| 摘要 |
A process for the preparation of a compound of the formula <IMAGE> I wherein R1 is alkyl of 1 to 3 carbon atoms, R2 is alkyl of 1 to 12 carbon atoms, R3 is alkyl of 1 to 4 carbon atoms comprising reacting a compound of the formula <IMAGE> II wherein R4 is a remainder of an easily cleavable ether, K is a protected ketone function in the form of ketal, thioketal or mixed ketal and R1 has the above definition with a magnesium organic compound reagent of the formula HalMg-CH2-R2A wherein Hal is a halogen and R2 is defined as above to obtain a compound of the formula <IMAGE> III wherein R1, R2 and K are defined as above, reacting the latter with an acylation agent to obtain a compound of the formula <IMAGE> IV wherein R5 is alkyl of 1 to 6 carbon atoms or aryl of 6 to 10 carbon atoms and R1, R2 and K are defined as above, reacting the latter with an appropriate alkylation agent to obtain a compound of the formula <IMAGE> V wherein R1, R2, R3 and K are defined as above, subjecting the latter to autoxidation to obtain a compound of the formula <IMAGE> VI wherein R1, R2, R3 and K are defined as above, reacting the latter with an acid to obtain a reconjugated 3-keto compound of the formula <IMAGE> VII wherein R1, R2 and R3 are defined as above and reacting the latter with a regio- and enantioselective reducing agent to obtain a compound of formula I and intermediates formed therein.
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