Asymmetric synthesis of the northern segment of ephedradine C

An asymmetric synthesis of the dihydrobenzofuran segment of ephedradine C h as been achieved. Key steps include a chiral oxazolidinone-mediated aldol r eaction to form a beta-hydroxy ester, followed by a novel debenzylation and concomitant intramolecular cyclisation with iodotrimethylsilane. An asymme tric Michael reaction with a homochiral lithium amide was used to form the third and final chiral centre. The absolute stereochemistry of these three centres was confirmed by X-ray crystal-structure determinations.