Synthesis, (1→3)-β-d-glucanase-binding ability and phytoalexin-elicitor activity of (R)-2,3-epoxypropyl (1→3)-β-d-pentaglucoside

The (1→3)-β-d-pentaglucoside was synthesized as its (R)-2,3-epoxypropyl glycoside via 2 + 3 strategy. The disaccharide donor 8 was obtained by 3-selective coupling of 2 with 4, followed by deallylation, and trichloroacetimidation. Meanwhile, the trisaccharide acceptor 12 was prepared by coupling of 10 with 4, followed by deacetylation. Condensation of 8 with 12, followed by epoxidation, and deprotection, gave the target pentaoside. The results of these bioassays demonstrated that the (1→3)-β-d-glucanase was obviously inactivated by 15 with kapp = 3.79 × 10−4 min−1. At the same time, we found that the 15 was more active as compared to the laminaripentaose in eliciting phytoalexin accumulation in tobacco cotyledon tissue, and it could be kept longer time than laminaripentaose, which indicated it is much more stable than laminaripentaose.