Synthesis of anomeric sulfur analogues of CMP-Neu5Ac containing tethered alkane or arene

A new approach to the synthesis of anomeric sulfur analogues of CMP-Neu5Ac containing alkane or arene linkage 1a-d is described. The procedure involves the high beta-stereoselectivity in sialylation of the peracetylated sialic acid methyl ester 4 with mercaptoalkyl (aryl) trichloroacetate 5a-d, followed by selective deprotection of the trichloroacetyl group to the corresponding hydroxyalkyl and hydroxyaryl thioglycosides 2a-d. Subsequent O-phosphitylation of 2a-d with respective 3a or 3c, followed by oxidation and deprotection led to the isolation of the target compounds 1a-d in good yields.