Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

A Bronsted base-promoted diastereoselective dimerization of azlactones.

ABSTRACT: A novel Brønsted base system for the diastereoselective dimerization of azlactones using trichloroacetate salts and acetonitrile has been developed. Desired products were obtained in good yields (60-93%) and with up to >19:1 dr after one hour of reaction. Additionally, the relative stereochemistry of the major dimer was assigned as being trans, by X-ray crystallographic analysis. The kinetic reaction profile was determined by using 1H NMR reaction monitoring and revealed a second order overall kinetic profile. Furthermore, by employing this methodology, a diastereoselective total synthesis of a functionalized analogue of streptopyrrolidine was accomplished in 65% overall yield.

SUBMITTER: Pinheiro DLJ

PROVIDER: S-EPMC5753058 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

A Brønsted base-promoted diastereoselective dimerization of azlactones.

Pinheiro Danielle L J DLJ Batista Gabriel M F GMF de Castro Pedro P PP Flores Leonã S LS Andrade Gustavo F S GFS Amarante Giovanni W GW

Beilstein journal of organic chemistry 20171213

A novel Brønsted base system for the diastereoselective dimerization of azlactones using trichloroacetate salts and acetonitrile has been developed. Desired products were obtained in good yields (60-93%) and with up to >19:1 dr after one hour of reaction. Additionally, the relative stereochemistry of the major dimer was assigned as being <i>trans</i>, by X-ray crystallographic analysis. The kinetic reaction profile was determined by using <sup>1</sup>H NMR reaction monitoring and revealed a seco ...[more]

PMID: 29564003

Similar Datasets

Chiral Bronsted base-promoted nitroalkane alkylation: enantioselective synthesis of sec-alkyl-3-substituted indoles.

Project description:A Brønsted base-catalyzed reaction of nitroalkanes with alkyl electrophiles provides indole heterocycles substituted at C3 bearing a sec-alkyl group with good enantioselectivity (up to 90% ee). Denitration by hydrogenolysis provides a product with equally high ee. An indolenine intermediate is implicated in the addition step, and surprisingly, water cosolvent was found to have a beneficial effect in this step, leading to a one-pot protocol for elimination/enantioselective addition using PBAM, a bis(amidine) chiral nonracemic base.

| S-EPMC3005818 | biostudies-literature

Bioinspired Bronsted Acid-Promoted Regioselective Tryptophan Isoprenylations.

Project description:Tryptophan-containing isoprenoid indole alkaloid natural products are well known for their intricate structural architectures and significant biological activities. Nature employs dimethylallyl tryptophan synthases (DMATSs) or aromatic indole prenyltransferases (iPTs) to catalyze regio- and stereoselective prenylation of l-Trp. Regioselective synthetic routes that isoprenylate cyclo-Trp-Trp in a 2,5-diketopiperazine (DKP) core, in a desymmetrizing manner, are nonexistent and are highly desirable. Herein, we present an elaborate report on Brønsted acid-promoted regioselective tryptophan isoprenylation strategy, applicable to both the monomeric amino acid and its dimeric l-Trp DKP. This report outlines a method that regio- and stereoselectively increases sp3 centers of a privileged bioactive core. We report on conditions involving screening of Brønsted acids, their conjugate base as salt, solvent, temperature, and various substrates with diverse side chains. Furthermore, we extensively delineate effects on regio- and stereoselection of isoprenylation and their stereochemical confirmation via NMR experiments. Regioselectively, the C3-position undergoes normal-isoprenylation or benzylation and forms exo-ring-fused pyrroloindolines selectively. Through appropriate prenyl group migrations, we report access to the bioactive tryprostatin alkaloids, and by C3-normal-farnesylation, we access anticancer drimentines as direct targets of this method. The optimized strategy affords iso-tryprostatin B-type products and predrimentine C with 58 and 55% yields, respectively. The current work has several similarities to biosynthesis, such as-reactions can be performed on unprotected substrates, conditions that enable Brønsted acid promotion, and they are easy to perform under ambient conditions, without the need for stoichiometric levels of any transition metal or expensive ligands.

| S-EPMC8153798 | biostudies-literature

Base-catalyzed diastereoselective trimerization of trifluoroacetone.

Project description:Amphiphilic fluorocarbons have unique properties that facilitate their self assembly and adhesion to both inorganic and biological substrates. Incorporation of these moieties into valuable constructs typically require complex synthetic routes that have limited their use. Here, the base-catalyzed diastereoselective synthesis of 6-methyl-2,4,6-tris(trifluoromethyl)tetrahydro-2H-pyran-2,4-diol is reported. Trimerization of trifluoroacetone in the presence of 5 mol% KHMDS delivers one of four diastereomers selectively in 81% yield with no column chromatography. Temperature screening revealed the reversibility of this trimerization and the funneling of material into the most thermodynamically stable oxane. Subsequent functionalization with boronic acids is reported.

| S-EPMC5584686 | biostudies-literature

Cobalt-promoted dimerization of aminoquinoline benzamides.

Project description:A method for aminoquinoline-directed, cobalt-promoted dimerization of benzamides has been developed. Reactions proceed in ethanol solvent in the presence of Mn(OAc)2 cocatalyst and Na2CO3 base and use oxygen as a terminal oxidant. Bromo, iodo, nitro, ether, and ester moieties are compatible with the reaction conditions. Cross-coupling of electronically dissimilar aminoquinoline benzamides proceeds with modest yields and selectivities.

| S-EPMC4352950 | biostudies-literature

Bronsted acid-promoted azide-olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A.

Project description:We report the first study of substrate-controlled diastereoselection in a double [3 + 2] dipolar cycloaddition of benzyl azide with α,β-unsaturated imides. Using a strong Brønsted acid (triflic acid) to activate the electron deficient imide π-bond, high diastereoselection was observed provided that a 1,1,3,3-tetraisopropoxydisiloxanylidene group (TIPDS) is used to restrict the conformation of the central 1,3-anti diol. This development provides a basis for a stereocontrolled approach to the aminopolyol core of (-)-zwittermicin A using a bidirectional synthesis strategy.

| S-EPMC3028999 | biostudies-literature

Bronsted acid-promoted glycosylations of disaccharide glycal substructures of the saccharomicins.

Project description:An acid-promoted glycosylation and alkynol cycloisomerization sequence provided direct access to the 2-deoxytrisaccharide corresponding to the fucose-saccharosamine-digitoxose substructure of saccharomicin B. In the course of this work, the absolute stereochemistry of the repeating fucose-saccharosamine disaccharide of saccharomicins was also confirmed.

| S-EPMC2783931 | biostudies-literature

Enantioselective bromocycloetherification by Lewis base/chiral Bronsted acid cooperative catalysis.

Project description:A binary catalyst system for the enantioselective bromocycloetherification of 5-arylpentenols is described. The combination of an achiral Lewis base and a chiral Brønsted acid affords good enantioselectivities for the cyclization of Z configured 5-arylpentenols to form bromomethyltetrahydrofurans. The constitutional site selectivity is highly dependent upon the aromatic substituent and the configuration of the double bond.

| S-EPMC3238797 | biostudies-literature

Asymmetric cooperative catalysis of strong Bronsted acid-promoted reactions using chiral ureas.

Project description:Cationic organic intermediates participate in a wide variety of useful synthetic transformations, but their high reactivity can render selectivity in competing pathways difficult to control. Here, we describe a strategy for inducing enantioselectivity in reactions of protio-iminium ions, wherein a chiral catalyst interacts with the highly reactive intermediate through a network of noncovalent interactions. This interaction leads to an attenuation of the reactivity of the iminium ion and allows high enantioselectivity in cycloadditions with electron-rich alkenes (the Povarov reaction). A detailed experimental and computational analysis of this catalyst system has revealed the precise nature of the catalyst-substrate interactions and the likely basis for enantioinduction.

| S-EPMC2993568 | biostudies-literature

Bidentate substrate binding in Bronsted acid catalysis: structural space, hydrogen bonding and dimerization.

Project description:BINOL derived chiral phosphoric acids (CPAs) are a prominent class of catalysts in the field of asymmetric organocatalysis, capable of transforming a wide selection of substrates with high stereoselectivities. Exploiting the Brønsted acidic and basic dual functionality of CPAs, substrates with both a hydrogen bond acceptor and donor functionality are frequently used as the resulting bidentate binding via two hydrogen bonds is expected to strongly confine the possible structural space and thus yield high stereoselectivities. Despite the huge success of CPAs and the popularity of a bidentate binding motif, experimental insights into their organization and origin of stereoinduction are scarce. Therefore, in this work the structural space and hydrogen bonding of CPAs and N-(ortho-hydroxyaryl) imines (19 CPA/imine combinations) was elucidated by low temperature NMR studies and corroborated by computations. The postulated bidentate binding of catalyst and substrate by two hydrogen bonds was experimentally validated by detection of trans-hydrogen bond scalar couplings. Counterintuitively, the resulting CPA/imine complexes showed a broad potential structural space and a strong preference towards the formation of [CPA/imine]2 dimers. Molecular dynamics simulations showed that in these dimers, the imines form each one hydrogen bond to two CPA molecules, effectively bridging them. By finetuning steric repulsion and noncovalent interactions, rigid and well-defined CPA/imine monomers could be obtained. NOESY studies corroborated by theoretical calculations revealed the structure of that complex, in which the imine is located in between the 3,3'-substituents of the catalyst and one site of the substrate is shielded by the catalyst, pinpointing the origin or stereoselectivity for downstream transformations.

| S-EPMC9749107 | biostudies-literature

Structure-Activity Relationship Studies of Cyclopropenimines as Enantioselective Bronsted Base Catalysts.

Project description:We recently demonstrated that chiral cyclopropenimines are viable Brønsted base catalysts in enantioselective Michael and Mannich reactions. Herein, we describe a series of structure-activity relationship studies that provide an enhanced understanding of the effectiveness of certain cyclopropenimines as enantioselective Brønsted base catalysts. These studies underscore the crucial importance of dicyclohexylamino substituents in mediating both reaction rate and enantioselectivity. In addition, an unusual catalyst CH···O interaction, which provides both ground state and transition state organization, is discussed. Cyclopropenimine stability studies have led to the identification of new catalysts with greatly improved stability. Finally, additional demonstrations of substrate scope and current limitations are provided herein.

| S-EPMC4618405 | 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