indices of hydrogen deficiency. The UV spectrum displayed
absorption maxima characteristic of indole chromophores at
285 and 222 nm, and the IR spectrum showed absorption
bands due to −NH (3405 cm−1) and ester carbonyl (1727
cm−1) functions. The 1H and 13C NMR data (Tables 1 and 2)
were similar to those of 1, except that the oxirane between C-19
and C-20 was reduced, as supported by the molecular formula
and the HMBC correlations of H-19 (δH 1.45 and 1.49, each
1H, m) with C-21 (δC 87.0), C-20 (δC 51.4), C-15 (δC 41.2),
and C-18 (δC 12.3). Taking the degrees of unsaturation into
consideration confirmed the absence of the oxirane ring.
Analysis of the 2D NMR data confirmed that the other parts
were the same as those of 1. Hence, the structure of 2 was
elucidated as shown, and it was named tabernaricatine B