ABSTRACT
A series of new 1,3-thiazole derivatives of maleopimaric acid 6a-f, 7a-f were synthesized and evaluated for anticancer, antibacterial and antifungal activities. Evaluation of cytotoxic activity against human embryonic kidney 293 cells (HEK293), human neuroblastoma cell line (SH-SY5Y), hepatocellular carcinoma cell line (HepG2) and human T-cell lymphoblast-like line (Jurkat), showed that introduction of the aminothiazole fragment at position 6 of the diterpenoid molecule leads to decrease of cell viability. Substance 3 was found to be the most active against all tested cell lines, inhibiting cell viability with IC50 values in the range of 2-24 µM. The structure-activity relationship of these compounds was studied and the results show that the compounds 6c and 7e exhibited in vitro antifungal activity against Candida albicans and also possessed antibacterial profile against Enterobacter aerogenes, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Proteus vulgaris.
Subject(s)
Anti-Bacterial Agents/pharmacology , Antifungal Agents/pharmacology , Antineoplastic Agents/pharmacology , Thiazoles/chemical synthesis , Thiazoles/pharmacology , Triterpenes/chemical synthesis , Triterpenes/pharmacology , Anti-Bacterial Agents/chemistry , Antifungal Agents/chemistry , Antineoplastic Agents/chemistry , Bacteria/drug effects , Candida albicans/drug effects , Cell Death/drug effects , Cell Line , Humans , Microbial Sensitivity Tests , Structure-Activity Relationship , Thiazoles/chemistry , Triterpenes/chemistryABSTRACT
The effect of Lewis base (LB) in the domino reaction between methyl diazoacetate and methyl acrylate has been studied. This domino process is initialized by a [3+2]-cycloaddition reaction to generate 3H-pyrazoline followed by a subsequent 1,3-H shift reaction forming 1H-pyrazoline as the more stable isomer. The rate of the first step is not sensitive to the presence of LBs (THF, Py, DMAP, DBU, and triphenylphosphine) as it was evidenced by kinetic nuclear magnetic resonance spectroscopy and quantum chemical modeling. LBs manifest remarkable catalytic effect on the second step of the reaction only acting as proton acceptor. DFT calculations reveal fine correlation between enthalpy of proton transfer from trans-3H-pyrazoline to LB and basic strength of the latter described in terms of BF3-affinity scale. Under conditions of LB catalysis the reaction rate of the first step (methyl diazoacetate and methyl acrylate interaction) limits the rate of 3H â 1H pyrazoline isomerization and, therefore, restricts catalytic efficiency of LB. An alternative mechanism for catalysis of the 1,3-dipolar cycloaddition through formation of triazene-like intermediate during reaction of diazo acetate with LB and following Michael addition of intermediate to alkene was carefully analyzed. This reaction scheme was not confirmed in our experiments.
