Synthesis and antibacterial evaluation of new monobactams.

Monobactams play an important role in antibiotic drug discovery. Based on the structural characteristics of aztreonam and its biological targets, six new monobactam derivatives (2a-c and 3a-c) were synthesized and their in vitro antibacterial activities were investigated. Compounds 2a-c showed higher activities against tested gram-negative bacteria than that of parent aztreonam. Monobactam 2c exhibited the most potent activities, with MIC ranging from 0.25 to 2 µg/mL against most bacteria.

ß-Lactamase inhibition profile of new amidine-substituted diazabicyclooctanes.

The diazabicyclooctane (DBO) scaffold is the backbone of non-ß-lactam-based second generation ß-lactamase inhibitors. As part of our efforts, we have synthesized a series of DBO derivatives A1-23 containing amidine substituents at the C2 position of the bicyclic ring. These compounds, alone and in combination with meropenem, were tested against ten bacterial strains for their antibacterial activity in vitro. All compounds did not show antibacterial activity when tested alone (MIC >64 mg/L), however, they exhibited a moderate inhibition activity in the presence of meropenem by lowering its MIC values. The compound A12 proved most potent among the other counterparts against all bacterial species with MIC from <0.125 mg/L to 2 mg/L, and is comparable to avibactam against both E. coli strains with a MIC value of <0.125 mg/L.

Synthesis and Antibacterial Activities of Amidine Substituted Monocyclic ß-Lactams.

BACKGROUND: Mononcyclic ß-lactams are regarded as the most resistant class of ß-lactams against a series of ß-lactamases, although they possess limited antibacterial activity. Aztreonam, being the first clinically approved monobactam, needs broad-spectrum efficacy through structural modification. OBJECTIVE: We strive to synthesize a number of monocyclic ß-lactams by varying the substituents at N1, C3, and C4 positions of azetidinone ring and study the antimicrobial effect on variable bacterial strains. METHODS: Seven new monobactam derivatives 23a-g, containing substituted-amidine moieties linked to the azetidinone ring via thiazole linker, were synthesized through multistep synthesis. The final compounds were investigated for their in vitro antibacterial activities using the broth microdilution method against ten bacterial strains of clinical interest. The minimum inhibitory concentrations (MICs) of newly synthesized derivatives were compared with aztreonam, ceftazidime, and meropenem, existing clinical antibiotics. RESULTS: All compounds 23a-g showed higher antibacterial activities (MIC 0.25 µg/mL to 64 µg/mL) against tested strains as compared to aztreonam (MIC 16 µg/mL to >64 µg/mL) and ceftazidime (MIC >64 µg/mL). However, all compounds, except 23d, exhibited lower antibacterial activity against all tested bacterial strains compared to meropenem. CONCLUSION: Compound 23d showed comparable or improved antibacterial activity (MIC 0.25 µg/mL to 2 µg/mL) to meropenem (MIC 1 µg/mL to 2 µg/mL) in the case of seven bacterial species. Therefore, compound 23d may be a valuable lead target for further investigations against multi-drug resistant Gram-negative bacteria.

Carbamates of 4'-demethyl-4-deoxypodophyllotoxin: synthesis, cytotoxicity and cell cycle effects.

In an attempt to generate compounds with superior bioactivity and reduced toxicity, 12 carbamates of 4'-demethyl-4-deoxypodophyllotoxin, N-(1-oxyl-4'-demethyl- 4-deoxypodophyllic)-α-amino acids amides, were synthesized and evaluated for antiproliferative activity and cell cycle effects. These synthesized compounds proved to be more hydrophilic, as well as improved or comparable in vitro cytotoxicities against four cell lines (A-549, HeLa, SiHa, and HL-60) compared with either parent DPT or anti-cancer drug VP-16. Furthermore, flow cytometric analysis exhibited that N-(1-oxyl-4'-demethyl-4-deoxypodophyllic)-d-α-methine amide (15f) induced cell cycle arrest in the G2/M phase in A-549 cells.