Alkaloids of the Amaryllidaceae. 27. Structures of 9-O-demethylhomolycorine and 5.alpha.-hydroxyhomolycorine. Alkaloids of Crinum defixum, C. scabrum, and C. latifolium. Assignment of aromatic substitution patterns from 1H-coupled carbon-13 spectra

Abstract

The isolation and characterization of the major crystalline alkaloids of three Crinum species, C. defixum, C. scabrum, and C. latifolium, are reported. A new alkaloid, 5a-hydroxyhomolycorine (1) has been isolated from C. defixum. The latter plant also contains an alkaloid identified as 9-0-demethylhomolycorine which differs in physical properties from that previously reported for this compound. Evidence is provided for the structure of 9-0-demethylhomolycorine by ' H and 13C NMR studies. In the latter, the exploitation of long-range ' H coupling in the 13C spectra of lactones in this series is found to be diagnostically useful in assigning aromatic substitution patterns. A survey of the CD spectra of lactone alkaloids of the benzopyrano[3,4-g]indole system indicates that this technique can provide useful structural information.The Crinum genus of the amaryllidaceae has a wide geographical distribution in the temperate and subtropical regions. The species C. defixum Ker-Gawl, C. latifolium L., and C. scabrum Herb. are indigenous to the Indian subcontinent. Several preliminary reports2 have established the presence of lycorine in each of these species and a more definitive study3 of C. defixum has shown the presence of caranine, crinamine, crinine, galanthamine, galanthine, haemanthamine, and hippeastrine from C. defixum grown in Holland.

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.…”

“…In fact, the EI-MS spectrum showed, beside the molecular ion at m/z 315, fragment peaks at m/z 190, 125, 124, and 96, in accord with the fragmentation mechanism characteristic for lycorenine-type alkaloids [10 -12]. From these data, the structure of 2 was identified as hippeastrine [10] [13] [14].…”

“…The large coupling between HÀC(4a) and H a ÀC(4) (13.6 Hz) pointed to their trans-diaxial orientation, characteristic for the haemanthamine series [19 -21]. The assignment of the 9-MeO group was supported by NOEs between 9-MeO and HÀC (10), and between HÀC(10) and HÀC (1). H a ÀC(11), H b ÀC(11), H a ÀC (12), and H b ÀC(12) were observed as ddd or m, which indicated a non-substituted ethano bridge [22].…”

Antimicrobial Activity of <i>Crinum d</i><i>efixum</i> Ker - Gawler Leaves

“…In the recent years a new alkaloid 5 α-hydroxyhomolycorine has also been isolated from Crinum defixum Ker -Gawler [9]. Ethanolic extract of dried leaves of Crinum defixum Ker -Gawler has been reported to exhibit a free radical scavenging [10], analgesic, anti-inflammatory properties [11]. Hence the present study was focused to evaluation of antimicrobial potential of the plant.…”

Four New Amaryllidaceae Alkaloids from Lycoris radiata and Their Cytotoxicity

“…Thus, the structure of 1 was determined to be 2-epi-O-demethyllycoramine. The molecular formula of lycoranine D (2) was determined to be C 15 Table 1). The 13 C NMR and DEPT spectra of 2 displayed 15 signals, including a methoxy group (δ C 56.2) and a methylenedioxy unit (δ C 101.7) (l " Table 1), which suggested that 2 possessed a skeleton with 13 C-atoms.…”