Dictyol

Compared to undamaged controls, amphipod-damaged seaweeds had up to 34% higher contents of the diterpenes dictyol E (65), dictyodial (66), and pachy-dictyol A (67) of which 65 deters feeding by the amphipods [137]. Remarkably this study not only relies on laboratory experiments but provides field data. In their natural environment previously heavily attacked algae were less susceptible to herbivory compared to those that had a record of low grazing. 

Almost a third of the reported brown algal chemistry comes from a single genus, Dictyota, which has elaborated a wealth of terpenes (>250) (Munro and Blunt 2005). Diterpenes dominate Dictyota chemistry and are typically di- and tricyclized, as seen in dictyol E (Fig. 1.6a) (Danise et al. 1977), amijiol (Fig. 1.6b) (Ochi et al. 1980), Fig. 1.6c (Tringali et al. 1984), and dictyoxetane (Fig. 1.6d) (Pullaiah et al. 1985). 

Specimens from Radio Is., North Carolina (not a true tropical system, see text for details) Pachydictyol A inhibits the sea urchin A. punctulata and dictyol A acetate inhibits this sea urchin species, the amphipod Ampithoe longimana, and the pinlish /,. rhomboides (Bolser and Hay 1996). Pachydictyol A, dictyol B acetate, dictyol E, and dictyodial, also obtained from the same specimens, cause larval mortality, abnormal development, and reduced growth in bryozoans and hydroid species (Schmitt et al. 1998)... 

Low susceptibility to reef fishes in Florida and produces secondary metabolites (Paul and Hay 1986). Specimens from Radio Is., North Carolina Pachydictyol A inhibits the fish Diplodus holbrooki. This compound and dictyol B inhibit the sea urchin A. punctulata (Hay et al. 1987) both compounds from North Carolina also inhibit the fish A. rhomboides (Hay et al. 1988b)... 

A group of guaiane diterpenoids including dictyol B acetate (149) and dictyotadiol... 

Similar strategies were used by Booker-Milburn et al. in approaches toward the synthesis of dictyol C and a-eudesmol [215], and by Blake et al. in approaches toward the synthesis of ophiobolin F and fusicoccin A [216]. 

As with other classes of terpenoid, the investigation of marine organisms has yielded a diversity of novel structural types. Dictyol A (90) and dictyol B (91) have been isolated from the brown alga Dictyota dichotoma and from the sea hare, Aplysia... 

Another example is the synthesis of the central hydroazulene unit 10 of dictyols (isolated from various marine algae, some of which exhibit antimicrobial activities), which has the correct configuration at C-l and C-7 and allows independent manipulation of functionalities for further transformations617. 

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