Biocatalytic route to <i>C</i>-4′-spiro-oxetano-xylofuranosyl pyrimidine nucleosides

<p>A facile access to <i>C</i>-4′-spiro-oxetano-xylofuranosyl nucleosides has been demonstrated for the first time through Lipozyme<sup>®</sup> TL IM-mediated regioselective acetylation of one of the primary hydroxyl group over the other primary and secondary hydroxyl groups in 3′-<i>O</i>-benzyl-4′-<i>C</i>-hydroxymethyl-<i>β</i>-D-xylofuranosyl nucleosides. Attempts to optimize a convergent route for these spironucleosides via selective manipulation of hydroxyl groups in 3-<i>O</i>-benzyl-4-<i>C</i>-hydroxymethyl-1,2-<i>O</i>-isopropylidene-α-D-xylofuranose were unsuccessful. Nevertheless; the present linear biocatalytic route efficiently afforded the <i>C</i>-4′-spiro-oxetanoxylofuranosyl nucleosides T and U in 47 and 38% overall yields, respectively, starting from corresponding furanose diol.</p>