Process for the preparation of 7-substituted-hept-6-enoic and -heptanoic acids and derivatives thereof.

Compounds of formula Iare disclosedwhereinXis -CH₂CH₂- or -CH=CH;R₁is an ester group inert to the reaction conditions; andRis an organic radical having groups which are inert under reducing conditions, with the proviso that, when R is triphenylmethyl, then R₁ additionally includes allyl and X is -OCH₂-or the free acid or a salt form or a further ester form or the δ-lactone, i.e. internal ester form thereof, in a state of purity such that the proportion of erythro to threo isomer is 99:1 : 0.9 or higher.