METHOD OF PREPARING STEROID DERIVATIVE KETALE, AND METHODS FOR PREPARATION OF COMPOUNDS Russian patent published in 2001 - IPC

FIELD: synthesis of biologically-active compounds. SUBSTANCE: invention provides method for preparing intermediates in synthesis of steroids with progestogenic activity, in particular ketal of steroid derivative with general formula I: (I), wherein R₁ expresses methyl or ethyl, R₂ hydroxyl, R₃ hydrogen, methyl or cyanomethyl, or R₂ and R₃ form together oxygen bridge; and R₄ expresses C2-C5-alkylene, consisting in that compound of the general formula II: (II), in which all symbols are the same as in formula I, is treated in presence of one or two ortho- ethers having formula III: (III) and IV: (IV), in which all symbols are the same as in formula I, by alcohol of general formula HOR₄OH, wherein R₄ is indicated above. EFFECT: enabled preparation of products with minimum amounts of impurities. 6 cl, 7 ex