2,3-Dialkyl-4-hydroxy-2-cyclopentenones with differently functionalised side chains yield predominantly all-cis 2,3-dialkyl-1-4,-dihydroxycyclopentanes on catalytichydrogenation. Epimerisation at C-12 (PG numbering) leads to prostaglandin synthons. Influence of the side-chain functions on these reactions is described.