AbstractA synthesis of 1,2‐cis‐configurated, non‐isosteric phosphonate analogues of aldose‐1‐phosphates is described. Treatment of 1‐O‐acyl‐glycoses1,7,13, and19with trialkyl phosphite in the presence of trimethylsilyl trifluoromethanesulfonate gave the 1,2‐cis‐configurated glycosylphosphonates2,4,8,10,14,16,20, and22as the major anomers and the 1,2‐trans‐configurated glycosylphosphonates3,5,9,11,15,17,21, and23as the minor anomers. The 1,2‐cis‐configurated phosphonates4,10,16, and22were deprotected to give the (β‐D‐glucopyranosyl)phosphonate6, the (β‐D‐mannopyranosyl)phosphonate12, the (β‐D‐ribofuranosyl)phosphonate18, and the (β‐D‐arabinofuranosyl)phosphonate24, respectively, in high yields. The preferred formation of 1,2‐cis‐configurated phosphonates is explained by postulating an equilibrium between the anomeric phosphonium‐salt intermediates (such as25and26) and a stabilization of thecis‐configurated salts thro