Taisho Pharmaceutical Co., Ltd.

Sumitomo Pharmaceuticals Company Limited

Itsuro Sugata

Noritaka Hamma

Takashi Katsumata

Yoshikazu Saito

Toshio Nishizawa

There are disclosed herein novel derivatives of 26,26,26,27,27,27-hexafluorovitamin D.sub.3 providing excellent pharmacological effects, and a process for the preparation thereof. These novel compounds are represented by the general formula ##STR1## wherein R.sub.1 and R.sub.2 each denotes a hydrogen atom or a protecting group for the hydroxyl group; R.sub.3 and R.sub.4 each denotes a hydrogen atom, a hydroxyl group or a protected hydroxyl group and R.sub.4 ' and R.sub.5 ' each denotes a hydrogen atom, or alternatively R.sub.3 and R.sub.3 ' together or R.sub.4 and R.sub.4 ' together denote an oxo group; provided that R.sub.3, R.sub.3 ', R.sub.4 and R.sub.4 ' cannot denote hydrogen atoms simultaneously. The process for the preparation comprises subjecting a previtamin D.sub.3 derivative represented by the formula ##STR2## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.3 ', R.sub.4 and R.sub.4 ' are as defined above, to thermal isomerization to give a vitamin D.sub.3 derivative represented by the general formula ##STR3## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.3 ', R.sub.4 and R.sub.4 ' are as defined above, and optionally subjecting it to a deprotection reaction.

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Toyonaka, Japan

Itsuro Sugata