Compound 5 was isolated as a light yellow powder. Its UV
spectrum showed absorption maxima at 295 and 227 nm,
suggesting indole chromophores, and the IR spectrum showed
−NH (3440 cm−1), ester carbonyl (1725 cm−1), and carbonyl
(1711 cm−1) bands. The molecular formula C47H58N4O7 was
established by HREIMS (m/z 790.4297 [M]+), which is 56 Da
higher than that of ervachinine C.7 Analysis of the NMR data
(Tables 1 and 2) indicated that 5 was also a vobasinyl−ibogan
bisindole alkaloid, and it was readily identified as a 2-oxopropyl
derivative of ervachinine C7 by the presence of signals at δC
208.2 (s), 46.6 (t), and 30.7 (q) in its 13C NMR spectrum. The
2-oxopropyl group was substituted at C-3′, as supported by the
HMBC correlations of H-3′ (δH 3.24) with the carbon at δC
208.2. In the ROESY spectrum of 5, H-17′α (δH 1.85) was
correlated with H-15′α; thus, the NOE correlation of H-3′ with
H-17′β (δH 2.68) suggested that H-3′ was β-oriented. Thus, the
structure of 5 was elucidated and named tabernaricatine E.
Compound 5 was isolated as a light yellow powder. Its UVspectrum showed absorption maxima at 295 and 227 nm,suggesting indole chromophores, and the IR spectrum showed−NH (3440 cm−1), ester carbonyl (1725 cm−1), and carbonyl(1711 cm−1) bands. The molecular formula C47H58N4O7 wasestablished by HREIMS (m/z 790.4297 [M]+), which is 56 Dahigher than that of ervachinine C.7 Analysis of the NMR data(Tables 1 and 2) indicated that 5 was also a vobasinyl−iboganbisindole alkaloid, and it was readily identified as a 2-oxopropylderivative of ervachinine C7 by the presence of signals at δC208.2 (s), 46.6 (t), and 30.7 (q) in its 13C NMR spectrum. The2-oxopropyl group was substituted at C-3′, as supported by theHMBC correlations of H-3′ (δH 3.24) with the carbon at δC208.2. In the ROESY spectrum of 5, H-17′α (δH 1.85) wascorrelated with H-15′α; thus, the NOE correlation of H-3′ withH-17′β (δH 2.68) suggested that H-3′ was β-oriented. Thus, thestructure of 5 was elucidated and named tabernaricatine E.
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