Late-stage deuteration of 13C-enriched substrates for T1 prolongation in hyperpolarized 13C MRI

A robust and selective late-stage deuteration methodology was applied to 13C-enriched amino and alpha hydroxy acidsto increase spin–lattice relaxationconstant T1 for hyperpolarized 13C magnetic resonance imaging. For the five substrates with 13C-labeling on the C1-position ([1-13C] alanine, [1-13C]serine, [1-13C]lactate, [1-13C]glycine, and [1-13C] valine), significant increase of their T1 was observed at 3 T with deuteriumlabeling (+26%, 22%, +16%, +25% and +29%, respectively). Remarkably, in the case of [2-13C] alanine, [2-13C]serine and [2-13C]lactate, deuteriumlabeling led to a greater than four fold increase in T1. [1-13C,2-2H] alanine, produced using this method, was applied to in vitro enzyme assayswith alanineaminotransferase, demonstrating a kinetic isotope effect.