Synthesis of Azasugars via Lanthanide-Promoted Aza Diels−Alder Reactions in Aqueous Solution

Aqueous aza Diels−Alder reactions of chiral aldehydes, prepared from carbohydrates, with benzylamine hydrochloride and cyclopentadiene, were promoted by lanthanide triflates. The exo / endo selectivities and diastereoselectivities of the reactions were elucidated by NMR, CD spectroscopy, and X-ray crystallography. The nitrogen-containing heterocyclic products were further transformed to azasugars, which are potential inhibitors against glycoprocessing enzymes.