A review on acridinylthioureas and its derivatives: biological and cytotoxic activity

Acridines possess two characteristics that have led many researchers to consider the agents interesting targets for future development as potential farmacophores: the planar acridine skeleton, which is able to intercalate into DNA, and the intense fluorescence of the agents. This review offers a study of the multifunctional character of acridines and the synthesis of novel acridine derivatives, with particular focus being placed on isothiocyanates and their congeners, e.g. thioureas, isothioureas, quaternary ammonium salts and platinum/gold conjugates. The review provides an overview of the structure, spectral properties, DNA binding and biological activity of acridinylthiourea congeners. These acridinylthiourea derivatives display significant cytotoxic activities against different types of cancer cell lines at micromolar concentrations. Copyright © 2017 John Wiley & Sons, Ltd.

Spectroscopic, structural and theoretical studies of novel, potentially cytotoxic 4-acridonecarboxamide imines

Ten novel, potentially intercalating 4-acridonecarboxamide azomethines and ketimines have been prepared by the condensation reaction of 9-oxo-9,10-dihydroacridine-4-carboxylic acid hydrazide with various aldehydes and ketones. The structures of the compounds were characterized spectroscopically by NMR ((1)H, (13)C, (15)N nuclei and 2D experiments), UV-vis, IR and fluorescence methods and by quantum chemical calculations using DFT at the B3LYP/6-311+G(d,p) level of theory and semiempirical ZINDO and AM1 methods. NMR chemical shift variations for C-4' were assessed due to changes in the polarizability of the imine C(4')=N(3') bond rather than direct inductive effects arising from the C-4' substituents. In concert with this was the reversed order observed for the N-3' chemical shifts with DFT-calculated atomic charges confirming the bond polarization. Both intra- and intermolecular hydrogen bonds between the acridone NH hydrogen and the amidic carbonyl oxygen were found to exist by FT-IR spectroscopy. Quantum chemical calculations were used to evaluate the configurational, tautomeric, conformational and hydrogen bonding states of the molecules as well as predict the NMR and IR data. The hypsochromic shifts observed in the UV-vis spectra upon changing from m-cresol to DMA, DMF or methanol were evaluated in terms of solvent polarity (giving rise to solvated excited state destabilization) and solvent aromaticity (giving rise to solvated excited state stabilization). The fluorescence of the compounds were modest, except for the 2,6-dichloro derivative, with respect to 9-isothiocyanatoacridine.

Methylation of Acridin-9-ylthioureas. Structure, Fluorescence and Biological Properties of Products

The structure, fluorescence, biological properties and S(N)-methylation reactions of ten 1,1-alkyl/aryl-disubstituted 3-(acridin-9-yl)thioureas 4 have been studied. Various reaction conditions allowed to obtain corresponding S-methyl 5 and S,N-dimethyl derivatives 6 in good yields. Structure and stereochemistry of the synthesized products are demonstrated by ab initio quantum chemical calculations and NMR techniques including PDQF-COSY, selective INEPT and NOE-difference experiments. Remarkable upfield 13C shifts of resonance signals of carbons C-4a, C-10a adjacent to acridine N-10 are characteristic of hydroiodides in contrast to free bases. Z configuration in isothioureas 7 with secondary amino rest in relation to E configuration of isothioureas with primary amino rest is discussed. Of the obtained products, some isothiourea salts 6 exhibit more than 2 orders of magnitude higher intensity of fluorescence, using 9-isothiocyanatoacridine as a standard. The obtained isothiourea hydroiodides 5 and dimethylisothiourea iodides 6 show remarkable biological activity against Mycobacterium tuberculosis.

Synthesis of pentacyclic 13-azadibenzo[a,de]anthracenes via anionic cascade ring closure

Bromine-lithium exchange using tert-butyllithium at -78 degrees C initiates a cascade process whereby either xanthone derivatives or pentacyclic 13-azadibenzo[a,de]anthracenes are produced in high yields. The reaction proceeds via a sequential intramolecular trapping of organolithium intermediates.