Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

A torquoselective 6? electrocyclization approach to reserpine alkaloids.

ABSTRACT: A highly torquoselective thermal triene 6? electrocyclization controls the relative stereochemistry between the C3 and C18 stereocenters of the dodecahydroindolo[2,3-a]benzo[g]quinolizine skeleton of reserpine-type alkaloids. Employing a tandem cross-coupling/electrocyclization protocol allowed us to form the requisite triene and ensure its subsequent cyclization. A novel low-temperature dibromoketene acetal Claisen rearrangement established the requisite exocyclic dienylbromide precursor for the palladium-catalyzed cross-coupling reaction.

SUBMITTER: Barcan GA

PROVIDER: S-EPMC3488149 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

A torquoselective 6π electrocyclization approach to reserpine alkaloids.

Barcan Gregg A GA Patel Ashay A Houk K N KN Kwon Ohyun O

Organic letters 20121005 21

A highly torquoselective thermal triene 6π electrocyclization controls the relative stereochemistry between the C3 and C18 stereocenters of the dodecahydroindolo[2,3-a]benzo[g]quinolizine skeleton of reserpine-type alkaloids. Employing a tandem cross-coupling/electrocyclization protocol allowed us to form the requisite triene and ensure its subsequent cyclization. A novel low-temperature dibromoketene acetal Claisen rearrangement established the requisite exocyclic dienylbromide precursor for th ...[more]

PMID: 23039026

Similar Datasets

Synthesis of ent-ketorfanol via a C-H alkenylation/torquoselective 6? electrocyclization cascade.

Project description:The asymmetric synthesis of ent-ketorfanol from simple and commercially available precursors is reported. A Rh(I) -catalyzed intramolecular C?H alkenylation/torquoselective 6??electrocyclization cascade provides a fused bicyclic 1,2-dihydropyridine as a key intermediate. Computational studies were performed to understand the high torquoselectivity of the key 6??electrocyclization. The computational results demonstrate that a conformational effect is responsible for the observed selectivity. The ketone functionality and final ring are introduced in a single step by a redox-neutral acid-catalyzed rearrangement of a vicinal diol to give the requisite carbonyl, followed by intramolecular Friedel-Crafts alkylation.

| S-EPMC4676713 | biostudies-literature

Ajmalicine and Reserpine: Indole Alkaloids as Multi-Target Directed Ligands Towards Factors Implicated in Alzheimer's Disease.

Project description:Alzheimer's disease (AD) is a multifactorial disorder characterized by exponential loss of memory and cognitive deficit involving several disease modifying targets (amyloid beta, beta-secretase, monoaminoxidase-B, and cholinesterase). The present study explores multi-target directed ligand approach using secondary metabolite reserpine (RES) and ajmalicine (AJM) obtained from Rauwolfia serpentina roots. Novel LCMS and HPLC methods were developed for identification and quantification of reserpine and ajmalicine. In vitro enzyme inhibition assays were performed to evaluate anti-cholinesterase, ?-site amyloid cleaving enzyme (BACE-1) inhibition and monoamine oxidase-B (MAO-B) inhibition, further analyzed with in silico analysis. Anti-amyloidogenic potential was studied using anti-aggregation studies along with TEM and circular dichroism (CD) analysis. In vitro neuroprotective potential against A? toxicity and anti-oxidative stress was demonstrated using PC12 cell cultures. Reserpine is a more potent dual cholinesterase inhibitor than ajmalicine (IC50 values of 1.7 ?M (AChE) and 2.8 ?M (BuChE)). The anti-aggregation activity of reserpine (68%) was more than ajmalicine (56%). Both compounds demonstrated neuroprotective activity against A?42 (92%) and H2O2 (93%) induced toxicity in PC12 cells against controls. Phytocompounds also inhibited MAO-B and BACE-1 enzymes in concentration dependent manner. Molecular docking studies indicated the strong binding of compounds to the catalytic site of targets. This novel study demonstrated that reserpine and ajmalicine as a multi-target directed ligand that have disease modifying potential for amelioration of AD.

| S-EPMC7180484 | biostudies-literature

An OMIC approach to elaborate the antibacterial mechanisms of different alkaloids

Project description:In the current study, RNA sequencing was used to comparatively elaborate the activities and the effects of the alkaloids, boldine, bulbocapnine, and roemerine along with the well-known antibacterial alkaloid berberine on Bacillus subtilis cells.

2018-07-17 | GSE104946 | GEO

Enantioselective total synthesis of (+)-reserpine.

Project description:A catalytic, enantioselective synthesis of (+)-reserpine is reported. The route features a highly diastereoselective, chiral catalyst-controlled formal aza-Diels-Alder reaction between a 6-methoxytryptamine-derived dihydro-β-carboline and an enantioenriched α-substituted enone to form a key tetracyclic intermediate. This approach addresses the challenge of setting the C3 stereogenic center by using catalyst control. Elaboration of the tetracycle to (+)-reserpine includes an intramolecular aldol cyclization and a highly diastereoselective hydrogenation of a sterically hindered enoate.

| S-EPMC3578295 | biostudies-literature

Origins of 1,6-stereoinduction in torquoselective 6? electrocyclizations.

Project description:A novel stereoselective electrocyclization developed for the total synthesis of reserpine has been explored by both experiment and theory. A stereocenter six atoms away from the newly forming chiral center is responsible for the diastereoselectivity of the ring closure. This stereogenic center, lying at the junction of two six-membered rings, defines the conformation of the substrates' fused ring skeleton that ultimately distinguishes between the two allowed, disrotatory triene geometries at the transition state. The presence of allylic strain in the disfavored transition state results in a torquoselective ring closure (dr up to 15.7:1).

| S-EPMC3632451 | biostudies-literature

Direct methoxypyridine functionalization approach to magellanine-type Lycopodium alkaloids.

Project description:A concise enantioselective approach to the tetracyclic core of the magellanine-type Lycopodium alkaloids is reported. Key to this approach is the use of the Hajos-Parrish reaction to set a challenging quaternary stereocenter, thereby guiding the stereoselectivity for the remainder of the synthesis, as well as the use of a palladium-mediated direct pyridine functionalization reaction to forge the tetracyclic core.

| S-EPMC3262889 | biostudies-literature

A Concise, Enantioselective Approach for the Synthesis of Yohimbine Alkaloids.

Project description:We report a concise, enantioselective synthesis of the yohimbine alkaloids (-)-rauwolscine and (-)-alloyohimbane. The key transformation involves a highly enantio- and diastereoselective NHC-catalyzed dimerization and an amidation/N-acyliminium ion cyclization sequence to furnish four of the five requisite rings and three of the five stereocenters in two operations. This route also provides efficient access to all four diastereomeric arrangements of the core stereotriad of the yohimbine alkaloids from a common intermediate. This platform approach in combination with the ability to access both enantiomers from the carbene-catalyzed reaction is a powerful strategy that can produce a wide range of complex alkaloids and related structures for future biomedical investigations.

| S-EPMC7185878 | biostudies-literature

Interrupted Fischer indolization approach toward the communesin alkaloids and perophoramidine.

Project description:A concise approach toward the total synthesis of the communesin alkaloids and perophoramidine is reported. The strategy relies on the use of the interrupted Fischer indolization to build the tetracyclic indoline core of the natural products. Studies to probe the scope and limitations of this plan are presented. Although the methodology does not tolerate a C8-allyl substituent en route to the challenging vicinal quaternary stereocenters, variation at C7 and on the C ring is permitted.

| S-EPMC3445034 | biostudies-literature

A tandem 1,3-H-shift-6π-electrocyclization-cyclic 2-amido-diene intramolecular Diels-Alder cycloaddition approach to BCD-Ring of atropurpuran.

Project description:An approach toward the BCD-ring of atropurpuran via a sequence of allenic 1,3-H shift, 6π-electron pericyclic ring closure, and intramolecular Diels-Alder cycloaddition of cyclic 2-amidodiene is described.

| S-EPMC3253247 | biostudies-literature

Photoinduced Changes in Aromaticity Facilitate Electrocyclization of Dithienylbenzene Switches.

Project description:The concepts of excited-state aromaticity and antiaromaticity have in recent years with increasing frequency been invoked to rationalize the photochemistry of cyclic conjugated organic compounds, with the long-term goal of using these concepts to improve the reactivities of such compounds toward different photochemical transformations. In this regard, it is of particular interest to assess how the presence of a benzene motif affects photochemical reactivity, as benzene is well-known to completely change its aromatic character in its lowest excited states. Here, we investigate how a benzene motif influences the photoinduced electrocyclization of dithienylethenes, a major class of molecular switches. Specifically, we report on the synthesis of a dithienylbenzene switch where the typical nonaromatic, ethene-like motif bridging the two thienyl units is replaced by a benzene motif, and show that this compound undergoes electrocyclization upon irradiation with UV-light. Furthermore, through a detailed quantum chemical analysis, we demonstrate that the electrocyclization is driven jointly and synergistically by the loss of aromaticity in this motif from the formation of a reactive, antiaromatic excited state during the initial photoexcitation, and by the subsequent relief of this antiaromaticity as the reaction progresses from the Franck-Condon region. Overall, we conclude that photoinduced changes in aromaticity facilitate the electrocyclization of dithienylbenzene switches.

| S-EPMC7458422 | 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