2-Azido-2-deoxycellulose: Synthesis and 1,3-dipolar cycloaddition

Abstract

Chitosan (1) was prepared by basic hydrolysis of chitin of an average molecular weight of 70000 Da, 1H-NMR spectra indicating almost complete deacetylation. N-Phthaloylation of 1 yielded the known N-phthaloylchitosan (2), which was tritylated to provide 3a and methoxytritylated to 3b. Dephthaloylation of 3a with NH2NH 2·H2O gave the 6-O-tritylated chitosan 4a. Similarly, 3b gave the 6-O-methoxytritylated 4b. CuSO4-Catalyzed diazo transfer to 4a yielded 95% of the azide 5a, and uncatalyzed diazo transfer to 4b gave 82% of azide 5b. Further treatment of 5a with CuSO4 produced 2-azido-2-deoxycellulose (7). Demethoxytritylation of 5b in HCOOH gave 2-azido-2-deoxy-3,6-di-O-formylcellulose (6), which was deformylated to 7. The 1,3-dipolar cycloaddition of 7 to a range of phenyl-, (phenyl)alkyl-, and alkylmonosubstituted alkynes in DMSO in the presence of CuI gave the 1,2,3-triazoles 8-15 in high yields. © 2008 Verlag Helvetica Chimica Acta AG.