Qxtension with the anion derived from his (2, 2, 2-trifluoroethyl)(methoxycarhonylmethyl)- phosphonate at-78 C afforded exclusively lo (Z)-a, B-unsaturated ester (6). In order to avoid or binimize any possible racemization of the chiral centre, the aldehyde (5) was used immediate-'ly, without purification, for the olefination step. Our strategy required that the olefination product (5) have the desired (Z) geometry of the double dond for the ...