Naturalproductman’s Blog

Hey, is that a natural product?!

Archive for June, 2009

An Elegant Approach for Piperidones

Posted by naturalproductman on June 30, 2009

Leon Ghosez and co-workers at CNRS in France has recently published in the ACIEE on a four component reaction to make piperidone ring systems.  It involves making an aza-diene that undergoes a Diels-Alder with an alpha-beta unsaturated carbonyl component for a total of five reactions in one flask!

multi-component

ACIEE paper

Posted in Cascade Reactions, Cycloaddition, Methodology, Multi-Component Coupling, Ring forming | Leave a Comment »

Enantioselective Biginelli Reaction

Posted by naturalproductman on June 30, 2009

Hee-Yoon Lee at KAIST has recently published in the European Journal of Organic Chemistry on a proline ester salt catalyzed asymmetric Biginelli reaction, which involves the coupling of an aryl aldehyde, urea, and a beta-ketoester to form a 3,4-dihydropyrimidin-2(1H)-one
(DHPM).  They used a t-butoxy proline ester (20 mol%) for optimal enantioselectivity (71:29).

biginelli reaction

European Journal of Organic Chemistry paper

Posted in Cascade Reactions, Mechanistic, Methodology, Multi-Component Coupling, Organocatalytic | 1 Comment »

A New Multicomponent Reaction

Posted by naturalproductman on June 29, 2009

Jie Wu et. al at Fudan University in China has recently published in Tetrahedron Letters on a nice multi-component cascade reaction between a bromobenzaldehyde, alkyne, diethyl phosphite and a primary amine in the presence of Pd(PPh3)2Cl2 and Cu(OTf)2 to form a 1,2-dihydroisoquinoline substrate.  The transformation involves a Sonogashira coupling followed by condensation with the amine and electrophilic cyclization.  Diethyl phosphite would nucleophilically add to the resultant intermediate to give the final product.

multicomponent

TL paper

Posted in Cascade Reactions, Methodology, Multi-Component Coupling, Ring forming, Transition Metal | Leave a Comment »

Erythrophlesins

Posted by naturalproductman on June 29, 2009

Masami Ishibashi and co-workers from Chiba University has recently published in Tetrahedron Letters on the isolation of erythrophlesins from Erythrophleum succirubrum.  The authors did some cell viability assays with and without TRAIL (Tumor necrosis factor (TNF)-related apoptosis-inducing ligand) against human gastric adenocarcinoma (AGS) cell lines in the presence of the isolated dimers.  At 10 micromlar concentration of the dimers, they noticed a significant drop (25% to 37%) in cell viability when they compared the cases with and without TRAIL.

cassain dimer

TL paper

Posted in Diterpenoids | Leave a Comment »

C-H Oxidation

Posted by naturalproductman on June 27, 2009

Miquel Costas and Xavi Ribas et al at the Universitat de Girona in Spain has recently published in ACIEE on a iron-catalyzed (1 mol%) aliphatic C-H oxidation of alkanes using hydrogen peroxide as the oxidant.  What’s notable is that these Fe catalyzed oxidations can be found in nature (ie:  cytochrome P450’s) and I wouldn’t be surprised if they were originally inspired to use iron because of iron’s occurence in nature.

fe catalysis

ACIEE paper

Posted in C-H activation, Methodology, Transition Metal | 2 Comments »

A Gold Cyclization

Posted by naturalproductman on June 27, 2009

Hashmi and co-workers at Ruprecht-Karls-Universität Heidelberg in Germany have recently published on a nice intramolecular cyclization between a furan and an alkynyl aryl ether using a gold catalyst.

cyclization

ACIEE paper

Posted in Cascade Reactions, Cycloaddition, Mechanistic, Methodology, Ring forming, Transition Metal | Leave a Comment »

[2+2+2] Cycloaddition

Posted by naturalproductman on June 26, 2009

Zuowei Xie at the Chinese University of Hong Kong has recently published in ACIEE on a Ni-catalyzed [2+2+2] cycloaddition reaction that involves the coupling of a 1,2-substituted alkyne, alpha,beta-unsaturated ester and a benzyne. Something interesting to note is when an unsymmetrical alkyne was used – phenyl,ethyl – this cycloaddition was regioselective.

2+2+2

ACIEE paper

Posted in Cascade Reactions, Cycloaddition, Methodology, Multi-Component Coupling, Transition Metal | Leave a Comment »

Bistramide

Posted by naturalproductman on June 26, 2009

David Kingston at Virginia Tech has recently published in the Journal of Natural Products on the isolation of some new anti-ovarian cancer amides, 3-oxo-bistramide K and bistramide A, from the tunicate Trididemnum cyclops.

bistramide

JNP paper

Posted in Spiroketals, Tetrahydropyran | Leave a Comment »

Total Synthesis of Himandrine

Posted by naturalproductman on June 25, 2009

Mohammad Movassaghi from MIT has recently published a three paged communication in JACS on the total synthesis of himandrine.  A key highlight of the synthesis includes an intramolecular Diels-Alder with a four-membered enamide-lactam (2-azetidinone group)  substituted on the diene in order to favor the s-cis conformation and also mask the resultant ketone in the natural product.  If you’ve seen his previous synthesis of galbulimima alkaloid GB-13, then you’ll notice that some of the reactions are remniscent of that synthesis.  This molecule is really cool and has good history with Lew Mander being one of the pioneers in the process of discovering this molecule.

himandrine

Did anybody else ever think that Professor Mander looks a little like Professor Larry Overman?  Maybe it’s kind of like how GB-13 looks like himandrine.
larry overman

vs.

Lewis Mander

JACS paper

Posted in Alkaloids | 4 Comments »

Mannich-Hydroamination Cascade

Posted by naturalproductman on June 25, 2009

Darren Dixon (University of Oxford) and Peng-Fei Xu (Lanzhou University) has recently published in Chemical Communications on a Mannich-hydroamination reactioncatalyzed by copper triflate.  This transformation is better in terms of efficiency/convergency compared to the intramolecular hydroaminations explored by other people out there.

cascade

Chem Comm paper

Posted in Cascade Reactions, Methodology, Ring forming, Transition Metal | Leave a Comment »

 
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