Cover Picture: Chem. Eur. J. 8/2002

Couladouros, Elias A.; Strongilos, A. T.; Papageorgiou, Vassilios P.; Plyta, Zoi F.

doi:10.1002/1521-3765(20020415)8:8<1757::aid-chem1757>3.0.co;2-r

Cited by 4 publications

(8 citation statements)

References 71 publications

(141 reference statements)

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“…These aldehydes resemble the common intermediate of most synthetic schemes so far reported for alkannin and shikonin, [44] with the additional advantage of orthogonal protection of the aromatic hydroxyl groups. As has recently been demonstrated, [28] …”

Section: Resultsmentioning

confidence: 59%

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Synthesis of Hydroxylated Naphthoquinone Derivatives

Couladouros

Strongilos

2002

Eur. J. Org. Chem.

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Section: Resultsmentioning

confidence: 59%

“…However, most reported syntheses concerning αprenylation [20Ϫ27] of aldehydes or acid derivatives were expected to result in multistep and ''tricky'' synthetic procedures. On the other hand, it has been demonstrated [28] that Scheme 2. Preparation of juglone derivatives; reagents and conditions: i) NaH, cat.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Hydroxylated Naphthoquinone Derivatives

Couladouros

Strongilos

2002

Eur. J. Org. Chem.

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“…The 1 H‐NMR chemical shifts of component D were observed at δ: 1.5–1.7 (triplet, 6H for methyl protons), 2.4–2.6 (doublet, 2H for the CH 2 group), 4.92 (singlet, 1H for the proton α to quinoid ring), 5.21 (singlet, 2H for the vinylic proton and the secondary hydroxyl proton), 7.2 (triplet for 3H for protons on the benzene ring and the quinine ring), 12.6 and 12.5 (singlets, 2H for the two perihydroxyl groups). The 1 H‐NMR chemical shifts of component D [(5,8‐dihydroxy‐4′‐methylpent‐3′‐enyl)‐1,4‐naphthoquinone] corresponded with the standard shikonin sample and the values in the literature, thus confirming its identity [33,36].…”

Section: Resultsmentioning

confidence: 99%

“…As the structural features of the dyes are responsible for their colour and dyeing properties, it is of interest to understand and structurally identify the colorants. In this study, the processes for extraction and separation of these naphthoquinones reported in the literature were used[18,20,21,26–32,34–36]; however, none of these yielded the purified colorants. Therefore, extraction, separation, chromatographic purification and spectroscopic characterisation of the major coloured constituents of the root were undertaken here.…”

Section: Introductionmentioning

confidence: 99%

Naphthoquinone colorants from Arnebia nobilis Rech.f

Arora

Gupta

Rastogi

et al. 2012

Coloration Technology

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The roots of Arnebia nobilis have traditionally been used as a colorant in food and cosmetic preparations. The deep red colour obtained is attributed to the presence of shikonin and its isomer alkannin and their derivatives. In this study, five colouring components were extracted from the roots of A. nobilis. These were separated and purified chromatographically and characterised using various spectrophotometric techniques. Three of the five components were identified. The major component was found to be alkannin β, β‐dimethylacrylate [5,8‐dihydroxy‐2‐(1′‐β, β‐dimethylacryloxy‐4′‐methylpent‐3′‐enyl)‐1,4‐naphthoquinone], accounting for nearly 25% of the total colouring matter. Alkannin acetate [2‐(1′‐acetoxy‐4′‐methylpent‐3′‐enyl)‐5,8‐dihydroxy‐1,4‐naphthoquinone] made up ca. 8% and shikonin [(5,8‐dihydroxy‐4′‐methylpent‐3′‐enyl)‐1,4‐naphthoquinone] contributed ca. 6% of the colouring matter. Polyester was dyed pink, nylon was dyed blue and all other substrates acquired a purple hue under similar dyeing conditions. The dyed fabrics showed excellent wash, rub and perspiration fastness; however, light fastness was found to be poor.

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“…5,9,12 The presence of 6, resulting from oxidation of 4 and/or 5, reflects the facile air oxidation reported for comparable compounds. 13 Experimental GC-MS analyses were performed on a Hewlett Packard 6890 gas chromatograph with a (5%)diphenyl-(95%)dimethyl-polysiloxane crosslinked column (30 m × 0.25 mm with 0.25 µm film) and a HP 5973 mass selective detector (EI, 70 eV). NMR spectra were recorded in CDCl 3 on a Varian GEM-300 spectrometer with chemical shifts reported in parts per million (δ) relative to tetramethylsilane for 1 H and relative to the centre line of the 77.0 ppm triplet of chloroform-d for 13 C; J values are given in Hz.…”

mentioning

confidence: 99%