Lycogalic acid

Lycogalic acid (131) and halitulin (132) represent unique analogs (Fig. 8) to the 3,4-diaryl pyrrole scaffold of the natural products previously discussed. Lycogalic acid (131) contains indole rings attached at both C-3 and C-4 of... 

Fig. 8 General Structure of Lycogalic Acid and Halitulin Natural Products...

In the report by Steglich for the isolation of lycogalic acid he also described his synthesis of lycogalic acid dimethyl ester (135) by his biomimetic approach (Scheme 26) as previously presented in Scheme 18. 

Furstner has also used his methodology [58] as presented in Scheme 24 for the preparation of lycogalic acid dimethyl ester (135) and this is presented in Scheme 27. The ability to access indole boronic acids is an important consideration for this particular route. 

Scheme 26 Steglich Group Synthesis of Lycogalic Acid Natural Products...

Steglich et al. also studied the constituents of the fruit bodies of Lycogala epidendrum [17] and isolated not only lycogarubins A-C (31-33) but also lycogalic acid A (35) [18], staurosporinone (36) [19], and arcyriarubin A (6) and arcyriaflavin A (7) previously isolated from Arcyria denudata. 

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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