A concise total synthesis of (+/-)-vigulariol.
Explore the source record for details and available documents.
Azo Compounds↗
Biomedical subjects
J Stephen Clark
Publications and source records attributed to J Stephen Clark.
Construction of fused polycyclic ethers by strategies involving ring-closing metathesis.
Large fused polycyclic ether natural products of marine origin are some of the most complex and formidable synthetic targets found in Nature, and they continue to fascinate and inspire those engaged in target-directed synthesis and the development of new synthetic methods. Novel strategies for the rapid and stereoselective assembly of fused polyethers have been devised in which ring-closing metathesis reactions are used to accomplish cyclic ether construction. Two-directional and iterative ring construction approaches involving ring-closing metathesis are being employed to assemble polyether sequences found in marine natural products such as the ciguatoxins and gambieric acids.
Cyclization↗
Tuneable asymmetric copper-catalysed allylic amination and oxidation reactions.
Asymmetric allylic amination or oxidation can be achieved by reaction of an alkene with a peroxycarbamate catalysed by a chiral copper bis-oxazoline complex, and the reaction can be tuned to give either the amination or oxidation product by reagent choice.
Alkenes↗
Rapid two-directional synthesis of the F-J fragment of the gambieric acids by iterative double ring-closing metathesis.
Explore the source record for details and available documents.
Animals↗
Construction of building-blocks for polyether synthesis using sequential catalytic ring-closing enyne and cross metathesis.
Highly functionalised six- and seven-membered cyclic ethers bearing a variety of side chains have been synthesised using ring-closing enyne metathesis and subsequent cross metathesis of the intermediate diene; one-pot enyne and cross metathesis has also been accomplished, allowing ring construction and side chain introduction to be performed in a single operation.
Alkynes↗
Anomalous intramolecular C-H insertion reactions of rhodium carbenoids: factors influencing the reaction course and mechanistic implications.
The intramolecular insertion of rhodium carbenoids into the alpha-C-H bonds of allylic ethers to give 3(2H)-furanones has been explored. Cyclopropanation is favored irrespective of the complex used for carbenoid generation or the substitution pattern of the allylic ether, unless a substituent is placed on the tether connecting the ether to the alpha-diazo ketone. Unusual acetal products resulting from an anomalous C-H insertion process are obtained in addition to the expected 3(2H)-furanones formed by conventional carbenoid C-H insertion. These acetals are the favored C-H insertion products in certain circumstances and particularly in cases where carbenoid generation is effected using an electron-deficient rhodium complex. Experiments with simple deuterium labeled substrates reveal that anomalous C-H insertion products arise by a mechanism that is distinct from that leading to the formation of conventional C-H insertion products. The formation of acetal products and the outcome of reactions performed using deuterium-labeled substrates suggest that a mechanism involving hydride migration to the rhodium center of the carbenoid is operative.
Journal Article↗
A concise and stereoselective synthesis of the A-ring fragment of the gambieric acids.
The A-ring fragment of the gambieric acids has been prepared by a short and efficient route. The key 3(2H)-furanone intermediate has been obtained by [2,3] rearrangement of an allylic oxonium ylide generated from intramolecular reaction of a crotyl ether with a copper carbenoid. A single stereogenic center has been set by using a chiral pool starting material and the other three have been established by using highly diastereoselective substrate-controlled transformations. [reaction--see text]
Ciguatoxins↗
Stereoselective synthesis of tetrahydropyran-3-ones by rearrangement of oxonium ylides generated from metal carbenoids.
The synthesis of tetrahydropyran-3-ones by copper-catalysed reactions of diazo ketone tethered allylic ethers has been explored. Product distribution can be explained by the intermediacy of a free ylide or direct rearrangement of a metal-bound ylide equivalent.
Journal Article↗
Exploration of the biomimetic synthesis of indole-diterpene mycotoxins: an unexpected cascade reaction during the attempted synthesis of emindole SB.
The key step in an attempted biomimetic synthesis of the indole-diterpene mycotoxin emindole SB delivers the pentacyclic compound resulting from 6-endo cyclisation instead of the product arising by the 5-exo reaction required in the putative biosynthetic pathway.
Biomimetics↗
Synthesis of the carbocyclic core of the cornexistins by ring-closing metathesis.
An advanced intermediate in the synthesis of the phytotoxins cornexistin and hydroxycornexistin has been synthesized. Sequential palladium-mediated sp(2)-sp(3) fragment coupling and ring-closing diene metathesis have been used to construct the nine-membered carbocyclic core found in the natural products. [reaction--see text]
Biological Factors↗
Synthesis of novel alpha-substituted and alpha,alpha-disubstituted amino acids by rearrangement of ammonium ylides generated from metal carbenoids.
[reaction: see text] A new and general four-step synthesis of protected alpha-substituted and alpha,alpha-disubstituted amino acids has been developed. The key step involves intramolecular ammonium ylide generation from a copper carbenoid with concomitant [2,3] rearrangement. The aromatic template serves as a tether, protecting group, and activating group for peptide coupling. The ylide rearrangement products can be converted into protected cyclic amino acids by ring-closing metathesis.
Amino Acids↗