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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.

The reaction of ,/3-unsaturated ketones with a THF solution of RMgX (3 mol equiv) and ZnCLyTMEDA (1 mol equiv) followed by NH4C1 gave 1,4-addition products. The products were contaminated by 1,2-addition products when R = Ph and Me but were essentially free of those compounds when R = n-Bu or i-Pr. The yields were highest when X = Cl. Thus the reaction of 2-cyclohexen-1 -one with a solution of n-BuMgCl and ZnCl2-TMEDA gave 3-n-butylcyclohexanone (1) in 96% yield.

1993 ring closure reactions ring closure reactions O 0130 -099Apparent Endo-Mode Cyclic Carbopalladation with Inversion of Alkene Configuration via Exo-Mode Cyclization-Cyclopropanation-Rearrangement.-Mechanisms of the cyclization of some dialkenes via carbopalladation are discussed by NMR spectroscopic analysis in terms of experimental results and literature informations.-(OWCZARCZYK, Z.; LAMATY, F.; VAWTER, E. J.; NEGISHI, E.; J.