Structural elucidation of fructose

1. STRUCTURAL ELUCIDATION OF FRUCTOSE Presented by; M Pharm (Pharmaceutical Chemistry) students Gunturu .Aparna Akshintala. Sree Gayatri Thota. Madhu latha Kamre. Sunil Daram. Sekhar University college of pharmaceutical sciences Department of pharmaceutical chemistry Acharya Nagarjuna University Guntur 1

2. STRUCTURAL ELUCIDATION OF FRUCTOSE 2

3. Fructose also known as levulose or fruit sugar is found in many fruits and in honey. It occur in combination with glucose in cane and beet sugars. The most important source of fructose is the polysaccharide inulin. Commercially, fructose is obtained by the hydrolysis of inulin. Crystalline D-fructose melts at 104 c, it is the sweetest of the sugars, but is seldom used in pure form .it exibits mutarotation; the specific rotation values of alfa- and beta –and equilibrium mixture are -21 , 133.5 and -92.3 ; respetively. 3

4. Fructose responds most of the usual properties of the ketonic and hydroxyl groups. A very important property of the fructose is that although it has no aldehydic group ,it reduces fehling solution and Tollen’s reagent. This reducing property of fructose is said to be due to the presence on an α-hydroxy ketonic group which is readily oxidised by fehling and Tollen’s reagent. Tartaric acid 4

5. Fructose from an insoluble calicium fructosate with lime water (difference from glucose) . This fact is utilised in the separation of glucose and fructose by the hydrolysis of sucrose. CONSTITUTION OF FRUCTOSE : From the qualitative and quantitative analysis ,fructose is found to have its molecular formula as C 6 H 12 O 6 Fructose is found to have five hydroxyl groups on five different carbon atoms . 5

6. Fructose forms a cyanohydrin and an oxime indicating the presence of carbonyl group, since fructose on oxidation with nitric acid gives a mixture of tartaric acid and glycolic acid (each having lesser number of carbon atoms), the carbonyl group is ketonic in nature. The formation of glycolic and tartaric acids indicates that the ketonic group is present at second position. 6

7. On reducing with sodium amalgam and water, fructose gives hexahydric acid and sorbitol and mannitol. Which on further reduction with hydriodic acid and red phosphorus gives 2-iodohexane and n-hexane which suggest that in fructose molecule the six carbon atoms are present in a straight chain. 7

8. Fructose on treatment with hydrogen cyanide gives cyanohydrin which on hydrolysis followed by reduction hydriodic acid and red phosphorus give n-butylmethylacetic acid, CH 3 CH 2 CH 2 CH 2 CH(CH 3 ).COOH The formation of this compound again indicates that the ketonic group present at second position . The straight chain structure of fructose may be written as n-butylmethylacetic acid Fructose 8

9. Tartaric acid Glycolic acid Fructose 9

10. CONFIGURATION OF FRUCTOSE: Since the above structure has three asymmetric carbon atoms it may exist in eight ( 2 3 =8) optical isomers. The exact configuration of the fructose is established by that it forms the same osazone as glucose indicating there by that the configurations of C 3 to C 6 atoms of fructose is same as that of glucose . Hence the complete open-chain formula of fructose may be written as below. 10

11. RING STRUCTURE OF FRUCTOSE: Fructose exhibits mutarotation and forms two methyl fructosides. That is α and β forms. The commercial and natural free fructose is most probably β -isomer with a pyranose ring. But the fructose found in sucrose (a disaccharide) and inulin (a polysaccharide) is present inn furanose ring which during hydrolysis is converted into more stable pyranose form. Lastly , since the fructose is laevorotatory and has D-configuration of glucose ,it is denoted by D(-)-fructose . D-Fructose 11