PREPARATION OF ISOTOPICALLY LABELED KETOGLUTARATES AND METHODS OF HYPERPOLARIZATION THROUGH SIGNAL AMPLIFICATION BY REVERSIBLE EXCHANGE (SABRE)

Disclosed are compounds of Formula (I), pharmaceutically acceptable salts thereof, and methods of preparation thereof, wherein R1, Xa, Xb, Xc, and Xd are as described in the specification. Further disclosed is an isotopic mixture of a compound of Formula (I), as well as a pharmaceutical composition containing a hyperpolarized compound of Formula (I). Also disclosed is a method of diagnosing or monitoring a patient suffering from cancer, the method including administering a pharmaceutical composition comprising an effective amount of a hyperpolarized ketoglutarate compound or a pharmaceutically acceptable salt thereof, and measuring the hyperpolarization of a compound of interest in the patient. Further disclosed is a method of preparing hyperpolarized ketoglutarate compounds for use in the above methods.