Synthesis of 2-NBDLG, a fluorescent derivative of l-glucosamine; the antipode of d-glucose tracer 2-NBDG

2-[N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-l-glucose [2-NBDLG] (2) is a long-awaited control substance compensating the non-specific uptake of 2-NBDG (1), which has been widely used as a fluorescent tracer for monitoring d-glucose uptake into single, living cells. A new synthetic method of optically pure l-glucosamine, which is not available as a natural product, has been developed. The first and one-step synthesis of 2-NBDLG (2) from l-glucosamine is also described.