Naturalproductman’s Blog

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Archive for May, 2009

Why is CDCl3 a Triplet?

Posted by naturalproductman on May 29, 2009

Ever wonder why when you’re taking a 13C NMR in deuterated chloroform and look at the solvent peak – there are three evenly spaced peaks with equal intensities?

The answer can be found in your good old sophmore organic chemistry textbook (*I recommend the Marc Loudon book) and/or a physical chemistry text. It turns out that 1H has a spin of 1/2 but 2H has a spin of 1. In the case of a proton (1H) the spin state will either be +1/2 or -1/2, and in the case of a deuterium (2H) the spin state will either be +1, 0 or -1. And since we’re not running the 13C NMR in a deuterium decoupled mode – we’ll see the splitting from deuterium onto the carbon. Because there are three states: +1, 0 and -1, then we’ll see the peak split into three lines.

That’s so amazing.

Posted in Random | 6 Comments »

Is That a 7-Membered Ring?

Posted by naturalproductman on May 28, 2009

Yong-Ping Yang at the Kunming Institute of Botany in China has published on the isolation of this seven membered ring treasure – these compounds were found to have anti-angiogenic effects on zebra fish models with microgram/mL activities.

7 membered
JNP paper

Posted in Diterpene, Seven-Membered Rings | Leave a Comment »

Whoa – Cyclopropanation

Posted by naturalproductman on May 28, 2009

Starting from enyne starting materials, Melanie Sanford and co-workers at the University of Michigan were able to make cyclopropane products using a transition metal and oxidizing agent.

cyclopropanation

Tetrahedron Paper

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

nBuLi Promoted Allene Synthesis

Posted by naturalproductman on May 28, 2009

Looks simple enough:  enyne reactions with amines to make allenes using just nBuLi – none of the fancy transition metal stuff.  Weiping Tang at the University of Wisconsin and coworkers have published this one in Tetrahedron.

allene

Tetrahedron paper

Posted in Methodology, Ring forming | Leave a Comment »

Cascade Metathesis

Posted by naturalproductman on May 28, 2009

Paul Hanson at the University of Kansas came out with a nice paper on cascade metathesis reactions.

cascade metathesis

Tetrahedron paper

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

Salinosporamide A

Posted by naturalproductman on May 28, 2009

Jeff Bode’s group at UPenn has come up with a new way to make salinosporamide using his carbene reaction. The intramolecular NHC reaction is a nice way to make the lactam framework of the molecule. You can check the paper out in Tetrahedron.

NHC reaction

Tetrahedron paper

Posted in Alkaloids, Carbene, Methodology, Ring forming, Umpolung | Leave a Comment »

Aldehydes Disguised

Posted by naturalproductman on May 28, 2009

Michael Krische at UT Austin has come out with a paper in ACIEE on these allyl alcohols that are masked aldehydes.

allyl alcohols

ACIEE paper

Posted in Methodology, Transition Metal | 1 Comment »

Allenyl Azide Chemistry

Posted by naturalproductman on May 28, 2009

Ken Feldman at Penn State has published on this type of chemistry before.  The question is – is it really practical industrially when you have to use a microwave reactor for these reactions?

azide
JOC paper

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

[2+2] Cycloadditions

Posted by naturalproductman on May 27, 2009

Tehshik P. Yoon’s group at the University of Wisconsin at Madison has recently published in JACS on a [2+2] cycloadditions using enones and a ruthenium catalyst.  The trick here was to use sunlight – it’s funny – that means a lot of chemistry labs should adapt their settings so that the rooms have windows if they want some of their reactions to work.
2+2

JACS paper

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

C-H insertion via Alkylidene Carbenes

Posted by naturalproductman on May 27, 2009

University of Wisconsin at Madison missed out by not giving Daesung Lee tenure, but it looks like he’s doing well in UIC – where recently he published a JACS paper on alkylidene carbenes and the C-H insertion process.  His technique in using nBuLi and TMS-diazomethane to generate an alkylidene carbene is a pretty neat reaction.

c-h insertion

JACS paper

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

 
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