Adenosine selective phosphorylation

Phosphorylation The monotriethylammonium salt of (1) reacts with an alcohol (ROH) in the presence of an acid catalyst (HOAc, TFA) and triethyl-amine in pyridine to give monoesters, R0P(0)(0H)2, in about 75-85% yield. This reaction is particularly useful for selective phosphorylation of the 5 -hydroxyl group of unprotected nucleosides. Thus adenosine can be converted into adenosine 5 -phosphate in 77% yield. 

The modes of action for niclosamide are interference with respiration and blockade of glucose uptake. It uncouples oxidative phosphorylation in both mammalian and taenioid mitochondria (22,23), inhibiting the anaerobic incorporation of inorganic phosphate into adenosine triphosphate (ATP). Tapeworms are very sensitive to niclosamide because they depend on the anaerobic metaboHsm of carbohydrates as their major source of energy. Niclosamide has selective toxicity for the parasites as compared with the host because Httle niclosamide is absorbed from the gastrointestinal tract. Adverse effects are uncommon, except for occasional gastrointestinal upset. 

Fullerton DA, Kirson LE, Jones SD, McIntyre RC (1996) Adenosine is a selective pulmonary vasodilator in cardiac surgical patients. Chest 109(1) 41—46 Gao Z, Li BS, Day YJ, Linden J (2001) A3 adenosine receptor activation triggers phosphorylation of protein kinase B and protects rat basophilic leukemia 2H3 mast cells from apoptosis. Mol Pharmacol 59(l) 76-82... 

In order to enhance affinity and selectivity for Brc-Abl, we modified the inhibitor methylating at positions I and II (Fig. 7.5d). The synthesis of the wrapping prototype recapitulates imatinib synthesis [38], as described in [39], To test whether the specificity and affinity for Brc-Abl improved, we conducted a spectrophotometric kinetic assay to measure the phosphorylation rate of peptide substrates in the presence of the kinase inhibitor at different concentrations. This assay couples production of adenosine diphosphate (ADP), the byproduct of downstream phosphorylation, with the concurrent detectable oxidation of reduced nicotinamide adenosine dinucleotide (NADH). The oxidation results upon transfer of phosphate from PEP (phospho-enolpyruvate) to ADP followed by the NADH-mediated reduction of PEP to lactate. Thus, phosphorylation activity is monitored by the decrease in 340 nm absorbance due to the oxidative conversion NADH->-NAD+ [34, 39]. 

One of the best examples of an enzymatic dephosphorylation for a synthetic purpose is shown in the entry 5 ofTable 13-6. A 5 -ribonucleotide phosphohydrolase was used in the synthesis of (-)-aristeromycin, a carbocyclic analog of adenosine. The (-)-enantiomer of aristeromycin shows some cytostatic and antiviral activity, while the (+)-enantiomer is inactive. The racemate ( )-5 -phosphorylated aristeromycin was resolved by selective hydrolysis of the (-)-enantiomer with the hydrolase. The (-)-alcohol and the (+)-5 -phosphate derivative were separated easily on a silica gel column. Hydrolysis of the (-t-)-enantiomer with calf intestinal phosphatase yielded pure (+)-alcohol. 

At relevant inotropic and vasorelaxant concentrations, milrinone is a selective inhibitor of peak III cAMP phosphodiesterase isozyme in cardiac and vascular muscle. This inhibitory action is consistent with cAMP-mediated increases in intracellular ionized calcium and contractile protein phosphorylation and relaxation in vascular muscle. Additional experimental evidence also indicates that milrinone is not a beta-adrenergic agonist nor does it inhibit sodium-potassium adenosine triphosphatase activity as do the digitalis glycosides. 

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