THE USE OF LITHIUM (ALPHA-METHYLBENZYL)ALLYLAMIDE FOR THE ASYMMETRIC-SYNTHESIS OF UNSATURATED BETA-AMINO ACID-DERIVATIVES

The unsaturated beta-amino acid derivatives 3R)-(E)-3-(N-tert-butoxyca rbonyl)aminohex-4-enoate and methyl N-tert-butoxycarbonyl)-amino-2-hyd roxyhex-4-enoate have been synthesised from lithium (S)-(alpha-methylb enzyl)allylamide and (E,E)-tert-butyl hex-2,4-dienoate. After a highly stereoselective conjugate addition of the lithium amide to the alpha, beta-unsaturated ester, or a highly stereoselective conjugate addition -electrophilic hydroxylation, the adducts are deallylated and the resu lting secondary amines converted to either a benzoyl amide or oxazolid inone. The N-alpha-methylbenzyl group is then removed with either form ic acid or using a dissolving metal reduction. These deprotection proc edures leave unsaturation in the molecules intact. (C) 1997 Elsevier S cience Ltd.