C₁₈ Dibenzocyclooctadiene Lignans from Kadsura philippinensis

Abstract

Four new C18 dibenzocyclooctadiene lignans, kadsuphilins A (1) and B (3), 6-epi-gomisin (2), and 1-demethylkadsuphilin A (4), along with eight known related metabolites, were isolated from an EtOAc fraction of an alcoholic extract of the aerial parts of Kadsura philippinensis growing in Taiwan. The structures of 1-4 were elucidated on the basis of spectroscopic analyses, including 2D NMR (HMQC, HMBC, and NOESY) experiments, and by comparison of their spectroscopic data with those of related metabolites. The configurations of the biphenyl and cyclooctadiene moieties were deduced from circular dichroism (CD) and NOESY NMR spectra, respectively. Some of the compounds showed radical-scavenging activity in a DPPH-HPLC method.

Stereoelectronic Effects on 1H Nuclear Magnetic Resonance Chemical Shifts in Methoxybenzenes

“…On the basis of the observations described herein, the hydroxy and methoxy substituents attached to C-3 and C-5 in the natural lignan rupestrin C, recently described by Suo et al, should be interchanged ,, The ability to extract as much information as possible from 1D 1 H NMR spectra alone is of special interest in cases where 2D NMR experiments are not readily accessible, for example, when modern high-throughput hyphenated HPLC−NMR methods or NMR probes with microcoils for mass-limited samples are used. …”

“…Moreover, a vast number of natural products contain partially O-methylated 1,2,3-benzenetriol moieties. Structure elucidation of such compounds can present a considerable challenge, requiring time-consuming 2D NMR experiments. , Examples confirming the large shift of H para upon O-methylation of an ortho-disubstituted phenol group include isoflavans, isoflavanones, natural dibenzocyclooctadienes,21a natural terphenyls,21b isoflavones,21c acridone alkaloids,21d homoflavonoids,21e and lignans . On the basis of the observations described herein, the hydroxy and methoxy substituents attached to C-3 and C-5 in the natural lignan rupestrin C, recently described by Suo et al, should be interchanged …”

Dibenzocyclooctadiene Lignans fromKadsura polyspermaand Their Antineurodegenerative Activities

“…Polysperlignan K (11) gave the molecular formula C 24 H 28 O 8 from its HRESIMS data at m/z 467.1675 [M + Na] + . The 1D NMR spectra exhibited 18 carbon atoms (including 12 aromatic ones, one methylene, three methines, and two secondary methyls) for the dibenzocyclooctadiene skeleton, in addition to a methylenedioxy group, three methoxy groups, and an acetyl group.…”

“…A 70% aqueous acetone extract of the stems of K. polysperma was partitioned between EtOAc and H 2 O. The EtOAc solubles were dried and subjected to silica gel, MCI CHP-20 gel, Sephadex LH-20, and Lichroprep RP-18 gel column chromatography (CC) and semipreparative HPLC to afford 11 new compounds, polysperlignans A–K ( 1 – 11 ), together with eight known lignans, interiotherin C ( 12 ), kadsurin ( 13 ), kadsuphilin A ( 14 ), isogomisin O ( 15 ), tiegusanin I ( 16 ), yunnankadsurin B ( 17 ), methyl schisantherin F ( 18 ), and ananolignan A ( 19 ) . The structures of the known compounds were determined by comparing spectroscopic data with literature values, and the absolute configurations of 1 and 7 were determined by X-ray analysis (CCDC and , respectively).…”

New Lignans from the Leaves and Stems of Kadsura philippinensis

“…is an evergreen vine, mainly distributed at low altitude onremote islands of Taiwan such as Green Island [9]. Our previous phytochemical studies on the EtOAc extracts of K. philippinensis resulted in the isolation of two novel triterpene dilactones and many lignans [10,11,12,13,14,15,16,17]. In this paper, we report the isolation and structure elucidation of three new C19 homolignans, named taiwankadsurins D-F, and two new C18 lignans, designated kadsuphilins N and O.…”