From carbohydrate-derived ketene dithioacetals to 1-<i>C</i>-thioglycals: a synthetic and theoretical insight

A strategy for the synthesis of 1-<i>C</i>-substituted thioglycals was developed from cyclic carbohydrate-derived ketene dithioacetals in a four-step sequence. The corresponding thioglycals, in two carbohydrate series, were first obtained by removal of the exocyclic glycosyl sulfoxide, followed by treatment with an organolithium reagent. Various electrophilic groups were introduced onto the thioglycal double bond after deprotonation and formation of a glycosyl lithium intermediate. A computational analysis was undertaken to gain a better understanding of the experimental results obtained in the two series.