The structure of phenindamine base and salts in the solute state

Abstract

Abstract High-field NMR (13C and 1H) studies of phenindamine are reported which establish structures of the free base and some of its salts in the solute condition. The base exists as a mixture of two isomers which differ in double bond position (9–9a or 4a–9a) while most salts are 9–9a isomers. The clinically employed tartrate (Thephorin) is exceptional in being a 4a–9a ene. Salts of both double bond type exist in solution as mixtures of protonated epimers of variable epimeric ratio, that of the tartrate in D2O being approximately 1:1.