| 摘要 |
The invention relates to a method of the preparation of a steroid derivative ketal according to the general formula I: <CHEM> wherein R1 is CH3 or C2H5; R2 is OH; R3 is H, CH3; C IDENTICAL CH, CH2Hal,, or CH2CN; or R2 and R3 together are O; R4 is (2-5C) alkylene; and Hal is Cl, Br or I, characterized in that the compound of formula II: <CHEM> wherein R1, R2 and R3 have the previously given meanings, is treated in the presence of an orthoester of formula III: <CHEM> or an orthoester of formula IV: <CHEM> wherein R4 has the previously indicated meaningor a mixture thereof with an alcohol according to the general formula HOR4OH, wherein R4 has the previously given meaning. |
