Facile Total Syntheses of Two Novel 4-Alkenyloxy-2,6-dihydroxyacetophenones

Huang, Chusheng; Zhang, Zhe; Li, Shuhua; Li, Yulin

doi:10.1039/a807504b

Cited by 5 publications

(2 citation statements)

References 7 publications

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“…The feasibility of this approach to the synthesis of 5,7,4′-tri- O -benzyl-kaempferol ( 22 ) was examined (Scheme ). Thus, condensation of hydroxyacetophenone 17 and 4-benzyloxybenzoic acid 18 was effected under EDCI in CH 2 Cl 2 , providing ester 19 (75%). Bromination of methyl ketone 19 with phenyltrimethylammonium tribromide (PTT) in THF afforded bromide 20 in a moderate yield of 49%; the corresponding dibromomethyl ketone was found to be the major byproduct.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Kaempferol 3-O-(3′′,6′′-Di-O-E-p-coumaroyl)-β-d-glucopyranoside, Efficient Glycosylation of Flavonol 3-OH with Glycosyl o-Alkynylbenzoates as Donors

Yang

Sun

et al. 2010

J. Org. Chem.

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Kaempferol 3-O-(3'',6''-di-O-E-p-coumaroyl)-β-D-glucopyranoside (1), an optimal metabolite of Scots pine seedlings for protection of deep-lying tissue against damaging UV-B, represents a typical acylated flavonol 3-O-glycoside. This compound was synthesized for the first time via two approaches. The first approach, starting with kaempferol, featured formation of the flavonol 3-O-glycosidic linkage with a glycosyl bromide under conventional PTC conditions. In the second approach, 5,7,4'-tri-O-benzyl-kaempferol was readily prepared from 2',4',6'-trihydroxyacetophenone and p-hydroxybenzoic acid, which was coupled with a glucopyranosyl o-hexynylbenzoate under the catalysis of a gold(I) complex to provide the desired 3-O-glycoside in excellent yield. A variety of the glycosyl o-hexanylbenzoates equipped with the 2-O-benzoyl group were also proven to be highly efficient donors for construction of the flavonol 3-O-glycosidic linkages.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Kaempferol 3-O-(3′′,6′′-Di-O-E-p-coumaroyl)-β-d-glucopyranoside, Efficient Glycosylation of Flavonol 3-OH with Glycosyl o-Alkynylbenzoates as Donors

Yang

Sun

et al. 2010

J. Org. Chem.

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“…Phenolics are a class of compounds known for their wide range of physiological actions, ranging from anti-inflammatory, anti-bacterial, anti-oxidative, anti-allergic, anti-hypertensive, antiischemic, anti-arrhythmic, anti-thrombotic, anti-carcinogenic, immune-stimulating and hypocholesterolemic [1][2][3][4]. They are common plant secondary metabolites found in herbs, fruit, vegetables, grains, tea, coffee beans, propolis, red wine and flavouring agents which form an integral part of the human diet [4][5][6][7].…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of 3-bromo-4,6-dibenzyloxy-2-hydroxy acetophenone, C22H19BrO4

Hill

Kuo

Bezuidenhoudt

2015

Zeitschrift Für Kristallographie - New Crystal Structures

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Source of materialTo a solution of 4,6-dibenzyloxy-2-hydroxyacetophenone (0.780 g, 2.24 mmol) in glacial acetic acid (10 ml), was added drop-wise a solution of bromine (0.13 ml, 2.24 mmol) in glacial acetic acid (2 ml) at room temperature over a period of 30 min and the reaction mixture stirred for 4 h at the same temperature. The reaction was quenched by the addition of water (20 ml) and the resulting solid was filtered off. The crude product was separated by preparative thin layer chromatography (PTLC, 7:3 n-hexane:acetone, R f = 0.55) to afford the title compound 4,6-dibenzyloxy-3-bromo-2-hydroxyacetophenone as a grey solid 0.58 g (94 %) and 4,6-dibenzyloxy-3,5-dibromo-2-hydroxyacetophenone as yellow needles 0.057 g (6 %). Crystals suitable for single crystal Xray determination were grown by slow evaporation from acetone. IR ( DiscussionPhenolics are a class of compounds known for their wide range of physiological actions, ranging from anti-inflammatory, anti-bacterial, anti-oxidative, anti-allergic, anti-hypertensive, antiischemic, anti-arrhythmic, anti-thrombotic, anti-carcinogenic, immune-stimulating and hypocholesterolemic [1][2][3][4]. They are common plant secondary metabolites found in herbs, fruit, vegetables, grains, tea, coffee beans, propolis, red wine and flavouring agents which form an integral part of the human diet [4][5][6][7]. Bromination of 4,6-dibenzyloxy-3-bromo-2-hydroxyacetophenone with Br 2 in HOAc gave 4,6-dibenzyloxy-3-bromo-2-hydroxyacetophenone and 4,6-dibenzyloxy-3,5-dibromo-2-hydroxyacetophenone in a 90:10 ratio. As expected, bromination occurred preferentially at C1 and not at C5 of the substrate, leading to the title compound as the main product. The position of bromination was confirmed by NOESY NMR spectroscopy where a strong NOE effect was evident between the aromatic hydrogen (H5), observed at d 6.12 ppm, and the four benzyl CH 2 protons were seen at 5.18 ppm and 5.06 ppm respectively. The molecular structure of the title compound is an example of a highly substituted acetophenone, with substituents including two benzyloxy groups, a hydroxyl and a bromine. The weak hydrogen bonding interaction between C42-H42×××O4 plays a marginal role in the packing due to its resulting in the alignment of the phenyl ring creating an essentially planar molecule with an r.m.s. deviation of 0.0797 Å (C1-C6, C21, C22, C41-C47, O1, O2, O4, Br1), with a maximum deviation 0.153(4) Å found for atom C45.

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