Asymmetric synthesis of oxazolidine nucleosides and related chemistry

Asymmetric synthesis of N-substituted oxazolidinyl nucleosides has been accomplished from L-isoserine, trans- and cis-Oxazolidine intermediates (4 and 5) were stereoselectively constructed from N-protected L-isoserine with a menthoxycarbonyl group by the condensation with benzoyloxy acetaldehyde dimethyl acetal in a ratio of 3.9 to 1 in favor of trans-isomer 4. The major isomer 4 was converted to enantiomerically pure beta- and alpha-N-L-menthoxycarbonyl oxazolidinyl thymine nucleosides 11 and 12 in 6 steps.