Stereoselective synthesis of 1,4,2-oxazaphosphorines as precursors of chiral α-aminophosphonic acids by intramolecular heterocyclization of β-aldiminoalkylphosphites

Article abstract of DOI:10.1002/hc.10054

The intramolecular version of nucleophilic addison of phosphites to imines was carried out for the first time taking as an example β-aldimino-alkylphosphites, formed from chlorophosphites and β-aldiminoalcohols [N-(benzylidene)-2-aminoethanol and R-(+)-N-(benzylidene)-2-aminobutanol-1]. In these reactions, stereoisomeric 1,4,2-oxazaphospho-rines were obtained in good yields. R-(+)-N-(benzylidene)-2-aminobutanol-1 being used as a precursor, nucleophilic attack by P(III) atone on electrophilic C atom of the C=N group proceeds stereospecifically with participation of only re-face of the two possible diastereotopic faces of the imine double bond to give the epimeric at phosphorus (3R, 5R)-2-(β-chloroethyl)-2-oxo-3-phenyl-5-ethyl-1,4,2-oxazaphosphorines as precursors of nonracemic α-aminophosphonic acids.