The resolution and absolute configuration by X-ray crystallography of the isomeric octopamines and synephrines

Abstract

Racemates of the naturally occurring biogenic amines, o-, m-, and p-octopamine and p-synephrine, have been resolved by the preparation of suitable diastereoisomeric salts with antipodes of appropriate organic acids. The circular dichroism (c.d.) curves of (–)-m-octopamine hydrochloride and (–)-m-synephrine hydrochloride were superimposable and of opposite sign to those of the corresponding (–)-p-derivatives. X-Ray crystallography of the (–)-3-bromocamphor-8-sulphonate salt of (–)-p-synephrine confirmed (for the first time by direct means in this series of compounds) that the absolute configuration of (–)-p-synephrine is R. It is concluded from the c.d. data that the absolute configuration of (–)-p-octopamine is also R.