A New Efficient Route for Multigram Asymmetric Synthesis of Alkannin and Shikonin

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

doi:10.1002/1521-3765(20020415)8:8<1795::aid-chem1795>3.0.co;2-v

Cited by 39 publications

(18 citation statements)

References 9 publications

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“…These peaks were found to be absent in component D. This may be because the purity of both the samples varies. The 1 H-NMR chemical shifts of component D were observed at d: 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 a to quinoid ring), 5.21 (singlet, 2H for the vinylic proton corresponded with the standard shikonin sample and the values in the literature, thus confirming its identity [33,36].…”

Section: Component D (Shikonin)supporting

confidence: 61%

“…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][27][28][29][30][31][32][34][35][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%

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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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Section: Component D (Shikonin)supporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Naphthoquinone colorants from Arnebia nobilis Rech.f

Arora

Gupta

Rastogi

et al. 2012

Coloration Technology

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“…Naturally occurring naphthoquinones A short and convergent approach for the synthesis of alkannin, shikonin, and shikalkin was already developed using a new synthetic approach with selective and highyielding enantioselectivity results which furnished the title compounds as pure crystalline precipitates (Couladouros et al 2002). (2 steps) 70%…”

Section: Generalmentioning

confidence: 99%

Larvicidal activity of naturally occurring naphthoquinones and derivatives against the West Nile virus vector Culex pipiens

et al. 2008

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Concentration-dependent mortality effects were observed for three pure synthetic natural products (alkannin, shikonin, and shikalkin) and three acetylated derivatives of shikonin against Culex pipiens (Culicidae: Diptera) for the first time. The larvicidal properties of all naphthoquinones were evaluated under laboratory conditions against the larvae of the mosquito species C. pipiens biotype molestus, the anthropophilic biotype of the C. pipiens mosquito species. Experimental data of the tested toxicity of quinones revealed generally high efficacy where shikonin (3.9 mg/L) was the most active followed by shikalkin (8.73 mg/L) and alkannin (12.35 mg/L). The insecticidal performance of shikonin-acetylated derivatives was also investigated, aiming at the same time in the establishment of the relationships between the structure and the activity of shikonin-type compounds with larvicidal activity against C. pipiens. Results indicated that naphthoquinones, compared with other natural compounds with larvicidal activity, are very toxic against mosquito larvae and could be a potential source of natural larvicidal substances. Finally, bioassays with shikonin derivatives also revealed that although hydroxylic groups seem to play a secondary role in efficacy, the quinone moiety is essential.

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“…BBr 3 ‐mediated demethylation resulted also in C‐5 epimerization and quinone tautomerization to provide a mixture of 18 and 5 (38:62, determined by 1 H NMR spectroscopy) in 45 % yield. Alternatively, based on Couladouros report,30 the conversion of terminal quinone 16 into 5‐ epi ‐hemi‐γ‐acinorhodin ( 18 ) was efficiently achieved by the sequence of reductive acetylation, oxidation, and hydrolysis. Thus, the one‐pot reduction of quinone 16 to hydroquinone with Zn and in‐situ acetylation with Ac 2 O and Et 3 N/4‐(dimethylamino)pyridine (DMAP) afforded 19 in an excellent yield of 90 %.…”

Section: Resultsmentioning

confidence: 99%

Synthetic Studies toward Actinorhodin and γ‐Actinorhodin by using a Homo‐coupling Strategy: Synthesis of Hemiactinorhodin and Hemi‐γ‐actinorhodin

2015

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A homo‐coupling strategy toward the synthesis of actinorhodin and γ‐actinorhodin has been explored. The monomeric unit was synthesized by employing an efficient combination of Dötz benzannulation and oxa‐Pictet–Spengler reactions. Attempts towards oxidative homo‐coupling of the pyranonaphthalene monomer intermediate to give dimer were unsuccessful. Later, monomer pyranonaphthalene was carried forward to complete the synthesis of hemiactinorhodin and hemi‐γ‐actinorhodin.

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A New Efficient Route for Multigram Asymmetric Synthesis of Alkannin and Shikonin

Cited by 39 publications

References 9 publications

Naphthoquinone colorants from Arnebia nobilis Rech.f

Naphthoquinone colorants from Arnebia nobilis Rech.f

Larvicidal activity of naturally occurring naphthoquinones and derivatives against the West Nile virus vector Culex pipiens

Synthetic Studies toward Actinorhodin and γ‐Actinorhodin by using a Homo‐coupling Strategy: Synthesis of Hemiactinorhodin and Hemi‐γ‐actinorhodin

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