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
2
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 interconverted and you should think of the process of aldehyde-tohemiacetal-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