Dodecadepsipeptide

Valinomycin and the Enniatins. Neutral ionophores such as the cycHc dodecadepsipeptide valinomycin [2001-95-8] C H QN O g, (Fig. 8) from StreptomjcesJulvissimus (179), and the cycHc hexadepsipeptides enniatin [11113-62-5] and beauvericin [26048-05-5] from fungi (180—182),... 

Valinomycin (137) is a macrocyclic dodecadepsipeptide and has shown an unequalled K+/Na discrimination.5" As a consequence of this prime ionophorous behaviour many studies have been carried out on both the free ligand and on its metal complexes, and here discussion is restricted to the nature of the metal complexes. 

For examfde, cydic dodecadepsipeptide antibiotic valinomycin (18) is refure-sented as Cydo-(D-Val-Lac-Val-D-Ifyv)3 where Lac and Hyv re esent lactic add and cr-oxyisobutyric add, re ctively. ValinonQrcin selectively binds K, when it acts as an antibiotic. As shown in Fig. 31, valinomycin takes a bracelet structure and has a cavity in the middle with a diameter of 6—7A. Sizes of hydrated cations are... 

Various lipophilic natural product antibiotics that have a hydrophobic exterior and a shielded hydrophilic interior capable of binding and transporting ions are known as ionophores. The three ionophores that are most commonly used as probes of ion transport across mitochondrial membranes are the Streptomyces cyclic dodecadepsipeptide valinomycin (57), gramicidin pentadecapeptides (e.g., valine-gramicidin A,... 

Valinomycin is a dodecadepsipeptide, which is to say that it contains twelve residues with alternating peptide and ester groupings. Its sequence... 

For examfde, cyclic dodecadepsipeptide antibiotic valinomycin (18) is represented as Cyclo D-Val-Lac-Val-D-ifyv)3 where Lac and Hyv re esent lactic acid and a-oxyisobutyric add, re ctively. ValinoiiQrcin selectively binds K, when it acts as an antibiotic. As shown in Fig. 31, valinomycin takes a bracelet structure and has a cavity in the middle with a diameter of 6—7A. Sizes of hydrated cations are 4.5—5.0 A for K, Rb, and Cs and 5.5—7.4 A for Na and Li . It is understandable that the cavity fits in with K. Carbonyl groups are distributed along the inside wall of the cavity which is necessarily polar. Alifdiatic side chains form the outside wall of the bracelet whidi is necessarily nonpolar. Valinomycin binds in the hydro-0ulic interior of the cavity and transports the ion across the lipid bilayer of the cell... 

Valinomycinis probably the best known and characterized of the natural ionophoretic, antibiotic compounds. It is a K -selective carrier molecule that is produeed by Streptomyces fulvissimusy It is a dodecadepsipeptide comprised of 12 alternating amino and hydroxy aeids to form a neutral, macrocyclic ionophore (Fig. 1). 

Valinomycin is a macrocyclic dodecadepsipeptide with 12 subunits — amino- and hydroxycarboxylic acids — which are connected by alternate peptide and ester bonds. It consists of three identical fragments D-Hylv-D-Val-L-Lac-L-Val (Fig. 1). Although the valinomycin structure has been discussed in a recent review on complex formation of monovalent cations with biofunctional ligands it is described here in some detail... 

Valinomycin A cyclic dodecadepsipeptide whose antibiotic activity is due to its abihty to transport cations, preferentially potassium ions, across bacterial cell membranes, thus disturbing the membrane potential. 

Acetoxypropanal, the hydroformylation product of vinyl acetate, can also be used in a Strecker a-amino acid synthesis to provide threonine, as well as being a source of chiral 2-hydroxypropanal, which is a very useful building block in the syntheses of steroids, antibiotics, and peptides For example, the potassium ionophore vali-nomycin, a dodecadepsipeptide that displays significant antibiotic activity, contains three chiral moieties derived from 2-hydroxypropanal. 

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