Synthesis of linear and cyclic guazatine derivatives endowed with antibacterial activity

Antibiotic resistance has reached alarming levels in many clinically-relevant human pathogens, and there is an increasing clinical need for new antibiotics active on drug-resistant Gram-negative pathogens who rapidly evolve towards pandrug resistance phenotypes. Here, we report on two related classes of guanidinic compounds endowed with antibacterial activity. The two best compounds (9a and 13d) exhibited the most potent antibacterial activity with MIC values ranging 0.12–8 μg/ml with most tested pathogens, including both Gram-positive and Gram-negative bacteria. Interestingly, MIC values were not affected (1–8 μg/ml) when measured using recent clinical isolates with various antibiotic resistance determinants. The results reported herein identify guazatine derivatives as an interesting starting point for the optimization of a potentially novel class of antibacterial agents.     

Synthesis and antibacterial activity of novel neamine derivatives

Synthesis and activity of derivatives at the O5 or O6 positions of 1-N-((S)-4-amino-2-hydroxybutyryl)-3′,4′-dideoxyneamine, which is the neamine moiety of arbekacin, were reported. Among these results, the 5-O-aminoethylaminocarbonyl derivative showed effective activity against Staphylococcus aureus expressing a bifunctional aminoglycoside-modifying enzyme AAC(6′)-APH(2″).     

Synthesis and antibacterial activity of C6-carbazate ketolides

A novel series of ketolides containing heteroaryl groups that are linked to the erythronolide ring via a C6-carbazate functionality has been successfully synthesized. Careful modulation of the heteroaryl groups, the length and degree of saturation of the C6-carbazate linker, and the substituents present on each of the carbazate nitrogens led to compounds with potent activity against key bacterial respiratory pathogens. The best analogs of this series had in vitro and in vivo (sc dosing) profiles that were comparable to telithromycin.     

Synthesis and antibacterial activity of derivatives of 6-O-allylic acylides

A series of novel acylide derivatives have been synthesized from erythromycin A via a facile procedure. By applying this procedure, cyclic carbonation to C-11,12 position, acylation to C-3 hydroxyl, and deprotection provided the desired acylides. These compounds showed antibacterial activity against both macrolide-susceptible strains and macrolide-resistant strains. Because of existence of 6-O-allyl substitution, these derivatives can be used as intermediates for further structural modification.     

Synthesis and antibacterial activity of novel 6-O-substituted erythromycin A derivatives

A series of novel 6-O-substituted erythromycin A derivatives has been synthesized. Good in vitro antibacterial activity has been demonstrated for analogues incorporating a variety of structural features. The methodology disclosed is expected to find application in the design of future macrolide antibiotics that target the prevalent bacterial resistance problem.     

Synthesis and antibacterial activity of 3-O-acyl-6-O-carbamoyl erythromycin A derivatives

A series of 3-O-acyl-6-O-carbamoyl erythromycin A derivatives has been synthesized. Several functional groups were identified as the optimal C3-substituents, and the best compounds in this series possess potent in vitro antibacterial activity against erythromycin-susceptible and erythromycin-resistant bacteria.     

Synthesis and antibacterial activity of egonol derivatives

Synthesis of egonol derivatives, 5-(3'-chloropropyl)-7-methoxy-2-(3',4'-methylenedioxyphenyl)benzofuran 1, 5-(3'-bromopropyl)-7-methoxy-2-(3',4'-methylenedioxyphenyl)benzofuran 2, 3-[2-(1,3-benzodioxol-5-yl)-7-methoxy-1-benzofuran-5-yl]propanal 3, 5-(3'-iodopropyl)-7-methoxy-2-(3',4'-methylenedioxyphenyl)benzofuran 4, 5-[3-(3'-bromopropyloxy) propyl]-7-methoxy-2-(3',4'-methylenedioxyphenyl)benzofuran 5, 3-[2-(1,3-benzodioxol-5-yl)-7-methoxy-1-benzofuran-5-yl]propylmethanoate 6, 3-[2-(1,3-benzodioxol-5-yl)-7-methoxy-1-benzofuran-5-yl]propyloleate 7, 5-[3'-hydroxypropyl]-6-bromo-7-methoxy-2-(3',4'-methylenedioxyphenyl)benzofuran 8, 4-[2-(1,3-benzodioxol-5-yl)-7-methoxy-1-benzofuran-5-yl]butanenitrile 9, 3-[2-(1,3-benzodioxol-5-yl)-7-methoxy-1-benzofuran-5-yl]propylbenzoate 10, 5-[3'-hydroxypropyl]-7-methoxy-3-nitro-2-(3',4'-methylenedioxyphenyl)benzofuran 11 and their antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Candida albicans and Escherichia coli are reported. The starting material egonol 5-[3'-(hydroxy)propyl]-7-methoxy-2-(3', 4'methylenedioxyphenyl)benzofuran was isolated from seeds of Styrax officinalis L. The structural elucidication of these compounds (1-11) was established using 1D ((1)H, (13)C), 2D NMR (HMBC, HMQC, COSY) and LCMS spectroscopic data. While egonol and some synthesised new compounds show similar antibacterial activity and MIC values against S. aureus, B. subtilis, C. albicans and E. coli, other new derivatives show different activity against S. aureus, B. subtilis, C. albicans and E. coli.     

Synthesis and antibacterial activity of novel enolphosphate derivatives

A new class of enolphosphates derivatives, the 1-alkenyldiphosphates, was designed and a rapid and efficient synthesis for these compounds was developed. These new molecules showed interesting in vitro antibacterial activities (MIC) against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative pathogens including Pseudomonas aeruginosa and Escherichia coli.     

Synthesis and antibacterial activity of desosamine-modified macrolide derivatives

Structural factors behind erm macrolide resistance were studied through synthesis of new macrolide derivates possessing truncated desosamine sugar moieties and subsequent determination of their antibacterial activity. Synthesized compounds with 2'-deoxy and 3'-desmethyl desosamine rings demonstrated decreased antibacterial activity on the native Staphylococcus aureus strain and were inactive against constitutively resistance S. aureus. The obtained results indicate that steric repulsion between the dimethylated A2058 and desosamine ring cannot be considered as a primary reason for erm-resistance.     

Synthesis of coumarin derivatives with cytotoxic, antibacterial and antifungal activity

The synthesis and selective biological screening of 7-hydroxy-4-methyl-2H-chromen-2-one (2), 7-hydroxy-4,5-dimethyl-2H-chromen-2-one (15) and some of their derivatives were carried out. Compound 13 was found to be most potent cytotoxic agent with LD50 = 126.69 microg/ml. In antibacterial assay the compounds showed a broad spectrum of activities. Compound 11 exhibited a very high degree of plant growth inhibition at three levels of concentration. Compound 4 showed very promising antifungal activity against Candida albicans. Compounds 12 and 13 demonstrated excellent antioxidant activity.     

Synthesis and antibacterial activity of O-substituted nocathiacin I derivatives

The synthesis and antibacterial activity of a series of new nocathiacin I derivatives (1-12) containing polar water solubilizing groups is described. Most of these compounds exhibited potent antibacterial activity and have improved water solubility. In addition, compounds 5, 7-9 also exhibited potent in vivo activity.     

Synthesis and antibacterial activity of 9-substituted minocycline derivatives

A number of 9-acylamino and 9-sulfonylamino derivatives of minocycline have been synthesized for structure-activity relationship studies. These compounds showed activity against both tetracycline-susceptible and tetracycline-resistant strains. Many of the 9-sulfonylamino derivatives exhibited improved antibacterial activity against a number of tetracycline- and minocycline-resistant Gram-positive pathogens.     

Synthesis and antibacterial activity of 3-keto-6-O-carbamoyl-11,12-cyclic thiocarbamate erythromycin A derivatives

A series of 3-keto-6-O-carbamoyl-11,12-cyclic thiocarbamate erythromycin A derivatives has been synthesized. The best compounds in this series possess potent in vitro antibacterial activity against erythromycin-susceptible and erythromycin-resistant bacteria.     

The synthesis and antibacterial activity of totarol derivatives. Part 1: modifications of ring-C and pro-drugs.

A series of analogues of, and potential pro-drugs derived from, the potent antibacterial diterpene totarol (1) were synthesized in order to elucidate the minimum structural requirements for antibacterial activity and to seek compounds with good bioavailability in vivo. These analogues varied in the structural features of their aromatic rings and the prodrugs were O-glycosylated derivatives. They were tested in vitro against three gram-positive bacteria: beta-lactamase-positive and high level gentamycin-resistant Enterococcus faecalis, penicillin-resistant Streptococcus pneumoniae, and methicillin-resistant Staphylococcus aureus (MRSA); and against the gram-negative multi-drug-resistant Klebsiella pneumoniae. None of the analogues was more potent than totarol itself, which is effective against these gram-positive bacteria at MIC values of 7 microM. The results were evaluated in terms of a structure-activity relationship and this showed that a phenolic moiety was essential for potent antibacterial activity. Amongst the pro-drugs, totaryl alpha-D-mannopyranoside (22) proved the most active in vitro (MIC 18 microM). The in vivo antibacterial activities of compounds 1, 22 and totarol beta-lactoside (23) were assessed in a mouse model of infection, but they were found to be ineffective. Compounds 1 and 22 were shown to be cytotoxic towards proliferating human cell cultures, CH 2983, HeLa, and MG 63, but only at concentrations of > 30 microM.     

Synthesis and antibacterial activity of some new derivatives of pyrazole

In this study, we report the synthesis and antibacterial activity of a new series of 5-amido-1-(2,4-dinitrophenyl)-1H-4-pyrazolecarbonitriles. Our results show that all compounds exhibit antimicrobial activities against methicillin susceptible Staphylococcus aureus and methicillin resistant S. aureus with MIC values of 25.1 and 91.0 μM.     

Synthesis and antibacterial activity of 4'-O-heteroarylcarbamoyl derivatives of macrolide

A series of novel 4'-position modified macrolide derivatives has been synthesized via a facile procedure. Their in vitro antibacterial activities against constitutively erythromycin-resistant strains were evaluated. Among the derivatives tested, compound 8a which has 11,12-carbamate and 4'-O-heteroarylcarbamoyl groups was found to have potent activity against most resistant bacteria.     

Synthesis and antibacterial activity of 6-O-heteroarylcarbamoyl-11,12-lactoketolides

A new series of erythromycin A derivatives, the 6-O-heteroarylcarbamoyl-11,12-lactoketolides, with activity against macrolide-resistant streptococci, are described. Structurally, these macrolide antibiotics are characterized by a heteroaryl side chain attached to the macrolactone core through a carbamate linkage at the C6 position, as well as 11,12-gamma-lactone and 3-keto functionalities. The synthesis and antibacterial activity of this new series of ketolides are discussed.     

Synthesis,anti-bacterial and anti-protozoal activities of amidinobenzimidazole derivatives and their interactions with DNA and RNA

Amidinobenzimidazole derivatives connected to 1-aryl-substituted 1,2,3-triazole through phenoxymethylene linkers 7a–7e, 8a–8e, and 9a–9e were designed and synthesised with the aim of evaluating their anti-bacterial and anti-trypanosomal activities and DNA/RNA binding affinity. Results from anti-bacterial evaluations of antibiotic-resistant pathogenic bacteria revealed that both o-chlorophenyl-1,2,3-triazole and N-isopropylamidine moieties in 8c led to strong inhibitory activity against resistant Gram-positive bacteria, particularly the MRSA strain. Furthermore, the non-substituted amidine and phenyl ring in 7a induced a marked anti-bacterial effect, with potency against ESBL-producing Gram-negative E. coli better than those of the antibiotics ceftazidime and ciprofloxacin. UV–Vis and CD spectroscopy, as well as thermal denaturation assays, indicated that compounds 7a and 8c showed also binding affinities towards ctDNA. Anti-trypanosomal evaluations showed that the p-methoxyphenyl-1,2,3-triazole moiety in 7b and 9b enhanced inhibitory activity against T. brucei, with 8b being more potent than nifurtimox, and having minimal toxicity towards mammalian cells.     

Synthesis and antibacterial activity of 5-methylphenanthridium derivatives as FtsZ inhibitors

5-Methylphenanthridium derivatives were designed, synthesized and evaluated for their in vitro antibacterial activity and cell division inhibitory activity against various Gram-positive and -negative bacteria. Among them, compounds 5A2, 5B1, 5B2, 5B3, 5C1 and 5C2 displayed the best on-target antibacterial activity with an MIC value of 4 µg/mL against B. subtilis ATCC9372 and S. pyogenes PS, showing over 2-fold better activity than sanguinarine. The SARs showed that the 5-methylphenanthridium derivatives with the alkyl side chains at the 2-postion, especially the straight alkyl side chains exerted better on-target antibacterial activity.     

Synthesis and antibacterial activity of alaremycin derivatives for the porphobilinogen synthase

The preparation and the antibacterial activity of alaremycin derivatives such as their CF₃-derivatives and (R)- and (S)-4-oxo-5-acetylaminohexanoic acid for the porphobilinogen synthase (PBGS), were described. The IC₅₀ values of the antibacterial activity of the prepared materials for the inhibitor of PBGS, were determined using PBGS assay.