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天然有机化学的期刊J. Nat. Prod.
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ABSTRACT: Two new amphilectane-type diterpenes, 8-isocyanato-15 formamidoamphilect-11(20)-ene(1) and 8-isothiocyanato-15-formamidoamphilect-11(20)-ene (2), along with two known derivatives, 8-isocyano-15Sample TextSample Textformamidoamphilect-11(20)-ene (3) and 7-formamidoamphilect-11(20),15-diene (4), were isolated from the sponge Stylissa cf. massa. Diterpenes bearing two different isonitrile-related functionalities, as in 1−3, are rare. The coexistence of these compounds, all of which possess the identical carbon skeleton,in the same sponge specimen suggests interconversion among them. All the isolated compounds were tested for antimalarial activity. Compound 3 proved approximately 10 times more active than 1 and 2, indicating the importance of the isonitrile moiety to antimalarial activity versus the isocyanate and isothiocyanate groups, respectively. Compound 4, which contains only the formamide group, was inactive at the highest concentration tested. Sesquiterpenes and diterpenes possessing isonitrile and related functionalities are unique and exclusively marinederived natural products. Terpene skeletons, which include the spiroaxane and pupukeanane types for the sesquiterpenes and the amphilectane and cycloamphilectane for the diterpenes, are rare in nature. Such skeletons are also associated closely with certain sponge genera reported as sources of terpenes in this class. Specifically, diterpenes of the amphilectane type bearing isonitrile, isocyanate, isothiocynate, and formamide functionalities have been isolated from only a few sponge genera, including Hymeniacidon,1 Cribochalina,2 Stylissa,3 and Cymbastela.4 It has been reported that such functionalities, especially isonitrile, contribute to the biological activities, particularly for those compounds that are reported to have antimalarial activity.4b,5 Recently we reported the isolation and antimalarial activities of a series of isonitrile amphilectenes from the sponge Stylissa cf. massa (Carter) (then identified as belonging to the genus Ciocalapata).6 Extended investigation of the remaining extract fractions led to the isolation of two new bifunctionalized amphilectenes, 8-isocyanato-15-formamidoamphilect-11(20)-ene (1) and 8-isothiocyanato-15-formamidoamphilect-11(20)-ene (2), and two known derivatives, 8-isocyano-15-formamidoamphilect- 11(20)-ene (3) and 7-formamidoamphilect-11(20),15-diene (4). The chemical structures of the two known diterpenes were identified by spectroscopic analysis, including MS, UV, IR, and NMR spectra, and by comparison with data from previously published reports.1,4b |
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