4-(D-Glucosamino)-7-nitrobenzoxadiazole: synthesis, anomers, spectra, TLC behavior, and applications

A new synthesis of the known fluorescent compound 3 (4-(D-glucosamino)-7-nitro-2,1,3- benzoxadiazol-4-yl) is reported, starting from D-glucosamine and non-fluorescent 4-aryloxy-7- nitrobenzofurazans, 4a-e, 5. The α and β anomers are easily interconverted but can be separated by TLC (Rf β > Rf α). The non-fluorescent new congener 8 {2-(N-(2',4',6'-trinitrophenyl)- amino)-2-deoxy-D-glucose} and the related known compound 9 {2-(N-(2',4'-dinitrophenyl)- amino)-2-deoxy-D-glucose} have anomers that may be seen in NMR spectra, but are too rapidly interconverted for TLC separation. The UV-Vis and fluorescence spectra of 3 depend markedly on solvent polarity. The TLC method allows the analytical determination of glucosamine from pharmaceutical preparations by conversion into 3 and detection by its fluorescence.