Synthesis Of Protected Phenolic Galactopyranoside And Protected Gal(α1→2)Glc

Sugar,protein,nucleic acids and lipids are the four most basic life substance in the biological molecules,and so far the carbohydrates are found to be the most abundant organic molecules in nature,which is involved to almost all the biosynthesis and metabolism.The syntheses of the carbohydrates are inherent difficult due to their hydroxyl groups and α-and/or β-isomers while forming the glycosidic bonds.So the synthesis investigation of the carbohydrates was mainly focused on glycoside fragments with special bioactivity.In this paper,the syntheses of the glycoside compounds such as hydroquinone galactopyranosides and protected disaccharide galactopyranosyl(al->2)glucopyranoside with certain bioactivity have mainly been studied.Though sugar itself has rare medicinal function,a lot of carbohydrate derivatives are regarded as therapeutic and adjuvant drug.Phenolic glycoside,such as glycosides of phenol,naphthol,anthraquinone,coumarin and flavonoid,is a kind of glycoside which is formed by dehydration reaction of the phenolic hydroxyl groups of the ligands and sugar.Phenolic glycosides are widespread in plant roots,stems,leaves and seeds,and have the important bioactivities such as antibiotics and antitumor activity,and some of them have been developed as drugs.For example,salicin,its chemical name is 2-(methyl)phenyl β-D-glucopyranoside,exists in the bark of aspen and willow,its main function is to allay a fever and treat rheumatism;arbutin is 4-hydroxyphenyl β-D-glucoside,distributed widely in the Ericaceae and rosaceae,has antitussive,antiasthmatic,antibacterial,whitening,and other pharmacological functions.In this paper,with D-galactose as a raw material,seven kinds of protected hydroquinone galactoside donors were synthesized through multi-steps reactions such as protection,deprotection,and so on.The receptors(hydroquinone monobenzyl ether,hydroquinone monoacetate,hydroquinone monobenzoate)were obtained by monobenzylation,monoacetylization and monobenzoylation of the hydroquinone.And then,the 15 kinds of different stereoselective coupling products were obtained by the coupling reaction of the six kinds of donors and three kinds of receptors,respectively.a-D-galactosyl oligosaccharides and their conjugates are widely distributed in biological field.The disaccharide(Gal(α1→2)Glc)is a part of the lipoteichoic acid(LTA)which is the primary immune stimulating ingredients in Gram-positive bacteria’s cytoderm;in addition,Gal(α1→2)Glc is the moity of the cobra venom factor(CVF)capable of killing selectively cancer cells.High-efficient construction of 1,2-cis glycosidic bond is the committed step to synthesize the bioactive fragment.Therefore,syntheses of a donor isopropyl-2-O-benzoyl-3-O-allyl-4,6-O-benzylidene-β-D-1-thiogalactopyranoside and a receptor methyl-3,4,6-O-benzoyl-β-D-glucopyranoside and their coupling to obtain stereospecifically a protected Gal(α1→2)Glc.The syntheses of 15 kinds of protected phenolic galactopyranoside and protected Gal(α1→2)Glc provide an important experimental basis for stereospecific construction of a-glycosidic bond and/or β-glycosidic bonds,and also be apparently helpful for the development,application and further research of some bioactive carbohydrates.