Hyperpolarized fumarate via parahydrogen.

We produce hyperpolarized [1-13C]fumarate in the proton nuclear spin singlet state by pairwise trans-addition of parahydrogen to a molecular precursor using a ruthenium-based catalyst in water. The proton singlet state is transformed into observable carbon magnetization by radiofrequency pulses to enhance the 13C signal by a factor of 1000 using 50% para-enriched hydrogen gas.