AbstractBoth (3R,5S)‐ and (3R,5R)‐gingerdiols were synthesized. Their 1,3‐diol motifs were derived from enantiopure epoxy chiral building blocks that were readily accessible from D‐gluconolactone. The effect of deuterating the OH groups of the natural isomer on its optical rotation was also examined. In the course of the syntheses of the targets, an unexplored cross‐metathesis (CM) reaction of unprotected 5‐substituted pent‐1‐ene‐3,5‐diols was investigated, in which the CM product readily underwent an allylic epimerization and oxidation, as the starting diols rearranged into ketones with unprecedented ease. These problems were eventually resolved by performing the CM reaction in toluene in the presence of phenol. The cause of these unexpected, yet very interesting phenomena, was determined to be the presence of the unprotected OH group at C‐5 of the 5‐substituted pent‐1‐ene‐3,5‐diol. A mechanistic rationale is also presented.