1,4-Naphthoquinone derivatives

The third pathway involved in the quinones biosynthesis is the isoprenoid route. This pathway is primarily important for the formation of prenyl side chains of prenylquinones (ubiquinone, menaquinone, plastoquinones, etc.). The side chains of ubiquinones and prenylated naphthoquinones derive from polyprenyl diphosphates. 

Naphthoquinone derivatives Bulbine capitata SiOj B+Hx B + MeOH — Identification 73 10... 

Michael addition of di- and tri-hydric phenols to /V-cinnamoylimidazoles followed by a lactonisation offers a route to 4-aryI-3,4-dihydrocoumarins and their [/]-benzologues <00S123>. The lactonisation of the naphthoquinone derivative 66 is sensitive to the acidic cyclising medium and it is possible to obtain the thermodynamically less stable o-quinone derivative exclusively (Scheme 44) <00TL3007>. Some related quinones have been obtained from 1-benzylisoquinolines via an arylnaphthoquinone <00T6O23>. 

S. Arai, M. Oku, M. Miura, T. Shioiri, Catalytic Asymmetric Epoxidation of Naphthoquinone Derivatives under Phase-Transfer Catalyzed Conditions , Synlett, 1998,1201-1202. 

Dihydro-1,4- and -1,2-naphthoquinone derivatives(1461 and 1463) in a mixture of ethanol and chloroform were oxidized with iron(III) chloride in dilute hydrochloric acid to naphthoquinones (1462 and 1464) (67JOC3210). 

As the final example of the simplified treatment of an aromatic ring, a novel potential energy calculation of a naphthoquinone derivative (36) with a program called EENY will be briefly mentioned (155). This program seems to resemble WMIN in that it calculates only van der Waals energy. The rotation around the cyclopropyl-quinonoid bonds is calculated to have a barrier of about 10 kcal/mol. In this and another case (156), the results could be considerably improved by full relaxation MM calculations. 

Buffinton, G.D., Olhnger, K., Brunmark, A., and Cadenas, E., 1989, DT-diaphorase catalyzed reduction of 1,4-naphthoquinone derivatives and glutathione-conjugates. Biochem. J. 257 561-571... 

SCHEME 48. Catalytic asymmetric epoxidation of naphthoquinone derivatives under phase transfer catalyzed conditions... 

Brand Name(s) AquaMEPHYTON, Mephyton, Vitamin K1 Chemical Class Naphthoquinone derivative... 

Methyl, 2-hydroxymethyl-, and 2-formylanthraquinones in the heart wood of teak (Tectona grandis, Verbenaceae) are effective in inhibiting termite activity (105). Several naphthoquinone derivatives including lapachol are thought to impart marine borer resistance to woods, e.q. that of Tabebuia quayacan (Bignoniaceae) (108). 

Al Shafei et a/.110 have conveniently prepared several fused naphthoquinone derivatives by condensing ambident compounds, having N—N, N—O, or N—S nucleophilic centers, with 2,3-dichloronaphthoquinones (62), under PT conditions. 

A new synthetic route to alkyl-substituted quinones has relied on the photochemical reaction of 2,3-dichloro-l,4-naphthoquinone with a thiophene derivative (77CL851). Irradiation of a benzene solution of the quinone and thiophene by a high pressure mercury lamp gave photoadduct (295) in 56% yield. Desulfurization of this compound over Raney nickel (W-7) gave the 2-butyl-1,4-naphthoquinone derivative (296 Scheme 62). Alkyl-substituted quinones such as coenzyme Q and vitamin K, compounds of important biological activity, could possibly be prepared through such methodology. 

The rhodium complex 219 gave the naphthoquinone derivative 220 with DMAD182 there was no attack at the triazole ring. 

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. 

Chiral bis(oxazoline)/Copper(II) complexes are evaluated for asymmetric Diels-Alder reaction of naphthoquinone derivatives, and moderate levels of enantiomeric excess are observed in certain cases [56] (Eq. 8A.33). 

A large number of quinones of the general structure 7 are known, where X corresponds to a heterocyclic residue containing one or more rings, and the chemistry of these has been reviewed extensively [6-8], If X consists of a benzenoid or aza-benzenoid ring system, then such compounds are best regarded as anthraquinone analogues. In the case of other heterocyclic residues, they may be considered as 1,4-naphthoquinone derivatives. 

Scheme 25 Generation of methylsulfonium ylides in DMSO-based cellulose carbanilation mixtures, trapping by 3,4-dehydro-a-tocopheryl acetate (67), and quick color testing for their presence by naphthoquinone derivative 69...

Because of such extensive application in folk medicine, it is easy to understand the interest that the lapachol, the related naphthoquinones a-lapachone, P-lapachone and other naphthoquinones derivatives, have aroused as potential drugs. In fact, a broad variety of biological activities have been described for this kind of compounds. Some examples are antitumor promoting activities [11-12], inactivators of human cytomegalovirus protease [13], antiprotozoal activity [14], trypanocidal activity [15], anticancer activity [16], and antibacterial and antifungal activities [17]. 

Human cytomegalovirus (HCMV) disease is the most common life-threatening opportunistic viral infection in the inmunocompromised. HCMV protease, a serine protease, plays a critical role in capsid assembly and viral maturation and is an attractive target for antiviral chemotherapy. Slater et al investigated the interaction of various 1,4-naphthoquinones derivatives with HCMV protease. They identified potent irreversible naphthoquinones inhibitors of HCMV protease which covalently modify... 

Many synthetic applications have been reported of the photochemical reactions of halogen-substituted 1,4-naphthoquinones with 1,1-diarylethenes487 90, and with related electron-rich alkenes such as 1-aryl-l-trimethylsilyloxyethenes491 93, 2-trimethylsilyloxy-1-alkenes494, 2-methoxy-l-alkenes495 and allyltributylstannane496,497. The process is exemplified by the reaction of 2-bromo-3-methoxy-1,4-naphthoquinone derivatives (152) with 1,1-diphenylethene487 (equation 129). 

The rifamycins were first isolated by Sensi et al.3) from Nocardia mediterranei as a complex mixture (Rifamycins A—E). Addition of diethylbarbiturate to the fermentation medium led to the sole production of rifamycin B6 which was obtained in crystalline form. Its structure has been determined by chemical7,and X-ray analysis9. The rifamycins might easily have excaped detection altogether, since rifamycin B has no antibacterial activity. However, it is spontaneously oxidized to rifamycin 0 and hydrolyzed to rifamycin S, a naphthoquinone derivative reduction yields the naphthohydroquinone derivative rifamycin SV (Fig. 4). These compounds inhibit the growth of Gram-positive bacteria at concentration as low as 0.0025 jug/ml. 

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