《糖生物学》课程教学课件（讲稿）04 reactions of the anomeric centre-1

Reactions of the anomericcenter-I1

Reactions of the anomeric center-I 1

HHHHCH,OHCH,OHCH,OH000HOHOHOHHHSHHHHOHOHOHOHOHOHOHHHHHHOHβanomeropen-chainformα.anomerequilibrium in solutioncrystallizebelow98°Ccrystallizeabove98°CHHCH,OHCH,OH0HOHOHHH,OH,Oequilibrium mixture of α andβHHHOHO-HOH[α] = +52.6OHOHHHHOHpureβanomerpureαanomermp 146°C,[α]=+112.20mp150°C,[α]=+18.72

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The anomeric centreOHOHH20HOCOHHOHOOHOHOHβ-glucopyranosea-glucopyranose62%38%AxialEquatorial3

The"anomeric centre"" O OH HO HO OH OH O OH HO HO OH OH H2O !-glucopyranose "-glucopyranose 38% 62% Axial&& Equatorial&&& 3

Acetal formation and hydrolysisMe.OMeOMe0R+HHOMe+ H+ROHOMeRReHHHHHMeOHOMeMeOMe+HORH+HRO=OMeRROMeOCH十HMeHHHH+HOHOMeH+ROHREOMeOHAH4

Acetal&forma1on&and&hydrolysis&& R H OH OMe H+ R H O O Me H H R H OMe MeOH + H+ R H OMe OMe R H OMe OMe H+ H+ R H O O Me H Me R H OMe HOH R H O OMe H H R H OH OMe H+ R H MeOH + O 4

Acetals and hemiacetals are in thesame oxidation state as carbonylsand it is therefore not surprisingthat they are readily inter-converted and you should think ofthe process of aldehyde-to-hemiacetal-to-acetal asonereversible rxn5

Acetals and hemiacetals are in the same oxidation state as carbonyls and it is therefore not surprising that they are readily inter￾converted and you should think of the process of aldehyde-to￾hemiacetal-to-acetal as one reversible rxn. 5

Fischer glycosylationOHOHOH?+H+HOHOHCOHHOHOHC-H+OHOHROHOHOHRCC+H+HOHOHOORHOOHHOHO-H+④OHOHOHGlycosylcationPresenceof an oxygensubstituentαtotheanomeric carbon, makes any carbocation formedtheremorestable6

Fischer&glycosyla1on&& O OH HO HO OH OH +H+ -H+ O OH HO HO OH OH H O OH HO HO OH O OH HO HO OH R O H O OH HO HO OH OH R O OH HO HO OH OR +H+ -H+ Presence"of"an"oxygen"subs:tuent"α"to"the" anomeric"carbon,"makes"any"carboca:on"formed" there"more"stable" Glycosyl&& ca1on 6

DisaccharidesComposedof Glucose纤维二糖β-qlycoside bondrotateCH20HOHCH20HCellobioseC=hemiacetalHOCH2CHO-OHHO-two glucose unitsareducingsugar三HO.HOHjoined Cito C4HOHOHOLCH2OHasap-glycosideXC=acetalHO!-OHβ-glycosidebondnon-reducing sugarHa-giycosidebondsCH2OHHOCHβ-glycosidebondx-glycosidebondHOHOCH20HHO-HOCH2OHHOCHO.HOCHOHHOHO.OHHO-HOTrehaloseHO!GentiobioseMaltoseHOCH2人HO.two glucose unitstwo glucose unitstwo glucose unitsHO!OHjoined Ci to Cijoined C1 to C4joined C1 to C6as two ar-glycosidesas an ar-glycosideas a p-glycoside麦芽糖海藻糖龙胆二糖7

麦芽糖 龙胆二糖 海藻糖 纤维二糖 7

Maltose,MaltsugarSince1937SKINGOLDENarbeusMALTEDPANCAKE&WAFFLEFLOURBLUEBERRY21RS10)METWTARS-OI.beautybodyandskin.com8buyfoodsale.com

Maltose,&Malt&sugar& beautybodyandskin.com buyfoodsale.com 8

β-glycosidebondOHrotateHOLactoseCH20HH20HHO.6CH2?H-4-O-p-D-Galactopyranosyl-D-glucoseHOTOH/BHC[β-anomerisdrawn]HHO.H(HOC=hemiacetalHOWHO"CH2OHH6areducing sugarA=galactoseHO,'OHp-glycosidebondHB.=qlucoseA=qlucosesucrose16CH20HaHOCH2Xα-D-Glucopyranosyl-p-D-fructofuranosiderotateB=fructose180°β-D-Fructofuranosyl-α-D-glucopyranosideCHOH2COHHOHQ:OHOHHOHOTHOHglycoside bonds Ho3CH2OHH.CH2OHHOHC=acetal6'non-reducing sugarβ-D-Fructofuranose9

9

HOCH2OHHOHCH2OHHOHHOHOHO-CH2galactoseHOHHO-HHHOCH20HrHOHOHOCH2glucose0HOraffinoseHHOHOXHHOCH20HHOCH2HOHOfructose0HOn=1 stachvose-Hn=2verbascosesucroseHOCH2HO.棉子糖，蜜三糖OHOFHO水苏糖HO/HO00OH毛蕊花糖.OHHOCβ-cyclodextrinHOOHHO0HOOHOH'OHHOT环糊精0OHOOHOH10-OH

棉子糖，蜜三糖 水苏糖 毛蕊花糖 环糊精 10