Synthesis and relaxivity of gadolinium-based DOTAGA conjugated 3-phosphoglycerate

The synthesis and characterization of a gadolinium-based contrast agent conjugated to 3-phosphoglycerate (Gd-3PG) are reported. The synthetic steps are optimized to incorporate a selective deprotection strategy for a primary tert-butyl dimethyl silyl (TBS) hydroxyl over a secondary one. The relaxivity of Gd-3PG shows characteristic improvement, likely due to secondary sphere effects and/or an increase in molecular weight (5.39 ± 0.14 mM^-1 s^-1 at 1.4 T and 37 °C). Michaelis-Menten enzymatic kinetics was measured on the modified 3PG-arm and it showed similar activity to the native 3PG metabolite, K_m = 240 ± 30 μM. This agent and future versions of this type of GBCA, which are conjugated to glycolytic metabolites, were designed to monitor in vivo allosteric regulatory events in glycolytic processes.