Chem 109 C Bioorganic Compounds Fall 2019 HFH1104 Armen Zakarian Office: Chemistry Bldn 2217 http://labs.chem.ucsb.edu/~zakariangroup/courses.html CLAS Instructor: Dhillon Bhavan [email protected] update sections covered: see syllabus in Chapter 20: all except 20.13 - the anomeric effect 20.17, 20.19 (artificial sweeteners) Carbohydrates: Stereochemistry of Glucose known: an aldohexose Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment conclusion K-F synthesis arabinose glucose + mannose C2 epimers Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment conclusion K-F synthesis arabinose glucose + mannose C2 epimers HNO , heat glucose 3 aldaric acid mannose optically active! Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment CO2H conclusion K-F synthesis H OH arabinose glucose + mannose HO H C2 epimers HO H H OH HNO , heat glucose 3 aldaric acid CO2H mannose optically active! Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment CO2H conclusion K-F synthesis H OH arabinose glucose + mannose HO H C2 epimers HO H H OH HNO , heat glucose 3 aldaric acid CO2H not structures mannose optically active! 1,2,7,8 Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment CO2H conclusion K-F synthesis H OH arabinose glucose + mannose HO H C2 epimers HO H H OH HNO , heat glucose 3 aldaric acid CO2H not structures mannose optically active! 1,2,7,8 HNO , heat 3 aldaric acid arabinose optically active! Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment CO2H conclusion K-F synthesis H OH arabinose glucose + mannose HO H C2 epimers HO H H OH HNO , heat glucose 3 aldaric acid CO2H not structures mannose optically active! 1,2,7,8 HNO , heat 3 aldaric acid arabinose optically active! 3 or 4 Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment 3 or 4 conclusion Carbohydrates: Stereochemistry of Glucose known: an aldohexose experiment 3 or 4 conclusion Carbohydrates: Shortening the Chain PROBLEM What two monosaccharides can be degraded to O a. D-ribose H OH H OH H OH OH b. D-arabinose O HO H H OH H OH OH Carbohydrates: Shortening the Chain PROBLEM What two monosaccharides can be degraded to O a. D-ribose H OH H OH H OH OH b. D-arabinose O HO H H OH H OH OH Carbohydrates: Cyclic Hemiacetals OH HO O 36% HO HO OH OH α-D-glucopyranose HO OH HO HO O OH acyclic glucose HO O 64% HO OH 0.02% HO β-D-glucopyranose in aqueous solution Carbohydrates: More Classification O O pyran furan O OH HO O OH HO HO OH HO OH OH pyranose furanose Carbohydrates: Haworth projections fundamental reactivity + H R R R R R O + HO R HO O+ HO O R R H -H+ R hemiacetal section 16.9 anomeric hydroxyl group Carbohydrates: Cyclic Hemiacetals fundamental reactivity + H R R R R R O + HO R HO O+ HO O R R H -H+ R hemiacetal section 16.9 forms a furanose Carbohydrates: Cyclic Hemiacetals PRACTICE PROBLEM Draw the following sugars using the Haworth projections: a. β-D-galactopyranose b. α-L-glucopyranose Carbohydrates: Cyclic Hemiacetals Glucose - most stable aldohexose: HO HO O HO OH HO HO OH HO OH HO O O HO OH HO OH HO mannose galactose Carbohydrates: Glycosides Formation of glycosides: trans cis HO O HO O OR OR cis trans HO O HO OR O OR α-glycoside β-glycoside Carbohydrates: Glycosides mechanism for glycoside formation: H+ HO HO O H HO O HO + OH HO O HO - H2O HO HO H HO HO HO R HO O HO O HO HO HO HO + + HO O+ O -HB OR HO H R HO B an α-glycoside HO HO HO R R HO oxycarbenium HO O HO O O+ OR cation HO HO HO H -HB+ HO B a β-glycoside Carbohydrates: Glycosides N-glycoside formation: HO O+ HO OH oxycarbenium cation Carbohydrates: Reducing and Non-reducing OH HO HO O HO OH HO OH HO Tollens reagent: HO HO O Ag+, HO– reducing sugar: aldehyde reactivity is accessible HO HO O HO OCH2CH3 HO non-reducing sugar: stable acetal Carbohydrates: Disaccharides 6 HO OH O HO OH HO 1 OH HO 4' O HO O O O O HO OH OH HO HO HO HO HO 1' an α-1,4'-glycosidic linkage an β-1,4'-glycosidic linkage lactose HO HO O HO HO O OH O HO HO OH an α-linkage at glucose a β-linkage at fructose sucrose - table sugar Carbohydrates: Disaccharides 6 HO OH O HO OH HO 1 OH HO 4' O HO O O O O HO OH OH HO HO HO HO HO 1' an α-1,4'-glycosidic linkage an β-1,4'-glycosidic linkage lactose HO HO O HO HO O OH O HO PRACTICE PROBLEM HO OH which ones are reducing an α-linkage at glucose sugars ? a β-linkage at fructose sucrose - table sugar Carbohydrates: Disaccharides Disaccharide identification, similar to PROBLEM 68 fully O-methylated disaccharide X disaccharide X H+ CH3I R Ag2O R OH OCH3 R R Carbohydrates: Disaccharides Disaccharide identification, similar to PROBLEM 68 fully O-methylated disaccharide X disaccharide X H+ CH3I R Ag2O R OH OCH3 R R Carbohydrates: Common Polysaccharides starch: 20% 80% Carbohydrates: Common Polysaccharides cellulose: 90% of cotton, 50% of wood Carbohydrates: Common Polysaccharides cellulose: 90% of cotton, 50% of wood Carbohydrates: Common Polysaccharides cellulose: 90% of cotton, 50% of wood Carbohydrates: Common Polysaccharides Carbohydrates: Common Polysaccharides PRACTICE PROBLEM 53 A D-aldopentose is oxidized by nitric acid to an optically active aldaric acid. A Wohl degradation of the aldopentose leads to a monosaccharide that is oxidized by nitric acid to an optically inactive aldaric acid. Identify the aldopentose Carbohydrates: Common Polysaccharides PRACTICE PROBLEM 51 Monosaccharide A is a diastereomer of D-lyxose. Treatment of A with nitric acid forms an optically inactive aldaric acid. A undegoes a Kiliani- Fischer synthesis to form B and C. B is oxidized by nitric acid to an optically active aldaric acid, and C is oxidized to an optically inactive aldaric acid. Wohl degradation of A forms D, which is oxidized by nitric acid to an optically inactive aldaric acid. Wohl degradation of D forms a D-aldotriose. Identify A, B, C, and D..