A CONVENIENT SYNTHESIS OF N-(7-DIMETHYLAMINO-4-METHYLCOUMARIN-3-YL)-MALEIMIDE INCORPORATING A NOVEL VARIANT OF THE PECHMANN REACTION

A new synthesis of the fluorescent, thiol-reactive compound N-(7-dimethylamino-4-methylcoumarin-3-yl)maleimide (6) is reported. Pechmann condensation of 3-dimethylaminophenol (1) and ethyl 2-acetamido-3-oxobutyrate (2) leads directly, in modest yield to the substituted 3-acetamidocoumarin (3) which is readily converted into the required compound (6) by standard means. In contrast to the previously reported synthesis of compound (6), no separation of structural isomers is required during the reaction sequence.