Process of making an alpha-anomer enriched 2-deoxy-2,2-diflouro-d-ribofuranosyl sulfonate and use thereof for making a beta nucleoside

摘要

A process of preparing an alpha-anomer enriched 2-deoxy-2,2-difluoro-D-ribofunanosyl sulfonate, which is useful as an intermediate in the preparation of a beta nucleoside, such as gemcitabine, an anti-tumor agent. A beta-2-deoxy-2,2-difluoro-D-ribofunanosyl sulfonate is heated and converted to an alpha-2-deoxy-2,2-difluoro-D-ribofunanosyl sulfonate in the absence of an effective amount of a sulfonate salt to facilitate the conversion. In addition, an anomeric mixture of an alpha-anomer and a beta-anomer of 2-deoxy-2,2-difluoro-D-ribofunanosyl sulfonate can be dissolved in a mixture of water and a solvent and heated to produce a lactol, which may be further converted to an alpha-anomer enriched 2-deoxy-2,2-difluoro-D-ribofunanosyl sulfonate.