Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from para -Hydrogen.

The SABRE-Relay hyperpolarization method is used to enhance the 1 H and 13 C NMR signals of lactate esters, which find use in a wide range of medical, pharmaceutical, and food science applications. This is achieved by the indirect relay of magnetization from para -hydrogen, a spin isomer of dihydrogen, to OH-containing lactate esters via a SABRE-hyperpolarized NH intermediary. This delivers 1 H and 13 C NMR signal enhancements as high as 245- and 985-fold, respectively, which makes the lactate esters far more detectable using NMR. DFT-calculated J -couplings and spin dynamics simulations indicate that, while polarization can be transferred from the lactate OH to other 1 H nuclei via the J -coupling network, incoherent mechanisms are needed to polarize the 13 C nuclei at the 6.5 mT transfer field used. The resulting sensitivity boost is predicted to be of great benefit for the NMR detection and quantification of low concentrations (<mM) of lactate esters and could provide a useful precursor for the production of hyperpolarized lactate, a key metabolite.