Mixed Biogenesis Mevalonate-Benzenoid Precursor

Compounds of Mixed Biogenesis Mevalonate — Benzenoid Precursor 

The acetone extracts of Halichondria panicea yielded (52) five new related triprenylphenols , panicein-A, -Bi, -B2, -B3 and -C, each containing an aromatic sesquiterpenoid moiety linked to a quinol or quinone system, except for panicein-B2, which is the corresponding chromenol of panicein-B3 and probably an artifact of isolation. The structures of the paniceins are shown in Chart 14. 

Chart 14. Structures of paniceins, triprenylphenols from Halichondria panicea 

Structures for panicein-Bi (120) and B2 (121), the corresponding quinone and chromenol of panicein-Ba, respectively, and the structure for panicein-A (119) were proved by chemical interrelation with pani-cein-Ba. 

In the sesquiterpenoid moiety the paniceins have the uncommon feature of an aromatic ring which, notably, has been encountered already in renieratene (126) and isorenieratene (127). These are arylcarotenoids found in the sponge Reniera japonica (syn. Halichondria panicea) 183, 184), which also yielded a third aromatic carotenoid renierapurpurin (130) 185). 

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Compounds of mixed biogenesis originating partly from mevalonate and partly from a benzenoid precursor have been found in four Dictio-ceratida and in one apparently unrelated species (Table 6). 

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