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Archive for October, 2009

Englerin A Synthesis

Posted by naturalproductman on October 30, 2009

Mathias Christmann and co-workers at TU Dortmund University in Germany have reported on the total synthesis of englerin A – a sesquiterpene with highly attractive bioactivity.  The seven membered ring was accessed via a ring closing metathesis reaction.

englerin A

ACIEE paper

Posted in Methodology, Sesquiterpenes, Seven-Membered Rings, Transition Metal | Leave a Comment »

Indole Coupling

Posted by naturalproductman on October 30, 2009

Igor Larrosa and co-workers at the Queen Mary University of London have recently reported on the intermolecular coupling between an indole and a benzoic acid fragment to arylate an indole using a palladium catalyst.

indole coupling

 

OL paper

Posted in C-H activation, Methodology, Transition Metal | Leave a Comment »

A Novel Rearrangement

Posted by naturalproductman on October 30, 2009

Min Shi and co-worker at the Shanghai Institute of Organic Chemistry have reported in Organic Letters on a Pd-catalyzed tandem rearrangement that converted a vinyl cyclopropene into a methylene indene substrate. Para-benzoquinone was used to oxidize Pd(0) into Pd(II).
pd rearrangement

OL paper

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

Jiadifenolide

Posted by naturalproductman on October 30, 2009

Yoshiyasu Fukuyama and co-workers have recently published in Organic Letters on the isolation of two molecules – jiadifenolide and jiadifenoxolane A – with neurotrophic activities.

neurotrophic

OL paper

Posted in Sesquiterpenoids | Leave a Comment »

Alotaketals A and B

Posted by naturalproductman on October 30, 2009

Raymond Andersen’s group at the University of British Columbia has recently reported in Organic Letters on the isolation of a novel sesquiterpenoid structure dubbed alotaketal.  This compound and its related structure has cAMP activating abilities with EC50 of 18 and 240 nM.  The spiroketal structures were isolated from the marine sponge Hamigera.

alotaketal

OL paper

Posted in Sesquiterpenoids, Spiroketals | 2 Comments »

Total Synthesis of Vinigrol

Posted by naturalproductman on October 30, 2009

Well it’s been done – vinigrol has been around since 1987 and Phil Baran’s group at Scripps has finally reported the synthesis for the molecule.  A key step in this synthesis is the bromonitrile [3+2] cycloaddition to install the methyl-hydroxy equivalent accross an olefin.

vinigrol

JACS paper

Posted in Cycloaddition, Diterpenoids, Methodology | Leave a Comment »

Quinone Reactivities

Posted by naturalproductman on October 29, 2009

Gianluca Sbardela and co-workers at Università degli Studi di Salerno in Italy have recently published in Tetrahedron Letters on a cascade cyclization process involving the use of a alpha-bromo-quinone system.

bromoquinone


TL paper

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

Intramolecular Oxy-Michael

Posted by naturalproductman on October 29, 2009

Jayanta Ray and co-workers at IIT Kharagpur have recently published in Tetrahedron Letters on synthesis of polycyclic furans and tetrahydrofurans via an intramolecular oxy-Michael addition using either a reductant or a base to effect the transformation.  I think I’ve seen similar substrates but they underwent a hetero-Diels-Alder reaction.

not a diels alder

 

Tetrahedron Letters paper

Posted in Conjugate Additions, Methodology, Ring forming | Leave a Comment »

Super Lewis Acid

Posted by naturalproductman on October 29, 2009

Martin Oestreich and co-workers at the Universitat Munster have recently published in ACIEE on the synthesis and use of a cationic silylium ion with a ferrocenyl unit in the backbone.  They synthesized the silylium cation via hydride abstraction of a silane using a trityl-borate complex.  The catalyst was used to allow for the low temperature setting of the Diels-Alder reaction – ie:  -78 degrees Celsius.

silylium

 

ACIEE paper

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

Look What I Can Do!

Posted by naturalproductman on October 29, 2009

Being able to introduce oxygens to certain positions and take off specific atoms in an already complex looking molecule is just another one of the synthetic chemist’s puzzles.  Kazuo Nagasawa and co-workers at the Tokyo University of Agriculture and Technology have recently published in Tetrahedron on manipulating the structure of vitamin D to make different analogues of the compound.  When I first saw the transformation, I just knew that they had to use OsO4 to selectively place a hydroxy in the C-1 position.

vitamin D analogues

 

Tetrahedron Paper

Posted in Triterpenoids | Leave a Comment »

 
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