Naturalproductman’s Blog

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Archive for December, 2009

Total Synthesis of Palau’amine

Posted by naturalproductman on December 30, 2009

Someone was bound to do it, but wow – Phil Baran and co-workers have synthesized palau’amine recently and reported their route in ACIEE.
palau'amine
ACIEE paper

Posted in Alkaloids, Cascade Reactions, Methodology, Trophy Targets | Leave a Comment »

Decarboxylative Coupling

Posted by naturalproductman on December 29, 2009

Masahiko Miura and co-workers at Osaka University have recently published in Organic Letters on a C-C bond forming process that involves the decarboxylation of cinnamic acid to form a new bond with vinyl bromides.  The palladium (II) acetate catalyst required the use of stoichiometric LiOAc and LiCl additives.

coupling
OL paper

Posted in Methodology, Polyenes, Transition Metal | Leave a Comment »

Pumiliotoxin via Intramolecular Diels-Alder

Posted by naturalproductman on December 29, 2009

Stephen Fearnley and co-worker at CUNY at York College have recently published in JOC on the synthesis of pumiliotoxin via an intramolecular Diels-Alder reaction by refluxing the substrate containing an oxazolone dienophile in dichloro-ethylaluminum in 1,2-dichlorobenzene.  The cyclic oxazolone can become opened with methyl lithium to afford a methylamide.

imda

JOC paper

Posted in Alkaloids, Cascade Reactions, Cycloaddition, Methodology, Ring forming | Leave a Comment »

Hetero-Diels-Alder: A Multi-Component Approach

Posted by naturalproductman on December 29, 2009

Robert Batey and co-workers at the University of Toronto have recently published in JOC on the synthesis of tetrahydroquinolines from a hetero-Diels Alder using BF3 etherate as the Lewis Acid.

hetero da

JOC paper

Posted in Alkaloids, Cascade Reactions, Cycloaddition, Diels-Alder, Methodology, Multi-Component Coupling, Named Reactions | Leave a Comment »

Hydroformylation followed by Reduction/Cyclization

Posted by naturalproductman on December 29, 2009

Andre Mann and co-workers at CNRS have recently published in Organic Letters on a clever approach to form nitrogen containing rings from azide-containing bis-alkenes – the protocol calls for a hydroformylation followed by reduction of the azide and simultaneous cyclization/reduction to form alkaloids, lupinine and epiquinamide.

hydroformylation

OL paper

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

9-deoxygelsemide

Posted by naturalproductman on December 29, 2009

Giovanni Vidari and co-workers at the Universitat di Pavia in Italy have recently published in Organic Letters on the synthesis of 9-deoxygelsemide, a compound foud from a plant Gelsemium elegans Benth. found in Japan. This compound had an EC50 of 22.6 micromolar against A549 lung tumor cells.

deoxygelsemide

OL paper

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

Celogentin C Synthesis

Posted by naturalproductman on December 29, 2009

Based on his progress towards Lyconadin, we know that Steven Castle at BYU likes his radical chemistry.  His group has recently published in JACS on the synthesis of a cyclic peptide, celgentin C.  This compound has even stronger activity at tubulin polymerization (IC50 = 0.8 micromolar) compared to the already known compound, vinblastine (IC50 = 3.0 micromolar).  Interestingly, Gong Chen and co-workers at Pennsylvania State University have recently published in ACIEE on their synthesis of the same compound.

celogentin

JACS paper

Chen’s ACIEE paper

Posted in Cascade Reactions, Conjugate Additions, Macrocycles, Methodology, Peptides, Radical Chemistry, Ring forming | Leave a Comment »

Aldehyde Insertion

Posted by naturalproductman on December 29, 2009

Ruben Martin and co-workers from the Institute of Chemical Research of Catalonia in Spain have recently published in JACS on the synthesis of cyclic ketones from bromo-aryl-aldehydes.  There is a loss of HBr and as a result, they have successfully obtained benzocyclobutenones, which look highly strained just by looking at them – three adjacent sp2 centers in a four membered ring.

aldehyde

JACS paper

Posted in C-H activation, Cascade Reactions, Methodology, Ring forming, Transition Metal | Leave a Comment »

Allyl-Aryl Coupling

Posted by naturalproductman on December 29, 2009

Masaya Sawamura and co-workers at Hokkaido University have recently published in JACS on an aryl-allyl coupling where he used an aryl boronic acid to displace an allylic acetate via an Sn2 prime fashion. The metal used was palladium (II) acetate that made the cationic palladium species in-situ with silver hexafluoroantimonate, and this reaction is also stereospecific, retaining the ee from the starting allylic acetate.

aryl allyl

JACS paper

Posted in cross coupling, Methodology, Sn2 prime, Transition Metal | Leave a Comment »

Triphenylphosphine as a catalyst

Posted by naturalproductman on December 26, 2009

Xiaofeng Tong and co-workers at the East China University have recently published in Chemistry – A European Journal on the coupling of tosyl imines and alkynes to produce conjugated double bonds.

pph3

Chemistry a European Journal paper

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

 
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