Skeletal rearrangement of seven-membered iminosugars: Synthesis of (−)-adenophorine, (−)-1-epi-adenophorine and derivatives and evaluation as glycosidase inhibitors

An alternative synthetic strategy towards (−)-adenophorine based on a tandem Staudinger/azaWittig/alkylation/ring contraction sequence is reported allowing late stage introduction of pseudoanomeric substituents on the piperidine ring. Biological evaluation indicates that (−)-adenophorine is a moderate α-l-fucosidase inhibitor.