Creating new substances, sometimes just for the sake of the creation act itself, is an undeniable part of chemists’ nature. Having flawless analytical data of a newly prepared sample always fills one with mystical joy and feeling of omnipotence. And some chemical creatures are so bizarre that the very fact of their isolation and characterization causes reverence of fellow chemists. So welcome to the chemical Panoptikum, a collection of all sorts of weird structures from the recent literature. Don’t be surprised to meet boron very often here, it’s a really weird element. Continue reading “Chemical Panoptikum #1”
Although not as exciting as it used to be, Fujita’s crystalline sponge technology has reached another milestone. This time the group could determine the absolute configuration of a natural product elatenyne. Burton lab from Oxford attempted (and not once) the total synthesis of the product with a sole purpose to assign its structure and absolute configuration. But to achieve that, one needs a good reference analytical data of the natural sample in the first place. And this was the bottleneck for the featured compound. Owing to its almost symmetrical structure, the molecule doesn’t rotate the polarized light by a lot (the latest [α]D values from Burton and Kim labs were −1.6° and +0.80° for two enantiomers). But reported data for ‘natural’ elatenyne varied from +19° to −10°. Which would make ambiguous even a qualitative judgement about the synthesized compound.
And as you can imagine, the molecule doesn’t easily crystallize in a conventional way. So it was an ideal case to try soaking a crystalline sponge in a solution of the compound. Remarkably, Fujita’s group needed only 5 μg of the freshly isolated compound for the analysis. As the result, they confirmed that Burton’s structure was correct.
No comments on bioactivity though.
Another cool paper from Mankin lab showed up in Nature Chemical Biology. This time researchers were looking at the detailed mechanism of translational arrest by two macrolide antibiotics, erythromycin and telithromycin.
Via series of mutations authors identified a single amino acid in the nascent peptide chain that determines selectivity and promiscuity of ribosome stalling by either of two antibiotics. To prove their point, they created an unnatural mutant gene with engineered selectivity to TEL.
While major implications of the study are dealing with antibiotic resistance and ways to overcome it, the authors coin an interesting evolutionary speculation. They suggest that the ribosome stalling could be another mechanism for gene regulation. In this case the sequence of some peptides could evolve in order to recognize small molecules during translation of the protein itself. And this could be another way to react on the environmental stimuli.
I guess that calls for another whole-transcriptome and cross-species genomic mining study for identification of such sequence−cofactor pairs.
By the way, a rare case, they did molecular dynamics simulation but didn’t include any pretty picture from it in the main text of the manuscript! That’s what happening when one has enough experimental data.
Büschleb et al. (ACIE)
A collection of OC tidbits selected by Hanessian and Overman groups. Featuring a dozen of natural products, each full of densely-packed stereocenters; 29 oldschoolishly lengthy synthetic schemes including three hundred intermediates that undergo all sorts of electrocyclic reactions and crazy cascades. Read in limited quantities to prevent overexcitement.
And, of course, I liked this guy (or girl?) at the frontispiece (the only thing one can get for free from Angewandte preview without subscription) in high-energy conformation overcoming some activation barrier.
Nicolaou et al (JACS)
KCN loves gold.
Picado et al. (JOC)
Turning failures into victories: if the reaction works, it’s just another row in a table. If it doesn’t, it can be a whole new paper!
Pan, Qin et al. (Org Lett)
A question without answer: how come this stereochemistry
… given this:
Patil et al. (JOC)
Simplicity is the new beauty (via orgchem.by).
Mishra and Biswas (JOC)
Another example of beautiful simplicity.
Babij, McCuscer et al. (OPR&D)
Expanded list of chemical shifts for commond (and not so common but green) solvents [open access!]