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[reaction: see text] An efficient asymmetric synthesis of the vasopeptidase inhibitor BMS-189921 was accomplished. Two short enantioselective syntheses of the common key intermediate (S)-alpha-aminoazepinone 6b were developed. Olefin 3 was converted to 6b via asymmetric hydrogenation. Alternatively, enyne 12 was converted to racemic alpha-aminoazepinone 15b, which was transformed to 6b by a practical dynamic resolution.

1-(Piperidin-4-yl)-1H-imidazo[4,5-b]pyridin-2(3H)-one ( 1) is a privileged substructure found in >1000 unique CGRP receptor antagonists. Two practical and efficient syntheses of 1 are described from complementary starting materials. One route features a chemoselective reductive amination, while the second route utilizes a Pd-catalyzed amination using an ammonia surrogate to overcome an issue of poor selectivity.

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An efficient and practical heterogeneous bimetallic Pd-Cu/C catalyst was identified as an alternative to Raney nickel for the highly diastereoselective hydrogenation of imines prepared from prochiral ketones and r-phenylethylamines. Chiral amines were obtained with diastereomeric excess (de) up to 94% using Pd-Cu/ C, while conventional Pd-C catalysts afforded only 72% de. Optimization showed that a robust process required a palladium/ copper ratio of 4:1. Evidence for the influence of catalyst pretreatment which may change the structure of the catalyst and/or metal oxidation states on the selectivity of the reaction is discussed. The bimetallic catalyst system provided consistent results on scale and performed reliably on a variety of substrates.