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Archive for the ‘Mechanistic’ Category

The enamine is formed through an oxazolidinone intermediate

Posted by naturalproductman on February 4, 2016

When I think of organocatalysis, I usually think of a carbonyl compound forming an enamine intermediate, which in turn attacks an electrophile. The enamine is usually formed when the carbonyl compound reacts with a proline-derived catalyst. By using Gaussian and experimental KIE calculations, Matthew Vetticatt and co-workers at Binghamton University reported in JACS on the way that the enamine compound is formed: through an oxazolidinone intermediate.

oxazolidinone

JACS paper

 

A review article on determining the transition state structures based on KIEs.

Posted in Computational, Isotope effects, Mechanistic | Leave a Comment »

2 Reagents, 2 mechanisms, same product

Posted by naturalproductman on January 28, 2016

Srinivasan Chandrasekaran and colleague at the Indian Institute of Science have reported in Tetrahedron on a mechanistically interesting transformation involving a geminal aminooxygenation of a vinyl arene. Two different reaction conditions were identified: one with m-CPBA, the other with a hypervalent iodine reagent. The former underwent a deuterium shift on the gem-dideuterated-styrene starting material and the latter does not.

01.28.2016 naturalproductman.gif

Tetrahedron paper

Posted in Cascade Reactions, Hypervalent Iodine, Mechanistic, Methodology | Leave a Comment »

JOC papers of interest 11/24/2015

Posted by naturalproductman on November 24, 2015

James White and co-workers reported on the synthesis of Huperzine A.

Christopher Marvin and co-workers from Hendrix College reported in JOC on the synthesis of tetrabenazine through a photoredox reaction to afford the piperidone moiety.

Young-Ger Suh and co-workers from Seoul National University reported on the synthesis of galiellalactone.

Ronaldo Pilli and co-workers from  Universidad Estadualde Campinas have reported on the synthesis of cryptomoscatone E3.

Scott Denmark and colleague reported on an asymmetrice 2,3-Wittig rearrangement.

JOC 11.24.2015 FKY

Posted in Alkaloids, Light Mediated, Mechanistic, Methodology, Sigmatropic Rearrangements, Total Synthesis | Leave a Comment »

From gene clusters to biosynthesis of natural products

Posted by naturalproductman on October 16, 2015

Leadlay (University of Cambridge) and Sun (Wuhan University) and co-workers have reported in Chemical Science on thiotetronate biosynthesis.

gene

Chemical Science paper

Posted in Biosynthesis, Mechanistic, Thiotetronate | Leave a Comment »

Evans enolate in solution

Posted by naturalproductman on October 5, 2015

David Collum and colleague have reported in JACS on the solution structure of an Evans enolate.
Evans

JACS paper

Posted in Computational, DFT, Mechanistic, Methodology | Leave a Comment »

Mechanistic study of the asymmetric Nazarov cyclization

Posted by naturalproductman on October 1, 2015

Kendall Houk and co-workers reported in JACS on a mechanistic investigation on a reaction discovered by Tius: the asymmetric Nazarov cyclization catalyzed by a thiourea-primary amine catalyst.

DFT

JACS paper

Posted in Computational, DFT, Mechanistic, Named Reactions, Nazarov cyclization | Leave a Comment »

Going from a diol to a tetrahydropyran in salinomycin

Posted by naturalproductman on September 25, 2015

Peter Leadlay and co-workers from the University of Cambridge have reported in ACIE on the enzyme that makes the tetrahydropyran ring in salinomycin. The tetrahydropyran is proposed to come from a diol where one of the hydroxy groups is in the beta-position to a ketone and subsequently dehydrates to form an enone. The enone undergoes an intramolecular Michael reaction to form the tetrahydropyran. However, when the reaction is done in vitro with the purified enzyme, they don’t see the enone intermediate, so I wonder if it is a processive reaction; in other words, the enone forms in the enzyme active site without being released and cyclizes to the tetrahydropyran.

salinomycin

ACIE paper

Posted in Biosynthesis, Chemical Biology, Enzymes, Mechanistic, Polyketides, Tetrahydropyran | Leave a Comment »

Triazoline + light

Posted by naturalproductman on September 4, 2015

Miguel Garcia-Garibay and co-workers at UCLA have reported in Organic Letters on a denitrogenation reaction of a triazoline using light to make an aziridine.
triazole
OL paper

Posted in Computational, Light Mediated, Mechanistic, Methodology | Leave a Comment »

Newman-Kwart reaction mechanism

Posted by naturalproductman on July 13, 2015

Hafize Ozcan and co-workers from Trakya University in Turkey have reported in Tetrahedron on an interesting mechanistic investigation of the Newman-Kwart reaction.

Newman-Kwart

Tetrahedron paper

Posted in Cascade Reactions, Computational, DFT, Electrocyclization, Mechanistic, Methodology, Named Reactions, Newman-Kwart, Sigmatropic Rearrangements | Leave a Comment »

α-Ketol rearrangement

Posted by naturalproductman on June 9, 2015

Ulrich Koert and co-workers from Philipps-University Marburg have reported in Organic Letters on an alpha-ketol rearrangment.They heat the reaction in a sealed tube to 70 degrees and the solvent is in DCM – with 2.5 mol equivalents of BF3 etherate, sounds a bit harsh – but nonetheless an interesting sigmatropic rearrangement.

 
ketol
OL paper

Posted in Cascade Reactions, Mechanistic, Methodology | Leave a Comment »

 
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