Streptomyces echinoruber sp. nov. produces several red pigments. The major component, rubrolone, has been identified as 8(R),9(R),10(S),10a(R)-tetrahydro-9,10,1Oa,11-tetrahydroxy-3,8-dimethyl-l-propyl-6aH(S)-pyrano [2",3": 5',4]furo [2',3': 5,6]azuleno[2,3-c]pyridine-5,13-dione (1) by single crystal X-ray analysis of a suitable derivative.A second pigment, B, is probably structurally closely related.Streptomyces echinoruber (X-14077, NRRL 8144) isolated from a sample of soil collected in eastern The culture produced one major pigment, A (rubrolone), a structurally related minor component B, a third pigment C which was not obtained pure, as well as traces of several other red compounds.The three pigments A, B and C were separated by thin-layer chromatography on silica gel F254 plates using methanol-chloroform (1: 3) as a solvent system. The Rf values were as follows: pigment B, 0.28; pigment A, 0.13; and pigment C, 0.03.Assays on the fermentation were carried out by separating the crude pigment mixture on thin-layer plates and estimation of the compounds by means of UV spectroscopy at 520 rim".The broth filtrate obtained after a fermentation of culture X-14077" was extracted with n-butanol and the solvent removed at reduced pressure and low temperature. The residue contained the major pigment A in a concentration of about 20% together with a minor pigment B and other pigments. Separation of the pigments A, B, and C by chromatography on silica gel using chloroform with increasing amounts of methanol as eluant afforded the compounds in a purity of 70-80%. Further purification was obtained by adsorption on XAD2 resin followed by elution with water containing increasing amounts of methanol. carbons.The dissociation constants were measured to be pKa1~1.37, pKa2-=6.36 and pKa3-12.8.It was soon recognized from these physical-chemical data that the empirical formula of the red pig-
