Stereoselective synthesis of enantiopure cyclic alpha-aminophosphonic acids: Direct observation of inversion at phosphorus in phosphonate ester silyldealkylation by bromotrimethylsilane

The paper describes a simple, direct synthesis of enantiopure cyclic alpha-aminophosphonic acids on the basis of silyldealkylation and followed by hydrolysis of the parent diastereoisomeric cyclic 1,4,2-oxazaphosphorines, which have been obtained by intramolecular stereospecific nucleophilic addition of phosphites to imines. In this approach, the high diastereoselectivity of the stereocontrolling penultimate step is preserved by conversion of the intermediate ester to the final phosphonic acid under very mild, nonracemizing conditions. (C) 2008 Wiley Periodicals, Inc.