New methodology for the synthesis of homochiral unsaturated amines

New methodology for the synthesis of chiral propargyl amines is described. A chiral (N)-Boc-l,3-amino alcohol, derived by the homologation of (L)- alanine with diazomethane, has been synthesised and this was then used, via reaction with a series of diethyl acetals, in the synthesis of chiral 1,3- tetrahydrooxazines (aminals). The structure of the aminals was determined, by both solution NMR and X- ray crystallographic methods, to exist as a twist chair structure with unusual conformational properties. The aminals were then functionalised with the Grignard reagent of (trimethylsilyl)acetylene, in the presence of boron trifluoride diethyl etherate, to give novel, ring opened, unsaturated amino alcohols. The subsequent unmasking of the required amines was then carried out by oxidation and subsequent retro-Michael elimination. The degree of chiral induction was determined via the Moshers amide method, and ranged from moderate to excellent