Conformationally locked 3'-azido-C-4'-spirooxetano-xylonucleosides T, U, C and A have
been synthesized by following chemo-enzymatic convergent route. One of the 3'-azido-C-4'-
spirooxetano-xylonucleosides, i.e. T was converted into 3'-amino-C-4'-spirooxetano-xylothymidine by
reduction of azide to amine with H2/Pd-C in ethyl acetate in quantitative yield. The crucial step in the
synthesis of spirooxetano-xylonucleosides is the Lipozyme® TL IM-mediated exclusive diastereoselective
acetylation of 4-C-hydroxymethyl group in dihydroxysugar derivative, 3-azido-3-deoxy-4-Chydroxymethyl-
1,2-O-isopropylidene-α-D-xylofuranose in quantitative yield. The diastereoselective
monoacetylation of 4-C-hydroxymethyl in dihydroxysugar derivative was unambiguously confirmed
by X-ray crystal study on the tosylated compound obtained by the tosylation of Lipozyme® TL IM -
mediated monoacetylated sugar derivative. The broader substrate specificity and exclusive selective
nature of Lipozyme® TL IM can be utilised for the development of environmentally friendly methodologies
for the synthesis of different sugar-modified nucleosides of importance.
Keywords: C-4`-Spirooxetano-xylonucleosides, chemo-enzymatic synthesis, lipozyme® TL IM, diastereoselectivity.
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