Fatty acids: XXII partial synthesis of racemic helenynolic acid from crepenynic acid by a possible biosynthetic route and the discovery ofcis‐9,10‐epoxyoctadec‐12‐ynoic acid inHelichrysum bracteatum seed oil

Racemic helenynolic acid has been prepared from crepenynic acid by epoxidation followed by base‐catalyzed rearrangement. This may be the pathway by which helenynolic acid is produced inHelichrysum bracteatum seed oil from the crepenynic acid also present. A reinvestigation of the epoxy acids in this oil has shown thatcis‐9,10‐epoxyoctadec‐12‐ynoic acid accompanies the coronaric acid previously identified.