Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Stereocontrolled regeneration of olefins from epoxides.

ABSTRACT: Through treatment with NaI and trifluoroacetic anhydride, which presumably forms trifluoroacetyl iodide in situ, epoxides can be converted to olefins. This reaction now has been shown to tolerate remote olefins without loss of their individual stereochemistry. A reaction sequence involving regiospecific epoxidation of an isoprenoid alcohol, conversion of the alcohol to an azide, and cycloaddition with an acetylene, followed by conversion of the epoxide back to the original olefin, has allowed stereocontrolled preparation of triazole bisphosphonates with a farnesyl or a geranylgeranyl substituent. This strategy may be applicable selective protection of an alkene in other polyolefins, including substrates for metathesis reactions.

SUBMITTER: Wills VS

PROVIDER: S-EPMC4778745 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Stereocontrolled regeneration of olefins from epoxides.

Wills Veronica S VS Zhou Xiang X Allen Cheryl C Holstein Sarah A SA Wiemer David F DF

Tetrahedron letters 20160301 12

Through treatment with NaI and trifluoroacetic anhydride, which presumably forms trifluoroacetyl iodide <i>in situ</i>, epoxides can be converted to olefins. This reaction now has been shown to tolerate remote olefins without loss of their individual stereochemistry. A reaction sequence involving regiospecific epoxidation of an isoprenoid alcohol, conversion of the alcohol to an azide, and cycloaddition with an acetylene, followed by conversion of the epoxide back to the original olefin, has all ...[more]

PMID: 26955189

Similar Datasets

Stereocontrolled synthesis of spiroketals via Ti(Oi-Pr)4-mediated kinetic spirocyclization of glycal epoxides with retention of configuration.

Project description:A Ti(Oi-Pr)4-mediated kinetic spiroketalization reaction has been developed for the stereocontrolled target- and diversity-oriented synthesis of spiroketals. In contrast to most existing methods for spiroketal synthesis, this reaction does not rely upon thermodynamic control over the stereochemical configuration at the anomeric carbon. Stereochemically diverse glycals are first alkylated at the C1-position to introduce a hydroxyl-bearing side chain, then epoxidized stereoselectively. Treatment with Ti(Oi-Pr)4 leads to an unusual kinetic epoxide-opening spirocyclization (spirocycloisomerization) with retention of configuration at the anomeric carbon. The reaction is proposed to proceed via a chelation-controlled mechanism and has been used to form five-, six-, and seven-membered rings with stereochemically diverse substituents. This approach may also be useful for the related intermolecular beta-mannosidation reaction. This Ti(Oi-Pr)4-mediated spirocyclization is stereochemically complementary to our previously reported MeOH-induced spirocyclization, which proceeds with inversion of configuration, and together, these reactions provide comprehensive access to systematically stereochemically diversified spiroketals.

| S-EPMC2553756 | biostudies-literature

Aminodiols via stereocontrolled oxidation of methyleneaziridines.

Project description:A highly diastereoselective Ru-catalyzed oxidation/reduction sequence of bicyclic methyleneaziridines provides a facile route to complex 1-amino-2,3-diol motifs. The relative anti stereochemistry between the amine and the vicinal alcohol are proposed to result from 1,3-bischelation in the transition state by the C1 and C3 heteroatoms.

| S-EPMC3993784 | biostudies-other

Stereocontrolled Synthesis of Kalihinol C.

Project description:We report a concise chemical synthesis of kalihinol C via a possible biosynthetic intermediate, "protokalihinol", which was targeted as a scaffold en route to antiplasmodial analogs. High stereocontrol of the kalihinol framework relies on a heterodendralene cascade to establish the target stereotetrad. Common problems of regio- and chemoselectivity encountered in the kalihinol class are explained and solved.

| S-EPMC5854479 | biostudies-literature

Stereocontrolled Total Synthesis of (-)-Stemaphylline.

Project description:Homologation of readily available ?-boryl pyrrolidines with metal carbenoids is especially challenging even when good leaving groups (Cl- ) are employed. By performing a solvent switch from Et2 O to CHCl3 , efficient 1,2-metalate rearrangement of the intermediate boronate occurs with both halide and ester leaving groups. The methodology was used in the total synthesis of the Stemona alkaloid (-)-stemaphylline in just 11 steps (longest linear sequence), with high stereocontrol (>20:1 d.r.) and 11?% overall yield. The synthesis also features a late-stage lithiation-borylation reaction with a tertiary amine containing carbenoid.

| S-EPMC5484348 | biostudies-literature

Stereocontrolled Synthesis of (+)-Plagiogyrin A.

Project description:Plagiogyrin A (1) was first isolated from the fronds of Plagiogyria matsumureana. Structurally, it features an α-ketoaldehyde functional group in its hemiacetal form, fused in a cis-substituted lactone ring. We have successfully synthesized the skeleton of this natural product by employing a stereocontrolled aldol reaction followed by the installation of the α-ketoaldehyde moiety derived from the mild oxidation of an α-diazoketone. Finally, anhydrous acidic conditions released the protected diol and provided the required cyclized hemiacetal.

| S-EPMC5378675 | biostudies-literature

A stereocontrolled synthesis of (+)-saxitoxin.

Project description:A concise stereoselective total synthesis of (+)-saxitoxin is described. A silver(I)-initiated hydroamination cascade constructs the bicyclic guanidinium ion core from a alkynyl bisguanidine. This sequence creates two C-N bonds, one C-O bond, and three rings and forms a single stereoisomer in a single synthetic transformation. This process enabled us to complete the synthesis of (+)-saxitoxin in 14 steps from N-Boc-l-serine methyl ester.

| S-EPMC3320040 | biostudies-literature

Stereocontrolled α-Galactosylation under Cooperative Catalysis.

Project description:A recent discovery of a cooperative catalysis comprising a silver salt and an acid led to a dramatic improvement in the way glycosyl halides are glycosidated. Excellent yields have been achieved, but the stereoselectivity achieved with 2-O-benzylated donors was poor. Reported herein is our first attempt to refine the stereoselectivity of the cooperatively catalyzed galactosylation reaction. Careful optimization of the reaction conditions along with studying effects of the remote protecting groups led to excellent stereocontrol of α-galactosylation of a variety of glycosyl acceptors with differentially protected galactosyl donors.

| S-EPMC8142852 | biostudies-literature

Calpain inhibition by peptide epoxides.

Project description:A Ca2+-activated cysteine proteinase (calpain II) was purified from chicken gizzard smooth muscle by use of isoelectric precipitation, (NH4)2SO4 fractionation, chromatography on DEAE-Sepharose CL-6B, Reactive-Red 120-agarose and Mono Q. The apparent second-order rate constants for the inactivation of calpain by a series of structural analogues of L-3-carboxy-trans-2, 3-epoxypropionyl-leucylamido-(4-guanidino)butane (E-64) were determined. The fastest rate of inactivation was observed with L-3-carboxy-trans-2, 3-epoxypropionyl-leucylamido-(4-benzyloxy-carbonylamino)buta ne. It was possible to determine the active-site molarity of solutions of calpain by titration with E-64. When incubated with Ca2+, calpain underwent several steps of intermolecular limited proteolysis, via multiple pathways, followed by a slower loss of enzymic activity. The proteolytic steps preceding the loss of activity did not affect the rates of reaction of calpain with E-64 analogues.

| S-EPMC1152644 | biostudies-other

Iridium-catalyzed (Z)-trialkylsilylation of terminal olefins.

Project description:A complex of commercial [Ir(OMe)(cod)](2) and 4,4-di-tert-butyl-2,2-bipyridine (dtbpy) catalyzes the Z-selective, dehydrative silylation of terminal alkenes, but not 1,2-disubstituted alkenes, with triethylsilane or benzyldimethylsilane in THF at 40 degrees C. Yields and Z-stereoselectivity were significantly improved by 2-norbornene, in contrast with other sacrificial alkenes. The reaction is compatible with many functional groups including epoxides, ketones, amides, alcohols, esters, halides, ketals, and silanes. alpha,beta-Unsaturated esters were unreactive. The reaction probably proceeds through a Heck-type mechanism.

| S-EPMC2830331 | biostudies-other

Diastereoselective synthesis of diketopiperazine bis-?,?-epoxides.

Project description:Functionalized diketopiperazines (dioxopiperazines) are an important class of molecules in medicinal chemistry and material science. Herein we report a diastereoselective synthesis of diketopiperazine bis-?,?-epoxides via the oxidation of exocyclic olefins. Although six diastereomers may be formed by this approach, only one or two of them were observed.

| S-EPMC3096722 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

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