Thiovalidamine derivatives of manno- and gluco-type: Remote activation and anchimeric assistance

The oxazolidone (3) derived from validamine (1) was dithiocarbonylated, on treatment with NaH followed by CS₂-Mel, to the N,O-dicarbodithioate (6). On treatment with NaH-Mel, this afforded the manno-type thiovalidamine derivative (7) and then the gluco-type thiovalidamine derivative (8) following the pathway shown in Scheme 2: an activation at a C=S group by methylation, transferring this activation to a remote position accompanied with decarboxylation, and cyclization of the neighboring group to the transferred position (C-3).