Development of New Methods for Structure Determination and Biocatalysis

New NMR Methods – MDEC

Advances in NMR instrumentation have pushed the limits of small-molecule NMR, with higher fields allowing better signal dispersion and modern probe design permitting analysis and quantification on the nanomolar level. One of the remaining limitations of small molecule NMR is the ability to obtain relative configuration of small molecules.  Since the 1959 report by Karplus,  the use of coupling constants to determine relative configuration in conformationally rigid small molecules has become routine.

More recently, J-based configuration analysis has been applied to determine the relative stereochemistry of complex acyclic and macrocylic small molecules and natural products. The utility of J-based methods relies on the ability to measure discrete coupling constants between protons (JHH), which can be difficult in molecules with complex multiplets and significant signal overlap. We have developed a method that can simultaneously decouple multiple signals to greatly simplify signal overlap. This pulse can be integrated with other 1D experiments, such as 1D-TOCSY, to isolate individual signals in complex spectra. 

NMR readings
An MDEC experiment to isolate individual coupling constants in menthol

Development of Novel Methods for Biotransformation

Biocatalysis has become an important component in the toolbox of the pharmaceutical and fine-chemical industries, with bioenzymes being used as reagents in multi-step synthetic processes. The biggest role for biocatalysis in the pharmaceutical sector lies on the chemo-, regio-, and stereoselectivity properties that biological systems can achieve. Biocatalyzed reactions can also be carried out in H­2O, without the use of protecting groups and under mild temperatures.

As the pharmaceutical industry continues to expand its biocatalysis capabilities, there is still a limitation in the strategies to identify new reactions and enzymes. The majority of biocatalyzed reactions focus on desymmeterizations and resolutions. The more widespread application of large-scale biocatalysis is currently restricted because of the limited number of commercially available synthetically useful enzymes and limited development speed. Discovery methods that can tap into the full potential of enzyme-catalyzed reactions, such as carbon bond-forming reactions (C-C, C-N, C-O, C-X), will expand the toolbox for this growing field.

We have developed a biotransformation discovery platform that takes advantage of our marine-derived bacteria collection and the use of labeled synthetic substrates. The strategy that we developed utilizes the incorporation of a 13C label on the synthetic substrate, and allows 13C NMR spectroscopy tp be used as a primary screening tool. Because of the low natural abundance of 13C, the use of labeled substrates provides a sensitive technique to distinguish products of biotransformation.

Platform for discovery of novel biotransformations using NMR