenium-catalyzed direct arylation reaction. This discovery allowed for the development of a robust and high-yield arylation protocol that was demonstrated on a multikilogram scale using carboxylate as the cocatalyst. Finally, a practical, scalable, and chromatography-free synthesis of the biaryl core of Anacetrapib is described.

CRTH2 Antagonist MK-7246: A Synthetic Evolution from Discovery through Development

In this paper, we report the development of different synthetic routes to MK-7246 (1) designed by the Process Chemistry group. The syntheses were initially designed as an enabling tool for Medicinal Chemistry colleagues in order to rapidly explore structure-activity relationships (SAR) and to procure the first milligrams of diverse target molecules for in vitro evaluation. The initial aziridine opening/cyclodehydration strategy was also directly amenable to the first GMP deliveries of MK-7246 (1), streamlining the transition from milligram to kilogram-scale production needed to support early preclinical and clinical evaluation of this compound. Subsequently a more scalable and cost-effective manufacturing route to MK-7246 (1) was engineered. Highlights of the manufacturing route include an Ir-catalyzed intramolecular N-H insertion of sulfoxonium ylide 41 and conversion of ketone 32 to amine 31 in a single step with excellent enantioselectivity through a transaminase process. Reactions such as these illustrate the enabling impact and efficiency gains that innovative developments in chemo- and biocatalysis can have on the synthesis of pharmaceutically relevant target molecules.

Discovery of MK-7246, a selective CRTH2 antagonist for the treatment of respiratory diseases

In this manuscript we wish to report the discovery of MK-7246 (4), a potent and selective CRTH2 (DP2) antagonist. SAR studies leading to MK-7246 along with two synthetic sequences enabling the preparation of this novel class of CRTH2 antagonist are reported. Finally, the pharmacokinetic and metabolic profile of MK-7246 is disclosed.

Practical Synthesis of a Potent Bradykinin B1 Antagonist via Enantioselective Hydrogenation of a Pyridyl N-Acyl Enamide

A practical and efficient synthesis of bradykinin B(1) antagonist 1 is described. A convergent strategy was utilized which involved synthesis of three fragments: 3, 6, and 7. Cross coupling of fragments 6 and 7 followed by amidation with 3 enabled efficient synthesis of 1 in 19 steps total, a 35% overall yield from commercially available pyridine 10. The key to the success of the synthesis was the development of a fluorodenitration step to install the fluorine in pyridine 7 and a catalytic enantioselective hydrogenation of N-acyl enamide 9 to set the stereochemistry.

Highly asymmetric dihydroxylation of 1-aryl-1′-pyridyl alkenes

Abstract The asymmetric dihydroxylation of 1-aryl-1′-pyridyl alkenes afforded the diols in high yield and excellent enantioselectivity.

A Practical Synthesis of Renin Inhibitor MK-1597 (ACT-178882) via Catalytic Enantioselective Hydrogenation and Epimerization of Piperidine Intermediate

A practical enantioselective synthesis of renin inhibitor MK-1597 (ACT-178882), a potential new treatment for hypertension, is described. The synthetic route provided MK-1597 in nine steps and 29% overall yield from commercially available p-cresol (7). The key features of this sequence include a catalytic asymmetric hydrogenation of a tetrasubstituted ene-ester, a highly efficient epimerization/saponification sequence of 4 which sets both stereocenters of the molecule, and a short synthesis of amine fragment 2.

Modeling a Crowdsourced Definition of Molecular Complexity

This paper brings together the concepts of molecular complexity and crowdsourcing. An exercise was done at Merck where 386 chemists voted on the molecular complexity (on a scale of 1-5) of 2681 molecules taken from various sources: public, licensed, and in-house. The meanComplexity of a molecule is the average over all votes for that molecule. As long as enough votes are cast per molecule, we find meanComplexity is quite easy to model with QSAR methods using only a handful of physical descriptors (e.g., number of chiral centers, number of unique topological torsions, a Wiener index, etc.). The high level of self-consistency of the model (cross-validated R(2) ∼0.88) is remarkable given that our chemists do not agree with each other strongly about the complexity of any given molecule. Thus, the power of crowdsourcing is clearly demonstrated in this case. The meanComplexity appears to be correlated with at least one metric of synthetic complexity from the literature derived in a different way and is correlated with values of process mass intensity (PMI) from the literature and from in-house studies. Complexity can be used to differentiate between in-house programs and to follow a program over time.

Remote Electronic Control in the Regioselective Reduction of Succinimides: A Practical, Scalable Synthesis of EP4 Antagonist MF-310

A practical large-scale chromatography-free synthesis of EP4 antagonist MF-310, a potential new treatment for chronic inflammation, is presented. The synthetic route provided MF-310 as its sodium salt in 10 steps and 17% overall yield from commercially available pyridine dicarboxylate 7. The key features of this sequence include a unique regioselective reduction of succinimide 2 controlled by the electronic properties of a remote pyridine ring, preparation of cyclopropane carboxylic acid 3 via a Corey-Chaykovsky cyclopropanation, and a short synthesis of sulfonamide 5.

Practical Synthesis of a Renin Inhibitor via a Diastereoselective Dieckmann Cyclization

A scalable synthesis of a potent renin inhibitor (1) is described. The absolute stereochemistry is set via an unprecedented diastereoselective Dieckmann cyclization directed by a remote chiral protecting group. This transformation enables preparation of chiral 1,3-[3.3.1]-diazabicyclononenes by desymmetrization of alkyl-esters, with selectivities ranging from 4 to 17:1.