The suitably functionalized cyclopentanone derivatives 12, 13, 19, and 37 serve as common precursors for the synthesis of various prostaglandins, prostaglandin-1,15-lactones, and unnatural analogues thereof. All of them contain a 2-butynyl entity which is elaborated into the intact aside chain of the targets either via a sequence comprising ring closing alkyne metathesis/Lindlar reduction or via alkyne cross metathesis (ACM)/ Lindlar reduction. These novel approaches are distinguished by (i) the ready accessibility of the required cyclopentenone substrates via a three-component coupling reaction, (ii) the inherent flexibility which allows one to make a series of analogues starting from these common platforms, (iii) a small number of steps, and (iv) an excellent overall yield. The key alkyne metathesis reactions are efficiently catalyzed either by the tungsten alkylidyne complex (t-BuO)(3)W drop CCMe3 or, preferentially, by a catalyst formed in situ from Mo[hT(t-Bu)(Ar)]3 and CH2Cl2, the reactivity of which can be fine-tuned by varying the Ar substituent on the amido ligands. These organometallic tools exhibit a remarkable application profile, tolerate an array of polar groups, rigorously distinguish between different ct-electron systems, and catalyze the reactions under conditions that are sufficiently: mild to preserve even highly sensitive functionalities. The structures of the macrocyclic prostaglandin lactone derivatives 22 and 32 were characterized by-X-ray crystallography.