This article presents a novel catalytic method by combining phase-transfer catalyst, benzyltriethylammonium chloride, with 4-dimethylaminopyridine for the syntheses of glycosyl esters from substituted phenoxyaeetie ac...This article presents a novel catalytic method by combining phase-transfer catalyst, benzyltriethylammonium chloride, with 4-dimethylaminopyridine for the syntheses of glycosyl esters from substituted phenoxyaeetie acids and the peracetate of α-D-l-bromosugars to produee eight novel β-glyeosyl esters in high yields. The struetures of the syn-thesized eompounds were established by IR, MS, ^1H NMR, and ^13C NMR speetra and elemental analyses.展开更多
From the 1-BuOH-soluble fraction of a MeOH extract of the leaves of Symplocos cochinchinensis var. philippinensis, 12 compounds were isolated. Spectroscopic analyses of compounds 1 - 3 established their structures to ...From the 1-BuOH-soluble fraction of a MeOH extract of the leaves of Symplocos cochinchinensis var. philippinensis, 12 compounds were isolated. Spectroscopic analyses of compounds 1 - 3 established their structures to be megastig-mane glycosides, named symplocosionosides A-C. The absolute structure of 1 was determined by the modified Mosher’s method. Compound 4 was found to be a neolignan glucoside and named symplocosneolignan. The structures of com-pounds 5 and 6, named symplocosins A and B, were elucidated to be the saponins of hederagenin sugar esters. The structures of the remaining known compounds (7 - 12) were identified by comparison of spectroscopic data with those reported in the literature.展开更多
This paper reports that four new glycosyl esters of Vanillic Acid were synthesized by the reaction of vanillic acid with O-acetylglucopyranosyl bromide or O-acetylgalacopyranosyl bromide,O-acetylxylopyranosyl bromide ...This paper reports that four new glycosyl esters of Vanillic Acid were synthesized by the reaction of vanillic acid with O-acetylglucopyranosyl bromide or O-acetylgalacopyranosyl bromide,O-acetylxylopyranosyl bromide and O-acetyllactosyl bromide in the presence of Ag2O respectively;and vanillic acid-4-β-D-2’,3’,4’,6’-acetyl glucoside-β-D-2",3",4",6"-acetyl glucoester by vanillic acid with O-acetylglucopyranosyl bromide in the presence of Bu4NBr.Their structures were confirmed by IR,1H NMR,13C NMR,HMBC and MS.And spectra data proved that the products are of β-configuration.展开更多
Despite the significant progress in carbohydrate chemistry,there remains a pressing need for efficient and practical glycosylationmethods using simple glycosyl donors and with high atom economy.Herein,a new protocol f...Despite the significant progress in carbohydrate chemistry,there remains a pressing need for efficient and practical glycosylationmethods using simple glycosyl donors and with high atom economy.Herein,a new protocol for glycosylation with glycosyl chloride donors under palladium-catalyzed conditions is developed.PdII complex serves as a Lewis acid to promote the activation of glycosyl chloride for the formation of oxocarbeniumion intermediate.This new method is operationally simple,robust,and enables efficient synthesis of both O-and N-glycosides with a broad substrate scope.In particular,it offers an easy access to a range of N-ribonucleoside analogs.展开更多
Saffron （Crocus sativus） cells can synthesize crocin, crocetin digentiobiosyl ester, in suspension cultures. The crocin family biosynthesis mechanism was studied using high pressure liquid chromatography （HPLC） to...Saffron （Crocus sativus） cells can synthesize crocin, crocetin digentiobiosyl ester, in suspension cultures. The crocin family biosynthesis mechanism was studied using high pressure liquid chromatography （HPLC） to determinate the glucosyltransferase activity and to develop a method for synthesizing medicine from saffron cells. Previous studies indicated that two glucosyltransferases might be involved in the formation of crocetin glucosyl- and gentiobiosyl-esters. GTasel formed an ester bond between crocetin carboxyl groups and glucose moieties while GTase2 catalyzed the formation of glucosidic bonds with glucosyl ester groups at both ends of the molecule. These enzymes can catalyze the formation of crocetin glucosides in vitro. GTasel activity is higher during the first four days of crocin glucosides biosynthesis, but decreases after four days. The formation and accumulation of crocin increase during the first six days and stabilized on the eighth day.展开更多
基金Supported by the National Natural Science Foundation of China(No.20674023).
文摘This article presents a novel catalytic method by combining phase-transfer catalyst, benzyltriethylammonium chloride, with 4-dimethylaminopyridine for the syntheses of glycosyl esters from substituted phenoxyaeetie acids and the peracetate of α-D-l-bromosugars to produee eight novel β-glyeosyl esters in high yields. The struetures of the syn-thesized eompounds were established by IR, MS, ^1H NMR, and ^13C NMR speetra and elemental analyses.
文摘From the 1-BuOH-soluble fraction of a MeOH extract of the leaves of Symplocos cochinchinensis var. philippinensis, 12 compounds were isolated. Spectroscopic analyses of compounds 1 - 3 established their structures to be megastig-mane glycosides, named symplocosionosides A-C. The absolute structure of 1 was determined by the modified Mosher’s method. Compound 4 was found to be a neolignan glucoside and named symplocosneolignan. The structures of com-pounds 5 and 6, named symplocosins A and B, were elucidated to be the saponins of hederagenin sugar esters. The structures of the remaining known compounds (7 - 12) were identified by comparison of spectroscopic data with those reported in the literature.
文摘This paper reports that four new glycosyl esters of Vanillic Acid were synthesized by the reaction of vanillic acid with O-acetylglucopyranosyl bromide or O-acetylgalacopyranosyl bromide,O-acetylxylopyranosyl bromide and O-acetyllactosyl bromide in the presence of Ag2O respectively;and vanillic acid-4-β-D-2’,3’,4’,6’-acetyl glucoside-β-D-2",3",4",6"-acetyl glucoester by vanillic acid with O-acetylglucopyranosyl bromide in the presence of Bu4NBr.Their structures were confirmed by IR,1H NMR,13C NMR,HMBC and MS.And spectra data proved that the products are of β-configuration.
基金G.C.thanks NSFC-91753124,NSFC-21672105,NSFC-21421062,and NSFC-21725204 for financial support for this work.
文摘Despite the significant progress in carbohydrate chemistry,there remains a pressing need for efficient and practical glycosylationmethods using simple glycosyl donors and with high atom economy.Herein,a new protocol for glycosylation with glycosyl chloride donors under palladium-catalyzed conditions is developed.PdII complex serves as a Lewis acid to promote the activation of glycosyl chloride for the formation of oxocarbeniumion intermediate.This new method is operationally simple,robust,and enables efficient synthesis of both O-and N-glycosides with a broad substrate scope.In particular,it offers an easy access to a range of N-ribonucleoside analogs.
文摘Saffron （Crocus sativus） cells can synthesize crocin, crocetin digentiobiosyl ester, in suspension cultures. The crocin family biosynthesis mechanism was studied using high pressure liquid chromatography （HPLC） to determinate the glucosyltransferase activity and to develop a method for synthesizing medicine from saffron cells. Previous studies indicated that two glucosyltransferases might be involved in the formation of crocetin glucosyl- and gentiobiosyl-esters. GTasel formed an ester bond between crocetin carboxyl groups and glucose moieties while GTase2 catalyzed the formation of glucosidic bonds with glucosyl ester groups at both ends of the molecule. These enzymes can catalyze the formation of crocetin glucosides in vitro. GTasel activity is higher during the first four days of crocin glucosides biosynthesis, but decreases after four days. The formation and accumulation of crocin increase during the first six days and stabilized on the eighth day.
