Chlorodifluoromethyl-substituted monosaccharide derivatives—radical activation of the carbon–chlorine-bond

The dithionite-mediated addition of BrCF2Cl to 3,4-di-O-pivaloyl-d-xylal (1) generated preferably 1-CF2Cl-substituted products, that is, (2-bromo-2-deoxy-3,4-di-O-pivaloyl-β-d-xylopyranosyl)-chlorodifluoromethane and (2-deoxy-3,4-di-O-pivaloyl-β-d-threo-pentopyranosyl)-chlorodifluoromethane. Selected chlorodifluoromethyl-substituted monosaccharide derivatives were hydrodechlorinated or alkylated at the CF2Cl-group using tin reagents under radical reaction conditions. Thus, hydrodechlorinations of (2,3,4-tri-O-acetyl-6-deoxy-α-l-galactopyranosyl)-chlorodifluoromethane and of methyl 3,4-di-O-acetyl-2-C-chlorodifluoromethyl-2,6-dideoxy-α/β-l-glucopyranoside are reported using tri-n-butyltin hydride initiated by AIBN. UV-initiated allylations are reported for reactions of (2-deoxy-3,4-di-O-pivaloyl-β-d-threo-pentopyranosyl)-chlorodifluoromethane, (2,3,4-tri-O-acetyl-6-deoxy-α-l-galactopyranosyl)-chlorodifluoromethane, 1,3,4,6-tetra-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-α-d-glucopyranose, 1,3,4,6-tetra-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-α-d-mannopyranose and methyl 3,4-di-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-α/β-d-rabinopyranoside with allyltri-n-butyltin.

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