Toward hyperpolarized molecular imaging of HIV: synthesis and longitudinal relaxation properties of 15N-Azidothymidine

Previously unreported N-15 labeled Azidothymidine (AZT) was prepared as an equimolar mixture of two isotopomers: 1-N-15-AZT and 3-N-15-AZT. Polarization decay of N-15 NMR signal was studied in high (9.4T) and low (similar to 50mT) magnetic fields. N-15 T-1 values were 45 +/- 5s (1-N-15-AZT) and 37 +/- 2s (3-N-15-AZT) at 9.4T, and 140 +/- 16s (3-N-15-AZT) at 50mT. N-15-AZT can be potentially N-15 hyperpolarized by several methods. These sufficiently long N-15-AZT T-1 values potentially enable hyperpolarized in vivo imaging of N-15-AZT, because of the known favorable efficient (i.e., of the time scale shorter than the longest reported here N-15 T-1) kinetics of uptake of injected AZT. Therefore, 3-N-15-AZT can be potentially used for HIV molecular imaging using hyperpolarized magnetic resonance imaging.