Production of a novel red pigment, rubrolone, by Streptomyces echinoruber sp. nov. II. Chemistry and structure elucidation.

Abstract
S. echinoruber produces several red pigments. The major component, rubrolone, was identified as 8(R),9(R),10(S),10a(R)-tetrahydro-9,10,10a,11-tetrahydroxy-3,8-dimethyl-1-propyl-6aH(S)-pyrano[2",3":5'',4]furo[2'',3'':5,6]azuleno[2,3-c]pyridine-5,13-dione by single crystal X-ray analysis of a suitable derivative. A 2nd pigment, B, is probably structurally closely related.