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Archive for the ‘Asymmetric’ Category

From carboxylic acid to ketone

Posted by naturalproductman on January 26, 2016

Peter Schreiner and co-workers from Justus-Liebig University have reported in ACIE on an asymmetric Dakin-West reaction. I am reminded of a similar transformation from carboxylic acid chlorides to trifluoroketones reported by Samir Zard’s group. From my own experience, the Zard reaction also works with just a carboxylic acid as the starting material (except, as pointed out – is not an asymmetric reaction).

 

ACIE paper

Posted in Asymmetric, Cascade Reactions, Dakin-West, Methodology, Named Reactions | 2 Comments »

Back to Back Method Papers: Allenamide + Aldehyde = alpha-Alkylation

Posted by naturalproductman on January 22, 2016

Fernando Lopez and co-workers at Universidad de Santiago de Compostela have reported in Chemical Communications on a gold/organocatalyst-cocatalyzed alpha alkylation of aldehydes. Interestingly Jose Gonzalez and co-workers at Universidad de Oviedo also reported in Chem Comm on a gold/organocatalyst reaction.

 

Chem Comm paper

 

Chem Comm paper 2

Posted in Allenes, Asymmetric, Cascade Reactions, Cooperative Catalysis, Gold, Methodology, Organocatalytic, Transition Metal | Leave a Comment »

Oxetane to tetrahydropyran

Posted by naturalproductman on January 20, 2016

Jeannie Sun and colleague at the Hong Kong University of Science and Technology have reported in ACIE on an intramolecular Sn2 reaction to convert a symmetrical oxetane ring to a tetrahydropyran.

 

ACIE paper

Posted in Asymmetric, Cascade Reactions, Methodology, Tetrahydropyrans | Leave a Comment »

Crystalline Sponge Method to Determine Absolute Configuration

Posted by naturalproductman on January 19, 2016

X-ray crystallography is usually a good method to determine the relative configuration of natural products (i.e. diastereomers) containing more than one stereocenter. However, the method of determining the absolute configuration of natural products is very difficult by just using X-ray crystallography. Here’s a paper from the labs of Sylvia Urban (RMIT University) and Makoto Fujita (University of Tokyo)  that reports on the use of the crystalline sponge method to determine the absolute stereochemistry of elatenyne.

 

ACIE paper 

 

Other ways to determine absolute configuration by X-ray crystallography include derivatization with a chiral reagent then crystallizing, using the effects of anomalous dispersion (Friedif values).

Posted in Asymmetric, New Techniques, Tetrahydrofuran | Leave a Comment »

Cascade cyclization

Posted by naturalproductman on November 10, 2015

Hiroaki Sasai and co-workers at Osaka University have reported in ACIE on a domino reaction involving the coupling between an allenoate ester and dienones.
allenoate

ACIE paper

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

Asymmetric Passerini reaction

Posted by naturalproductman on November 3, 2015

When I saw the Passerini reaction in the title, I thought of the use of an Ugi reaction in the synthesis of dysibetaine by the Kobayashi group. Bin Tan and co-workers at South University of Science and Technology in China have reported in JACS on a phosphoric acid catalyzed Passerini reaction.

Passerini

JACS paper

Posted in Asymmetric, Methodology, Multi-Component Coupling, Organocatalytic | Leave a Comment »

Enantioselective Intermolecular Cross-Rauhut–Currier

Posted by naturalproductman on November 3, 2015

Junliang Zhang and co-workers from East China Normal University have reported in ACIE on an asymmetric Cross-Rauhut-Currier reaction.

coupling

ACIE paper

Posted in Asymmetric, Methodology, Named Reactions, Organocatalytic | Leave a Comment »

Asymmetric spiroketalization

Posted by naturalproductman on October 29, 2015

Seijiro Matsubara and co-workers at Kyoto University have reported in ACIE on the use of an aminothiourea catalyst to form spiroketals asymmetrically.

amino

ACIE paper

Posted in Asymmetric, Methodology, Organocatalytic, Spirocycles | Leave a Comment »

Spongidepsin

Posted by naturalproductman on October 1, 2015

Isaac Kraus and co-workers from Brandeis University report on a formal synthesis of spongidepsin through a homocrotylation. This is an interesting variant of usual crotylations, they made it into the “homolog” form by using a cyclopropane in conjugation to the boron in the reagent – very clever.

spongidepsin

JACS paper

Posted in Asymmetric, Methodology | Leave a Comment »

Halomon synthesis

Posted by naturalproductman on September 30, 2015

Noah Burns and co-workers at Stanford have reported in JACS on some deceptively simple looking molecules.

halogen
JACS paper

Posted in Asymmetric, Halogenated, Methodology, Total Synthesis | Leave a Comment »

 
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