Trantzschel, T. and Bernarding, J. and Plaumann, M. and Lego, D. and Gutmann, T. and Ratajczyk, T. and Dillenberger, S. and Buntkowsky, G. and Bargon, J. and Bommerich, U. (2012):
Parahydrogen induced polarization in face of keto-enol tautomerism: proof of concept with hyperpolarized ethanol.
In: Physical Chemistry Chemical Physics, 14 (16), pp. 5601-5604. [Article]

Abstract

Hyperpolarization (HP) techniques are increasingly important in magnetic resonance imaging (MRI) and spectroscopy (MRS). HP methods have the potential to overcome the fundamentally low sensitivity of magnetic resonance (MR). A breakthrough of HP-MR in life sciences and medical applications is still limited by the small number of accessible, physiologically relevant substrates. Our study presents a new approach to extend PHIP to substrates that primarily cannot be hyperpolarized due to a steady intramolecular re-arrangement, the so-called keto-enol tautomerism. To overcome this obstacle we exploited the fact that instead of the instable enol form the corresponding stable ester can be used as a precursor molecule. This strategy now enables the hydrogenation which is required to apply the standard PHIP procedure. As the final step a hydrolysis is necessary to release the hyperpolarized target molecule. Using this new approach ethanol was successfully hyperpolarized for the first time. It may therefore be assumed that the outlined multi-step procedure can be used for other keto-enol tautomerized substances thereby opening the application of PHIP to a multitude of molecules relevant to analyzing metabolic pathways.

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