Synthetic study and structural analysis of the antifreeze agent xylomannan from Upis ceramboides.
The novel antifreeze factor, xylomannan, first isolated from the freeze-tolerant Alaskan beetle Upis ceramboides , demonstrates a high degree of thermal hysteresis, comparable to that of the most active insect antifreeze proteins. Although the presence of a lipid component in this factor has not yet been verified, it has been proposed that the glycan backbone consists of a β-D-mannopyranosyl-(1→4)-β-D-xylopyranose-disaccharide-repeating structure according to MS and NMR analyses. In this contribution, we report the stereoselective synthesis of the tetrasaccharide β-D-mannopyranosyl-(1→4)-β-D-xylopyranosyl-(1→4)-β-D-mannopyranosyl-(1→4)-D-xylopyranoside, a structural component of xylomannan. Our synthesis features the use of 2-naphthylmethyl (NAP)-ether-mediated intramolecular aglycon delivery (IAD) as the key reaction in obtaining β-mannopyranoside stereoselectively. Various donors for NAP-IAD were tested to determine the most suitable for the purposes of this synthesis. Fragment coupling between a disaccharyl fluoride and a disaccharide acceptor obtained from a common β-D-mannopyranosyl-(1→4)-β-D-xylopyranoside derivative was successfully carried out to afford the desired tetrasaccharide in the presence of Cp(2)HfCl(2)-AgClO(4). Structural analysis of the resulting synthetic tetrasaccharide using NMR techniques and molecular modeling was performed in order to demonstrate the presence of the proposed xylomannan linkages in this molecule.
RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. aishiwa@riken.jp
Akihiro
A
Ishiwata
Ayaka
A
Sakurai
Yoshiyuki
Y
Nishimiya
Sakae
S
Tsuda
Yukishige
Y
Ito
D000818:Animals; D001517:Coleoptera / Q000737:chemistry*; D003451:Cryoprotective Agents / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009844:Oligosaccharides / Q000138:chemical synthesis / Q000737:chemistry*
D003451:Cryoprotective Agents; D009844:Oligosaccharides; C570461:xylomannan