Chiroptical properties of 4-substituted flavans

Snatzke, Günther; Znatzke, F.; Tokes, A. L.; Rákosi, M.; Bognár, R.

doi:10.1016/0040-4020(73)80037-7

Cited by 48 publications

(26 citation statements)

References 18 publications

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“…On the contrary, the trans-4-hydroxyflavan 21 does not follow the rule because the axial 4-hydroxy group forces the heterocyclic ring into a flat sofa conformation which makes the chiral third sphere contribution (substituent at C-4) overrule the second one (helicity of the heterocyclic ring). 40 This effect was also observed for other chromane derivatives possessing an axial substituent at C-4. 41,42 Although the influence of the heterocyclic oxygen on chiroptical properties has been recognized by Korver and Wilkins 43 and van Rensburg et al 44 in a series of naturally occurring flavan-3-ols with known absolute configuration (e.g., 22-24), Snatzke et al 13 explained this effect with the influence of the hydroxy group attached at C-7 or at C-7 and C-5 of ring A and asserted that the same helicity rule is valid for the unsubstituted, chiral chromane chromophores as for the chiral tetralins.…”

Section: 3-dihydrobenzo[b]furan and Chromanementioning

confidence: 65%

“…A substituent in pseudoaxial position at the benzylic atom gives rise to sign inversion of the 1 L a band due to -conjugation of the pseudoaxial *-orbital with the -and *-orbitals. Snatzke et al 40 also reported that in the case of 4-substituted fla- (Table 5) in all the (−)-(6aR;11aR)-pterocarpans 52-57 (Table 4). These CD bands of the chromane chromophore determine the CD feature of pterocarpans and can be unambiguously used for their configurational assignments, since it has been proven earlier in this article that the different substitution patterns of the aromatic ring do not In summary, the characteristic 1 L b and 1 L a bands of the chromane chromophore were used for the determinations of absolute configuration in a series of pterocarpans since they have a considerably more intense contribution than that of the 2,3-dihydrobenzo[b]furan chromophore and their signs were not influenced by the substitution pattern of the aromatic ring.…”

Section: Pterocarpan Chromophorementioning

confidence: 89%

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Chiroptical properties of 2,3‐dihydrobenzo[b]furan and chromane chromophores in naturally occurring O‐heterocycles

et al. 2001

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The correlation between the helicity (absolute conformation) of the O-heterocyclic ring of chiral 2,3-dihydrobenzo[b]furan (1) and chromane (2) derivatives and their (1)L(b) band CD was investigated. The same helicity rule was found for both unsubstituted chromophores: P/M helicity of the heterocyclic ring leads to a negative/positive CD within the (1)L(b) band. While the substitution of the fused benzene ring by achiral substituents does not change this helicity rule for the chromane chromophore, it leads to its inversion for the 2,3-dihydrobenzo[b]furan chromophores. On the basis of these observations, the published absolute configurations of natural flavonol and pterocarpan derivatives were confirmed and the configurational assignments of several natural neolignans revised.

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Section: 3-dihydrobenzo[b]furan and Chromanementioning

confidence: 65%

Section: Pterocarpan Chromophorementioning

confidence: 89%

Chiroptical properties of 2,3‐dihydrobenzo[b]furan and chromane chromophores in naturally occurring O‐heterocycles

et al. 2001

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“…In the CD spectrum, 5 gave a positive Cotton effect at 305 nm, along with two negative Cotton effects at 285 and 326 nm, and corresponding to the absolute configurations of R (C-2), R (C-3Љ), R (C-4Љ) and S (C-5Љ). 10,11,13) Guangsangon N (6) was obtained as a brown amorphous (Fig. 1) and CD spectrum (with three negative Cotton effects at 269, 288 and 303 nm, and a positive Cotton effect at 333 nm), the relative configurations of H-3Љ, H-4Љ and H-5Љ were assigned as all-trans, and the absolute configurations of C-3Љ, C-4Љ, C-5Љ and C-2 were assigned as R, R, S and S, respectively.…”

Section: Resultsmentioning

confidence: 99%

New Diels-Alder Type Adducts from Morus macroura and Their Anti-oxidant Activities

Dai

Wang

et al. 2004

Chem. Pharm. Bull.

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Fractionation of the ethanolic extract of the stem bark of Morus macroura resulted in the isolation of four new Diels-Alder type adducts, named guangsangons K-N (1, 2, 5, 6), together with two known compounds, mulberrofuran G (3) and K (4). Their structures were determined on the basis of spectroscopic analyses and chemical methods. Furthermore, by means of 1 H-NMR variable temperature experiments and the Cotton curves in the circular dichroism (CD) spectra, the stereochemistry of four new compounds was elucidated. The isolated new compounds showed good activity on anti-oxidant in vitro, with the inhibitory rates of MDA being from 91.8 to 100.0% at concentrations of 10 ؊5 mol/l.

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“…The 2R : 3R configuration was confirmed by the CD measurement. 9,11,12) From these data, 3 was determined to be 5,3Ј,3-trihydroxy-7,4Ј-dimethoxyflavanone. The positions of two methoxyl signals (3.82, 3.94) were determined by HMBC.…”

Section: -10) 13mentioning

confidence: 99%

“…However, compound 3 is a new natural product. Compounds 4-8 were identified as 3Ј,4Ј,5Ј,5-tetramethoxy-6,7-methylenedioxyisoflavone, 10,13,14) 3Ј-methoxy-4Ј,5-dihydroxy-6,7-methylenedioxyisoflavone, 10,11,15) 3Ј,4Ј-dimethoxy-5Ј,5-dihydroxy-6,7-methylenedioxyisoflavone, 16,17) 4Ј,5-dimethoxy-3-hydroxy-6,7-methylenedioxyisoflavone, 18,19) and 5-methoxy-4Ј-hydroxy-6,7-methylenedioxyisoflavone 10) on the basis of their NMR spectral data and by comparison of their physical 1368 Vol. 50, No.…”

Section: -10) 13mentioning

confidence: 99%

New Isoflavones and Flavanol from <i>Iris potaninii</i>

Purev

Purevsuren

Narantuya³

et al. 2002

CHEMICAL & PHARMACEUTICAL BULLETIN

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Iris potaninii MAZIM. (family Iridaceae) has been used in traditional Mongolian medicine for the treatment of various diseases, such as bacterial infections, cancer, and inflammation. Some benzoquinones isolated from Iris species have been used as anticancer agents in modern Chinese medicine. 1,2) In our previous papers we reported that 10 new flavones, a new isoflavone, two new quinones, and five new peltogynoids were isolated and their structures elucidated from other species of the genus.3-5) This paper describes the structure elucidation of two isoflavones (1, 2) and one flavanone (3) isolated from the roots of this plant. Results and DiscussionThe methanolic extract of the underground parts of I. potaninii was subjected to repeated chromatography on columns of silica gel, Labor RP-18, and Sephadex LH-20 and preparative thin-layer and HPLC to obtain compounds 1-9. Compound 1 was isolated as a colorless crystal. The high-resolution electron impact mass spectrum (HR-EI-MS) of 1 showed the [M] ϩ at m/z: 360.0845, in agreement with the molecular formula C 18 H 16 O 8 (Calcd 360.0831). The 1 H-NMR spectrum of 1 showed signals for three aromatic protons, and one olefinic proton along with signals for three methoxy groups. The broad-band decoupled 13 C-NMR spectrum showed resonances for all 18 carbons in molecule 1, which included three methyl, four methine, and 11 quater- The UV spectrum by the application of diagnostic shift reagents showed absorbance at l max (MeOH) (nm): 214, 260, 292, 375 sh, (ϩAlCl 3 ) 216, 264, 296 sh, 388 (unchanged), (ϩNaOAc) 272, 392. The bathochromic shift with NaOAc (260®272) indicates the presence of a free hydroxyl group at position C-7, 6) while an absence of large bathochromic shifts in band-I with AlCl 3 and NaOMe indicates that the C-5 and C-4Ј positions are free or substituted. , 6,3,4-trimethoxy-7,8,5-trihydroxyisoflavone (1), 7,4-dimethoxy-8,3,5-trihydroxy-6-O-b b-D-glucopyranosylisoflavone (2), and 5,3,3-trihydroxy-7,4-dimethoxyflavanone (3) have been isolated from the underground parts of Iris potaninii along with known isoflavones (4-8) and iriflophenone (9). The structures of the new compounds were determined using NMR and mass spectroscopic methods.

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Chiroptical properties of 4-substituted flavans

Cited by 48 publications

References 18 publications

Chiroptical properties of 2,3‐dihydrobenzo[b]furan and chromane chromophores in naturally occurring O‐heterocycles

Chiroptical properties of 2,3‐dihydrobenzo[b]furan and chromane chromophores in naturally occurring O‐heterocycles

New Diels-Alder Type Adducts from Morus macroura and Their Anti-oxidant Activities

New Isoflavones and Flavanol from <i>Iris potaninii</i>

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