Monosaccharides Kiliani-Fischer synthesis

Much of the chemistry of monosaccharides is the familiar chemistry of alcohols and aldehydes/ketones. Thus, the hydroxyl groups of carbohydrates form esters and ethers. The carbonyl group of a monosaccharide can be reduced with NaBH4 to form an alditol, oxidized with aqueous Br2 to form an aldonic acid, oxidized with HNO3 to form an aldaric acid, oxidized enzymatically to form a uronic acid, or treated with an alcohol in the presence of acid to form a glycoside. Monosaccharides can also be chain-lengthened by the multistep Kiliani-Fischer synthesis and can be chain-shortened by the Wohl degradation. 

What monosaccharides would be formed in a Kiliani-Fischer synthesis starting with one of these ... 

Reduction of an aldose forms one alditol reduction of a ketose forms two alditols. Br2 oxidizes aldoses, but not ketoses ToUens reagent oxidizes both. Aldoses are oxidized to aldonic acids or aldaric acids. Aldoses and ketoses react with three equivalents of phenyUiydrazine, forming osazones. C-2 epimers form identical osazones. The Kiliani-Fischer synthesis increases the carbon chain of an aldose by one carbon— it forms C-2 epimers. The Ruff degradation decreases the carbon chain by one carbon. The OH groups of monosaccharides react with acetyl chloride to form esters and with methyl iodide/silver oxide to form ethers. 

Kiliani-Fischer synthesis (p. 931) molecular recognition (p. 921) monosaccharide (p. 922) mutarotation (p. 935)... 

Show the common reactions of monosaccharides that were presented in this chapter oxidation with nitric acid oxidation with bromine reduction with sodium borohydride esterification glycoside formation and the Kiliani-Fischer synthesis. 

Kiliani-Fischer synthesis 1161 Lsugar 1142 monosaccharides 1140 mutarotation 1149 N-glycosides 1169... 

The Kiliani—Fischer synthesis extends chains of monosaccharides using the formation of a cyanohydrin to generate the additional stereogenic center. In the first step, one enantiomeric form of an aldose reacts with HCN to give a mixture of diastereomeric cyanohydrins. We recall that the formation of an additional stereogenic center in a chiral compound results in some stereoselectivity. A mixture results, but because diastereomers have different physical properties, the reaction mixture can be separated to give two cyanohydrins. 

The Ruff degradation and the Wohl degradation both cleave the carbonyl-bearing carbon from a monosaccharide to form a new monosaccharide of one fewer carbon. The Nef reaction adds one carbon to a monosaccharide to form a new monosaccharide, as does the Fischer-Kiliani synthesis. 

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