Monensin sodium salt

Scheme 9. Synthesis of (+)-monensin sodium salt (sodium salt of 1).

FIGURE 16 3 (a) The structure of monensin (b) The structure of the sodium salt of monensin showing coordination of Na yellow) to the six oxygens shown in red in the structural formula Flydrogen atoms have been omitted from the model for clarity... 

This experiment describes the preparation and evaluation of two liquid-membrane Na+ ion-selective electrodes, using either the sodium salt of monensin or a hemisodium ionophore as ion exchangers incorporated into a PVG matrix. Electrodes prepared using monensin performed poorly, but those prepared using hemisodium showed a linear response over a range of 0.1 M to 3 X 10 M Na+ with slopes close to the theoretical value. 

You will note that the oxygen atoms attached to carbons 5 and 12 in 43 reside in proximity to the C-9 ketone carbonyl. Under sufficiently acidic conditions, it is conceivable that removal of the triethylsilyl protecting groups would be attended by a thermodynamically controlled spiroketalization reaction.30 Indeed, after hydro-genolysis of the C-26 benzyl ether in 43, subjection of the organic residue to the action of para-toluenesulfonic acid in a mixture of methylene chloride, ether, and water accomplishes the desired processes outlined above and provides monensin methyl ester. Finally, saponification of the methyl ester with aqueous sodium hydroxide in methanol furnishes the sodium salt of (+)-monensin [(+)-1], Still s elegant synthesis of monensin is now complete.13... 

Although the acidic antibiotics do not show the high selectivity characteristic of the neutral ones, there is still some preference, a strong one for monovalent as compared with divalent cations, and within the monovalent cations a variation from one acid to another. Monensin prefers sodium to potassium. The larger nigeridn, (X7), prefers potassium to sodium its silver, potassium, and sodium salts are isomorphous and anhydrous. Crystal structure determinations on the silver salt were carried out independently by workers in the U.S.A. (78) and in Japan... 

Monensin and its sodium salt are slightly sol in water more sol in hydrocarbons very sol in other organic solvents. 

Monensin (14.12), isolated from Streptomyces cinnamonensis, is a fully hydrogenated pyranyl-furyl-furyl-dioxaspirodecyl derivative of butyric acid, mol. wt. 670 (Lutz, Winkler and Dunitz, 1971). The sodium salt is more soluble in hydrocarbons than in water. It is used to promote growth of cattle, acting by changing active transport in anaerobic rumen bacteria, which favours survival of strains which produce nutritive aliphatic acids. It is also used to treat coccidiosis in chicks. For another example, see gramicidin D (p. 605). 

The structure of the sodium salt of monensin is depicted in Figure 16.3b, where it can be seen that four ether oxygens and two hydroxyl groups surround a sodium ion. The alkyl groups are oriented toward the outside of the complex, and the polar oxygens and the metal ion are on the inside. The hydrocarbon-like surface of the complex permits it to carry its sodium ion through the hydrocarbon-like interior of a cell membrane. This disrupts the normal balance of sodium ions within the cell and interferes with important processes of cellular respiration. Small amounts of monensin are added to animal feed to kill parasites that live in the intestines of chickens, cows, etc. Compounds such as monensin and the crown ethers that affect metal ion transport are referred to as ionophores ( ion carriers ). 

Milling Yellow G [51569-18-7]. Salted out three times with sodium acetate, then repeatedly extracted with EtOH. [McGrew and Schneider JACS 72 2547 1950. See entry under Chlorazol Sky Blue FF. Monensin [17090-79-8] M 670.9. Purified by chromatography. 

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