Crystallography Without Crystallizing: An Update

I wrote here about a very promising X-ray crystallography technique which produces structures of molecules that don't even have to be crystalline. Soaking a test substance into a metal-organic-framework (MOF) lattice gave enough repeating order that x-ray diffraction was possible.

The most startling part of the paper, other than the concept itself, was the determination of the structure of the natural product miyakosyne A. That one's not crystalline, and will never be crystalline, but the authors not only got the structure, but were able to assign its absolute stereochemistry. (The crystalline lattice is full of heavy atoms, giving you a chance for anomalous dispersion).

Unfortunately, though, this last part has now been withdrawn. A correction at Nature (as of last week) says that "previously unnoticed ambiguities" in the data, including "non-negligible disorder" in the molecular structure have led to the configuration being wrongly assigned. They say that their further work has demonstrated that they can determine the chemical structure of the compound, but cannot assign its stereochemistry.

The other structures in the paper have not been called into question. And here's where I'd like to throw things open for discussion This paper has been the subject of a great deal of interest since it came out, and I know of several groups that have been looking into it. It is my understanding that the small molecule structures in the Nature paper can indeed be reproduced. But. . .h...

Source: In the Pipeline - September 16, 2013 Category: Chemists Tags: Analytical Chemistry Source Type: blogs