70(P-57) ヤドクガエルAtelopus zetekiの毒zetekitoxinの構造解析(ポスター発表の部)

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Zetekitoxin (ZTX,1) was first reported in 1969 by Mosher et al. as a potent water-soluble low molecular weight toxin from the Panamanian frog, Atelopus zeteki. The pharmacology of ZTX was reported by Ranney et al. in 1970 that ZTX produced sustained hypotension, delayed cardiac conduction, and various disturbances of cardiac rhythm in hearts of mammals. However, since this frog was become to be under the protection, the sample supply was strictly restricted. For this reason, the structure of ZTX had been kept unknown for almost 30 years. We now present the structure of ZTX deduced by using the long term stored ZTX and spectroscopic technique. ZTX (approximately 300μg) was obtained as 4:1 mixture (^1H NMR) of the structurally similar compounds by sequential HPLC on the ion exchange columns, and the structure of the major component was attempted to be determined. The molecular weight was determined by HR-ESIMS (50% MeOH) [M+H]^+ m/z 553.1369 (calcd for [C_<16>H_<25>N_8O_<12>S_1]^+ m/z 553.1313). [M-SO_3+H]+ m/z 473.1725 (calcd for (C_<16>H_<25>N_8O_9)+ m/z 473.1744). The NMR experiments, TOCSY, HSQC, HMBC, NOESY, and NOE difference spectra, enabled us to deduce the relative stereostructure of ZTX. ZTX was suggested to be a derivative of saxitoxin (STX), which has an N-hydroxy-δ-lactam ring connected to C6 and N7 of STX. Further, the presence of a spiro-ring at C11 of STX was suggested, which contained an N-hydroxy carbamate and 1,3-dihydroxy isopropyl branch. The location of ?OSO_3H group was presumed to be at C21 according to the ^1H NMR chemical shift of CH_2-21 (4.25ppm). These partial structures were supported by the data of ESI/MS/MS.
天然有機化合物討論会の論文
2000-10-01

70(P-57) ヤドクガエルAtelopus zetekiの毒zetekitoxinの構造解析(ポスター発表の部)

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