ANOMERIC O-ALKYLATION OF O-ACETYL-PROTECTED SUGARS

Anomeric O-alkylation of 2,3,4,6-tetra-O-acetyl-protected glucose, galactose, and mannose (1a-c) and of hepta-O-acetyllactose 5 with decyl triflate (2) in the presence of NaH as the base and in DME or DEE as solvents afforded directly decyl glycosides 3a-c and 5, respectively, in good yields. The anomeric diastereo control is temperature dependent, furnishing at room temperature preferentially the beta-anomers. Similarly, reaction of 5 with the triflate 8 of the spacer 7 or with the triflate 10 or nonaflate 11 of 3-O-protected sphingosine 9 gave at room temperature mainly beta-lactosides 12 and 13, respectively. Thus, important intermediates for the synthesis of amphiphilic carbohydrate derivatives and for glycoconjugate synthesis are readily accessible.