Arabinose, configuration Kiliani-Fischer synthesis

Arabinose, configuration of. 982 Kiliani-Fischer synthesis on. 995 Arachidic acid, structure of, 1062 Arachidonic acid, eicosanoids from, 1069-1070... 

Application of the Kiliani-Fischer synthesis to the aldopentose D-arahinose produces aldohexoses D-glucose and D-mannose. Because the Kiliani-Fischer synthesis incorporates the stereocenters of D-arabinose without changes, D-glucose and D-mannose must have the same configurations at carbons 3,4, and 5 as does D-arabinose at carbons 2, 3, and 4, respectively. Furthermore, D-glucose and D-mannose must differ only in their configuration at carbon 2. 

The Kiliani-Fischer synthesis lengthens a carbohydrate chain hy adding one carhon to the aldehyde end of an aldose, thus forming a new stereogenic center at C2 of the product. The product consists of epimers that differ only in their configuration about the one new stereogenic center. For example, the Kiliani-Fischer synthesis converts D-arabinose into a mixture of D-glucose and D-mannose. 

When the Kiliani-Fischer synthesis is performed on the sugar known as (-)-arabinose, the two sugars known as (-l-)-glucose and (+)-mannose are obtained. This means that (-l-)-glucose and (-l-)-mannose are C-2 epimers in other words, they have the same configuration at C-3, C-4, and C-5. Consequently, (-b)-glucose... 

Further, when the two acids were separated and the Fischer-Kiliani synthesis was performed, (H-)-glucose and (+)-mannose were obtained. Fischer s proof then depended, in part, on the relationship between the structure of D-glucose and D-arabinose, and Fischer s problem was to determine the configurations of C-2 and C-3 of D-arabinose. 

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