A convenient synthesis of codeine and morphine

Acid-catalysed cyclization of 1-(3,5-dihydroxy-4-methoxybenzyl)-N-formyl-1,2,3,4,5,8-hexahydro-6-methoxyisoquinoline (2c), where the benzyl group is symmetrically substituted, gave N-formyl-2-hydroxynordihydrothebainone (4c) exclusively. The 2-hydroxyl substituent could be removed selectively in high yield, via the 1-phenyltetrazol-5-yl ether (4d), to yield N-formylnordihydrothebainone (4e). (-)-N-Formylnordihydrothebainone (4e) was reduced to (-)-dihydrothebainone (4a). The conversion of 4a to codeine (1b) and morphine (1a) has already been recorded.