Stereoselective Synthesis of Unnatural beta-Amino Acids from Nitroethane via 5,6-Dihydro-4H-1,2-oxazin-3-ylacetates

摘要

The reduction of easily available methyl 5,6-dihydro-4H-1,2-oxazin-3-ylacetates provides an efficient route to different diastereomerically pure unnatural beta-amino acids. A two-step protocol including reduction of the C=N bond of the initial oxazine with sodium cyanoborohydride during the first step and hydrogenation of the N-O bond during the second step produced the target beta-ami-no acid esters with higher stereoselectivity than obtained with conventional catalytic hydrogenation.