Chemistry of ethyl 2-{[t-butoxycarbonyl(methyl)amino]methyl}-3-hydroxy-3-phenyl (or 3-vinyl)propionate: mechanistic considerations in the formation of tetrahydro-1,3-oxazin-2-ones

Abstract

The threo- and erythro-selective aldol condensation of ethyl 3-[t-butoxycarbonyl(methyl)amino]- propionate with benzaldehyde gave the benzylic alcohol-substituted aminopropionate ethyl 2-{[t-butoxycarbonyl(methyl)amino]methyl}-3-hydroxy-3-phenylpropionate as a diastereoisomeric mixture. On treatment with methanesulphonyl chloride and triethylamine, the threo-isomer was converted into ethyl 3-methyl-2-oxo-6-phenyl-3,4,5,6-tetrahydro-2H-1,3-oxazine-5-carboxylate, and the erythro-isomer gave simply its corresponding mesate derivative. The mechanism for this transformation is discussed.