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