Mitsubishi Chemical Industries Limited

Yoshiyuki Takeda

Shinichiro Koga

Osamu Kawashima

Yutaka Fukuda

Shiro Furukawa

Yasukazu Ogino

Disclosed herein is an improved process for preparing 1RS-3'RS epimer of aminated phthalideisoquinolines represented by the general formula (I): ##STR1## wherein R.sup.1 and R.sup.2 are independently hydrogen atom or a lower alkoxy group, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently hydrogen atom, amino group or a lower alkoxy group with at least one of R.sup.3 -R.sup.6 being amino group, and R.sup.7 is a lower alkyl group. The improvement comprises, after having reduced a mixture of epimers of corresponding nitro compounds of the general formula (I) wherein the amino group is replaced by nitro group into the amino compounds (I), treating said amino compound at a temperature in the range of 20.degree.-100.degree. C. in an aliphatic lower alcohol in the presence of an alkali to epimerize 1RS-3'SR epimer of said amino compound into said 1RS-3'RS epimer thereof.

Process for the epimerization of aminated phthalideisoquinolines

A mixture of various dinitroanthraquinone isomers prepared from anthraquinone by mixed acid nitration is subjected to a suspension treatment at a temperature above 50.degree. C. with a mixed acid of a content satisfying the following three equations and then the crystals of 1,5-dinitroanthraquinone are separated:

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Kitakyusyu, Japan

Yoshiyuki Takeda