Isonitrile biosynthesis in a marine sponge

Hagadone, Mark R.
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Ever since the discovery in 1957 of a naturally occurring isocyano metabolite in a terrestrial microorganism, the biogenesis of the isocyano group has been an intriguing unsolved scientific puzzle. The first marine-derived isocyano compounds were isolated from sponges in 1973, when the question of their biogenesis arose. While these questions are superficially identical they differ fundamentally in that all known terrestrial isocyanides are derivatives of amino acids, while all known marine isocyanides are of terpenoid origin. Another characteristic feature of the marine metabolites is their frequent co-occurrence with formamido and isothiocyanato derivatives sharing the same carbon skeleton. The first biogenetic hypothesis dealt with the interrelationship of these three functions. Because N-formyl compounds are more frequently encountered than isocyano derivatives, the relationship of these two functions became the first objective, which was extended to encompass the origin of the isothiocyanato function. Natural 2-isocyanopupukeanane (1, R = NC) was degraded to the 2-amino (2, R = NH2 ) compound, from which 13C labeled formamide (3, R=NH13CHO), isothiocyanato (4, R = N13CS), and isocyano (5, R = N13C) were synthesized. The synthetic experiments were carried out by a newly developed technique on living sponges, Ciocalypta sp., on the north shore of O'ahu. Semisynthetic precursors were enclosed in gelatin capsules and surgically embedded in the animals by researchers equipped with SCUBA. After incubation times varying from 2 to 4 weeks the animals were removed from their habitat and analyzed by gas chromatographic I mass spectrometric techniques. It was conclusively demonstrated that 2- isocyanopupukeanane (1) is the precursor of the formamido and isothiocyanato functions and that the reverse reaction does not take place. In the course of this work the first naturally occurring isocyanato compound, 2- isocyanatobisabolene (6) was isolated from the sponge, ciocalypta sp. Some of the results of this work have been published. [1,2]
Thesis (Ph. D.)--University of Hawaii at Manoa, 1991.
Includes bibliographical references (leaves 78-83)
Available also on microfiche
xiii, 83 p. leaves, bound ill. 29 cm
Sponges -- Physiology, Isocyanides
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