lecture 25 - Digitoxose Carbohydrates Chapter 25 Digitoxose...

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Carbohydrates Carbohydrates Chapter 25 Chapter 25 Digitoxose Digitoxose ± Digitoxose: a monosaccharide obtained from the hydrolysis of digitoxin. ± Digitoxin: obtained from the ornamental flowering plant “Foxglove” and use as a medicine for heart deseases Carbohydrates ± Carbohydrate Carbohydrate : a polyhydroxyaldehyde , a polyhydroxyketone , or a compound that gives either of these compounds after hydrolysis Photosynthesis
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Carbohydrates Carbohydrates ± Monosaccharide Monosaccharide : a carbohydrate that cannot be hydrolyzed to a simpler carbohydrate they have the general formula C n H 2n 2n O n , where n varies from 3 to 8 aldose : a monosaccharide containing an aldehyde group ketose : a monosaccharide containing a ketone group Monosaccharides Monosaccharides ± Monosaccharides are classified by their number of carbon atoms Hexose Heptose Octose Triose Tetrose Pentose Formula Name C 3 H 6 O 3 C 4 H 8 O 4 C 5 H 10 O 5 C 6 H 12 O 6 C 7 H 14 O 7 C 8 H 16 O 8 Monosaccharides ± There are only two trioses aldehyde group ketone group Monosaccharides Monosaccharides ± Glyceraldehyde contains a stereocenter and exists as a pair of enantiomers CH O C HO H CH 2 OH C 2 OH H ( S )-Glyceraldehyde ( R )-Glyceraldehyde Fischer Projections ± Fischer projection: Fischer projection: a two dimensional representation for showing the configuration of carbohydrates horizontal lines represent bonds projecting forward vertical lines represent bonds projecting to the rear D,L D,L Monosaccharides Monosaccharides ± In 1891, Emil Fischer made the arbitrary assignments of D -a n d L - to the enantiomers of glyceraldehyde H 2 OH CHO 2 OH H DD L-Glyceraldehyde D-Glyceraldehyde [ α ] 25 = +13.5 [ α ] 25 = -13.5
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D,L D,L Monosaccharides Monosaccharides ± According to the conventions proposed by Fischer D - monosaccharide: a monosaccharide that has the same configuration at its penultimate carbon as D -g lyceraldehyde; that is, its -O H i s on the right when written as a Fischer projection D,L D,L Monosaccharides Monosaccharides ± According to the conventions proposed by Fischer L - monosaccharide : a monosaccharide that has the same configuration at its penultimate carbon as L lyceraldehyde; that is, its on the left when written as a Fischer projection ± Here are the two most abundant D -a ldotetroses and the two most abundant D ldopentoses in the biological world D,L Monosaccharides D-Erythrose D-Threose CH 2 OH CHO OH OH H H CH 2 OH CHO OH H HO H D-Ribose 2-Deoxy-D- ribose CH 2 OH CHO OH OH H H CH 2 OH CHO OH H H H OH H H D-aldotetroses D-aldopentoses D,L D,L Monosaccharides Monosaccharides ± And the three most abundant hexoses CH 2 OH H C H 2 H O D-Fructose CHO H H H 2 H D-Glucose H 2 H H H D-Galactose Amino Sugars ± Amino sugar: Amino sugar: a sugar that contains an -NH 2 group in place of an H gr o u p only three amino sugars are common in nature N cetyl -D lucosamine (a component of chitin) is a derivative of D Amino Sugars Amino Sugars ± Amino sugar: Amino sugar: a sugar that contains an 2
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This note was uploaded on 09/06/2009 for the course CHEM chem 12 AB taught by Professor Valentin during the Spring '09 term at Evergreen Valley.

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lecture 25 - Digitoxose Carbohydrates Chapter 25 Digitoxose...

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