Journal ArticleDOI
Total Syntheses of Amphidinolide T1, T3, T4, and T5
TLDR
It is shown that the inversion of a single and seemingly remote stereocenter (C12) in one of the building blocks not only affects the efficiency and stereochemical outcome of the RCM step but also exerts a significant influence on the course of the acyl-Negishi reaction, allowing a radical manifold to compete with productive cross coupling.Abstract:
A concise, flexible, and high yielding entry into the family of amphidinolide T macrolides, a series of cytotoxic natural products of marine origin, has been developed. All individual members, except amphidinolide T3 (3), derive from compound 39 as a common synthetic intermediate which is formed from three building blocks of similar size and complexity. The fragment coupling steps involve a highly diastereoselective SnCl(4) mediated reaction of the furanosyl sulfone derivative 11 with the silyl enol ether 18 and a palladium-catalyzed Negishi type coupling reaction between the polyfunctional organozinc reagent derived from iodide 32a and the enantiopure acid chloride 24b. The 19-membered macrocyclic ring is then formed by a high yielding ring closing metathesis (RCM) reaction of diene 33 catalyzed by the "second generation" ruthenium carbene complex 34. The efficiency of the RCM transformation stems, to a large extent, from the conformational bias introduced by the syn-syn-configured stereotriad at C12-C14 of the substrate which constitutes a key design element of the synthesis plan. The use of Nysted's reagent 38 in combination with TiCl(4) was required for the olefination of the sterically hindered ketone group in 36, whereas more conventional alkene formations were unsuccessful for this elaboration. Finally, it is shown that the inversion of a single and seemingly remote stereocenter (C12) in one of the building blocks not only affects the efficiency and stereochemical outcome of the RCM step but also exerts a significant influence on the course of the acyl-Negishi reaction, allowing a radical manifold to compete with productive cross coupling.read more
Citations
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Journal ArticleDOI
Marine natural products.
TL;DR: This review covers the literature published in 2014 for marine natural products, with 1116 citations referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms.
Journal ArticleDOI
Palladium-catalyzed cross-coupling reactions in total synthesis.
TL;DR: In this Review, highlights of a number of selected syntheses are discussed, demonstrating the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.
Journal ArticleDOI
Advances in transition metal (Pd, Ni, Fe)-catalyzed cross-coupling reactions using alkyl-organometallics as reaction partners.
Journal ArticleDOI
Metathesis Reactions in Total Synthesis
Kyriacos C. Nicolaou,Kyriacos C. Nicolaou,Paul G. Bulger,Paul G. Bulger,David Sarlah,David Sarlah +5 more
TL;DR: Examples of total syntheses in which metathesis reactions of olefins, enynes, and alkynes played a crucial role and which imparted to these endeavors certain elements of novelty, elegance, and efficiency are highlighted.
Journal ArticleDOI
Stability and reactivity of N-heterocyclic carbene complexes
TL;DR: The use of N-heterocyclic carbenes as ligands for transition metals has increased dramatically in the last few years, spurred on by their remarkable successes in the areas of metathesis chemistry and coupling reactions as discussed by the authors.
References
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BookDOI
Metal-catalyzed cross-coupling reactions
TL;DR: In this paper, the authors present an approach to the formation of C-X (X = N, O, S) bonds in metal-catalyzed cross-coupling reactions.
Journal ArticleDOI
The Preparation and Synthetic Utility of tert-Butyldiphenylsilyl Ethers
TL;DR: The utility of tert-butyldiphenylsilyl chloride as a reagent for the protection of hydroxyl groups was explored in this article, where the corresponding tert-BDPSi ethers have much greater stability to acids, and under...
Journal ArticleDOI
Acceleration of the Dess-Martin Oxidation by Water
TL;DR: The Dess-Martin periodinane (DMP) was used in the synthesis of rapamycin this article, and the resulting DMP was crystalline and completely soluble in CH2Clz and CDC13.
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Direct, regiospecific 2-lithiation of pyridines and pyridine 1-oxides with in situ electrophilic trapping
TL;DR: La lithiation est faite en presence de perfluoroacetone ou de SiClMe 3 : obtention de pyridines et de leur N-oxydes substitues en 2 ou disubstitues in 2,6.
Journal ArticleDOI
Ruthenium Carbene Complexes with Imidazolin-2-ylidene Ligands Allow the Formation of Tetrasubstituted Cycloalkenes by RCM
TL;DR: Ruthenium carbene complexes 2-8 bearing one or two imidazolin-2-ylidene ligands are highly active catalysts for all types of ring closing metathesis reactions (RCM) as mentioned in this paper.