Erythrose 4-phosphate, acid hydrolysis

L-xy/o-Hexulosonic acid has been prepared via oxidation of 3,4 5,6-di-0-iso-propylidene-L-sorbose and the racemic derivative (296) was produced on thermolysis of the ozonide (27) (see Chapter 3). 3-Deoxy-D-uw6i/io-[l- C]heptulosonic acid 7-phosphate has been synthesized by addition of potassium [ C]cyanide to 2-deoxy-D-ara6i o-hexose 6-phosphate, hydrolysis, and selective oxidation of the resulting 3-deoxyheptonic acid 7-phosphates at C-2 with potassium chlorate-vanadium(v) oxide. A one-step synthesis of a mixture of 3-deoxy-D-r/6o- and -D-araWno-heptulosonic acid 7-phosphates is based on a metal-ion-catalysed reaction of o-erythrose 4-phosphate with oxalacetate. ... 

Prokaryotic organisms synthesise a primary form of vitamin pyridoxol 5 -phosphate from 1-deoxy-D-xylulose 5-phosphate (l-deoxy-D-t/treo-pent-2-ulose 5-phosphate) and 2-amino-2-deoxy-D-threo-tetronic (2-amino-2-deoxy-D-threonic) acid, known as 4-(phosphohydroxy)-L-threonine or 4-hydroxy-i-threonine 4-phosphate. Phosphohydroxythreonine arises from D-erythrose 4-phosphate, a product of decomposition of D-fructose 6-phosphate. Non-phosphorylated forms (pyridoxal, pyridoxol and pyridoxamine) are produced by hydrolysis of the corresponding phosphates. Animals do not synthesise vitamin Bg de novo, only convert the non-phosphorylated forms in the Hver, erythrocytes, and other tissues into the corresponding phosphates and the individual forms of each other. Pyridoxal 5 -phosphate arises by oxidation of pyridoxol 5Lphosphate and transamination of pyridoxal 5 -phosphate provides pyridoxamine 5Lphosphate. Both these forms of vitamin Bg are catalytically active. Pyridoxal 5 -phosphate... 

The p3nranose or furanose structure of the esters appears to influence the rate of hydrolysis. Thus glucose 6-phosphate which can form a pyranose ring is more stable than fructose 6-phosphate which can only form a furanose ring. The acid lability of some compounds such as glycolaldehyde phosphate , erythrose 4-phosphate and erythrulose phosphate may be partly due to the fact that they cannot form ring structures. Furthermore ribose 5-phosphate is more stable than ribulose 5-phosphate and in this case the difference is presumably due to the fact that the former can form a furanose ring while the latter can only exist in the linear form. 

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