Eisai Company, Limited

Eisai Chemical Co., Ltd.

Akio Imai

Hideaki Watanabe

Yasushi Ishihama

Tomohide Tanaka

Takashi Kajima

Akiyo Ohtsuka

Tomio Tsurugi

Takeo Kanai

Homare Shinohara

Yukio Narabu

Katsuhiko Sato

Takashi Endo

Toshiyuki Ichinohe

Makoto Uemura

Kazumi Oishi

The present invention provides novel polymorphic crystals (A) to (C) having excellent handling properties and an extremely low content of residual solvent of donepezil used as a precursor for production of donepezil hydrochloride having an excellent action as a medicament, and an industrial process for producing the same. Further, the novel polymorphic crystals (A) to (C) according to the present invention are characterized by the powder X-ray diffraction pattern and/or IR absorption peaks of donepezil represented by the following formula:

Donepezil polycrystals and process for producing the same

Donepezil hydrochloride, 1-benzyl-4-[(5,6-dimethoxy-1-indanon)-2-yl]methylpiperidine hydrochloride, is provided here in the form of four polymorphs which are stable against heat and humidity in the pharmaceutical use. They can be industrially produced. They are specified by peaks in X-ray powder diffraction pattern and absorption peaks in infrared absorption spectra in potassium bromide.

Polymorphs of donepezil hydrochloride and process for production

A process is provided for the preparation of an aminothiadiazolylacetyl halide derivative represented by the following formula (II): ##STR1## wherein R.sup.1 represents a lower alkyl, cycloalkyl or halogenated lower alkyl group; and R.sup.2 represents an amino-protecting group or a hydrogen atom, or a salt thereof, which process uses as the starting material a compound represented by the following formula (I): ##STR2## wherein R.sup.1 and R.sup.2 have the same meanings as defined above, or a salt thereof.

Process for the preparation of aminothiadiazolylacetyl halide derivtives

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Ibaraki, Japan

Akio Imai