Unusual stereospecificity in the hydrogenation of an isopropenyl function with Wilkinson's catalyst; a route to chiral methyl valine

Abstract

Catalytic hydrogenation with H³H in the presence of Wilkinson's catalyst of (2RS)-(E)-[4-²H]-2-acetylamino-3-methylbut-3-enoic acid gave a mixture of (2SR, 3SR, 4RS)-[4-³H²H]-N-acetylvaline [(8) and (9)] and 2SR, 3RS, 4SR-[4-³H²H]-N-acetylvaline [(6) and (7)] in the radio 19:1 by ³H n.m.r. spectroscopy of the derived valines; a similar reduction with ²H₂ of 1,5-(Z)-4, 7-DIAZA-7-[1-4-(nitrobenzyloxycarbonyl)-2-methylprop-2-enyl]-3-phenoxymethyl-2-thiabicyclo[3.2.0]hept-3-en-6-one gave a mixture of dideuterio-isomers (11) and (12), in the ratio 3 : 7 by ¹H n.m.r. spectroscopy of the derived valines.