The Corynantheine‐Heteroyohimbine Group

Corynanthean, eburnan, secoleuconoxine, and pauciflorine alkaloids from Kopsia pauciflora

“…In the 7S oxindoles, 1 and 2, the chemical shifts of H-9 were observed at d 7.34 and 7.35 (Table 1), respectively, due to paramagnetic deshielding as a result of proximity of H-9 with the N-4 lone pair. However, the chemical shift of H-9 was found to be relatively more shielded (d 7.14) in the case of 4, indicating the opposite configuration, i.e., 7R (Brown, 1983). This conclusion was also supported by NOE experiments (Fig.…”