| 摘要 |
A compound of the formula <IMAGE> I in which <IMAGE> is either a 3-keto- DELTA 4-system or a 3-keto - DELTA 1,4-system or a 3-OR4- DELTA 5-system in which R4 is hydrogen or a protector group of hydroxy, R is methyl -CH2OH or -CH2OR', in which R' is a protector group of hydroxy, R1 and R'1 are individually selected from the group consisting of methyl, a branched alkyl not possessing hydrogen in the beta position of 5 to 8 carbon atoms, aryl of up to 10 carbon atoms, heteroaryl of up to 10 carbon atoms and at least one heteroatom chosen from nitrogen, sulfur and oxygen and benzyl, n and m, are individually numbers 0 or 1, R2 and R3 are hydrogen or R2 is fluorine and R3 is formyloxy or acetyloxy and the dotted lines in position 9(11) indicate the optional presence of a second bond which is useful for the preparation of compounds of formula A.
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