Browse
Submit Data
Databases
API
Help

Dataset Information

14 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Using Neighboring-Group Participation for Acyclic Stereocontrol in Diastereoselective Substitution Reactions of Acetals.

ABSTRACT: Neighboring-group participation of an ester enabled stereocontrol in substitution reactions of acyclic acetals. The ester group formed a trans-fused dioxolenium ion intermediate, which underwent a substitution reaction at the acetal carbon atom to afford the product with high diastereoselectivity. Neighboring-group participation was confirmed by isolating dioxolane products resulting from nucleophilic addition at C-2 of a 1,3-dioxolenium ion intermediate. Using a pivaloate ester as the participating group in combination with strong nucleophiles produced substitution products with diastereoselectivities of ≥90:10.

SUBMITTER: Ramdular A

PROVIDER: S-EPMC7337985 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Highly diastereoselective Pd-catalyzed carboetherification reactions of acyclic internal alkenes. Stereoselective synthesis of polysubstituted tetrahydrofurans.

Project description:A highly diastereoselective synthesis of substituted tetrahydrofurans bearing stereocenters at C2 and C1' via Pd-catalyzed carboetherification reactions of acyclic internal alkenes is described. Use of an improved catalyst composed of Pd(2)(dba)(3)/S-Phos provides products with up to >20:1 dr. The stereoselective preparation of tetrahydrofurans containing three stereocenters, including a molecule structurally related to simplakidine A, is also reported.

| S-EPMC2837786 | biostudies-literature

Highly Diastereoselective Michael Reactions Using ?-Nitrocarbonyl Nucleophiles.

Project description:We have discovered a highly diastereoselective Michael reaction of ?-substituted, ?-nitrocarbonyl compounds to deliver highly functionalized stereodiads containing fully substituted nitrogen-bearing centers. Good to excellent yields and diastereoselectivities are observed. This transformation is tolerant of various types of carbonyl groups on the nucleophilic partner, as well as a range of unsaturated electrophiles. Mechanistic investigations are consistent with internal hydrogen bonding in the nitroalkane tautomer as the major factor in the control of diastereoselectivity in these transformations.

| S-EPMC4795467 | biostudies-literature

Metal Triflate-Promoted Allylic Substitution Reactions of Cinnamyl Alcohol in the Presence of Orthoesters and Acetals.

Project description:The product distribution of ethers formed from the reaction of cinnamyl alcohol with orthoesters in the presence of indium (III) triflate (InOTf)3 is dependent on both the reaction temperature and catalyst loading. Carrying out the reaction at room temperature under low loadings of the catalyst leads to a facile reaction generating the unexpected secondary allyl ether as the major product. In contrast, carrying out the reaction under higher catalyst loadings at elevated temperatures provides the expected primary linear ether in high yield and with excellent selectivity. The etherification reaction is also effective in the presence of acetals and ketals in place of orthoesters and allows for the development of the procedure to encompass a telescoped etherification protocol in which the acetal is generated in situ.

| S-EPMC6776978 | biostudies-literature

Does neighboring group participation by non-vicinal esters play a role in glycosylation reactions? Effective probes for the detection of bridging intermediates.

Project description:Neighboring group participation in glycopyranosylation reactions is probed for esters at the 3-O-axial and -equatorial, 4-O-axial and -equatorial, and 6-O-sites of a range of donors through the use tert-butoxycarbonyl esters. The anticipated intermediate cyclic dioxanyl cation is interrupted for the axial 3-O-derivative, leading to the formation of a 1,3-O-cyclic carbonate ester, with loss of a tert-butyl cation, providing convincing evidence of participation by esters at that position. However, no evidence was found for such a fragmentation of carbonate esters at the 3-O-equatorial, 4-O-axial and -equatorial, and 6-O positions, indicating that neighboring group participation from those sites does not occur under typical glycosylation conditions. Further probes employing a 4-O-(2-carboxy)benzoate ester and a 4-O-(4-methoxybenzoate) ester, the latter in conjunction with an (18)O quench designed to detect bridging intermediates, also failed to provide evidence for participation by 4-O-esters in galactopyranosylation.

| S-EPMC2669227 | biostudies-literature

Neighboring group participation in the transition state of human purine nucleoside phosphorylase.

Project description:The X-ray crystal structures of human purine nucleoside phosphorylase (PNP) with bound inosine or transition-state analogues show His257 within hydrogen bonding distance of the 5'-hydroxyl. The mutants His257Phe, His257Gly, and His257Asp exhibited greatly decreased affinity for Immucillin-H (ImmH), binding this mimic of an early transition state as much as 370-fold (Km/Ki) less tightly than native PNP. In contrast, these mutants bound DADMe-ImmH, a mimic of a late transition state, nearly as well as the native enzyme. These results indicate that His257 serves an important role in the early stages of transition-state formation. Whereas mutation of His257 resulted in little variation in the PNP x DADMe-ImmH x SO4 structures, His257Phe x ImmH x PO4 showed distortion at the 5'-hydroxyl, indicating the importance of H-bonding in positioning this group during progression to the transition state. Binding isotope effect (BIE) and kinetic isotope effect (KIE) studies of the remote 5'-(3)H for the arsenolysis of inosine with native PNP revealed a BIE of 1.5% and an unexpectedly large intrinsic KIE of 4.6%. This result is interpreted as a moderate electronic distortion toward the transition state in the Michaelis complex with continued development of a similar distortion at the transition state. The mutants His257Phe, His257Gly, and His257Asp altered the 5'-(3)H intrinsic KIE to -3, -14, and 7%, respectively, while the BIEs contributed 2, 2, and -2%, respectively. These surprising results establish that forces in the Michaelis complex, reported by the BIEs, can be reversed or enhanced at the transition state.

| S-EPMC2526054 | biostudies-literature

Catalytic diastereoselective petasis reactions.

Project description:Multicomponent Petasis reactions: the first diastereoselective Petasis reaction catalyzed by chiral biphenols that enables the synthesis of syn and anti ?-amino alcohols in pure form has been developed. The reaction exploits a multicomponent approach that involves boronates, ?-hydroxy aldehydes, and amines.

| S-EPMC4673970 | biostudies-literature

Participation of alkoxy groups in reactions of acetals: violation of the reactivity/selectivity principle in a Curtin-Hammett kinetic scenario.

Project description:Nucleophilic substitution reactions of acetals having benzyloxy groups four carbon atoms away can be highly diastereoselective. The selectivity in several cases increased as the reactivity of the nucleophile increased, in violation of the reactivity/selectivity principle. The increase in selectivity with reactivity suggests that multiple conformational isomers of reactive intermediates can give rise to the products.

| S-EPMC4702254 | biostudies-literature

Stereocontrolled glycoside and glycosyl ester synthesis. neighboring group participation and hydrogenolysis of 3-(2'-benzyloxyphenyl)-3,3-dimethylpropanoates.

Project description:[reaction: see text] The 2-O-[3-(2'-benzyloxyphenyl)-3,3-dimethylpropanoate] and 2-O-[3-(2'-benzyloxy-4',6'-dimethylphenyl)-3,3-dimethylpropanoate] esters enable the synthesis of a range of beta-glucosides and alpha-mannosides through neighboring participation in excellent yield, and are removed by hydrogenolysis in concert with the cleavage of benzyl esters in the presence of other esters making them particularly well suited to the stereocontrolled synthesis of glycosyl esters.

| S-EPMC2615466 | biostudies-literature

Iridium-Catalyzed Diastereoselective and Enantioselective Allylic Substitutions with Acyclic ?-Alkoxy Ketones.

Project description:The asymmetric alkylation of acyclic ketones is a longstanding challenge in organic synthesis. Reported herein are diastereoselective and enantioselective allylic substitutions with acyclic ?-alkoxy ketones catalyzed by a metallacyclic iridium complex to form products with contiguous stereogenic centers derived from the nucleophile and electrophile. These reactions occur between allyl methyl carbonates and unstabilized copper(I) enolates generated in?situ from acyclic ?-alkoxy ketones. The resulting products can be readily converted into enantioenriched tertiary alcohols and tetrahydrofuran derivatives without erosion of enantiomeric purity.

| S-EPMC4969080 | biostudies-literature

Diastereoselective Prins-type reaction of cycloalkenylcyclopropanol silyl ethers and alpha,beta-unsaturated aldehyde acetals.

Project description:Electrophilic addition of 1-(1-cyclohexenyl)-1-cyclopropanol trimethylsilyl ether to alpha,beta-unsaturated aldehyde acetals under Lewis acidic conditions proceeds with good to excellent diastereoselectivity to afford spirocyclobutanones containing three contiguous stereocenters. A convenient entry to enantioselective syntheses is available by use of a nonracemic C2-symmetric acetal. Elaboration of the resulting adducts provides ready access to medium-sized carbocycles.

| S-EPMC2597285 | 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