Natural abundance carbon 13 nuclear magnetic resonance spectroscopy of antifreeze glycoproteins.

Synthesis and antifreeze activity of fish antifreeze glycoproteins and their analogues

“…[47][48][49] The conformation of the AFGPs in the presence of ice has not been elucidated to date, although most researchers agree on an amphipathic structure with a hydrophilic face containing exposed hydroxyl groups of the sugars and a hydrophobic face containing the exposed methyl groups of both the amino acids and the N-acetyl groups. [50][51][52][53][54][55][56][57][58][59][60][61][62] The nature of the interactions involved in the ice-binding process also remains uncertain, but the creation of many hydrogen-bonds between the hydroxyls of the sugars and the ice lattice remains to date the major hypothesis to explain the strong bonding of AFGPs to ice. [63][64][65] Interestingly, recent studies with AFPs suggest that these molecules bind onto ice crystals via their hydrophobic faces [66][67][68][69][70] rather than their hydrophilic ones as initially suggested.…”

Total synthesis of (.+-.)-justicidin P. A new lignan lactone from Justicia extensa

“…precursor. Justicidin A, in turn, can be prepared from another natural lignan, diphyllin (3).48,5 Several syntheses of diphyllin and justicidin A have appeared in the literature.5 6 A potentially convenient way to construct these arylnaphthalene lactones would involve conjugate addition of aryldithiane anion to 2-butenolide followed by alkylation with aryl aldehyde. In fact, several groups have successfully employed this methodology in the synthesis of various lignans.…”

Chemical synthesis of some mono- and digalactosyl O-glycopeptides

“…Therefore, benzyl derivatives were preferred to acetyl or benzoyl derivatives, (iii) Amino acid protecting groups, on the other hand, must be stable in acid medium because of the acid-catalyzed nature of the glycosylation reaction.10 Ideally, the removal of glycosyl Z-L-Thr-Thr-OBzl (10) 0 Chemical shifts in ppm relative to Me"Si as internal reference in CDC13. 6 Abbreviations: Bzl4 = 2,3,4,6-tetra-O-benzyl; Z = JV-(benzyloxycarbonyl); OBzl = benzyl ester; ONp = o-nitrophenyl ester; Bzl4-a -D-Gal-»Z-L-Thr-Gly-OBzl = benzyl yV-(benzyloxycarbonyl)-0- (2,3,4,6-tetra-0-benzyl-a-D-galactopyranosyl)-L-threonylglycinate. c Indicates glycosylated threonine.…”