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406-4 Sugars Di and Rings

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406-4 Sugars Di and Rings Wood Chemistry Wood Chemistry Hemiacetal Formation O - O Wood Chemistry R C H OH R C H PSE 406/Chem E 470 R C H .. O O + OR R H R H Lecture 4 Hemiacetal More Sugars: Disaccharides and Rings A hemiacetal is a compound having the C(OH)OR group that results from the reaction of an aldehyde with one mole of an alcohol. Sugar molecules contain an aldehyde group and lots of alcohol groups. PSE 406 - Lecture 4 1 PSE 406 - Lecture 4 2 Hemiacetal Formation in Important Monosaccharide Wood Chemistry Sugars Wood Chemistry Projections C H 2O H CH 2 O H H C O.. H H H C O CHO C O H C O H O H H C CH OH O H H C H OH 2 OH H O C C H H H HO C C O HO H H O H H H O H O HO H OH OH C H OH HO OH 2 C H2O H HO OH H OH HO C H O H HO C H H OH .. O OH OH H H C C O C C H OH H H OH CH2 OH H H H C C C C H OH H OH Fischer Haworth Chair Configuration Notes Notes PSE 406 - Lecture 4 3 PSE 406 - Lecture 4 4 1 1 Wood Chemistry Conformation: The Chair Wood Chemistry Conformation: Other Forms a=axial a e=equatorial e HO CH2OH O HO OH OH Skew Boat Chair b-d-glucopyranose Boat The most stable form of a sugar in a six membered ring is in the chair formation. The substituent groups on the molecule are either in an axial or equatorial position depending on what gives the most stable molecule. Check out the 3D version We won’t be worrying about these forms. of the above sugar on the notes page. PSE 406 - Lecture 4 5 PSE 406 - Lecture 4 6 Wood Chemistry The Haworth Projection Wood Chemistry Formation of Anomers OH H CH2OH l Ring closure creates new H l This is a very common O O way that wood chiral center at C1; new HO OH pair C1 epimers termed HO H chemists draw sugars H OH HO OH anomers. For d sugars, in the ring form. H OH OH the following is true: a D glucopyranose l In this projection, the » alpha form: OH below the OH thick bonds are l Substituents are ring H perpendicular to the » beta form: OH above the parallel to the plane of ring H O plane of the paper the paper and lie either HO l For l sugars, the opposite HO OH above or below the H is true. OH plane of the molecule H H b D glucopyranose PSE 406 - Lecture 4 7 PSE 406 - Lecture 4 8 2 2 Wood Chemistry Nomenclature Wood Chemistry Mutarotation CH2OH C H2OH H O Notes CH2O H O H OH O O O H H H O H H H H OH H H OH H HO H OH H OH H H HO OH H H H OH H O H OH CH2OH H O H H O H b-d-glucopyranose CH2OH a -d-glucopyranose OH OH b-d-xylopyranose H b-d-xylofuranose H H CH(OH)2 H C O H OH H OH H HO HO H H OH CH2OH H H OH O O CH2OH CH2OH d-glucose (hydrate form) H d-glucose (open chain) HO H H HO H H H O O OH OH O H H H OH H OH H O H OH H H HO H OH H H O H H O H H OH H OH a-d-xylofuranose a-d-glucofuranose b-d-glucofuranose a-d-xylopyranose PSE 406 - Lecture 4 9 PSE 406 - Lecture 4 10 Wood Chemistry Fischer to Haworth Wood Chemistry Fischer Formula Manipulation l In order to convert a Fischer projection of a sugar to l Manipulation of Fischer formulas will change a Haworth project, certain rules must be followed in conformation of structures so this must be done order to maintain correct orientation of the molecule. carefully as in the following example. l Remember, the horizontal bonds in the Fischer Br H o o C2H5 90 90 H CH3 rotation C H Br exchange projection (solid wedges) are out of the plane and the 2 5 rotation CH3 H groups C2H5 CH3 vertical wedges (broken wedges) are into the plane. Br (R) (S) (R) CH3 CH3 exchange groups H H OH C OH H H C2H5 C2H5 CH3 CH C H C2H5 3 2 5 Br Br (R) (S) PSE 406 - Lecture 4 11 PSE 406 - Lecture 4 12 3 3 Monosaccharides Wood Chemistry Fischer to Haworth Wood Chemistry D Versus L, Part II 1 CHO H OH H OH H OH 2 6 H OH H OH C H2OH CH2OH H OH 3 O H H OH H OH HO 5 HO H 4 O OH HO H HO H 4 1 H HO O H 5 3 H OH H O HOH2C H 2 OH 6 CH2OH CH2OH CH2OH O OH OH OH H HO HO H H H OH H H l Modify the Fischer formula so that all of the ring atoms lie along OH OH a vertical line. When rotating substituents around a chiral b-D-Glucopyranose b-L-Glucopyranose carbon, to keep the correct configuration, after a 90 rotation, the opposite substituents must be switched. Mirror Images l Proceed around the Haworth formula placing the groups on the (Enantiomers) left above the hexagon and those on the right below the plane. PSE 406 - Lecture 4 13 PSE 406 - Lecture 4 14 Wood Chemistry Linkages Between Sugars Wood Chemistry Linkages Between Sugars l In the tree, monosaccharides l The glycosidic linkage CH2OH OH are linked through enzymatic between the glucose units is processes. O O CH2OH OH OH between the b C1 of one O O OH OH l Linkage proceeds through a OH glucose to C4 of the other OH dehydration process (loss of HO O OH glucose. So this bond is a HO OH CH2OH O H2O). b(1®4) linkage. OH CH OH l Cellobiose 2 The bond between the 4-O-(b-D-Glucopyranosyl)-D-Glucopyranose glucoses units in cellobiose l The glucose molecules in Cellobiose the drawing on the right are 4-O-(b-D-Glucopyranosyl)-D-Glucopyranose is a glycosidic bond. Once l Cellobioseis disaccharide opposite to make drawing linked, the glucose unit on produced from the partial C6 the left is no longer a hydrolysis of cellulose. It is the b(1®4) linkage easy. CH2OH hemiacetal , it is now an not naturally found in wood. C5 O C4 acetal . l The squiggly bond on C1 OH C 1 HO C2 OH above means it can be either C3 a or b. OH PSE 406 - Lecture 4 15 PSE 406 - Lecture 4 16 4 4 Cellulose polymerized by Wood Chemistry condensation reactions Wood Chemistry More Disaccharides CH2OH l Neither of these CH2OH l Removal of uridine diphosphate(UDP) during polymerization O Uridine O sugars are found in OH HO O O wood. Sucrose occurs HO CH2OH O=P -O- OH OH O naturally in sugarcane Sucrose - O=P -O a-D-Glucopyranosyl-b-D-Fructofuranoside O C H2OH OH and in sugar beets. O HO HO O O H O Maltose is formed CH OH + HO O CH2OH 2 HO OH C H OH HO 2 through the O O O OH CH2OH degradation of starch. OH OH HO O OH OH C H OH OH OH 2 Maltose O HO HO O O + UDP 4-O-(a-D-Glucopyranosyl)-D-Glucopyranose HO O O HO O CH2OH OH C H2OH PSE 406 - Lecture 4 17 PSE 406 - Lecture 4 18 Wood Chemistry Reducing End Groups l Sugars containing aldehydes and ketones are referred to as reducing sugars. l These sugars will reduce copper in a specific reducing substances test. The aldehyde or ketone groups are oxidized by the copper. l Sucrose is not a reducing substance + 1+ RC HO + C u2 RC O OH + C u PSE 406 - Lecture 4 19 5 5.
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