Jonathan R. Dimmock

Anticonvulsant properties of various acetylhydrazones, oxamoylhydrazones and semicarbazones derived from aromatic and unsaturated carbonyl compounds.

Various acetylhydrazones, oxamoylhydrazones and semicarbazones were prepared as candidate anticonvulsants with a view to examining the viability of a putative binding site hypothesis. Atomic charge calculations were undertaken to determine the hydrogen bonding capacities of various molecules. The biological results obtained revealed that in general the acetylhydrazones and semicarbazones afforded good protection against convulsions while the oxamoylhydrazones were significantly less active. These data suggest that terminal electron-donating groups enhanced the hydrogen bonding capabilities and anticonvulsant properties of these molecules.

Evaluation of the semicarbazones, thiosemicarbazones and bis-carbohydrazones of some aryl alicycylic ketones for anticonvulsant and other biological propertie

Summary A number of aryl alicyclic ketones were converted to their corresponding semicarbazones, thiosemicarbazones and bis-carbohydrazones. Anticonvulsant activity was displayed by most of the compounds in the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) screens when given intraperitoneally to mice. However, on oral administration to rats, a marked selective activity in the MES screen only was noted. X-ray crystallography on five semicarbazones was undertaken in order to find correlations between the shapes of these molecules and anticonvulsant properties. The thiosemicarbazones displayed greater cytotoxicity to P388D1 and L1210 cells than the semicarbazones while a number of human tumors and different viruses were, in general, insensitive to representative compounds.

Some aryl semicarbazones possessing anticonvulsant activitie

Summary A number of aryl semicarbazones displayed anticonvulsant activity in the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) screens when administered intraperitoneally to mice. When given by the oral route to rats, protection was afforded in the MES but not scPTZ tests. Correlations were noted between the σ and σ * values of the aryl substituents, the interplanar angles made by the aryl rings with the adjacent carbimino groups and the shapes of certain semicarbazones determined by X-ray crystallography, and the activities in the rat oral MES screen. Molecular modeling studies revealed a number of statistically significant descriptors which contributed to anticonvulsant activity.

1-p-Chlorophenyl-4,4-dimethyl-5-diethylamino-1-penten-3-one hydrobromide, a sulfhydryl-specific compound which reacts irreversibly with protein thiols but reversibly with small molecular weight thiols

1-p-Chlorophenyl-4,4-dimethyl-5-diethylamino-1-penten-3-one hydrobromide (CDDP) has been shown to react selectively with small molecular weight and protein thiols. The reaction of this compound with thiols can be monitored directly owing to the large decrease (approximately 21,000 M-1 cm-1 at 310 nm) in extinction coefficient subsequent to thiol addition. CDDP reacted stoichiometrically with large molecular weight (greater than 11,000) protein thiols. However, with small molecular weight thiols (less than 500) the reaction was less than stoichiometric, indicating a significant degree of back-reaction. The forward and reverse rate constants have been estimated. The fact that the reaction is reversible enables CDDP to be used for the direct monitoring of the oxidation of small molecular weight thiols.

Cytotoxic analogues of 2,6-bis(arylidene)cyclohexanones.

A series of 2,6-bis(arylidene)cycloalkanones (1) and related compounds containing one or two substituents at the four position of the cyclohexyl ring were prepared and shown to display cytotoxic activity towards murine P388 and L1210 cells as well as human Molt 4/C8 and CEM T-lymphocytes. In some of the series of compounds, positive correlations were noted between the potencies of the enones and the magnitude of the Hammett sigma values of the aryl substituents. Four representative compounds were cytotoxic to a number of human tumours in vitro, particularly towards colon cancer and leukemic cells. A noteworthy feature of the compounds prepared in this study is that, in general, they were well tolerated when administered to rodents. A number of lead molecules emerged from this investigation as well as guidelines for future expansion of these series of compounds.

Cytotoxic 2,6-bis(arylidene)cyclohexanones and related compounds

A number of 2-arylidenecyclohexanones 1, 2, 6-bis(arylidene)cyclohexanones 2 and related Mannich bases 3-5 were prepared. Various torsion angles as well as atomic charges on olefinic carbon atoms were determined by molecular modelling on all compounds. These molecules showed cytotoxicity towards murine P388 and L1210 cells as well as to human Molt 4/C8 and CEM T-lymphocytes. The average cytotoxicity of the dienones 2 was more than three times greater than was found with the monoarylidene analogues 1, and, in general, were slightly more cytotoxic than the Mannich bases 3-5. A number of the compounds displayed potency towards a panel of human tumour cell lines and most of the representative compounds in series 2-5 were selectively toxic to colon cancers and leukaemic cells.

Cytotoxic Thiol Alkylators

Various classes of cytotoxic compounds which alkylate cellular thiols are described namely alpha,beta-unsaturated ketones, alpha-methylene-gamma-lactones, azines of Mannich bases, imexon, isothiocyanates, a benzoacronycine as well as activation by thiols prior to alkylation. The mechanisms of action of some of the molecules, such as the formation of reactive oxygen species, are presented. The cytotoxicity of a number of drugs can be influenced by modulation of the concentration of thiols including the observation that potencies can be increased by thiol activation. The ability of certain thiol reagents to reverse multidrug resistance as well as some miscellaneous actions of thiol alkylators are described.

Evaluation of Mannich bases of 2-arylidene-1,3-diketones versus murine P388 leukemia

Abstract A number of novel Mannich bases of 2-arylidene-1,3-diketones were shown to have some activity versus P388 lymphocytic leukemia in mice. PMR spectroscopy revealed that most of these compounds underwent intramolecular cyclization in deuterium oxide to give cyclic enols and the ratio of cyclic to acyclic species was probably influenced by steric considerations. Attempts to prepare rigid analogues of the Mannich bases of the acyclic 2-arylidene-1,3-diketones led to a further example of intramolecular cyclization in which dicycloalkano[ b,e ]pyrandiones or alternatively Michael adducts were produced. In general, these latter compounds did not have activity in the P388 leukemia screen.

Evaluation of some Mannich bases of cycloalkanones and related compounds for cytotoxic activity

Abstract A number of Mannich bases of cycloalkanones and related quaternary ammonium compounds were prepared for cytotoxic evaluation in order to examine the theory that sequential release of alkylating agents produces increased bioactivity compared to related compounds containing only 1 potential alkylating site. Many of the compounds had significant activity against murine L1210 cells and various human tumours. Some correlations between structure and activity were noted but the biological data did not support the view that potential sequential liberation of cytotoxic species produced compounds with increased potency. The formation of various oximes and oxime benzoates as candidate prodrugs was achieved but in general these compounds were not cytotoxic at the concentrations utilized. This observation may be due to the fact that the oximes were much more stable in deuterated phosphate buffered saline over a period of 48 h at 37°C than the Mannich bases, as revealed by 1 H-NMR spectroscopy.

The cytotoxic properties and preferential toxicity to tumour cells displayed by some 2,4-bis(benzylidene)-8-methyl-8-azabicyclo[3.2.1] octan-3-ones and 3,5-bis(benzylidene)-1-methyl-4-piperidones

This study demonstrated that replacement of the axial protons on the C2 and C6 atoms of various 1-methyl-3,5-bis(benzylidene)-4-piperidones 3 by a dimethylene bridge leading to series 2 lowered cytotoxic potencies. Four compounds 2a and 3a-c emerged as lead molecules based on their toxicity towards different neoplasms and their selective toxicity for malignant rather than normal cells. Some possible reasons for the disparity between the IC(50) values in the two series of compounds are presented based on molecular modeling, logP values and respiration in rat liver mitochondria.