Diazapolycyclic compounds. XXVI. Reactivity of epoxy- and dihydroxy derivatives of diazaquinone adducts

Treatment of epoxy and dihydroxy derivatives of diazaquinone adducts with concentrated sulfuric acid yields the respective oxo derivatives, while the reaction of the epoxides with boron trifluoride etherate affords trans-fluorohydrines.     

Thermodynamic properties of anthraquinone derivatives

The enthalpies of solution of a series of anthraquinone derivatives in dioxane at various dilutions were determined by isothermal calorimetry.     

Acidities of anthraquinone and its hydroxy derivatives

The acidities of anthraquinone and its 1- and 6-hydroxy derivatives were studied. It is shown that the anthrone ring in the anthrapyridone molecule displays a strong electron-acceptor effect that stabilizes the anion during the development in the pyridone ring of a negative charge as a result of ionization; as a consequence of this, anthrapyridone and 1-hydroxyanthrapyridone are considerably stronger acids than 2-pyridone and 3-hydroxy-2-pyridone, respectively.Communication VII from the series Structure and Properties of Dyes. See [1] for communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1373–1376, October, 1978.     

Solvatochromism of the green fluorescence protein chromophore and its derivatives

The solvatochromic behavior of the green fluorescence protein (GFP) chromophore (p-hydroxybenzylideneimidazolone, p-HBDI) and its derivatives (p-methoxybenzylideneimidazolone, p-MeOBDI, and N-methyl-p-hydroxybenzylideneimidazolonium iodide, p-HBDIMe+) was studied using UV-vis-absorption spectroscopy in a wide array of solvents. The relative contribution of specific (polarity) vs nonspecific (hydrogen-bonding) solvation to the absorbance spectra was studied. On the basis of these data, we discuss the nature of the absorption peak of the protonated and deprotonated forms of the wild-type GFP.     

Synthesis of chiral oxa- and azacycle-fused anthraquinone derivatives

A convenient protocol for the synthesis of chiral pyran and piperidine ring-fused anthraquinone derivatives has been developed from (R)-2,3-O-cyclohexylidene-glyceraldehyde using sequential applications of enyne metathesis, Diels–Alder reaction and aromatization as key steps.     

Structures and tautomeric interconversions of anthraquinone imine derivatives

Substituted 1-hydroxy-9,10-anthraquinone-9-imines have been found to exhibit tautomeric interconversions between the 9,10- and 1,10-quinonoid forms in the solid state as well as in solution. Single-crystal X-ray crystallography was used to study the structures of 4-(N-acetyl-p-tolylamino)-9-amino-1,10-anthracenedione and 4-hydroxy-1-phenylamino-10-mesitylimino-9(10H)-anthracenone at ambient and low temperatures. The former compound gave crystals belonging to the monoclinic space group P2_l/c and, at 295 K,a=9.684(2),b=16.371(3),c=12.097(2) å,=110.41(1), V=1797 å³,Z=4, R(F)=0.042, and GOF=0.863. The latter compound gave crystals belonging to the monoclinic space group C2/c and, at 295 K,a=38.158(8),b=6.322(2),c=19.325(4) å,=101.78(2),V=4564 å³,Z=8, R(F)=0.052, and GOF=0.981, while at 150 K,a=37.852(6),b=6.245(1),c=19.235(4) å,=102.81(1),V=4434 å³,R(F)=0.047, and GOF=1.006. Comparison of the geometric parameters of the two compounds illustrates the considerable zwitterionic nature of the first, a distinctive feature of which is a very short bond N(9)-C(9) whose length is essentially equal to that of a double bond. Molecular modeling studies using AMI semiempirical calculations were shown to be capable of satisfactorily reproducing the energetics of the tautomeric equilibrium once the medium effect was taken into account.     

Thermolysis of symmetrical dithiobiurea and thioureidoethylthiourea derivatives

Microwave and thermal heterocyclization of N,N′‐disubstituted hydrazinecarbothioamide 1a,b and substituted thioureidoethylthioureas 2a–c as well as 1‐phenyl‐3[2‐(3‐phenylthio‐ureido)phenyl]thiourea 6 are reported. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:535–541, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10188     

Synthesis with silicon derivatives: non symmetrical derivatization of symmetrical diamines

The conversion of symmetrical diamines to monoamides via the use of cyclic silicon-nitrogen compounds as intermediates is described.     

Preparations of anthraquinone and naphthoquinone derivatives and their cytotoxic effects

Chrysophanol and 1,8-di-O-hexylchrysophanol derivatives having nucleic acid bases at position 5 were synthesized. Furthermore, derivatives of menadione substituted at position 11 (type A naphthoquinone derivatives) or methylmenadione substituted at position 7 (type B naphthoquinone derivatives) modified with nucleic acid bases, amines and thiocyano, selenocyano or thioacetyl groups were synthesized. The cytotoxic effects of these derivatives on HCT 116 cells, which poorly express P-glycoprotein (P-gp), and Hep G2 cells, which stably express P-gp, were evaluated by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results were compared with those obtained using 5-fluorouracil (5-FU), which has been used clinically. Several of these derivatives exhibited markedly higher potent cytotoxic effects not only on HCT cancer cells but also Hep G2 cancer cells as compared with 5-FU.     

Photochemical studies: Chromones,bischromones and anthraquinone derivatives

Photochemical reaction is a chemical reaction initiated by the absorption of energy in the form of light resulting in different types of reaction. Chromones, bischromones and anthraquinones are the bichromophoric molecules which contain the carbonyl group and double bond in conjugation. Photochemical reactions of these compounds result in the formation of such molecules which are not obtained via conventional methods. This review article describes the photochemical transformations of chromones, bischromones and anthraquinone derivatives and here main emphasis has been laid upon the intramolecular photochemical H-abstraction reactions that provide many exotic heterocyclics as the final photoproducts.     

Spectrophotometric and spectrofluorimetric investigation of aggregation of some anthraquinone derivatives

The behaviour of some anthraquinone derivatives in aqueous solution has been studied by absorption and fluorescence spectrophotometry. The results point to the presence of molecular aggregates in solution, also confirmed by polarographic determinations.     

Synthesis of novel,azasugar-modified anthraquinone derivatives and their cytotoxicity

A series of novel, azasugar-modified 2-monosubstituted, 2,6- and 2,7-bissubstituted anthraquinone derivatives have been synthesized by the nucleophilic substitution of N-alkylamino azasugar with mono-, bis（2-chloroacetamido）anthraquinones. Their cytotoxic activities against HeLa and MCF-7 ceils were preliminarily evaluated and compound 9a with mono-azasugar pendant at 2-position showed similar activity to the control drug （Cisplatin）.     

Substituent effects in the one-electron reduction of anthraquinone derivatives

Polarographic reduction against (C₂H₅)₄NBr as background in dimenthyformamide has been applied to 17 anthraquinones with - and -substituents. There are two pronounced half-waves, which correspond to two one-electron degrees of reduction, a semiquinone anion being formed as intermediate. An ESR signal is produced when this radical is formed by electrolysis with a cathode potential equal to E_1/2. The observed E_1/2 fit Hammett's equation closely. The relation E_1/2 to donor-acceptor aspects of the substituents is discussed.     

New anthraquinone derivatives from the roots of Berchemia floribunda

A new naphthoquinone-anthraquinone dimer named floribundiquinone E(1)and a new anthraquinone 2-acetylphyscion(2)were isolated from the roots of Berchemia floribunda Brongn.Their structures were elucidated on the basis of spectroscopicmethods.     

Condensation of o-diamino derivatives of anthraquinone and naphthoquinone with mesityl oxide

Anthraquinone- and naphthoquinonediazepines are formed by the reaction of 1,2- and 2,3-diamino-9,10-anthraquinones and 2,3-diamino-1,4-naphthoquinones with mesityl oxide. It was shown by spectral methods that naphthoquinonediazepine exists in two tautomeric forms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 138–141, January, 1976.