Covering: 2002 to August 2017.This review highlights recent RCM reactions towards the synthesis of sterically congested natural products. It offers an insight into various synthetic targets and approaches and provides information on the evolution of catalysts as powerful tools enabling the use of increasingly challenging diene precursors.

The synthesis of the C1-C27 fragment of hemicalide, a marine metabolite displaying a unique potent antiproliferative activity, has been accomplished. The synthetic approach highlights a remarkably efficient ring-closing metathesis reaction catalyzed by Nolan ruthenium indenylidene complexes to elaborate the highly substituted δ-lactone framework.

A strategy for the assembly of the entire carbon backbone of a stereoisomer of the antitumor marine natural product hemicalide has been investigated. The devised convergent approach relies on Horner–Wadsworth–Emmons and Julia–Kocienski olefination reactions for the construction of the C6=C7 and C34=C35 double bonds, respectively, an aldol reaction to create the C27−C28 bond, and a Suzuki–Miyaura cross‐coupling as the endgame to form the C15−C16 bond.

The development of an intramolecular rhodium(I)-catalyzed Pauson-Khand reaction of alkoxyallene-ynes with a proximal alkoxy group is reported. This reaction, in the presence of a [Rh(cycloocta-1,5-diene)Cl]2/propane-1,3-diylbis(diphenylphosphane) system under a CO atmosphere, constitutes a powerful tool for selectively accessing carbo- and heterobicyclo[5.3.0] frameworks featuring an enol ether moiety. Through this procedure, a straightforward access to guaiane skeletons with a tertiary hydroxy group at the C10 position was achieved.

This review highlights recent innovative synthetic strategies developed for the stereoselective construction of natural complex decalin systems. It offers an insight into various synthetic targets and approaches and provides information for developments within the area of natural products as well as synthetic methodology.

Af ormal [3+ +2] cyclization mediated by silver(I) oxide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is described herein. Through ab road variety of carbonyl compounds, this system can promote cyclization reactions with high yield (up to 85 %) and diastereoselectivity(up to 95:5) for as traightforward access to complex and congestedd ihydrofuran derivatives in one step under mild conditions. Based on DFT studies, the proposed mechanism would involve an allenyl silver intermediate.

Natural products • Multi-step synthesis • Thapsigargin • Titanium(II) complexes • Rhodium(I) complexes.

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