Stereoselective synthesis of 1,2-cis- and 2-deoxyglycofuranosyl azides from glycosyl halides Original Research Article

Protected 1,2-cis glycofuranosyl azides with α-d-ribo, β-d-arabino and 2-deoxy-2-fluoro-β-d-arabino configurations were efficiently prepared from the appropriate 1,2-trans glycosyl halides bearing non-participating O-2 substituent by inversion with sodium azide under phase transfer catalytic conditions (80–85% yields, 90–96% de). The same method failed to result in sufficiently good β-selectivity starting from 2-deoxy-3,5-di-O-(p-toluoyl)-α-d-erythro-pentofuranosyl chloride (5α) (40% de). The selectivity in favour of the protected 2-deoxy-β-d-erythro-pentofuranosyl azides was greatly improved (74–80% de) by treating 5α and its p-chlorobenzoyl analog 6α with cesium or potassium azide in dimethylsulfoxide at room temperature (83–85% yields).