Asymmetric synthesis of the northern segment of ephedradine C. A novel dihydrobenzo[b]furan formation

An asymmetric synthesis of the dihydrobenzo[b]furan segment of ephedradine C has been achieved utilising a chiral oxazolidinone in an aldol reaction t o form a B-hydroxy ester, followed by a novel debenzylation and concomitant intramolecular cyclisation with iodotrimethylsilane as key steps. An asymm etric Michael reaction with a homochiral lithium amide was used to form the third and final chiral centre. (C) 1999 Elsevier Science Ltd. All rights r eserved.