Suzuki−Miyaura Approach to JNJ-26076713, an Orally Active Tetrahydroquinoline-Containing α<sub>V</sub>β<sub>3</sub>/α<sub>V</sub>β<sub>5</sub> Integrin Antagonist. Enantioselective Synthesis and Stereochemical Studies
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An improved scale-up synthesis was required for the αVβ3/αVβ5 integrin antagonist 1, which had demonstrated oral efficacy in eye disease models of angiogenesis and vascular permeability. A stereodefined, quinoline-substituted, unsaturated ester was conveniently prepared by a Suzuki−Miyaura coupling to facilitate exploration of multiple methods of asymmetric reduction. The catalytic chiral hydrogenation of the corresponding unsaturated acid (Z-5b) with a ruthenium-based metal precursor and the (R)-XylPhanePhos ligand proved particularly efficient and economical. The resulting (3S)-quinoline-containing intermediate was reduced to an equal mixture of tetrahydroquinoline diastereomers. The undesired diastereomer could be recycled to the desired one by an oxidation/reduction protocol. The absolute stereochemistry of 1 was established as 3S,3‘S by a combination of X-ray diffraction and chemical means.
