PREPARATION OF 9,10-SECOCHOLESTA-5,7,10 (19) - TRIENES

摘要

A process for the preparation of 9,10-secocholesta-5, 7, 10 (19) - trienes of the formula wherein R1 is hydrogen or a protecting group for the hydroxy function, to which R1 is bound, R2 and R3 are hydrogen or OR1, whereby the groups R1, R2, and R3 may be selected independently from each other, characterized in that in a first step a transition metal halide of the formula M (z)X2 (II) wherein M(z) is W(VI), Nb(V), Mo(V), Ti(IV), Ti (III) or Fe (III), X is chloride, bromide or iodide, z is an integer from 3 to 6, is reduced with 1 to z equivalents of an alkyl metal compound or a metal hydride to a corresponding low-valent metal reagent under an inert gas atmosphere in a waterfree ether or a hydrocarbon, in a second step a compound of the formula 1630 ד' באב התשס" א - July 24, 2001 wherein R1, R2, R3 are defined above, A and B taken together are either an epoxide of the formula -(-OCH2)- or an exocyclic double bond of the formula =CH2, dissolved in an above mentioned solvent, is added to the in the first step prepared low-valent, metal reagent and is allowed to react, in a third step the so obtained reaction product is worked up and the product of formula I is obtained.