Synthesis of per-O-alkylated 5-thio-D-glucono-1,5-lactones and transannular participation of the ring sulphur atom of 5-thio-D-glucose derivatives on solvolysis under acidic conditions

Per-O-alkylated 5-thio-D-glucono-1,5-lactones (33)–(35) were synthesized via acetolysis or hydrolysis of the corresponding methyl glycosides (21)–(23). Transannular participation of the sulphur atom on acid methanolysis of 3,6-di-O-acetyl-5-S-acetyl-1,2-O-isopropylidene-5-thio-α-D-glucofuranose and on acetolysis of the glycosides (21)–(23) was confirmed. These reactions gave unexpected 4-substituted derivatives (14), (28) and (29). Furthermore, similar participation on C-2 and C-6 was suggested from the formation of 2,5-dideoxy-2,5-epithio-4,6-di-O-methyl-D-mannose dimethyl acetal.