A novel route to chiral unsaturated amines

Recently, there has been much effort directed toward the synthesis of chiral unsaturated alcohols. One of the best methodologies requires the synthesis of a chiral 1, 3-dioxolane, which is then ring-opened stereospecifically with a suitable organosilicon nucleophile. Removal of the auxiliary then reveals the desired homochiral alcohol. However, no analogous methodology exists for the preparation of homochiral unsaturated amines. The aim of this project is to develop a synthesis of these amines by ring opening of a chiral tetrahydro-1,3- oxazine; oxidation and removal of the chiral auxiliary would reveal the desired amine. The synthesis of a suitable 1, 3-amino alcohol chiral auxiliary is described. This was prepared by one-carbon homologation of (S)-alanine with sodium cyanide, and hydrolysis of the resulting nitrile. The chiral β-amino acid produced was then reduced. The synthesis of tetrahydro-1, 3-oxazines is described. These were prepared initially from direct condensation of the amino alcohol and an aldehyde, and later by an acetal exchange reaction between the amino alcohol and the relevant diethyl acetal. Information about the structure of the aminal has been determined. Attempted extension of the Noyori acetalisation to the preparation of tetrahydro-1, 3-oxazines is also outlined. The ring-opening reaction of tetrahydro-1, 3-oxazines with allyltrimethylsilane is described. These reactions did not result in significant amounts of product being formed. Further work necessary is outlined