Bromotyrosine derivatives first isolation

This class of bromotyrosine derivatives contains one spirocyclohexadienylisoxazo-line ring system. The first two alkaloids in this class are fistularin-1 (94) and fistularin-2 (95) isolated from the marine sponge Aplysina fistularis forma fulva by Gopichand and Schmitz in 1979 (68). Both compounds contain a spirocyclohexadienyhsoxazoline, a bromotyramine, and a C3 unit. 

Purpuramines A-I (179-187) exhibited antibacterial activity against Staphylococcus aureus, but phenylpymvic acid oxime (188) was not active. Purpuramine J (189) was isolated from the Fijian sponge Psammaplysilla (Druinella) sp., along with purpuramine I (187), aplysamine 2 (172), and eight other bromotyrosine derivatives (86). Purpuramine J (189) is the first bromotyrosine derivative containing an A-oxide functionality, which is considered rare in marine natural products. 

Quite surprisingly, the first attempt to demonstrate the conversion of tyrosine into bromotyrosine derivatives was unsuccessful (175). In that experiment, Verongia aerophoba failed to incorporate radioactivity from U- " C -L-tyrosine into aerothionin (68), aeroplysinin-1 (14) and the dienone 1. Inactive aerothionin (68) was also isolated when the sponge was fed with U- C -L-ornithine and CH3- C methionine. However, the sponge utihzed these amino acids for the synthesis of fatty acids. A very slow rate of biosynthesis might account for these results. 

Bromotyrosine derivatives were first isolated in the process of searching for antibiotics from marine sources. The dienone 1, aeroplysinin-1 (14), and aerothionin (68) are the earliest antimicrobial bromotyrosine derivatives (2,14,58). The antibacterial and antifungal activities of the bromotyrosine alkaloids are summarized in Table IV and... 

---