(-)-galanthaminium bromide

The crystal structure and absolute configuration of the title compound, C17H22NO3+. Br-, the hydrobromide salt of the alkaloid galanthamine, is reported. The tetrahydroazepine ring is in a chair conformation, the dihydrofuran ring in an envelope conformation and the cyclohexene ring between an envelope and a half-chair conformation. The axial hydroxy group forms an intramolecular hydrogen bond with the O atom of the dihydrofuran ring. The N-methyl group is in an axial position, while in galanthamine it is in an equatorial position.