A general method for the synthesis of sugar 2-C-sulfonic acids by 1 --> 2 arylthio group migration in acid-sensitive thioglycosides. Direct transformation of thiotrityl ethers into C-sulfonic acids.

[reaction: see text] Fully protected triphenylmethyl 2-O-mesyl-1-thio-beta-d-gluco- (14) and -alpha-d-mannopyranoside (28) were transformed by a stereoselective intramolecular 1 --> 2 trans-arylthio migration into methyl 2-S-triphenylmethyl-alpha-d-manno- (15) and -beta-d-glucopyranoside (29), respectively, using NaOCH(3) as nucleophile. The 2-S-triphenylmethyl ethers (15 and 29) were directly oxidized to sugar 2-C-sulfonic acids by using oxone (2KHSO(5), KHSO(4), K(2)SO(4)). Compounds (21, 23, 32, and 35) are the first representatives of secondary sugar C-sulfonic acids.