Hyperpolarization of amino acid derivatives in water for biological applications.

We report on the successful synthesis and hyperpolarization of N-unprotected α-amino acid ethyl propionate esters and extensively, on an alanine derivative hyperpolarized by PHIP (4.4 ± 1.0% ¹³ C-polarization), meeting required levels for in vivo detection. Using water as solvent increases biocompatibility and the absence of N-protection is expected to maintain biological activity.