Binding and transport of alkali and alkaline earth metal ions by synthetic macrolides containing tetrahydropyran rings

Tajima, Ichiro; Okada, Masahiko; Sumitomo, Hiroshi

doi:10.1021/ja00404a020

Cited by 38 publications

(20 citation statements)

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“…The second is the alkyloxygen scission (b) of the ester linkage, which gives a trans-disubstituted tetrahydropyran ring (SN2 type reaction) or a mixture of cis-and trans-disubstituted tetrahydropyran rings (SN1 type reaction) (10). The third is the C(l)-0(6) bond scission (c) giving rise to trans-disubstituted or a mixture of trans-and cis-disubstituted -lactone rings (11), depending on the types of reactions. Among these, the last mode of bond cleavage is less likely to take place, because the C(l)-0(6) bond (1.390 Á) is much shorter than the ordinary C-0 bond and hence less reactive according to the recent theory of Kirby et al23…”

Section: Resultsmentioning

confidence: 99%

“…6,7 In contrast, cationic polymerization of 6,8-dioxabicyclo[3.2.1]octan-7-one (bicyclic lactone) having the same skeleton as that of the bicyclic lactam above yielded highly selectively 10-, 20-, and 25membered cyclic oligoesters (macrolides) composed of alternating tetrahydropyran ring and ester moieties.8"10 Among these, 20-and 25-membered macrolides act as ion carriers and can be regarded as model compounds for naturally occurring neutral ionophores. 11 Bicyclic acetals, lactones, and lactams consisting of a bicyclo[3.2.1]octane skeleton are relatively easily prepared and there have been a number of publications concerning f Molecular Structure Laboratory, The University of Arizona. their polymerizations.2,4,5 On the contrary, syntheses of bicyclic compounds containing a more strained bicyclo-[2.2.2]octane skeleton are in general difficult and therefore the studies dealing with the polymerization of heterobicyclic monomers of this type have been limited.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and ring-opening polymerization of bicyclic lactones containing a tetrahydropyran ring. 2,6-Dioxabicyclo[2.2.2]octan-3-one

Okada¹,

Sumitomo²,

Atsumi³

et al. 1986

Macromolecules

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis and ring-opening polymerization of bicyclic lactones containing a tetrahydropyran ring. 2,6-Dioxabicyclo[2.2.2]octan-3-one

Okada¹,

Sumitomo²,

Atsumi³

et al. 1986

Macromolecules

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“…For our purpose, however, there is a simpler experimental system that can mimic a cell membrane and ion transport. It has been demonstrated that ionophores can mediate the movement of K + between two aqueous phases are separated by a common organic layer 33–35. The K + -nonactin complex that forms in one aqueous phase can partition into the organic layer.…”

Section: Resultsmentioning

confidence: 99%

Alternating Pattern of Stereochemistry in the Nonactin Macrocycle Is Required for Antibacterial Activity and Efficient Ion Binding

et al. 2009

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Nonactin is a polyketide antibiotic produced by Streptomyces griseus ETH A7796. It is active against a range of Gram positive organisms, acting as an ionophore that has a high selectivity for K + ions. Among the polyketides, nonactin has a unique structure. It is a 32-membered, cyclic tetraester generated from four monomers of nonactic acid, two of which are (+)-nonactic acid and two of which are (−)-nonactic acid. The monomers are arranged (+)-(−)-(+)-(−) in the macrocycle so that nonactin has S4 symmetry and is achiral. As the structure of nonactin is unique, so is the biosynthesis of the compound. There is much evidence that after an early achiral intermediate, there are two mirror image biosynthesis pathways, one for the synthesis of each enantiomer of nonactic acid. Emerging evidence suggests that the two pathways arose from gene duplication followed by divergent evolution. The central question, therefore, raised by both the structure and the biosynthesis of nonactin concerns the benefit, if any, to the producing organism in initially selecting for, and then maintaining, two independent pathways for nonactic acid synthesis and for generating only the achiral diastereoisomer of nonactin.To understand why achiral nonactin is the naturally generated diastereoisomer we prepared through synthesis two alternate diastereoisomers of nonactin, one prepared solely from (+)-nonactic acid and one prepared solely from (−)-nonactic acid, referred to here as 'all-(+)-nonactin' and 'all-(−)-nonactin' respectively. Both all-(+)-nonactin and all-(−)-nonactin were more than 500-fold less active against Gram positive organisms than nonactin confirming that the biosynthesis of both nonactic acid enantiomers, and their incorporation into nonactin, is necessary for biological activity. To understand the lack of antibacterial activity we used isothermal calorimetry to measure the association constant K a , ΔG, ΔH and ΔS of formation for the K + , Na + and NH 4 + complexes of nonactin and all-(−)-nonactin. The natural diastereoisomer had a high selectivity for K + to which it bound approximately 880-fold better than all-(−)-nonactin. We used a picrate partitioning assay to confirm that all-(−)-nonactin, unlike nonactin, could not partition K + ions into organic solvent. To complement the thermodynamic data we used a simple experimental model to mimic ion transport. Using two concentric glass tubes we arranged for two aqueous samples to be separated by a CHCl 3 layer. By following the co-transport of picrate anion from one aqueous layer to the other, through the organic phase, we were able to measure the rates of K + transport that were facilitated by the ionophores. Whereas nonactin allowed for efficient K + transport, all-(−)-nonactin was completely nigel.priestley@umontana.edu. Supporting Information Available: 1 H and 13 C NMR spectra and mass spectra for compounds 8 to 17. This material is available free of charge via the Internet at

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“…The possible interference of pH gradient was largely avoided in the present work because of the use of the buffered aqueous donor and receiver solutions [14] . The concentration of metal chloride in donor solutions was 100-folds that of the metal-ion picrate in order to increase the chemical potential of the cation and thus led to linear correlation of transport percentage with time ( fig.…”

Section: Resultsmentioning

confidence: 99%

Cyclic peptides-assisted transport of metal ions across liquid-organic membrane

Huang

et al. 2001

Chin.Sci.Bull.

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The formation of alkali and alkaline-earth metal picrate complexes with cyclo(Pro-Gly) n ionophores (1, n = 3; 2, n = 4) can facilitate the migration of metal ions across a bulk liquid CH 2 Cl 2 membrane. The migration behavior was studied by measuring the solution absorption at 356 nm, using a UV/Vis spectrophotometer, and the rates can be determined by comparing the initial absorption of donor solutions with the absorption of the corresponding receiver solutions as the function of time. It was found that cyclic peptide 1 shows higher transport activity for the studied alkali and alkaline-earth metal ions than compound 2, which is related to the backbone flexibility of the cyclic peptides. The findings in this work suggest that the rate of ionophore-facilitated ion transport depends not only on the ability of complex formation in aqueous phase, but also on the ability of complex dissociation in organic phase.

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Binding and transport of alkali and alkaline earth metal ions by synthetic macrolides containing tetrahydropyran rings

Cited by 38 publications

References 1 publication

Synthesis and ring-opening polymerization of bicyclic lactones containing a tetrahydropyran ring. 2,6-Dioxabicyclo[2.2.2]octan-3-one

Synthesis and ring-opening polymerization of bicyclic lactones containing a tetrahydropyran ring. 2,6-Dioxabicyclo[2.2.2]octan-3-one

Alternating Pattern of Stereochemistry in the Nonactin Macrocycle Is Required for Antibacterial Activity and Efficient Ion Binding

Cyclic peptides-assisted transport of metal ions across liquid-organic membrane

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