Research On Stereoselective Syntheses Of Several L-menthyl Glycopyranosides And Extractive Of Chitin And Derivatives From Shrimp Crab Shell

Glucosides are one important Carbohydrate derivatives,their aglycon contain all kinds of Natural Ingredients.Most of them have characteristic physiological activities and medical values;Some can be used as natural pigments or colouring matters.Rencently,the physiological function of glucoside was getting more attention,due to the rapid development for glycobiology,glycomics and Biocarbohydrate Chemistry,Especially the effect of antibiotic and nucleosidein in antiphlogosis,antibacteria,antitumor and anti-HIV,which make it became a hot issue at new drug research.In this paper,one kinds of practicable flavor precursors compounds was mainly studied.Menthols,for their inherent mint flavor and refreshing feeling,have been widely used as additives for food-additive,medicines,tabaccoes for orial introduction,etc.These compounds are also knows to process dinstic pharmacological utility as antiseptics,mild local anesthetic and counterirritants.However,menthols are often have mingle rough taste,it be elicits buring,warming and tingling sensations when exposed in mouth.Moreover,the flaw of tendency to sublimate and slight solubility in water has limited their wider use.With an aim to enhance the thermostability and water-solubolity,the glycosidation reaction of menthols was extensively investigated.In this paper,with some common sugar and L-menthol as raw menterial,several menthyl glycosides was stereoselectivity synthetized through many different menthods.Related compounds were characterized by melting point,rotation,infrared spectra(IR),nuclear magnetic resonance(NMR)and mass spectra(MS),etc.The experiment result indicated that donor which activated by thioglycoside and trichloroacetimedate show satisfying active in coupling reaction.Peculiarly 1,2-trans configuration product were obtained with nearly stereospecificity when the big resistance group that has strong effect of Neighbouring Group Participation(NGP)was introduced.Unfortunately,when ordinary catalyst were used,penta-O-benzoyl galactopyranose donor was failed coupling with menthol due to it's low-active.After compared with other methods,we determine employ Fischer-Helferich method,in which toluene as solvent,pentaacetyl-suger donor was coupled with L-menthol(mole ration was 1:1.5)at reflux atmosphere,and with Zinc Chloride as optimum catalyst.For some sugars,single stereo-configurational products can be unexpectedly obtained through time-control with higher stereoselectivity.Therefore,our research can provide broad guidance for the stereoselective syntheses and applicationof the flavor precursors.At last,all the target compounds was processed with the solubility and thermo-stability test.The result showed that these compounds have higher thermostability,most of them also have certain dissolubility in water,particularly,the water solubility of compound 33,one kind of menthyl disaccharide,was up to 30%(g/100 g,20?).For this reason,these compounds were especially suit for food derivatives as well as medicines,their utilizations may hope for futher extending.In addition,we have got chitin,protein,CaCO3 and astacene by integration method with local fishery operation discarded shrimp and crab shell as raw materials.Deacetylation of chitin was taken to obtained chitosan,and subsequent degradation reaction was carried to afford glucosamine hydrochloride.Extraction process was also discussed.Besides,we put forward that twice-leach liquors were cyclic utilization,can it not only increased the acid-base efficiency,but also effectively reduced pollution which caused by effluent discharge.These methods are promised to have the reference significance for reuse of aquatic products processing waste and green extraction of chitin with high additional value.