Phenylsulfinyl-lithium exchange on glycosyl phenylsulfoxides leads to configurationally stable anomeric carbanions which can react stereoselectively with electrophiles. Thus, the reaction of 3,4-O-isopropylidene-α-l-fucopyranosyl phenylsulfoxide with tBuLi followed by treatment with isobutyraldehyde led to the α-configured C-glycoside; the β-anomer furnished the corresponding β-C-glycoside.
alpha-L-fuco-, alpha-D-gluco-, beta-D-gluco-, and alpha-D-mannopyranose have been synthesized from the corresponding glycosyl phenyl sulfoxide through phenylsulfinyl-lithium exchange, to generate an anomeric carbanion, and subsequent reaction with a carbon electrophile. The reactions were stereospecific and proceeded with retention of the configuration at the anomeric center. Improved yields of C-glycosides
double bond, controlled by substitution on the substrate. For the synthesis of 1-C-fucopyranosides (37, 38, and 42) a new method based on the use of fucosyl phenyl sulfoxides (35 and 41) was employed. An anomeric carbanion is generated through phenylsulfinyl-lithium exchange, which reacted with electrophiles with retention of configuration at the anomeric center. The required fucosyl sulfoxides were prepared