Regioselectivity of rhodium nitrene insertion. Syntheses of protected glycals of l-daunosamine, d-saccharosamine, and l-ristosamine.

[reaction: see text] The carbamate-protected glycals of naturally occurring 3,4-cis-3-amino-2,3,6-trideoxyhexoses (l-daunosamine, d-saccharosamine, and l-ristosamine) were prepared from noncarbohydrate starting materials. The short, high-yield syntheses are based on the chemoselective insertion of a rhodium nitrene in an allylic C-H bond rather than in a C-H bond that is alpha to an oxygen substituent.