Anomeric Thioglycosides Give Different Anomeric Product Distributions under NIS/TfOH Activation.

The reaction of a series of anomeric thioglycosides with various glycosyl acceptors and N-iodosuccinimide/catalytic triflic acid was investigated with respect to reactivity and anomeric selectivity. In general, ß-configured donors were found to give a more ß-selective reaction outcome compared to their α-configured counterparts. The relative reactivity of various thioglycosides was measured through competition experiments, and the following order was established: phenyl, tolyl, methyl, ethyl, isopropyl, and 1-adamantyl.