Alkaloids from Hippeastrum equestre Herb. —5. Circular dichroism studies

Phytochemical and Biological Investigation of Hymenocallis littoralisSalisb.

“…These structural features were confirmed by 13 C-NMR, which showed, beside the signals of a tetrasubstituted aromatic ring, those of a lactone, a methylenedioxy moiety, and an N-methyl group at d(C) 164.6, 102.1, and 43.5, respectively [10]. The large coupling constant between HÀC(11b) and HÀC(11c) (J ¼ 9.4 Hz) in the 1 H-NMR spectrum of 2 implied trans-diaxial substitution, and the negligible coupling between HÀC(11b) and HÀC(5a) indicated an axial/equatorial disposition and, consequently, cis-fused B/C rings.…”

“…The downfield shift of C(11) at d(C) 81.05 in the 13 C-NMR spectrum indicated the presence of an 11-OH group [25]. The spectroscopic data of 3 were identical to those reported for 11-hydroxyvittatine [26], and this is the first report of this compound from the genus Hymenocallis.…”

“…13 C-NMR: 164.6 (s, C (7)); 147.9 (s, C(10)); 151.8 (s, C(9)); 145.9 (s, C(7a)); 139.3 (s, C(11a)); 118.5 (d, C(4)); 118.1 (s, C(3a)); 109.9 (d, C (8) (10)); 6.57 (s, HÀC (7) (4)). …”

The Brazilian Amaryllidaceae as a source of acetylcholinesterase inhibitory alkaloids

“…The crinine-type skeleton is uncommon in the genus Hippeastrum and the absolute configuration of its 5,10b-ethano bridge is ratified only by CD spectra or X-ray crystallography (Wagner et al 1996). As shown in Table 1 and Fig.…”

Alkaloids from Crinum erubescens Aiton

“…Although the basic crinane structure of 1 was well established by 1D and 2D NMR experiments, the absolute stereochemistry of the 5,10b-ethanophenanthridine alkaloids should be confirmed by CD spectroscopy. Indeed, the shape, amplitude and sign of the CD spectra are crucial for the correct orientation of the 5,10b ethano bridge in crinane variants (De Angelis and Wildman, 1969;Wagner et al, 1996). The CD spectrum of 1 displayed a positive and negative Cotton effect at ca.…”