Enantiomeric Neolignans and a Sesquiterpene from Solanum erianthum and Their Absolute Configuration Assignment

Abstract

One pair of new C-8-C-3'/C-7-O-C-4' linked neolignan enantiomers (1a/1b) and one new guaiane sesquiterpene (2) first featuring the 1(2),9(10)-conjugated double bond were isolated from the stems of Solanum erianthum (Solanceae). Their structures were characterized on the basis of extensive spectroscopic analyses, especially from their 2D nuclear magnetic resonance (NMR) spectra. The absolute configurations of 1a/2b were rigorously elucidated by electronic circular dichroism (ECD) experiments combined with the reversed helicity rule for the 2,3-dihydrobenzo[b]furan chromophore, and compound 2 is the first report on the sterochemical assignment of a guaiane sesquiterpene by using the allylic axial chirality rule for the conjugated diene chromophore in combination with the calculated ECD spectrum.

The Genus Solanum: An Ethnopharmacological, Phytochemical and Biological Properties Review

“…Although their molecular scaffold consists only of two phenylpropane (C6–C3) units, lignans exhibit an enormous structural diversity originating from various linkage patterns of these phenylpropane units. As the C-8–C-3′/C-7–O–C-4′ linked lignans containing two chiral centers (C-7 and C-8) comprise the core of 2, 3-dihydrobenzo[b]furan [480]. …”

“…Several neo-lignans, sisymbrifolin ( 433 ) from the fruits of S. sisimbriifolium [519], ficusal ( 442 ) from the roots of S. melongena [209], glycosmisic acid ( 439 ), simulanol ( 440 ) and balanophonin ( 443 ) from the whole plant of S. surattense [518] were identified. A pair of new C-8–C-3′/C-7–O–C-4′ linked neolignan enantiomers, 420 and 421 , were isolated from the stems of S. erianthum [480]. Lignanamides 424 – 432 and 434 were obtained from the roots of S. melongena [210].…”

Sesquiterpenes and lignans from the flower buds of Daphne genkwa and their nitric oxide inhibitory activities

“…By comparison of their observed and reported NMR data, the known compounds 215 were identified as oleodaphnal (2) (Taninaka et al 1999), (4S,5R,7S)-4,11-dihydroxy-guaia-1(2), 9(10)-dien (3) (Li et al 2016), threoguaiacylglycerol--O-4-coniferyl (4) (Cutillo et al 2003), longifloroside B (5) (Wang et al 2009), threo-3,3′-dimethoxy-4,8′-oxyneoligna-9,4′,7′,9′-tetraol-7(8)-ene (6) (Wang et al 2009), ()-nortrachelogenin (7) (Zhang et al 2013), ()-Matairesin (8) (Youssef and Frahm 1995), (+)-isolariciresinol (9) (Jutiviboonsuk et al 2006), ()-secoisolariciresinol(10) (Hong et al 2006), lariciresinol (11) (Subbaraju et al 1991), ()-justiciresinol (12), syringaresinol (13) (Niu et al 2001), medioresinol (14) (Li et al 2008), and pinoresinol (15) (Páska et al 2002). All compounds were evaluated for their inhibitory effects on the NO production in LPS-induced BV-2 microglial cells using the Griess assay.…”

The role of chlorine position in the electronic circular dichroism of chlorophenyl‐ethanol investigated by vibronic calculations

“…Semiempirical rules have actually allowed great progress in the ECD community and here we mention also those developed by Harada and Nakanishi, like the benzoate 4 and dibenzoate sector rules 5 . The latter was afterwards renamed “exciton chirality rule” 6 and has been extensively used to characterise the absolute configuration of natural products 7–17 …”

“…5 The latter was afterwards renamed "exciton chirality rule" 6 and has been extensively used to characterise the absolute configuration of natural products. [7][8][9][10][11][12][13][14][15][16][17] Notwithstanding the utility of these rules, in principle, a vibronic analysis is required to get a robust interpretation of weak ECD spectra with alternating signs, and use them for assigning absolute configurations. Actually, recent progress in computational methods have made the computation of vibronically resolved electronic spectra rather standard.…”