Method for selectively crystallizing a Z isomer of iopromide

摘要

The present invention relates to a method for selectively crystallizing Z isomer of iopromide of formula (I) comprising a) dissolving a crude iopromide comprising a mixture of E and Z isomers or a concentrate thereof in an alcohol, and b) heating the resulting alcohol solution to obtain crystalline of Z isomer of iopromide; and a method for preparing a composition comprising the crystalline Z isomer of iopromide.