Conjugate addition of organocuprates generated from copper (I) cyanide and vinyl stannanes useful in prostaglandin analog synthesis

A process for the preparation of a prostaglandin analog characterized by the formula:

• ##STR11## wherein ##STR12## A is ethylene or cis-vinylene;
• X is CH.sub.2 OE or CO.sub.2 R.sub.3 where E is H or an acid labile blocking group, R.sub.2 is lower straight or branched chain lower alkyl of 1 to 4 carbon atoms or phenyl and R.sub.3 is alkyl of 1 to 3 carbon atoms and R.sub.1 is butyl or ##STR13## where R.sub.4 is hexyl or ##STR14## where R.sub.5 is methyl or H, R.sub.6 is alkyl, branched alkyl or cycloalkyl of 5 to 7 carbon atoms, R.sub.7 is methyl, vinyl or H and R.sub.8 is n-alkyl, branched alkyl or alkylated cycloalkyl of 4 to 7 carbon atoms which process comprises the steps of:
• (a) reacting 2 equivalents of R.sub.1 Li wherein R.sub.1 is as defined above with E being an acid labile blocking group with 1 equivalent of CuCN in an aprotic solvent under an inert atmosphere at a temperature of from -78.degree. C. to 25.degree. C. to form a reaction product;
• (b) reacting the reaction product formed in step (a) with 1 equivalent of a substituted cyclopentenone of the structure:
• ##STR15## where Y is OH or OE, A is as defined above and X is as defined above where E at each occurance is an acid labile blocking group to form a reaction product;
• (c) quenching with an aqueous solvent or an acylating agent of the formula:
• ##STR16## where Z is Cl, Br or ##STR17## and R.sub.2 is as defined above;
• and (d) optionally hydrolyzing the product of step (c) with dilute acid to remove the acid labile blocking groups and form the above-described product where E is H.