Lina K. Mehta

Preparation of 3-substituted 6,7-dimethoxyquinoxalin-2(1h)-ones and studies of their potential as fluoroionophores

Improved routes to the quinoxalinone acid chloride 1 and the 3-methyl-quinoxalinone 21 are described. These intermediates are used to obtain the fluoroionophores 15–19 and 27–29, respectively. The effects of the complexation of metal ions by the fluoroionophores is discussed. A red pigment 26 is obtained from 21.

The elimination of an alkoxy group in the photo-Graebe–Ullmann conversion of 1-(2,5-dialkoxyphenyl)triazolopyridines into carbolines, and the preparation of α-, γ- and δ-carboline quinones

Photochemical decomposition of 1-(2,5-dialkoxyphenyl)triazolopyridines 7a, 21 and 33 resulted in elimination of an alkoxy group to give the alkoxycarbolines 9a and 35 in addition to the expected dialkoxycarbolines. The carbolines having either a methoxy and a isopropoxy substltuent 22, 34a and 34b or two methoxy groups 41 were oxidised with ceric ammonium nitrate to yield the α-, γ- or δ-carboline p-quinones 37, 38 and 42.

Synthesis, hydroxyl radical production and cytotoxicity of analogues of bleomycin

Two pyridine analogues of the metal complexing region of the anticancer drug bleomycin and two related but deactivated prodrugs have been linked to a 2,6-diphenylpyridine derivative as a DNA binding unit. The 2,6-diphenylpyridine system is structurally related to known amplifiers of the cytotoxicity of bleomycin. The conjugates were found to bind to DNA more strongly than bleomycin-A2 and were more cytotoxic than the corresponding compounds lacking the DNA binding unit. On exposure of a mixture of cells and prodrugs to hypoxia and then air, the prodrug containing the nitrohistidine unit was not bioreductively activated but the prodrug having an N-oxide group was bioreductively activated. This result represents a novel approach to the improvement of the therapeutic ratio of bleomycin analogues.

Photocatalytic degradation of trans-cinnamic, dihydrocinnamic, trans-caffeic, and dihydrocaffeic acids and characterization of the products.

Catalysed degradation of aqueous solutions of cinnamic 1, dihydrocinnamic 2, dihydrocaffeic 3 and trans-caffeic 4 acids in the presence of (TiO2) and UV radiation and the products identified by HPLC, and after treatment with diazomethane by GC-MS have been studied. A pH range of 3 to 11 was used. The four acids, in the presence of TiO2 in the dark, underwent little degradation. Extended irradiation of all the acids in the presence of TiO2 produced complete degradation as shown by TOC measurements. Initially the volume of carbon dioxide produced rose steadily to a constant value.

Synthesis of some substituted quinoxalines and polycyclic systems containing the quinoxaline nucleus

The synthesis is described of quinoxalines 11, 14, 15, 16, 20, 21, 23 and 25 of interest as intermediates. The preparation of 21 from 3 by the action of thiourea and the formation of the hexaazapentacycle 23 from sulfide 20 and butylamine are discussed. The methylation of the dione 10 is reinvestigated and the product found to be a mixture of 29 and 30. The preparation of dimethoxyquinoxaline podands, e.g., 32, 33, 34, 40 and 41, tricyclic crown ether 31 and pentacyclic crown ethers, e.g. 38, is described and the effects of metal ions on spectroscopic properties of 40 and 41 are reported.

Synthesis of some 24-membered tetralactam derivatives by an unexpectedly simple route, and some macrocyclic polyether dilactams

Abstract An unexpected reaction of 1,5-bis(arylamino)-3-oxapentanes 4, 21 and 22 with diglycolyl dichloride gave 24-membered macrocyclic tetralactams 18, 23 and 24 respectively, in a reaction involving two molecules of each reactant (2:2 process). This was in contrast to closely related reactions of α,ω-bis(arylamino)alkylethers 5 and 6 with diglycolyl, triglycolyl and tetraglycolyl dichlorides which yielded the macrocycles 9–14 by reaction of one molecule of each reactant (1:1 process). The phenyl nuclei in 14 and 18 were formylated to give 34, 35 and 36 . The aldehydes, 35 and 36 were condensed with a quinoxaline fluorophore to yield the diene 37 and the tetraene 38 respectively.

Synthesis and properties of prodrugs activated in hypoxia to give bleomycin analogues

Prodrugs bioreductively activated to bleomycin analogues are reported. The production of hydroxyl radicals in the presence of FE(II) and dioxygen by both the prodrugs and the activated products are determined and their in vitro cytotoxicity measured.

CHEMICAL KINETICS OF THE PHOTOCATALYTIC DEGRADATION OF TRANS-CINNAMIC, DIHYDROCINNAMIC, TRANS-CAFFEIC, AND DIHYDROCAFFEIC ACIDS

Quantitative studies of the catalysed degradation of aqueous solutions of cinnamic 1, dihydrocinnamic 2, trans-caffeic 3 and dihydrocaffeic 4 acids in the presence of TiO2 and UV radiation at pH 3 and 10 are reported. The phenolic and aliphatic unsaturated groups in caffeic acid 3 caused it to be adsorbed more strongly than the phenolic saturated acid 4, and these two acids were much more strongly adsorbed than cinnamic and hydrocinnamic acids. The kinetics of the degradation of each acid has been studied at pH 3 and 10. TIC analysis showed complete mineralisation of the acids after 9 h.

Experimental and calculated13C chemical shifts for α-, β-, γ- and δ-carbolines

The 13C NMR chemical shifts of the four carbolines 1,2,3,4‐tetrahydro‐β‐carboline, 6,7,8,9‐tetrahydro‐δ‐carboline, 3‐ethyl‐4‐azaindole and 5‐azaindole were assigned from various one‐ and two‐dimensional 1H and 13C NMR spectra. Comparison is made with the results of DFT/GIAO shielding calculations. Copyright

Preparation of 3-Ethyloxindole-4,7-quinone†

The preparation of 3-ethyloxindole-4,7-quinone 10 from 4,7-dimethoxyisatin 1 in four steps is described.