RESUMO
The acetal (O-glycoside) bonds of glycans and glycoconjugates are chemically and biologically vulnerable, and therefore C-glycosides are of interest as more stable analogs. We hypothesized that, if the O-glycoside linkage plays a vital role in glycan function, the biological activities of C-glycoside analogs would vary depending on their substituents. Based on this idea, we adopted a "linkage-editing strategy" for the creation of glycan analogs (pseudo-glycans). We designed three types of pseudo-glycans with CH2 and CHF linkages, which resemble the O-glycoside linkage in terms of bond lengths, angles, and bulkiness, and synthesized them efficiently by means of fluorovinyl C-glycosylation and selective hydrogenation reactions. Application of this strategy to isomaltose (IM), an inducer of amylase expression, and α-GalCer, which activates iNKT cells, resulted in the discovery of CH2-IM, which shows increased amylase production ability, and CHF-α-GalCer, which shows activity opposite that of native α-GalCer, serving as an antagonist of iNKT cells.
Assuntos
Galactosilceramidas , Glicosídeos , Polissacarídeos , Glicosilação , Polissacarídeos/química , Amilases/metabolismoRESUMO
We describe a new synthetic approach for C-linked glycolipid analogues, in which the cleavable O-glycosidic linkage is replaced by a carbon unit. Direct C-glycosylation of a conformationally constrained and stable C1-sp3 hybridized xanthate carbohydrate with carefully designed sphingosine units afforded the CH2-linked analogue of antitumor-active KRN7000 and its glucose congener.
RESUMO
C-Linked carbohydrate structure, in which the cleavable O-glycosidic linkage is replaced by a carbon unit, is a useful tool for functional analyses of glycoconjugates. We describe a synthetic method for α-CH2-linked disaccharide structures, such as Glc(1,6)-Glc, by stereoselective radical-coupling C-glycosylation between a conformationally constrained and stable C1-sp3 hybridized xanthate donor and a carefully designed acceptor.
