Synthesis of sulfur-linked analogues of nigerose, laminarabiose, laminaratriose, gentiobiose, gentiotriose, and laminaran trisaccharide Y

S-Linked Thiomimetics of Phytoalexin-Elicitor-Active, Branched Oligosaccharides, Their Synthesis, Protein-Binding Ability and Phytoalexin-Inducing Activity

“…On one hand, nucleophilic displacement of the iodine atom in 5-O-trisaccharide building block 20 could be obtained by reaction of the sodium salt of 1-thio-β--glucopyranose obacetyl-6-deoxy-6-iodo-1,2-O-isopropylidene-3-S- (2,3,4,6-tetra-O-acetyl-β--glucopyranosyl)-α--glucofuranose tained from 16, [6] with 14 in N,N-dimethylformamide at room temp. resulting in the hemiprotected branched di-(14) [3] with the sodium salt of the 1-S-acetyl-6 I ,3 II ,6 II -tetrathiotetrasaccharide 13 in N,N-dimethylformamide provided thiotrisaccharide 17 which, after treatment with chloro(4-methoxyphenyl)diphenylmethane in pyridine and acety-15 in a yield of only 30% (see Scheme 2). The β-thioacetate precursor 13 was obtained in a yield of 65% from the α-lation (Ǟ 18), detritylation with aqueous acetic acid (Ǟ 19) and subsequent replacement of the C-6 III primary hydroxy glycosyl bromide 2 by reaction with potassium thioacetate in N,N-dimethylformamide.…”

“…IV -di-β-Dby the sodium salt of 2,4-di-O-acetyl-3,6-di-S- (2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-1,3,6-trithio-β-D-glucopyraglucopyranosylthiogentiotetraose (12) has been prepared by a convergent approach involving the reaction of 1,2,4-tri-Onose afforded a tetrathiopentasaccharide, which resulted in the pentathiohexasaccharide 34 by a sequence of reactions acetyl-6-deoxy-6-iodo-3-S- (2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-3-thio-β-D-glucopyranose (10) with the sodium involving the 1-thioglycose 32 in reaction with 26. The hexathioheptasaccharide 39 was obtained conveniently by salt of 2,3,4-tri-O-acetyl-6-S- [2,4-di-O-acetyl-3,6-di-S-(2,3,4,6- IV -pentathio derivative 37, followed by deacylation.…”

“…IV -di-D-β-glucopyranosylthiogentiotetraose (34) and 3 III ,3 Introduction to be less prone to enzymatic inactivation as compared to Oligosaccharides which elicit molecular defense mecha-their O-linked natural counterpart. [2] In previous panisms in plants, otherwise known as oligosaccharins, have pers, [3] [4] we have developed a synthetic methodology which attracted much interest in recent years [1] and among these allows access to small thiooligosaccharides related to the are β-(1Ǟ6)-linked glucooligosaccharides with β-(1Ǟ3)-structure of phytoalexin elicitor branched glucooligosacchlinked glucosyl residues.…”

“…Preparation of 4 started from 1,2,3,4-tetra-O-acetyl-6-S- [2,4-di-O-acetyl-3,6-di-S-(2,3,4,6- [4] which gave the α--glycosyl bromide 2 by treatment with 33% hydrogen bromide in acetic acid, and was then transformed into the β-thioglycose derivative 4 by alkaline hydrolysis of the Salkylisothiouronium salt intermediate 3. The 6-deoxyiodo electrophilic counterpart 10 was prepared from 1, 2:5,6-di-O-isopropylidene-3-S-(2,3,4,6-tetra-O-acetyl-β--glucopyranosyl)-3-thio-α--glucofuranose (5) [3] in four steps. Removal of the isopropylidene groups with aqueous trifluoroacetic acid, treatment with chloro(4-methoxyphenyl)-diphenylmethane and acetylation gave the 6-O-methoxytrityl heptaacetates 7 and 8 as a 1:1 α/β-anomeric mixture which was separated by column chromatography.…”

“…[2] In previous panisms in plants, otherwise known as oligosaccharins, have pers, [3] [4] we have developed a synthetic methodology which attracted much interest in recent years [1] and among these allows access to small thiooligosaccharides related to the are β-(1Ǟ6)-linked glucooligosaccharides with β-(1Ǟ3)-structure of phytoalexin elicitor branched glucooligosacchlinked glucosyl residues. Comparison of the relative ability arides.…”