Synthesis and Biological Activities of Xyloglucan Trisaccharides

Native xyloglucan oligosaccharides are a kind of growth regulator in plant development. A xyloglucan trisaccharide: alpha-D-xylopyranosyl-(1, 6) -beta-D-glucopyranosyl-(1, 4)-D-glucopyranose (1) and its derivatives were synthesized by three monosaccharide units. Glycosylation of isopropyl 2, 3-di-O-acetyl-4, 6-O-benzylidene-1-thio-beta-D-glucopyranoside (3) as the donor with 4-methoxyphenyl 2,3 6-tri-O-benzoyl-beta-D-glucopyranoside(4) gave disaccharide(5). Deprotection of 4,6-O-benzylidene of compound 5 gave 6 as disaccharide acceptor. Then coupling of isopropyl 2,3 4-tri-O-benzyl-1-thio-beta-D-xylopyranoside(2) with 6 afforded alpha and beta trisaccharides(7) and separation of compound 7 gave 8(alpha) and 9 (beta). Global deprotection of compound 8 obtained trisaccharide 1. The whole route involves five steps and the total yield is 15%. Synthetic trisaccharides were added to the culture medium to detect their effects on tobacco growth. The results show that three synthesized oligosaccharides promote the growth of tobacco at the level of 1 mg/L. These results suggest that synthesized trisaccharides may be good prospects for the application in the control of plant growth.