Lycogalic acid from oxidative dimerization

Hoshino et al. described that in cultures of Chromobacterium violaceum, lycogalic acid (35, = chromopyrrolic acid) was derived from tryptophan [18]. It was therefore assumed that lycogalic acid (35) was formed by oxidative dimerization of 3-(indol-3-yl)pyruvic acid followed by reaction of the resulting 1,4-dicarbonyl intermediate with an equivalent of ammonia. On the basis of this idea, lycogarubin C (33) was synthesized from methyl 3-(indol-3-yl)pyruvate (37) in a simple one-pot process (Scheme 4). 

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