Preparation Of Glucosamine Oligosaccharides And Their Triterpene Saponins

Glucosamine oligosaccharides have been paid considerable attention due to the importance of their bioactivity. Series of chitooligosaccharides and glucosamine oligosaccharides derivatives were prepared by both degradation and trichloroacetimidate methods. Furthermore, a series of triterpene glycosides that composed of oleanolic acid, ursolic acid and glucosamine oligosaccharides were synthesized, and their structures were determined. The paper serves as the basis for testing bioactivities, revealing the relationships between structure and bioactivity.(1) Preparation and characterization of peracetylated chitooligosaccharides and chitiooligosaccharidesCleavage of chitin by means of sulfuric acid and acetic anhydride was discussed. The factors for influence on degradated products: material, temperature and time were tested via an orthogonal experiment. Eight oligosaccharides those are octaacetyl -diglucosamine 1, undecaacetyl-triglucosamine 2, tetradecaacetyl-tetraglucosamine 3, haptadecaacetyl-pentaglucosamine 4, A^TV-diacetylglucosamine 5, N,N',N" -triacetylglucosamine 6, A^W" W'^-tetraacetylglucosarnine 7 aadN,N',N",N'",N"" -pentaacetylglucosamine 8 were prepared efficiently, and their Chemical structures were confirmed by methods of IR, NMR, MS spectra.(2)Synthesis of glucosamine oligosaccharides derivatives using trichloroacetimidate methods A. Synthesis of chitiooligosaccharides derivatives.1,3,4,6-tetra-O-acetyl-2-deoxy-phthalimido-D-glucopyranose(10) was prepared from D-glucosamine hydrochloride 9.10 was converted into trichloroacetimidate donor 18 or 4-OH acceptor 16, then disaccharide! 9 was prepared after the glycosylation withthe promotion of trimethylsilyl trifluoromethanesulfonate (TMSOTf). Diglycoside 30 was prepared from 19 via deprotection, selective protection and Glycosylation reactions, then reacted with 18 or disaccharide donor 21 leading to the trisaccharide 31 or tetrasaccharide 34.B. Synthesis of 13 1 inked glucosamine oligosaccharides derivatives.Firstly, 6-OH acceptor 37d was glycosylated with donor 18 to provide disaccharide 38. Secondly, 38 was conserved into donor 41 or acceptor 40. Then trisaccharide 42 or tetrasaccharide 45 were synthesized through glycosylation method.C. Synthesis of 1 6 1 inked glucosamine oligosaccharides derivatives.3-OH acceptor 24 was glycosylated with donor 18 to provide 1 ?3 linked disaccharide 48, then 48 conserved into trichloroacetimidate which reacted with 24 to afford trisaccharide 52.(3) Synthesis of triterpene saponins of glucosamine and their oligosaccharides.Glucosamine and their oligosaccharides were coupled with antitumor activated oleanolic acid and ursolic acid. Series of oleanolic saponins or ursolic saponins with glucosamine oligosaccharides moiety were synthesized. The trityl oleanate 56b and trityl ursate 56c smoothly coupled with monosaccharide or oligosaccharides trichloroacetimidate at C-3OH with the presence of a catalytic amount of TMSOTf at low temperature (-70 ), providing the desired glycosides. Finally, oleanolic saponins(60a, 61 a, 63a, 65a, 67a, 69a, 71 a, 73a, 75a) and ursolic saponins(60b, 61 b, 63b, 65b, 67b, 69b, 71 b, 73b, 75b) were successfully synthesized by deprotection. Furthermore, The methyl ursate 56d couple with monosaccharide donor 18 and disaccharide donor 21 ,followed by removing protective groups to give saponins 78,79 and 81.