| abstract |
(57) [PROBLEMS] To provide a compound having steroid C 17,20 lyase inhibitory activity and useful as a prophylactic or therapeutic agent for tumors such as prostatic disease and breast cancer, and an optically active mixture of the compound as an optical isomer mixture. Providing efficient separation methods. The formula: embedded image [Wherein each symbol is as defined in the specification] or a salt thereof or a prodrug thereof, and a mixture of optical isomers are optically resolved using a resolving agent such as tartranic acid. A method for obtaining an optically active substance. |