Anti-cancer and anti-fungal evaluation of novel palladium(II) 1-phenyl-1H-tetrazol-5-thiol complexes

Synthesis and antibacterial activities of baulamycin A inspired derivatives

SbnE is an essential enzyme for staphyloferrin B biosynthesis in Staphylococcus aureus. An earlier study showed that natural product baulamycin A has in vitro inhibitory activity against SbnE and antibacterial potency. A SAR study with analogues of baulamycin A was conducted to identify potent inhibitors of SbnE and/or effective antibiotics against MRSA. The results show that selected analogues, including 11, 18, 21, 24a, 24c, 24m and 24n, exhibit single-digit micromolar inhibitory potencies against SbnE (IC50s = 1.81-8.94 μM) and 11, 24m, 24n possess significant activities against both SbnE (IC50s = 4.12-6.12 μM) and bacteria (MICs = 4-32 μg/mL). Biological investigations revealed that these substances possess potent cell wall disruptive activities and that they inhibit siderophore production in MRSA. Among the selected analogues, 7 has excellent antibiotic activities both gram-positive and -negative bacteria (0.5-4 μg/mL). Moreover, these analogues significantly impede biofilm formation in a concentration-dependent manner. Taken together, the results of the investigation provide valuable insight into the nature of novel baulamycin A analogues that have potential efficacy against MRSA owing to their membrane damaging activity and/or inhibitory efficacy against siderophore production.

Bioisosteric ferrocenyl 1,3-thiazolidine-4-carboxylic acid derivatives: In vitro antiproliferative and antimicrobial evaluations

To improve the antiproliferative effect of ALC67 (diastereomeric mixture of ethyl 2-phenyl-3-propioloyl-1,3-thiazolidine-4-carboxylate), its structure was modified via (i) bioisosteric substitution of the phenyl ring by the ferrocene unit and (ii) replacing the propiolamide side-chain in ACL67 with other acyl groups having differing electrophilicities. In this way, a small library of methyl N-acyl-2-ferrocenyl-1,3-thiazolidine-4-carboxylates (13 compounds in total) was created and characterized by spectral and crystallographic means. The last N-acylation step was highly diastereoselective toward the cis-diastereomer. In solution, most of the obtained compounds existed as a mixture of two rotamers and displayed a preference for the syn-orientation around the CN bond. A twisted 5T4 envelope conformation was adopted by the derivative containing the N-phenoxyacetyl group in the crystalline state. Two derivatives with chloroacetyl and bromoacetyl groups in the N-3 side chain were cytotoxic to fibroblasts and hepatocellular cancer cells in the low micromolar range (IC50(MRC5) = 9.0 and 11.8 μM, respectively, and IC50(HepG2) = 10.6 and 18.4 μM, respectively) causing an effect similar to the lead compound (IC50(HepG2) = 10.0 μM) and cisplatin (IC50(MRC5) = 4.0 μM and IC50(HepG2) = 7.7 μM). Several derivatives also manifested modest antimicrobial effects against the studied microbial strains (MICs in the range from 0.44 to 4.0 μmol/mL). Our findings demonstrated that the introduction of a ferrocene core facilitated the preparation of optically pure analogs of ALC67 and that the cytotoxicity of compounds may be enhanced by adding proper electrophilic centers to the N-acyl side-chain.

Tripodal Phosphine Oxide Ligand with Tetrazole Functionality

Abstract

Tris[2-(3′-cyanopropoxy)phenyl]phosphine oxide has been obtained via the alkylation of tris(2hydroxyphenyl)phosphine oxide with 4-bromobutyronitrile in the presence of K2CO3. The product structure has been elucidated by means of X-ray diffraction analysis. The terminal cyano groups in the obtained phosphine oxide have been converted into tetrazole rings via the click-reaction with NH4N3 to give a new hybrid tripodal propeller ligand, tris{2-[3′-(tetrazol-5′′-yl)propoxy]phenyl}phosphine oxide. Palladium(II) complexes of the prepared ligand and its short-linker analog, tris[2-(tetrazol-5′-ylmethoxy)phenyl]phosphine oxide, have been synthesized. Cytotoxicity of the ligands and their Pd(II) complexes has been studied.