Antibiotic substance produced by an unidentified Streptomyces culture (PRL 1642). Composed of 4 moles each of d-()-valine and d-()-α-hydroxyisovaleric acid, linked alternately by ester and amide bonds to form a 24-membered ring: Vining, Taber, Can. J. Chem. 35, 1109 (1957). Structure studies: Shemyakin et al., Tetrahedron Lett. 1963, 351, Tetrahedron 19, 995 (1963).
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