-
C-
galacto-Pyranosides with CHF and CF
2 substitutes for the glycosidic oxygen were prepared through a four-step sequence starting froma central 1-thio-1,2-
O-isopropylidene acetal alcohol and different
-fluoro- and
,
-difluoro acids. The key step in the synthesis is theoxocarbenium cyclization of an intermediate enol ether-thioacetal to a C1-substituted glycal.