Nucleic acid binding drugs. Part 12. X-Ray crystallographic and conformational studies on the anti-cancer drug m-AMSA and its mesyl derivative

Abstract

The crystal structures of the anti-tumour agent m-AMSA [4′-(acridin-9-ylamino)-3′-methoxymethanesulphonanilide] and its mesyl derivative, as free bases, have been determined. They show a very distinct orientation of the substituted phenyl ring with respect to the acridine group, compared with m-AMSA hydrochloride (J. M. Karle, R. L. Cysyk, and I. L. Karle, Acta Crystallogr., 1980, B36, 3012). This has been rationalised in terms of intra- and inter-molecular interactions, the latter with ionic species in the salt crystal. Conformational calculations are also reported on these compounds, which indicate that they have interconvertible conformational flexibility.