| Abstract
| - The suitably functionalized cyclopentanone derivatives 12, 13, 19, and 37 serve as common precursorsfor the synthesis of various prostaglandins, prostaglandin-1,15-lactones, and unnatural analogues thereof. Allof them contain a 2-butynyl entity which is elaborated into the intact α side chain of the targets either via asequence 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 requiredcyclopentenone substrates via a three-component coupling reaction, (ii) the inherent flexibility which allowsone 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 thetungsten alkylidyne complex (t-BuO)3W⋮CCMe3 or, preferentially, by a catalyst formed in situ from Mo[N(t-Bu)(Ar)]3 and CH2Cl2, the reactivity of which can be fine-tuned by varying the Ar substituent on theamido ligands. These organometallic tools exhibit a remarkable application profile, tolerate an array of polargroups, rigorously distinguish between different π-electron systems, and catalyze the reactions under conditionsthat are sufficiently mild to preserve even highly sensitive functionalities. The structures of the macrocyclicprostaglandin lactone derivatives 22 and 32 were characterized by X-ray crystallography.
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