tert-Butyldimethylsilyl O-protected chitosan and chitooligosaccharides: useful precursors for N-modifications in common organic solvents.
Carbohydr Res 2008;
343:2576-82. [PMID:
18768174 DOI:
10.1016/j.carres.2008.08.014]
[Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Revised: 08/07/2008] [Accepted: 08/11/2008] [Indexed: 11/23/2022]
Abstract
An efficient and chemoselective procedure for preparing highly organosoluble 3,6-di-O-tert-butyldimethylsilyl (TBDMS)-chitosan and chitooligosaccharides is reported. The selective modification of the chitooligosaccharides with 0.50 degree of N-acetylation was achieved by using TBDMSCl as the reagent in combination with DMF/imidazole. These protocols yielded partly TBDMS-substituted chitooligosaccharides that were subsequently reacted with TBDMSOTf in dichloromethane in order to silylate the remaining, more sterically hindered hydroxyl groups. In the case of the chitosan polymer, a mesylate salt of chitosan was silylated using TBDMSCl in DMSO, yielding full silylation of the hydroxyl groups without using N-protection groups. The silyl-protected polymers displayed excellent solubility in a number of common organic solvents. The 3,6-di-O-TBDMS-chitosan and chitooligosaccharides were reacted with acetic anhydride, and deprotected to obtain the corresponding N-acetyl derivatives (chitin and chitinoligosaccharide). Our results show that the readily prepared 3,6-di-O-TBDMS-chitosan and chitooligosaccharides are useful precursors for selective N-modifications in common organic solvents.
Collapse