A crystalline form of 33-epichloro-33-desoxyascomycin

Abstract

33-Epichloro-33-desoxyascomycin of formula I. and various tautomeric or solvated form thereof, in crystalline form, such as Form A and Form B its preparation involves appropriately converting amorphous compound of formula I, or compound of formula I in other than form A, or compound of formula I in other than form B, respectively, from a solution thereof under crystallization-inducing conditions or conditions inducing preferential crystallization of form A or B, respectively. Such crystals are particularly indicated for use in the preparation of topical galenical forms of the compound for pharmaceutical use, e.g.creams, emulsions and ointments.