1、Chapter 18 Biomolecules: Carbohydrates,18.1 Classification of Carbohydrates 18.2 Configurations of Monosaccharides 18.3 Cyclic Structures of Monosaccharides:Hemiacetal Formation 18.4 Monosaccharide AnomersMutarotation 18.5 Reactions of Monosaccharides 18.6 Disaccharides,Carbohydrate: (碳水化合物),Cm(H2O)
2、n,Glucose: (葡萄糖),C6H12O6 C6(H2O)6,Poly-hydroxylated aldehydes and ketones,Sugars:,The sugar, Starch, Cellulose Nucleic acid,Monosaccharides： a simple carbohydrate that cant be converted into smaller sugar by hydrolysis.,Photosynthesis: (光合作用),Ex. Glucose, fructose(果糖),P441, 14.1,18.1 Classification
3、of Carbohydrates,An oligosaccharide yields 3-10 monosaccha- rides units on hydrolysis.,Ex.: Sucrose(蔗糖),Table sugar,Disaccharide (双糖),Polysaccharides : hydrolyzed to more than 10 monosaccharide units.,Polyhydroxyaldehydes,Polyhydroxyketones,-ose: carbohydrate;,Monosaccharides: tri-, tetr-, pent-, he
4、x- and so on.,Glucose,(an aldohexose) (己醛糖),Fructose,(an ketohexose) (己酮糖),(an aldopentose) (戊醛糖),Ribose (核糖),18.2 Configurations of Monosaccharides,D and L Designation of saccharides,*,Glyceraldehyde (甘油醛),(+)-,(R)-,D-Glyceraldehyde,*,L-Glyceraldehyde,(S)-(-)-Glyceraldehyde,D: dextrorotation L: lev
5、orotation,P445, 14.3,(D)-Ribose,(D)-Glucose,(D)-Fructose,In Fischer projection, the -OH group at the loweststereocenter: (D) for right; (L) for left.,18.3 Cyclic Structures of Monosaccharides:Hemiacetal Formation,Intramolecular nucleophilic addition: the formation of a five- or six- membered cyclic
6、hemiacetal.,D-Glucose,D-Glucose, pyranose(吡喃糖),Haworth projection,P450,Sir (Walter) Norman Haworth1883-1950,Haworth made basic contributions to carbohydrate chemistry. He introduced,in 1925, the correct cyclic model for glucose, and structures of other monosaccharides (mannose, galactose, fructose)
7、were soon added. These were followed by structural work on disaccharides (maltose, cellobiose, lactose) and eventually the poly- saccharides starch, cellulose, inulin, glycogen and xylan. Haworth also established the correct structure of Vitamin C (which he named ascorbic acid), and his synthesis co
8、nstituted the first synthesis of any vitamin. Haworth was awarded the 1937 Nobel Prize in Chemistry (shared with Paul Karrer) for his research on carbohydrates and Vitamin C. He wasthe first British organic chemist to receive the Nobel.,http:/www.nobel.se/ chemistry/laureates/ 1937/haworth-bio.html,
9、Conversion from Fischer projection to Haworth projection:,18.4 Monosaccharide Anomers(差向异构体) :Mutarotation(变旋现象),D-Glucose,-D-Glucopyranose,-D-Glucopyranose,36 ： 64,mp： 146 148-155 D: +112.2 +18.7,D: +52.6,In a aqueous solution of pure anomer:,P452, 14.6,18.5 Reactions of Monosaccharides,Glycoside F
10、ormation(糖苷的生成):,The treatment of a hemiacetal with an alcohol in the present of an acid yields an acetal:,A saccaharide hemiacetal reacts with an alcohol under catalyisis of an acid to yield An acetal:,P454, 14.7,The features of the reaction: The anomeric OH has been replacedby an OR group.,(2) The
11、 productsglycosides are stable toneutral water. They arent in equibriumwith an open-chain form, and they dontshow mutarotation.,Glycosides are widespread in nature:,Salicin (水杨苷),Vanillic -D-Glucopyranose (香兰素-D-吡喃葡萄糖苷),Laetrile (苦杏仁苷),18.6 Disaccharides (双糖),Disaccharides are carbohydrates that yie
12、ld two monosaccharide molecules on hydrolysis.,Disaccharades are glycosides in which the alkoxy group attached to the anomeric carbon is derived from a secondary sugar molecules.,P460, 14.9,Maltose (麦芽糖), a 1,4- -glycoside 4-O-(-D-Glucopyranosyl)- -D-Glucopyranose,4-O-(-D-吡喃葡萄糖苷基)- -D-吡喃葡萄糖苷,- 1,4gl
13、ycosidic bond,A hemiacetal group,- 1,4glycosidic bond,Cellobiose (纤维二糖)，a-1,4-glycoside 4-O-(-D-Glucopyranosyl)- -D-Glucopyranose 4-O-(-D-吡喃葡萄糖苷基)- -D-吡喃葡萄糖苷,Both Maltose and Cellobiose are reducing sugars.,Both are in equilibrium with aldehyde forms,which can reduce Tollens of Fehlings reagent.,Both exhibit mutarotation.,Both have dramatic different biologicalproperties.,Sucrose(蔗糖), a 1,2-glycoside,2-O-( -D-Glucopyranosyl)- -D-fructofuranoside 2-O-( -D-吡喃葡萄糖苷基)- -D-呋喃果糖苷,Sucrose,
