Abstract Possible features controlling the anomeric ratios in the synthesis of the antiviral antibiotic dihydro-5-azathymidine have been examined. Replacement of the 3-and 5-(4- methylbenzoyl) protecting groups in 2-deoxy-D-erythro-pentofuranosyl chloride by benzyl groups led to changes in anomeric ratios in stannic chloride-mediated condensations with both 5-methyl-2, 4-bis (trimethylsilyl) triazine and 2, 4-bis (trimethylsilyl) thymine. Analysis ...