Okaramine C, a New Insecticidal Indole Alkaloid from Penicillium simplicissimum

Abstract

14'-CH3 1.65 s. 1.52 s. insecticidal activity toward the 3rd instar larvae of silkworm upon oral administration. One of them, okaramine A (1),1>3) is a new type ofindole alkaloid with a seven-ring system, the other one, okaramine B (2),2'3) being a derivative with a eitht-ring system. Since we were interested in the unique structure of okaramines, we tried to determine if okaramines or similar compounds were produced by other strains. As a result, Penicillium simplicissimum AHU8402 showed activity almost equivalent to AK-40, the producing strain of okaramines.4) In this paper, we report the isolation and structural elucidation of the insecticidal constituents of AHU 8402. Froman acetone extract of mycelia and media of this strain, three insecticidal compounds were isolated. Twoof them were identified as okaramine A (1) and okaramine B (2), and the third one seemed to be a new congener, which was termed okaramine C (3). High-resolution El mass spectrometry of 3 established its molecular formula as C32H36N4O3. The 1HNMR(Table I) and 13C-NMR(Table II) spectra showed