Heterocyclic Chemistry

1. Heterocyclic Chemistry Heterocyclic Chemistry

2. Heterocyclic Chemistry Physical properties of monosaccharides

3. Heterocyclic Chemistry Interconversion of glucose , mannose and fructose

4. Heterocyclic Chemistry I- Reduction of monosaccharides Since they contain carbonyl group in the form of aldehydic or ketonic group these groups can be reduced by reducing agents such as NaBH4 or catalytic hydrogenation (H2 / Ni) to the corresponding alcoholic group i.e. to a primary or secondary alcoholic group respectively. The name of the resulting polyhydroxy compound is derived by replacing the suffix ose in the sugar name by itol e.g1. Reduction of glucose to glucitol (sorbitol) where the aldehydic group is reduced to a primary alcoholic group that is not a stereogenic center

5. Heterocyclic Chemistry I- Reduction of monosaccharides

6. Heterocyclic Chemistry II- Oxidation of monosaccharides

7. Heterocyclic Chemistry II- Oxidation of monosaccharides b) Oxidation by nitric acid (HNO3) This reagent oxidize both aldehydic and primary alcoholic group to give dicarboxylic acid known as aldaric acid

8. Heterocyclic Chemistry II- Oxidation of monosaccharides

9. Heterocyclic Chemistry III- Glycosides formation (sugar acetals and ketals) Cyclic hemiacetal and cyclic hemiketal forms of monosaccharides convert to acetals and ketals (diethers) respectively upon reaction with alcohols in the presence of catalytic amounts of dry acids. The new C-O bond is called glycosidic linkage The alkoxy group at the anomeric carbon is known as aglycon and the formed acetal as glycoside These glycosides are non reducing sugars due to absence of free OH group at the anomeric carbon thus they can not reopen to give the open chain form which then undergoes oxidation.

10. Heterocyclic Chemistry IV- Ether formation

11. Heterocyclic Chemistry VI-Osazone formation (reaction with phenyl hydrazine) When aldoses and ketoses are treated with an excess of phenyl hydrazine, they are converted into well defined crystalline structures known as osazones that have different shapes thus they are used for identification purposes. An osazone is a phenyl hydrazone derivative of both C1 and C2 of an aldose or a ketose thus the configuration at these carbons is destroyed resulting in that a sugar and its epimer at C2 give the same osazone ( e.g. mannose and glucose) also a sugar and its functional isomer give the same osazone (e.g. glucose and fructose).

12. Heterocyclic Chemistry VI-Osazone formation (reaction with phenyl hydrazine)

13. Heterocyclic Chemistry VIII- Kiliani- Fischer synthesis This reaction is used to increase the length of the aldose chain where a new carbon is added and the original aldehydic group convert to a secondary alcoholic group and becomes atom number 2.

14. Heterocyclic Chemistry Di-, Oligo- and Poly-saccharides

15. Heterocyclic Chemistry Important disaccharides

16. Heterocyclic Chemistry Polysaccharides Polysaccharides contain hundreds or thousands of carbohydrate units All of them are non reducing sugars, since the anomeric carbons are connected through glycosidic linkages Examples: starch, glycogen and cellulose ; all of them are polymers of glucose There are two forms of starch; amylose and amylopectin Starch -Amylose (10-20 %) Starch- Amylopectin(80- 90 %)

17. Heterocyclic Chemistry Polysaccharides Glycogen (animal starch), structurally similar to amylopectin, containing both a(1 4) glycosidic linkages and a(1 6) branch points but it is more branched It is abundant in the liver and muscles. Cellulose (in plants and wood), it is unbranched polymer made of ß-D-glucose units i.e contains ß(1 4) glycosidic linkages