Bromo-olefins from Verongia Sponges

Bromo-Olefins from Verongia Sponges.—Full details have been published on the structural elucidation of the bromo-compounds Aeroplysinin-1, Aerothionin, and Homoaerothionin isolated from Verongia sponges. In addition, a new bromo-compound, designated Aeroplysinin-2, has been isolated from the same source, which has added further sustenance to biosynthesis commentary among this closely related group of compounds. 

Aeroplysinin-1, which shows antibacterial activity against Staphylococcus albus. Bacillus cereus, and B. subtilis, was isolated from the Mediterranean sponge Verongia ( s Aplysina) aerophoba. On the basis of spectral data, and degradation to the phenolic nitrile (77), structure (76) was assigned to 

Aeroplysinin-1 Some six months after preliminary publication of structure (76) for Aeroplysinin -1 the enantiomorphic (—)-isomer was isolated from the Caribbean sponge lanthella ardis. C.d. data established the absolute configuration of the (—)-isomer as (78), and this was later confirmed by X-ray analysis. The X-ray structure of ( +)-Aeroplysinin-l was determined later. In the period under review, Minale et al. have reported the isolation of the new bromo-compound Aeroplysinin-2 (79) from V. aerophoba, and furthermore they have shown that the compound undergoes facile photochemical reaction to (80) in daylight. 

Aerothionin and homoaerothionin are tetrabromo-compoimds, isolated from V. thiona and V. aerophoba, and have been shown to be the homologous spirocyclohexadienylisoxazoles (81a) and (81b), respectively. The related bromo-compounds (82) and (83) have been isolated previously from 

Verongia species,and it seems probable that 3,5-dibromotyrosine is a precursor of all the Verongia metabolites. The central C4N2 and C5N2chains of (81a) and (81b) are considered to be derived from ornithine and lysine, respectively. In view of the facile photochemical conversion of (79) into (80), it has been suggested that the natural amide (82) is derived biogenetically via lactone 

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