Patent ID: 8450477

Claim:
A process for manufacturing a compound of formula (I) which has cis-conformation and wherein R1 represents a 1-phenyl-C 1 -C 4 alkyl or 1-naphthyl-C 1 -C 4 alkyl group, wherein the phenyl or naphthyl moiety of R1 is unsubstituted or substituted with one or more C 1 -C 4 alkoxy groups and the carbon atoms in 2-, 3-, and/or 4-position of the alkyl part of R1 are,independently of the phenyl or naphthyl moiety of R1 and independently of one another, unsubstituted or substituted with C 1 -C 4 alkoxy and/or silyloxy, and R2 represents a C 1 -C 6 alkyl group or an unsubstituted or substituted benzyl group, in which process a compound of formula (II) wherein R3 represents a C 1 -C 6 alkyl group or an unsubstituted or substituted benzyl group, and R1 and R2 have the same meaning as in formula (I); is treated with a base at a temperature of 0° C. or less in a liquid aprotic solvent for a time period sufficient to obtain the compound of formula (I).