Practical Preparation of β‐Amino‐α‐Hydroxy Diesters: Key Intermediates for 1,4‐Oxazin‐2‐Ones

In the presence of a catalytic amount of amino acid hydrochloride, trans‐β‐phenylglycidic ester undergoes ring opening with high stereo‐ and regioselectivity when treated with glycine esters. Alkylation of the resulting β‐amino‐α‐hydroxy diesters with benzyl bromide, followed by cyclization to furnish the expected 1,4‐oxazin‐2‐ones, is also described.