Abstract
Starting from 1,2‐O‐isopropylidene‐D‐xylose, methyl 2,4‐anhydro‐3,5‐di‐O‐benzyl‐D‐lyxonate (4) was synthesized. Debenzylation and transformation of the primary hydroxyl group yielded methyl 2,4‐anhydro‐5‐N‐(t‐butoxycarbonyl)amino‐D‐lyxonate (9). While transesterification of 4 under basic reaction conditions was straightforward, an analogous reaction with 9 was not successful. After screening of several lipases, the enzymatic transesterification of 9 was achieved with lipase L2 from Candida antarctica to furnish the title compound 2,4‐anhydro‐5‐N‐(t‐butoxycarbonyl)amino‐D‐lyxonic acid in excellent yield. The stereochemistry at the oxetane ring was proven by an x‐ray structure of the intermediate methyl 2,4‐anhydro‐5‐azido‐D‐lyxonate.
Acknowledgements
We wish to thank Amélie Mourton and Solène Dussauge for preliminary experiments.