Structural characteristics of novel symmetrical diaryl derivatives with nitrogenated functions. Requirements for cytotoxic activity

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

NMR-based investigations of acyl-functionalized piperazines concerning their conformational behavior in solution

Selected N-benzoylated piperazine compounds were synthesized to study their conformational behavior using temperature-dependent 1H NMR spectroscopy. All investigated piperazines occur as conformers at room temperature resulting from the restricted rotation of the partial amide double bond. In the case of selected mono-N-benzoylated and unsymmetrically N,N'-substituted derivatives, the appearance of the 1H NMR spectrum was further shaped by the limited interconversion of the piperazine chair conformations. Therefore, two different coalescence points T C were determined and their resulting activation energy barriers ΔG ‡ were calculated to be between 56 and 80 kJ mol-1. In most of the cases, T C and ΔG ‡ for the amide site appeared to be higher than the corresponding values for the ring inversion. The influences of substituents on rotational and inversion barriers were analyzed by correlation to Hammett constants. The obtained results are discussed and interpreted in the context of literature data. An additional aryl substituent connected at the amine site led to reduced rotational and inversion barriers compared to the free secondary amine. To support and evidence the findings from the NMR analyses, single crystals of selected piperazines were obtained and XRD analyses were performed. To underline the results, two potential TGase 2 inhibitors were investigated showing energy barriers with similar values.

New insights into the structural requirements for pro-apoptotic agents based on 2,4-diaminoquinazoline, 2,4-diaminopyrido[2,3-d]pyrimidine and 2,4-diaminopyrimidine derivatives

As a continuation of our work on new anti-tumoral derivatives with selective pro-apoptotic activity in cancer cells, we describe the synthesis and the preliminary evaluation of the cytotoxic and pro-apoptotic activities of a series of pyrimidin-2,4-diamine derivatives that are structurally related to quinazolin-2,4-diamine and pyrido[2,3-d]pyrimidin-2,4-diamine derivatives. We also describe the structure-activity relationship studies carried out on four series' of quinazolin-2,4-diamine, 2-(alkylsulfanyl)-N-alkyl- and 2-(alkylsulfanyl)-N-alkylarylpyrido[2,3-d]pyrimidine and pyrimidin-2,4-diamine derivatives. The proposed preliminary pharmacophore consists of a flat heterocyclic ring, preferably a pyrido[2,3-d]pyrimidine, with two equivalent alkylarylamine chains, preferably N-benzyl- or N-ethylphenylamine, located in positions 2 and 4 of the ring, and with a preferred ALogP in the range 4.5-5.5. The nitrogen present in the central ring can act as hydrogen bond acceptors (HBA) whereas the amino group in the 4-position can act as a donor (HBD) or an HBA and the amino group in the 2-position can act as an HBD. On the basis of the analyzed structural profiles, different mechanisms of action can be suggested for the quinazolin-2,4-diamine, the 2-(alkylsulfanyl)-N-alkylpyrido[2,3-d]pyrimidin-4-amine and the pyrido[2,3-d]pyrimidin-2,4-diamine derivatives.

Synthesis and pharmacological screening of several aroyl and heteroaroyl selenylacetic acid derivatives as cytotoxic and antiproliferative agents

The synthesis and cytotoxic activity of a series of twenty six aroyl and heteroaroyl selenylacetic acid derivatives of general formula Ar-CO-Se-CH₂-COOH or Heterar-CO-Se-CH₂-COOH are reported. The synthesis was carried out by reaction of acyl chlorides with sodium hydrogen selenide, prepared in situ, and this led to the formation of sodium aroylselenides that subsequently reacted with α-bromoacetic acid to produce the corresponding selenylacetic acid derivatives. All of the compounds were tested against a prostate cancer cell line (PC-3) and some of the more active compounds were assessed against a panel of four human cancer cell lines (CCRF-CEM, HTB-54, HT-29, MCF-7) and one mammary gland-derived non-malignant cell line (184B5). Some of the compounds exhibited remarkable cytotoxic and antiproliferative activities against MCF-7 and PC-3 that were higher than those of the reference compounds doxorubicin and etoposide, respectively. For example, in MCF-7 when Ar = phenyl, 3,5-dimethoxyphenyl or benzyl the TGI values were 3.69, 4.18 and 6.19 μM. On the other hand, in PC-3 these compounds showed values of 6.8, 4.0 and 2.9 μM. Furthermore, benzoylselenylacetic acid did not provoke apoptosis nor did it perturb the cell cycle in MCF-7.

Novel potent organoselenium compounds as cytotoxic agents in prostate cancer cells

A series of 17 symmetrical substituted imidothiocarbamate and imidoselenocarbamate derivatives has been synthesized by reacting appropriately substituted acyl chlorides with alkyl imidothiocarbamates and alkyl imidoselenocarbamates. The antitumoral activities of the compounds were evaluated in vitro by examining their cytotoxic effects against human prostate cancer cells (PC-3). Five compounds showed interesting activity levels and 3p (IC(50)=1.85 microM) was 7.3 times more active than the standard etoposide used in the treatment of prostate cancer and emerges as the most interesting compound.

Biological profile of new apoptotic agents based on 2,4-pyrido[2,3-d]pyrimidine derivatives

In order to obtain less toxic antitumoral compounds we have looked for novel compounds with anticancer activity based on proapoptotic mechanisms. The compounds studied in this work are derivatives of bicyclic aromatic systems like pyrido[2,3-d]pyrimidines. The potential antitumoral activity of the compounds was evaluated in vitro by examining their cytotoxic effects against human breast, colon, and bladder cancer lines (MD-MBA-231, HT-29, and T-24). The data indicate that HC-6 is a potent anticancer drug showing dose-dependent cytostatic and proapoptotic effects through activation of two different signaling pathways namely a pathway leading to cell cycle arrest and a transcription-independent route leading to rapid apoptosis.