SYNTHESIS OF 1,3,2-OXAZAPHOSPHOLIDIN-4-ONES

The subject of this paper is the preparation of 1,3,2-oxazaphospholidi n-4-ones by reaction of phenyldichlorophosphine with The N-methyl amid es of alpha-hydroxy isobutyric acid and the two chiral carboxylic acid s (S) lactic acid and (R,S) mandelic acid, which leads to diastereomer ic products. Reaction control by means of P-31 n.m.r. demonstrates two surprising findings: the preferred generation of the thermodynamicall y less stable cis-isomer and an epimerization of the phosphorus chiral ity centre at room temperature.