Browsing by Author "Lu, Xin-An"

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Acyl and Silyl Group Effects in Reactivity-Based One-Pot Glycosylation: Synthesis of Embryonic Stem Cell Surface Carbohydrates Lc(4) and IV(2)Fuc-Lc(4)
(2012-03-14)
Hsu, Yun
;
Lu, Xin-An
;
Zulueta, Medel Manuel L.
;
Tsai, Chih-Ming
;
Lin, Kuo-I
Relative reactivity evaluations showed the graded arming of toluenyl thioglucosides by variously positioned silyl groups but not by their acyl counterparts. These findings were applied in reactivity-based one-pot assembly of linker-attached Lc(4) and IV(2)Fuc-Lc(4), which are components of human embryonic stem cell surface. The sugar-galectin-1 binding was also examined.
Regioselective One-Pot Protection of D-Glucosamine
(2010-11-05)
Chang, Ken-Lien
;
Zulueta, Medel Manuel L.
;
Lu, Xin-An
;
Zhong, Yong-Qing
;
Hung, Shang-Cheng
A highly regioselective one-pot transformation of 2-azido2-deoxy-1,3,4,6-tetra-O-trimethylsilyl-D-glucopyranose via sequential additions of various reagents was systematically studied, yielding the fully protected derivatives and the 1-, 3-, 4-, as well as 6-alcohols, respectively.
Synthesis of heparin oligosaccharides and their interaction with eosinophil-derived neurotoxin
(2012)
Hung, Shang-Cheng
;
Lu, Xin-An
;
Lee, Jinq-Chyi
;
Chang, Margaret Dah-Tsyr
;
Fang, Shun-lung
A convenient route for the synthesis of heparin oligosaccharides involving regioselective protection of D-glucosamine and a concise preparation of rare L-ido sugars from diacetone alpha-D-glucose is described. Stereoselective coupling of a D-glucosamine-derived trichloroacetimidate with a 1,6-anhydro-beta-L-idopyranosyl 4-alcohol gave the desired a-linked disaccharide, which was used as repeating unit for dual chain elongation and termination. Stepwise assembly from the reducing to the non-reducing end with a D-glucosamine-derived monosaccharide as starting unit furnished the oligosaccharide skeletons having different chain lengths. A series of functional group transformations afforded the expected heparin oligosaccharides with 3, 5 and 7 sugar units. Interaction of these oligosaccharides with eosinophil-derived neurotoxin (EDN), a cationic ribonuclease and a mediator produced by human eosinophils, was further investigated. The results revealed that at 5 mu g mL(-1), the heptasaccharide has sufficiently strong interference to block EDN binding to Beas-2B cells. The tri- and pentasaccharides have moderate inhibitory properties at 50 mu g mL(-1) concentration, but no inhibition has been observed at 10 mu g mL(-1). The IC(50) values of the tri-, penta- and heptasaccharides are 69.4, 47.2 and 0.225 mu g mL(-1), respectively.