Synthesis of [1-11C]D-glucosamine and evaluation of its in vivo distribution in rat with PET.

D-Glucosamine is a structural unit of many biologically interesting macromolecules. To investigate the feasibility of using labelled D-glucosamine as a tracer for anabolic processes, a two-step synthetic procedure for specifically labelling D-glucosamine in position 1 with carbon-11 was developed. [11C]Cyanide was reacted with an imine precursor, N-benzyl-D-arabinosylamine, to generate the [1-11]alpha-amino nitrile. Reduction to [1-11C]D-glucosamine was accomplished by catalytic hydrogenation using PdCl2 and the N-benzyl group was simultaneously removed. The total synthesis time from end-of-trapping of [11C]cyanide was 40-45 min and the decay-corrected radiochemical yield was 5-10% after HPLC isolation. The biodistribution of [1-11C]D-glucosamine in rat following i.v. bolus injection was investigated using positron emission tomography and showed that the availability of this substance for CNS anabolism is low with the primary limitation being the intact blood-brain barrier.