A Simple Biomimetic Synthesis of <i>dl</i>-Chamaejasmine, a Unique 3,3‘-Biflavanone

Two new promelacacinidin biflavonoids, mesquitol-(4α,5)-epimesquitol-4β-ol and a 3′,4′,7,8-tetrahydroxyflavanone(3,4)-ent-epimesquitol, were isolated among others from the heartwood of Acacia nigrescens. The flavanone derived dimer, characterized by a unique C(3) to C(4) bridge, which links the monomers via two stereogenic and sp 3 hybridized C-atoms, is the prototype of a new subgroup of the flavonoid family. Assessment of the absolute configuration of all five stereogenic centers of this novel flavanone-derived biflavonoid was achieved by correlating the chiroptical properties of the benzoyl chromophore to the absolute configuration of C(2) of the flavanone moiety and hence the absolute stereochemistry of the other four chiral centers.The flavonoids are one of the most prevalent groups of phenolic compounds in nature and display a wide range of biological and pharmacological properties. Biflavonoids, as the simplest members of the polymeric flavonoids, are known to display a variety of biological activities, such as anti-inflammatory activity, the inhibition of cytochrome P450 enzymes, antiviral activity, and neuroprotective effects, the latter suggesting their therapeutic potential against neurodegenerative diseases, including ischemic stroke and Alzheimer's disease [1]. The dimeric procyanidins B1 and B2 demonstrated potent antioxidative activity, whereas grape seed proanthocyanidin extract, containing a mixture of 75-80% oligomeric proanthocyanidin and 3-5% monomeric proanthocyanidin, has proven efficacy against the incidence of ischemia-reperfusion injury and apoptosis of cardiomyocytes and reduced foam cell development [2].Herein we report on the isolation and characterization of two new biflavonoids, mesquitol-(4α→5)-epimesquitol-4β-ol 1 and the flavanone-(3→4)-flavan-3-ol 3 from the heartwoord of Acacia nigrescens, belonging to a hitherto small group characterized by the rare pyrogallol A-ring as a structural feature. These are conveniently named promelacacinidins and, together with the related proteracacinidins, were the subject of recent publications demonstrating their occurrence in Acacia species [3][4][5][6][7] and in Prosopsis glandulosa [8]. To our knowledge, both these compounds are new, whereas the unique carboncarbon linkage (C-3 to C-4) of the flavanone-flavanol dimer merits special mention since it represents a prototype of a new class of biflavonoids.The structures of these compounds (as their permethylaryl ether acetate derivatives) were elucidated by spectroscopic methods, including NMR and CD analysis.The 1 H NMR spectrum of the octamethylether triacetate 2 of compound 1 in (CD 3 ) 2 CO (Table 1) exhibited eight O-methyl and three O-acetyl resonances typical of methylated phenolic groups and acetylated aliphatic hydroxyl groups respectively, which strongly suggested a dimer containing a flavanol unit linked to a flavan-3,4-diol terminal unit. ______ Dedicated to Prof. E. Malan, who initiated and supervised this research project, for a noteworthy contribution in the flavonoid field, and wh...

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“…This deduction was corroborated by FAB-MS with a molecular ion of m/z 730 and a molecular formula of C 40 H 42 O 13 .…”

mentioning

confidence: 70%

“…A perusal of the literature has revealed that the presence of the benzoyl chromophore in compound 4 and its known chiroptical properties offers the most tangible leverage to unravel the absolute stereochemistry of all the stereogenic centers [11][12][13][14].…”

mentioning

confidence: 99%

Two new promelacacinidin dimers, including a novel flavanone-flavanol dimer characterized by a unique C(3)-C(4) linkage, from the heartwood of Acacia nigrescens

et al. 2007

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“…5 However, the key reductive dimerization step in this synthesis provided methyl-protected 1 in only a 10% yield. To date, a non-racemic synthesis of either compound has not been documented.…”

Section: Introductionmentioning

confidence: 89%

Synthesis of 3-benzylidene-dihydrofurochromen-2-ones: promising intermediates for biflavonoid synthesis

Baron

Mead

2015

Heterocyclic Communications

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A route to 3-benzylidene dihydrofurochromen-2-ones from 2H-chromenes is described. Lactonization of 2H-chromenes was achieved using a two-step cyclopropanation-rearrangement sequence. Subsequent conversion of these intermediates to the corresponding α-benzylidene lactones was achieved by lithium enolate Aldol reaction, followed by base-promoted elimination of the aldolate mesylates. The alkene geometry was found to be base-dependent. While KOtBu favored formation of the E-isomer, DBU showed a slight preference for the Z-isomer. In further studies, these 3-benzylidene dihydrofurochromen-2-ones were converted to polyaromatic structures possessing all the required functionality for biflavonoid synthesis.

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“…As part of our ongoing efforts toward the asymmetric synthesis of 3,3′‐biflavanones, we have focused on the study of 4‐chromanone, exclusively. In addition, we have reported the cyclopropenes of 3‐diazochroman‐4‐one with phenylacetylene catalyzed by Rhodium (II) catalyst in good yield .…”

Section: Methodsmentioning

confidence: 99%

An Efficient Synthesis of 6‐oxa‐spiro[3.4]octan‐1‐one Derivates Through 3‐diazochroman‐4‐one and Alkene

Xiao

Zhang

et al. 2018

Adv Synth Catal

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Spiro[2,bicyclo [4.2.0]octane]-7'-one with fused and spirocyclic oxygen-containing rigid skeleton structure is obtained via Wolff rearrangement and cycloaddition with good yields. Then Spiro[2,2-dimethyl-benzofuran,hexahydro-isobenzofuran]-7'-one is synthesized by further Baeyer-Villiger oxidation. These two kinds of products have a special fused and spirocyclic oxygen-containing rigid skeleton structure and are reported by our group.

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A Simple Biomimetic Synthesis of dl-Chamaejasmine, a Unique 3,3‘-Biflavanone

Cited by 26 publications

References 25 publications

Two new promelacacinidin dimers, including a novel flavanone-flavanol dimer characterized by a unique C(3)-C(4) linkage, from the heartwood of Acacia nigrescens

Two new promelacacinidin dimers, including a novel flavanone-flavanol dimer characterized by a unique C(3)-C(4) linkage, from the heartwood of Acacia nigrescens

Synthesis of 3-benzylidene-dihydrofurochromen-2-ones: promising intermediates for biflavonoid synthesis

An Efficient Synthesis of 6‐oxa‐spiro[3.4]octan‐1‐one Derivates Through 3‐diazochroman‐4‐one and Alkene

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