Chapter 17 Carbohydrates （糖，碳水化合物）

1. Chapter 17 Carbohydrates （糖，碳水化合物） Ref: Wade, chapter 23 曾昭琼，第十九章

2. Carbohydrates (糖，碳水化合物) D-glucose (葡萄糖) D-fructose (果糖) Sugars (糖) They have the molecular formulas Cn(H2O)n

3. Carbohydrates (糖，碳水化合物) Polyhydroxyaldehydes, polyhydroxyketones, and compounds that can be hydrolyzed to them are classified as carbohydrates （多羟基醛、多羟基酮及凡是能水解得到多羟基醛或多羟基酮的化合物均是碳水化合物） 葡萄糖(glucose)、果糖(fructose)、半乳糖(galactose) 蔗糖(sucrose)、麦芽糖(maltose)、乳糖(lactose) 淀粉(starch)、纤维素(cellulose)

4. Classification of carbohydrates • monosacharides （单糖）★: simple sugar • 葡萄糖(glucose)、果糖(fructose)、半乳糖(galactose) • disaccharides （二糖） 蔗糖(sucrose)、麦芽糖(maltose)、乳糖(lactose) • oligosaccharides （寡糖） • polysaccharides （多糖） • 淀粉(starch)、纤维素(cellulose)

5. Monosaccharides单糖

6. 1. Classification of Monosaccharides • Polyhydroxy aldehydes arealdoses（醛糖） • Polyhydroxy ketones are ketoses（酮糖） • trioses 三碳糖，丙糖 • tetroses 四碳糖，丁糖 • pentoses 五碳糖，戊糖 • hexoses 六碳糖，己糖 • heptoses 七碳糖，庚糖 aldohexose 己醛糖 ketohexose 己酮糖

7. D/L:D and L notations are used to describe the configurations of carbohydrates (根据构型分类) D-glucose D-葡萄糖 L-glucose L-葡萄糖

8. 2. Structures of monosaccharides Relative configuration 相对构型 D- /L- ： erythreo- /threo- 赤式/苏式 Absolute configuration 绝对构型 R- /S- Open-chain structure 开链结构 Cyclic structure 环状结构

9. Family tree of D-aldoses ref: 图19-1 or figure 23-3 D-甘油醛 D-苏阿糖 D-赤藓糖 D-树胶糖 阿拉伯糖 D-核糖 D-木糖 D-异木糖 D-葡萄糖 D-甘露糖 D-半乳糖

10. erythreo- 赤式 threo- 苏式 Diastereomer 非对映体

11. epimers （差向异构体） 具有三个或三个以上手性中心的化合物，若只有一个手性中心不同，其它都相同，则互称为差向异构体（epimers）

12. Cyclic Structures of Monosaccharides ----Hemiacetal（半缩醛） Formation Haworth formulas Haworth formulas Anomeric carbon 异头碳，端基碳 β-D - (+)-glucopyranose α-D-(+)-glucopyranose anomer 端基（差向）异构体

13. D-葡萄糖(glucose) 除1-位碳外，其它碳上的羟基及羟甲基均处在平伏键上。

14. Drawing cyclic monosaccharides D-葡萄糖 (glucose) 把羰基碳放在最右侧，把环中氧原子放在右后方。

15. trans-, α- cis-, β - α-D-(+)-glucopyranose β-D - (+)-glucopyranose b-D-glucose is the predominant form at equilibrium

16. D-glucopyranose D-吡喃葡萄糖 α-D-glucopyranose α-D-吡喃葡萄糖 β-D-glucopyranose β-D-吡喃葡萄糖

17. D-ribofuranose D-呋喃核糖 α-D-ribofuranose α-D-呋喃核糖 β -D-ribofuranose β -D-呋喃核糖

18. Note … • If an aldose can form a five- or six-membered ring, it will exist predominantly as a cyclic hemiacetal • Six-membered rings are called pyranoses • Five-membered rings are called furanoses • Haworth projections allow us to see the relative orientation of the OH groups in the ring. • b- sugar is the predominant form at equilibrium.

19. D-fructose(果糖)

20. mutarotation (变旋现象)：a property of anomers At equilibrium, [α]D25 = +52.6° , including α- 36% β- 64% At equilibrium, [α]D25 = +52.6° , including α- 36% β- 64%

21. 3. Reactions of monosaccharides -C=O, -OH • (1) Side reactions in base: epimerization; enediol rearrangement • (2) Reduction: NaBH4 ; H2/catalyst, forming alditols (糖醇) • (3) Oxidation: • Bromine water (Br2-H2O); forming aldonic acid (glyconic acid, 糖酸) • HNO3; forming aldaric acid (糖二酸) • Tollens test; Feilling’s reagent; • (4) Formation of glycosides • (5) Etherification • (6) Acylation: ester formation • (7) Reaction with phenylhydrazines: osazones (糖脎) formation • (8) Chain shortening: the Ruff degradation • (9) Chain lengthening: the Kiliani-Fischer synthesis

22. Side reactions in base: • --------epimerization; enediol rearrangement • (差向异构化)；(烯二醇重排) 23-8 epimerization D-glucose D-葡萄糖 D-mannose D-甘露糖

23. D-fructose D-果糖 D-glucose D-葡萄糖 D-mannose D-甘露糖 enediol rearrangement

24. 23-9 (2) Reduction of Monosaccharides The carbonyl of aldoses and ketoses can be reduced by the carbonyl-group reducing agents to form alditols(糖醇)

25. (3) Oxidation of monosaccharides; reducing sugars 23-10 A) Br2-H2O The aldehyde groups can be oxidized Ketones and alcohols cannot be oxidized by Br2 Br2-H2O can be used to determine aldehydes and ketones

26. B) Nitric acid (HNO3)

27. C) Tollens test: Ag(NH3)2+ • Sugars that reduce Tollens reagent to give a silver mirror are called reducing sugar(还原性糖).

28. D) Periodic acid (HIO4) cleavage of sugars

29. (4) Formation of glycosides (糖)苷 The acetal (or ketal) of a sugar is called a glycoside. methyl α-D-glucopyranoside (甲基-α-D-(+)-吡喃葡萄糖苷 ) (mp, 165℃ [α]D25 = +158°) methyl β-D-Glucopyranoside (甲基- β-D-(+)-吡喃葡萄糖苷 ) (mp, 107℃ [α]D25 = -33°) Nonreducing sugars 非还原性糖

30. Mechanism of Glycoside Formation

31. Formation of an N-Glycoside

32. (5) Etherification 醚化 Reagents: CH3OSO3CH3-NaOH; CH3I-Ag2O Methyl 2,3,4,6-tetra-O-methyl-β-D-glucopyranoside 2,3,4,6-tetra-O-methyl-D-glucose (2,3,4,6-四-O-甲基葡萄糖）

33. (6) Acylation: ester formation 五乙酰葡萄糖 Reagents: RCOCl or RCOOCOR, base;

34. Reaction with phenylhydrazines: • ------osazones (糖脎) formation osazones (糖脎) D-fructose D-果糖 D-mannose D-甘露糖 D-mannose D-甘露糖

35. (8) Chain shortening: the Ruff degradation(降级) The Ruff degradation is used mainly for determination and synthesis of new sugars.

36. (9) Chain lengthening: the Kiliani-Fischer synthesis This method is used for synthesis of new sugars.

37. 4. Determination of the structure of monosaccharides (1) Fisher’s proof of the configuration of glucose degradation D-glucose degradation D-arabiose D-erythrose D-mannose HNO3 HNO3 Optically active product Meso-tartaric acid

38. (2) Determination of Ring Size Approach 1 The size of the ring can be determined from the structure of the open-chain form

39. 3 + HCOOH Approach 2 An acetal of the monosaccharide is oxidized with excess HIO4 + CH3OH

40. Problem:

41. Cellobiose 纤维二糖 Maltose 麦芽糖 5. Disaccharides 二糖

42. Lactose 乳糖 1,1’- link Sucrose 蔗糖 Which is a nonreducing sugar?

43. 6. Polysaccharides starch（淀粉） Amylose 直链淀粉

44. Amylopectin 支链淀粉

45. cellulose（纤维素）

46. Blood type（血型） is determined by the nature of the sugar bound to the protein on the surface of red blood cells

47. 核蛋白 nucleoprotein 核酸（RNA，DNA） Nucleic acid 蛋白质 protein 核苷酸（单体） Nucleotide 磷酸 Phosporic acid 核苷 Nucleoside 戊糖(2种:核糖, 脱氧核糖) pentose 碱基(5种) base 7. Nuleic acids 核酸

48. 核苷 Nucleoside 戊糖 pentose 脱氧核糖 deoxyribose 核糖 ribose 核糖核苷 ribonucleosides 脱氧核糖核苷 deoxyribonucleosides

49. 常见碱基(base) 脲嘧啶 uracil (U) 鸟嘌呤 guanine (G) 胸腺嘧啶 thymine(T) 腺嘌呤 adenine (A) 胞嘧啶 cytosine (C)

50. 在RNA中存在下列四种核苷： 脲苷 胞苷 腺苷 鸟苷 规则：嘧啶的1位和嘌呤环的9位分别和核糖的苷羟基相连