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Chapter18Biomolecules:Carbohydrates18.1ClassificationofCarbohydrates18.2ConfigurationsofMonosaccharides18.3CyclicStructuresofMonosaccharides:HemiacetalFormation18.4MonosaccharideAnomersMutarotation18.5ReactionsofMonosaccharides18.6DisaccharidesCarbohydrate:(碳水化合物)Cm(H2O)nGlucose:(葡萄糖)C6H12O6C6(H2O)6Poly-hydroxylatedaldehydesandketonesSugars:OOHOHHOHOOHCOHOHHOOHOHHHHHCH2OHThesugar,Starch,CelluloseNucleicacidMonosaccharides：asimplecarbohydratethatcan’tbeconvertedintosmallersugarbyhydrolysis.Photosynthesis:(光合作用)6CO2+6H2OSunlight6O2+C6H12O6Cellulose,starchCarbohydratesMonosaccharides(simplesugars)(单糖)Oligosaccharides(寡糖)Polysaccharides(多糖)Ex.Glucose,fructose(果糖)P441,14.118.1ClassificationofCarbohydratesAnoligosaccharideyields3-10monosaccha-ridesunitsonhydrolysis.Ex.:Sucrose(蔗糖)TablesugarSucrose(C12H22O11)+H2OGlucose(C6H12O6)+Fructose(C6H12O6)Disaccharide(双糖)Polysaccharides:hydrolyzedtomorethan10monosaccharideunits.Ex.:Cellulosehydrolysis~3000GlucosePolyhydroxyaldehydesPolyhydroxyketonesMonosaccharidesAldoses(醛糖)Ketoses(酮糖)-ose:carbohydrate;ThenatureofthecarbonylgroupAldo-Keto-COHOHHOOHOHHHHHCH2OHMonosaccharides:tri-,tetr-,pent-,hex-andsoon.Glucose(analdohexose)(己醛糖)CHOOHOHHHHCH2OHOCH2OHFructose(anketohexose)(己酮糖)COHOHOHOHHHHCH2OH(analdopentose)(戊醛糖)Ribose(核糖)18.2ConfigurationsofMonosaccharidesDandLDesignationofsaccharidesCOHOHHOOHOHHHHHCH2OHOHCHOOHOHOHHHHHCH2OHTurn90°COHOHHCH2OH*Glyceraldehyde(甘油醛)(+)-(R)-D-GlyceraldehydeCOHCH2OHHOH*L-Glyceraldehyde(S)-(-)-GlyceraldehydeD:dextrorotationL:levorotationP445,14.3L-GlyceraldehydeD-GlyceraldehydeCOHOHOHOHHHHCH2OHCOHOHHOOHOHHHHHCH2OHCHOOHOHHHHCH2OHOCH2OH(D)-Ribose(D)-Glucose(D)-FructoseCOHOHHOOHOHHHHHCH2OHOHHOHHHCH2OHCOHHOHHO(D)-Glucose(L)-GlucoseCHOOHOHHHHCH2OHOCH2OHCOHHHHCH2OHOCH2OHHOHO(D)-Fructose(L)-FructoseInFischerprojection,the-OHgroupattheloweststereocenter:(D)forright;(L)forleft.18.3CyclicStructuresofMonosaccharides:HemiacetalFormationIntramolecularnucleophilicaddition:theformationofafive-orsix-memberedcyclichemiacetal.COHOHHOOHOHHHHHCH2OHD-GlucoseOHOHOHCH2OHOHOHD-Glucose,pyranose(吡喃糖)HaworthprojectionOHOHCH2OHOHOOHHOCH2OHHOHOOHOHP450Sir(Walter)NormanHaworth1883-1950Haworthmadebasiccontributionstocarbohydratechemistry.Heintroduced,in1925,thecorrectcyclicmodelforglucose,andstructuresofothermonosaccharides(mannose,galactose,fructose)weresoonadded.Thesewerefollowedbystructuralworkondisaccharides(maltose,cellobiose,lactose)andeventuallythepoly-saccharidesstarch,cellulose,inulin,glycogenandxylan.HaworthalsoestablishedthecorrectstructureofVitaminC(whichhenamedascorbicacid),andhissynthesisconstitutedthefirstsynthesisofanyvitamin.Haworthwasawardedthe1937NobelPrizeinChemistry(sharedwithPaulKarrer)forhisresearchoncarbohydratesandVitaminC.HewasthefirstBritishorganicchemisttoreceivetheNobel.nobel.se/chemistry/laureates/1937/haworth-bio.htmlConversionfromFischerprojectiontoHaworthprojection:COHOHHOOHOHHHHHCH2OHCOHOHHOHOHHHHHOCH2OHTurn90°BendOHCHOOHOHOHCH2OHTurnC4C5bondinanticlockwiseOHOHOHCH2OHOHCHOOHOHCH2OHOHOOHHClosering12345OHOHOHCH2OHOHCHOOHOHCH2OHOHOOHH+OHOHCH2OHOHOOHH18.4MonosaccharideAnomers(差向异构体):Mutarotation(变旋现象)D-Glucoseα-D-GlucopyranoseTransβ-D-Glucopyranose36：64mp：146°148-155°[α]D:+112.2°+18.7°[α]D:+52.6°Inaaqueoussolutionofpureanomer:CisP452,14.6TransOCH2OHHOHOOHOHOCH2OHHOHOOHOHα-D-Glucopyranose(吡喃葡萄糖)β-D-Glucopyranose(吡喃葡萄糖)Cis18.5ReactionsofMonosaccharidesGlycosideFormation(糖苷的生成):Thetreatmentofahemiacetalwithanalcoholinthepresentofanacidyieldsanacetal:COROH+ROHH+CORORAsaccaharidehemiacetalreactswithanalcoholundercatalyisisofanacidtoyieldAnacetal:OCH2OHHOHOOHOH+ROHH+OCH2OHHOHOOHOCH3OCH2OHHOHOOHOCH3+β-D-GlucopyranoseMethyl-α-D-glucopyranoside(甲基-D-吡喃葡萄糖苷)(66%)β-(33%)P454,14.7Thefeaturesofthereaction:(1)Theanomeric–OHhasbeenreplaced(2)byan–ORgroup.(2)Theproducts─glycosidesarestabletoneutralwater.Theyaren’tinequibriumwithanopen-chainform,andtheydon’tshowmutarotation.Glycosidesarewidespreadinnature:OCH2OHHOHOOHOCO2HSalicin(水杨苷)OCH2OHHOHOOHOCHOCH3OVanillicβ-D-Glucopyranose(香兰素-β-D-吡喃葡萄糖苷)OCH2OHHOHOOHOOCH2HOHOOHOCHCNLaetrile(苦杏仁苷)18.6Disaccharides(双糖)Disaccharidesarecarbohydratesthatyieldtwomonosaccharidemoleculesonhydrolysis.Disaccharadesareglycosidesinwhichthealkoxygroupattachedtotheanomericcarbonisderivedfromasecondarysugarmolecules.P460,14.914‘OCH2OHHOHOOHOOCH2OHHOOHHOHMaltose(麦芽糖),a1,4'-α-glycoside[4-O-(α-D-Glucopyranosyl)-α-D-Glucopyranose][4-O-(α-D-吡喃葡萄糖苷基)-α-D-吡喃葡萄糖苷]α-1,4'glycosidicbondAhemiacetalgroupβ-1,4'glycosidicbond4‘1OCH2OHHOHOOHOOCH2OHHOOHOHHCellobiose(纤维二糖)，aβ-1,4'-glycoside[4-O-(β-D-Glucopyranosyl)-β-D-Glucopyranose][4-O-(β-D-吡喃葡萄糖苷基)-β-D-吡喃葡萄糖苷•BothMaltoseandCellobiosearereducingsugars.•Bothareinequilibriumwithaldehydeforms,whichcanreduceTollens’ofFehling’sreagent.•Bothexhibitmutarotation.•Bothhavedramaticdifferentbiologicalproperties.OCH2OHHOHOOHOCH2OHOHHOCH2OHOSucrose(蔗糖),a1,2'-glycoside12'Fructose[2-O-(α-D-Glucopyranosyl)-β-D-fructofuranoside][2-O-(α-D-吡喃葡萄糖苷基)-β-D-呋喃果糖苷Sucrose