Juglorubin

The isolation of Juglorubin (2) from cultures of Streptomyces spp., which produce a series of other hydroxynaphthoquinones, is described. 2 is a unique, unusually condensed ionic colorant with the formula C 28 H 17 NaO 11 . The structure of 2 was elucidated by X-ray structure analysis of the acetyl dimethyl derivative 4. Detailled spectral information is given for the previously unknown benzindenylid-quinone molecule, e.g. the assignment of the 13 C NMR signals. 2 is probably formed in a complex reaction from two Juglomycin C units involving a late C—C-bond cleavage.