PSYCHEDELIC 2DJ NMR

Although originally developed by physicists, NMR is one of those technologies that revolutionized chemistry. With enormous recent advances, it became a great tool for interrogating complex structures of peptides and nucleic acids. But there’s still plenty of room for improvement in the most basic its application, proton (1H) NMR.

Ever encountered in the literature peaks description like 2.3−4.5 (m, 15 H)? Yes, many spectra are very messy even for the most pure compounds. And multiplicity, which is a great tool for structure elucidation, becomes everyone’s foe. Possible solution to that is homonuclear broadband decoupling. It degenerates all proton signals to singlets (“pure shift spectra”), but also causes significant reduction in signal intensity. In 2013 Zangger group reported an imrpovement, which they called instant homo-decoupling. But all such manipulations have an obvious drawback, because valuable information from multiplets is lost.

In 2014 Morris group from Manchester further improved sensitivity and resolution of Zangger’s sequence and dubbed their method PSYCHE. Soon after that they combined it with 2DJ NMR.  So PSYCHEDELIC method appeared in Angewandte, which solved the major limitation of homo-decoupling by drawing pure shift proton spectrum in F2 dimension and coupling pattern in F1!

nmr_PSYCHE
a) ‘traditional’ proton NMR; b) PSYCHE spectrum with pure chemical shift in F2 dimension and multipled coupling in F1. Source

I can easily imagine how these new methods will facilitate fully automatic NMR spectra analysis and will change chemistry textbooks. In the meanwhile, for my relatively simple compounds I’ll continue using guidelines from classic Hoye’s paper and its addendum.

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Author: Slava Bernat

I did my PhD in medicinal chemistry/chemical biology of G protein-coupled receptors and then explored some chemical biology of non-coding RNA as a postdoc. Currently I'm working in a small biotech company in San-Francisco Bay area as a research chemist. I'm writing about science, which catches my attention in rss feed reader and some random thoughts or tutorials.

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