Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Rhodium-catalyzed endo-selective epoxide-opening cascades: formal synthesis of (-)-brevisin.

ABSTRACT: [Rh(CO)2Cl]2 is as an effective catalyst for endo-selective cyclizations and cascades of epoxy-(E)-enoate alcohols, thus enabling the synthesis of oxepanes and oxepane-containing polyethers from di- and trisubstituted epoxides. Syntheses of the ABC and EF ring systems of (-)-brevisin via all endo-diepoxide-opening cascades using this method constitute a formal total synthesis and demonstrate the utility of this methodology in the context of the synthesis of marine ladder polyether natural products.

SUBMITTER: Armbrust KW

PROVIDER: S-EPMC4586266 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Rhodium-catalyzed endo-selective epoxide-opening cascades: formal synthesis of (-)-brevisin.

Armbrust Kurt W KW Beaver Matthew G MG Jamison Timothy F TF

Journal of the American Chemical Society 20150518 21

[Rh(CO)2Cl]2 is as an effective catalyst for endo-selective cyclizations and cascades of epoxy-(E)-enoate alcohols, thus enabling the synthesis of oxepanes and oxepane-containing polyethers from di- and trisubstituted epoxides. Syntheses of the ABC and EF ring systems of (-)-brevisin via all endo-diepoxide-opening cascades using this method constitute a formal total synthesis and demonstrate the utility of this methodology in the context of the synthesis of marine ladder polyether natural produc ...[more]

PMID: 25984951

Similar Datasets

Epoxide-opening cascades promoted by water.

Project description:Selectivity rules in organic chemistry have been inferred largely from nonaqueous environments. In contrast, enzymes operate in water, and the chemical effect of the medium change remains only partially understood. Structural characterization of the "ladder" polyether marine natural products raised a puzzle that persisted for 20 years: Although the stereochemistry of adjacent tetrahydropyran (THP) cycles would seem to arise from a biosynthetic cascade of epoxide-opening reactions, experience in organic solvents argued consistently that such a pathway would be kinetically disfavored. We report that neutral water acts as an optimal promoter for the requisite ring-opening selectivity, once a single templating THP is appended to a chain of epoxides. This strategy offers a high-yielding route to the naturally occurring ladder core and highlights the likely importance of aqueous-medium effects in underpinning certain noteworthy enzymatic selectivities.

| S-EPMC2810534 | biostudies-literature

Ladder polyether synthesis via epoxide-opening cascades directed by a disappearing trimethylsilyl group.

Project description:Epoxide-opening cascades offer the potential to construct complex polyether natural products expeditiously and in a manner that emulates the biogenesis proposed for these compounds. Herein we provide a full account of our development of a strategy that addresses several important challenges of such cascades. The centerpiece of the method is a trimethylsilyl (SiMe(3)) group that serves several purposes and leaves no trace of itself by the time the cascade has come to an end. The main function of the SiMe(3) group is to dictate the regioselectivity of epoxide opening. This strategy is the only general method of effecting endo-selective cascades under basic conditions.

| S-EPMC3018858 | biostudies-literature

Water overcomes methyl group directing effects in epoxide-opening cascades.

Project description:Water is an effective promoter of the endo-selective opening of trisubstituted epoxides, enabling related cascades leading to a variety of substituted ladder polyether structures. When used in conjunction with a tetrahydropyran-templated nucleophile, water can overcome the powerful electronic directing effect of a methyl substituent at either site of the epoxide, making water a uniquely versatile medium and promoter of epoxide opening.

| S-EPMC2803343 | biostudies-literature

Evidence that epoxide-opening cascades promoted by water are stepwise and become faster and more selective after the first cyclization.

Project description:A detailed kinetic study of the endo-selective epoxide-opening cascade reaction of a diepoxy alcohol in neutral water was undertaken using (1)H NMR spectroscopy. The observation of monoepoxide intermediates resulting from initial endo and exo cyclization indicated that the cascade proceeds via a stepwise mechanism rather than through a concerted one. Independent synthesis and cyclization of these monoepoxide intermediates demonstrated that they are chemically and kinetically competent intermediates in the cascade. Analysis of each step of the reaction revealed that both the rate and regioselectivity of cyclization improve as the cascade reaction proceeds. In the second step, cyclization of an epoxy alcohol substrate templated by a fused diad of two tetrahydropyran rings proceeds with exceptionally high regioselectivity (endo:exo = 19:1), the highest we have measured in the opening of a simple trans-disubstituted epoxide. The origins of these observations are discussed.

| S-EPMC3084897 | biostudies-literature

Synthesis of cananodine by intramolecular epoxide opening.

Project description:Cananodine is a guaipyridine alkaloid with activity against liver cancer. Cananodine was synthesized using a remarkable intramolecular opening of a trisubstituted epoxide as the key step in construction of the seven-membered carbocycle of the target. The epoxide opening strategy allows all four stereoisomers of cananodine to be prepared.

| S-EPMC5722248 | biostudies-other

Endo-selective Pd-catalyzed silyl methyl Heck reaction.

Project description:A palladium (Pd)-catalyzed endo-selective Heck reaction of iodomethylsilyl ethers of phenols and aliphatic alkenols has been developed. Mechanistic studies reveal that this silyl methyl Heck reaction operates via a hybrid Pd-radical process and that the silicon atom is crucial for the observed endo selectivity. The obtained allylic silyloxycycles were further oxidized into (Z)-alkenyldiols.

| S-EPMC4291758 | biostudies-literature

Rhodium-catalyzed, P-directed selective C7 arylation of indoles.

Project description:The indole scaffold will continue to play a vital role in the future of drug discovery and agrochemical development. Regioselective direct arylation of indoles on the benzenoid moiety is a challenging task due to the inherent reactivity of the C2 and C3 positions. Here, we have developed an effective strategy for the regioselective direct arylation of indoles at the C7 position with (hetero)aryl bromides by the rational design of a directing group. The key to the high selectivity and reactivity of this method is the appropriate selection of a class of directing groups, N-PR2 (R = t Bu and c Hex), that are easily removed in the presence of the Wilkinson's catalyst. Using the present method as a key step, formal synthesis of marine alkaloid dictyodendrin B has also been demonstrated.

| S-EPMC6294599 | biostudies-literature

Iron-Catalyzed Reactions of 2-Pyridone Derivatives: 1,6-Addition and Formal Ring Opening/Cross Coupling.

Project description:In the presence of simple iron salts, 2-pyridone derivatives react with Grignard reagents under mild conditions to give the corresponding 1,6-addition products; if the reaction medium is supplemented with an aprotic dipolar cosolvent after the actual addition step, the intermediates primarily formed succumb to ring opening, giving rise to non-thermodynamic Z,E-configured dienoic acid amide derivatives which are difficult to make otherwise. Control experiments as well as the isolation and crystallographic characterization of a (tricarbonyl)iron pyridone complex suggest that the active iron catalyst generated in situ exhibits high affinity to the polarized diene system embedded into the heterocyclic ring system of the substrates, which likely serves as the actual recognition element.

| S-EPMC7687238 | biostudies-literature

Rhodium-NHC-Catalyzed gem-Specific O-Selective Hydropyridonation of Terminal Alkynes.

Project description:The dinuclear complex [Rh(μ-Cl)(η2 -coe)(IPr)]2 is an efficient catalyst for the O-selective Markovnikov-type addition of 2-pyridones to terminal alkynes. DFT calculations support a hydride-free pathway entailing intramolecular oxidative protonation of a π-alkyne by a κ1 N-hydroxypyridine ligand. Subsequent O-nucleophilic attack on a metallacyclopropene species affords an O-alkenyl-2-oxypyridine chelate rhodium intermediate as the catalyst resting state. The release of the alkenyl ether is calculated as the rate-determining step.

| S-EPMC9311084 | biostudies-literature

Total synthesis of ent-dioxepandehydrothyrsiferol via a bromonium-initiated epoxide-opening cascade.

Project description:In the first total synthesis of ent-dioxepandehydrothyrsiferol, the signature trans-anti-trans 7,7,6-fused tricyclic polyether framework was constructed in a single bromonium-initiated epoxide-opening cascade that incorporates both endo- and exo-selective epoxide openings, each directed by the substitution pattern of the epoxide (methyl groups). This study thus demonstrates the feasibility of a possible biogenesis.

| S-EPMC2760255 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data