An asymmetric synthesis of the antibiotic (+)-negamycin (1) has been achieved, starting from commercially available (5R,6S)-4-(benzyloxycarbonyl)-5,6-diphenyl-2,3,5,6-tetrahydro-4H-1,4-oxazin-2-one (2). The synthesis involved the stabilized Wittig olefination of the lactone carbonyl group of 2 and subsequent asymmetric hydrogenation to generate the corresponding all-syn oxazine 4 with excellent diastereoselectivity
(+)-Negamycin was synthesised employing the highly diastereoselective conjugate addition of lithium (alpha-methylbenzyl)benzylamide in the key step. The synthesis was completed in 13 steps starting from ethyl 4-chloroacetoacetate with an overall yield of 24 %. Copyright (C) 1996 Elsevier Science Ltd