Toyama Chemical Co., Ltd.

Nobuhisa Taya

Kaishu Momonoi

Takako Hori

Joji Nakano

Tetsuo Yamafuji

Hisaaki Chaki

Takashi Nagai

Hidetada Mikami

Shinji Miyabara

Masaaki Shibata

Isao Myoukan

Kenji Ohta

Keishi Funaki

This invention relates to a process for producing a compound represented by formula (6a) or (6b): ##STR1## wherein R.sup.2 represents a hydrogen atom or a hydroxyl-protecting group and R.sup.4 and R.sup.5, which may be the same or different, represents lower alkyl groups, using a compound represented by formula (2a) or (2b) obtained by preferential crystallization: ##STR2## and also to a compound represented by the following formula (7) which is an intermediate useful for producing the compound of formula (6a) or (6b): ##STR3## wherein R.sup.1 represents a group represented by formula (8): ##STR4## wherein R.sup.2 and R.sup.3 is as defined above and R.sup.3 represents a hydrogen atom, a group or a carboxyl protecting group represented by formula (9): ##STR5## or a group represented by formula (10): ##STR6## wherein R.sup.2 is as defined above.

Benzo[b]thiophen-5-yl derivative and process for producing the same

A novel isoindole derivative represented by general formula [1] or a salt thereof: ##STR1## which has an excellent antitumor activity and low toxicity.

Isoindole derivatives and salts thereof and antitumor agent comprising

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Shinminato, Japan

Nobuhisa Taya