Pvp. Pragnacharyulu et al., DIASTEREOMERIC 5,6-DIHYDROTHYMIDINES - PREPARATION, STEREOCHEMICAL ASSIGNMENTS, AND MNO2 OXIDATION STUDIES TO THYMIDINES, Journal of organic chemistry, 60(10), 1995, pp. 3096-3099
A useful method for the stereospecific synthesis of beta-thymidine and
beta-5,6-dihydrothymidine nucleosides is described. Condensation of m
ethyl 2-formylpropionate and methyl methacrylate with oxazolines 8 fur
nished the corresponding 2,2'-anhydrothymidine 11 and a 2:1 diastereom
eric mixture of 2,2'-anhydro-5,6-dihydrothymidine 10, respectively. Wh
ile DDQ oxidation of 10 furnished 11, active MnO2 resulted in a select
ive dehydrogenation hitherto unreported in nucleoside chemistry. The m
inor diasteromer 10b was quantitatively converted to 11, leaving 10a u
nchanged. A plausible explanation for this selectivity was based on th
e stereochemistry at C5 which was determined by one-dimensional NOE st
udies.