Oxazinones as Synthetic Intermediates for Enantiomerically Pure β-Amino Acids

Significance

The first catalytic ring opening of substituted oxazinones leading to the formation of β-amino esters is reported. The starting oxazinones are conveniently prepared in a one-pot protocol from the reaction of inexpensive aldehydes, malonic acid and ammonium acetate followed by sequential treatment with benzoyl chloride and isobutyl chloroformate. Treatment of the oxazinones with higher alcohols under bifunctional thiurea catalysis leads to the formation of enantiomerically enriched products with about 60% conversion. The unreacted (R)-oxazinones were separated from (S)-amino esters without loss in enantiomeric purities. From the brief study on R variation, it appears that the scope of the kinetic resolution process is extendable to aliphatic substrates.