1,4-Naphthoquinone properties

Malaysia, the seeds are poisonous and used to catch fish. The plant has not been studied for its pharmacological potentials. The ichthyotoxic property could involve some naphthoquinones and/or saponins. 

Naphthoquinone Derivatives, These dyes are generally not very colorfast and sometimes also fade. Anthraquinone derivatives have better properties (see Dyes, ANTHRAQUINONE). New developments are based on compounds that combine the chemical structure of phenothiazine or phenoselenazine derivatives with benzoquinone or naphthoquinone units (16). These dyes show good chemical stability. Naphthoquinone derivatives have yet to find a practical application as dyes in WORM disks because of the high expenditure for synthesis due to low yields. 

From about 1930 onwards, developments in the field of naphthoquinone dyes concentrated on the use of naphthazarin and intermediates for the preparation of violet, blue, and green acid and disperse dyes [1]. More recently there has been interest in the synthesis and color and constitution properties of simple colored naphthoquinones, stimulated by the fact that such dyes have similar tinctorial properties to the anthraquinones but a smaller molecular size. The naphthoquinones provide a useful alternative to the anthraquinones for certain specialized applications, e g., as pleochroic dyes with improved solubility for liquid-crystal displays. As a result, research interest in these chromogens remains unabated, even though they have failed to make any major impact as textile dyes [2-8],... 

ABSTRACT This review describes a group of compounds related to the prenyl naphthoquinone lapachol. They exhibit interesting biological activities. Various aspects of the identification, biosynthesis, chemistry and biological properties are discussed. 

Prokopenko et al described that some naphthoquinones normalized or increased the immune response in rats after intensive physical load. The naphthoquinones induced the development of immunostimulating properties in heavy red blood cells by direct action on cell membranes or indirectly through proteolytic enzymes secreted by hepatocytes [212]. Other activities described for several naphthoquinones related to lapachol are antipsoriatic [213], larvicidal and insecticidal, [214-215] molluscicidal [216], and mutagenicity in salmonella [217]. The potential use of lapachol in cosmetics has been published too [218]. 

Nicolaou and Hepworth used the Ipc2BCl reduction method in an efficient synthesis of naphthoquinone alkannin (65), which exhibits many interesting biological properties, such as antibacterial, antifungal, anti-inflammatory, and antitumor activities27 (Scheme 4.3w). The lithium anion of the bromonaphthalene 66 underwent a coupling reaction with the Weinreb amide 67 to provide the... 

The rifamycins have some remarkable chemical properties. Rifamycin SV can be obtained from the quinone rifamycin S by treating the latter with weak reducing agents such as ascorbic acid. It is fairly stable against oxidation by air and can form a stable sodium salt. This behaviour can be ascribed to the acylamino group in position 2. Unsubstituted naphthoquinone can only be reduced under much more drastic conditions, and once in the hydroquinone form it is very sensitive to oxidation. 

Several hundred semisynthetic derivatives have been prepared in an effort to obtain substances with better biological activities (for references see Ref.s)). Particularly positions 3 and 4 of the naphthoquinone ring system (numbering system as proposed by Prelog7 8) have been extensively substituted, since it has been shown that structural changes in these two positions do not critically affect the action of the substance on the target enzyme, the bacterial RNA polymerase (cf. Chapter 3.). They can, however, influence other parameters such as its ability to penetrate into cells, its pharmacokinetic properties and resorption, which are all important for clinical use as an antibiotic. Rifampicin (U.S. rifampin), which is a widely used orally active tuberculostatic agent, is a 3-(4-methyl piperazinyl)-iminomethyl derivative of rifamycin SV, synthesized via the 3-formyl derivative (Fig. 5)10 ... 

The analogue of 1 hydroxylated at C-6, e.g. 3-deoxyrabelomycin (20), was synthesized by Kraus and Wu using the excellent Michael acceptor properties of the extremely electron-deficient 3-acetyl-5-methoxy-1,4-naphthoquinone (17) [31, 32] (for related reactions of Eugster et al. compare [33]). The addition of 5-methyl-l,3-cyclohexadione (18) proceeded at 20-25 C without catalyst to afford adduct 19 after methylation. The subsequent intramolecular Michael-type reaction followed by elimination of methanol afforded more drastic conditions (NaOH, MeOH, 140 °C) and gave relatively low yields (27%) of a tetracyclic intermediate which was demethylated in the usual manner with AICI3 to yield 3-deoxyrabelomycin (20, Scheme 6). 

This model was used successfully to explain the different solvent dependencies of the rates of photoinduced charge for the dyad 23(8) and the naphthalene analogue (i.e., the methoxy groups are replaced by hydrogens) [67], Equation 27 has recently been used to explain the interesting contrasting photoinduced electron transfer properties of the two closely related covalently linked porphyrin-naphthoquinone dyads 80 and 81 [178]. It was found that dyad 80, whose quinone carbonyl groups are 6.7 A from the center of the porphyrin donor, exhibits photoinduced ET whose... 

Dyads 19 and 20 also feature a very rigid bicyclic scaffold between donor and acceptor, and show some unusual properties [98, 105]. The two molecules differ significantly only in the location of the naphthoquinone carbonyl groups relative to the porphyrin macrocycle. Dyad 19, whose quinone carbonyl groups are rela-... 

Naftazone (beta-naphthoquinone semicarbazone) is prepared by diazotization of sulfonic acid with beta-naphthol, and its properties are similar to those of... 

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