Incorporation of Protecting Groups in Organic Chemistry: A Mini-Review.

The approach of utilizing protecting groups (PGs) in organic chemistry has led to the successful syntheses of an array of useful organic compounds. This strategy has also addressed some of the complexities associated with many organic reactions. These PGs find useful applications in simple and complex reactions that involve the synthesis of large organic compounds such as peptides, and oligosaccharides. The fundamental role of PGs is to prevent undesired reactions that could hinder the progress or completion of such reactions. Ideal PGs must be utilized in this regard to achieve the desired objectives. This review describes the diverse protecting groups found in the literatures, the functional moieties for the protection, deprotection strategies, and their relevant applications in organic synthesis.

Benzamide and Benzamidine Compounds as New Inhibitors of Urokinasetype Plasminogen Activators.

BACKGROUND & METHOD: In this ongoing research, it is aimed to investigate the synthesis, structure identification and effects on urokinase-type plasminogen activators (uPA) and its receptor levels of 4-(3H-imidazo[4,5-b]pyridin-2-yl)-N-substituted benzamide and benzamidine derivatives. uPA levels obtained from 4b and 7d administration were similar to 5-FU (5-fluorouracil) for colorectal carcinoma cells (p<0.05). 4b and 7d significantly reduced uPAR (urokinase-type plasminogen activator receptor) levels on both cell lines (p<0.05). CONCLUSION: uPAR levels obtaining from 4b and 7d administration were similar to 5-FU for both cell lines colorectal (Colo205, CCL-222) and hepatocellular (HepG2, CCL-23) carcinoma cells (p<0.05).

Synthesis and Antioxidant Properties of New Oxazole-5(4H)-one Derivatives.

OBJECTIVES: To synthesize and characterize 4-(substituted benzylidene)-2-(substituted phenyl)oxazol-5(4H)-one derivatives (E1-E10), and evaluate them for antioxidant activity. MATERIALS AND METHODS: Required oxazole-5(4H)-one derivatives were synthesized in two steps to obtain novel hippuric acid derivatives (7-13); glycine and acylated appropriate benzoic acid derivatives were used and then, final compounds were obtained with condensation of 7-13 with appropriate benzaldehydes (E1-E10). These products were purified by column chromatography using ethyl acetate/n-hexane as eluent. All the compounds were unequivocally characterized using the combination of 1H and 13C-nuclear magnetic resonance, mass spectrometry (ESI-MS), and elemental analysis. The inhibition of lipid peroxidation and its effects on hepatic cytochrome P450-dependent ethoxyresorufin-O-deethylase (EROD) enzyme were determined in rats in vitro. RESULTS: The most active analogue on the microsomal EROD activity was E3 which inhibited the microsomal EROD activity (89%) and was similarly better than that of the specific inhibitor caffeine (85%) at 10-3 M concentration. CONCLUSION: The findings of this study indicate that the synthesized compounds, such as E3, display significant antioxidant activity.

Identification of a novel series of N-phenyl-5-[(2-phenylbenzimidazol-1-yl)methyl]-1,3,4-oxadiazol-2-amines as potent antioxidants and radical scavengers.

In this study, some novel 5-[[2-(phenyl/p-chlorophenyl)-benzimidazol-1-yl]-methyl]-N-substituted phenyl-1,3,4-oxadiazol-2-amine derivatives (28-45) with an oxadiazole ring were synthesized. The antioxidant properties and radical scavenging activities of the compounds were investigated employing various in vitro systems: hepatic microsomal NADPH-dependent inhibition of lipid peroxidation levels, scavenging of DPPH free radicals, and inhibition of microsomal ethoxyresorufin O-deethylase activity (EROD). Compounds 34 and 41 were found to be good scavengers of DPPH radicals (76% and 84%) when compared to BHT (90%). Almost all of the compounds examined were found to possess a good inhibitor effect on the microsomal EROD activity. Moreover, 32 and 41 were more active analogs (97% and 98%) on the microsomal EROD activity than caffeine (85%).

Antioxidant and antifungal properties of benzimidazole derivatives.

Antioxidant and radical scavenging properties of a series of 2-[4-(substituted piperazin-/piperidin-1-ylcarbonyl)phenyl]-1H-benzimidazole derivatives were examined. Free radical scavenging properties of compounds 11-30 and 33 were evaluated for the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide anion radical. In addition the inhibitory effects on the NADPH-dependent lipid peroxidation levels were determined by measuring the formation of 2-thiobarbituric acid reactive substances (TBARS) using rat liver microsomes. Compound 33 which has a p-fluorobenzyl substitutent at position 1 exhibited the strongest inhibition (83%) of lipid peroxidation at a concentration of 10(-3) M, while the nonsubstituted analogue 13 caused 57% inhibition. This result is fairly consistent with the antimicrobial activity results against both Staphylococcus aureus and Candida albicans.

Synthesis and antimicrobial activity of some novel 2-[4-(substituted piperazin-/piperidin-1-ylcarbonyl)phenyl]-1H-benzimidazole derivatives.

In this study, we report the synthesis and antimicrobial evaluation of several new 4-(1H-benzimidazol-2-yl)benzamides (11-30) and 5-chloro-1-(p-fluorobenzyl)-2-{4-[(4-methylpiperazin-1-yl)carbonyl]phenyl}-1H-benzimidazole (33). Compound 20 exhibited the best antibacterial activity with MIC value of 6.25 microg/mL against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA). Significant antifungal activities were obtained with the compounds 13, 14, 18, 19, and 33 with MIC values of 3.12 microg/mL which are close to fluconazole.

Synthesis and antioxidant properties of novel N-methyl-1,3,4-thiadiazol-2-amine and 4-methyl-2H-1,2,4-triazole-3(4H)-thione derivatives of benzimidazole class.

Some novel 1-methyl-4-(2-(2-substitutedphenyl-1H-benzimidazol-1-yl)acetyl)thiosemicarbazides (16a-20a), 5-[(2-(substitutedphenyl)-1H-benzimidazol-1-yl)methyl]-N-methyl-1,3,4-thiadiazol-2-amines (17b-20b), and 5-[(2-(substitutedphenyl)-1H-benzimidazol-1-yl)methyl-4-methyl-2H-1,2,4-triazole-3(4H)-thiones (16c-20c) were synthesized and tested for antioxidant properties by using various in vitro systems. Compounds 16a-20a were found to be a good scavenger of DPPH radical (IC(50), 26 microM; IC(50), 30 microM; IC(50), 43 microM; IC(50), 55 microM; IC(50), 74 microM, respectively) when compared to BHT (IC(50), 54 microM). Noteworthy results could not be found on superoxide radical. Compound 19b, which is the most active derivative inhibited slightly lipid peroxidation (28%) at 10(-3)M concentration. Compound 17c inhibited the microsomal ethoxyresorufin O-deethylase (EROD) activity with an IC(50)=4.5 x 10(-4)M which is similarly better than the specific inhibitor caffeine IC(50)=5.2 x 10(-4)M.

Synthesis and antioxidant capacities of some new benzimidazole derivatives.

In this study, we prepared some new oxadiazolyl benzimidazole derivatives and investigated their antioxidant properties by determination of microsomal NADPH-dependent inhibition of lipid peroxidation levels (LP assay) and microsomal ethoxyresorufin O-deethylase activity (EROD assay). Some of these compounds 20, 23 had slightly inhibitory effects (28%) on the lipid peroxidation levels at 10(-3 )M concentration lower than standard BHT (65%). 5-[2-(Phenyl)-benzimidazol-1-yl-methyl]-2-mercapto-[1,3,4]-oxadiazole 16 was found to be more active than caffeine on the ethoxyresorufin O-deethylase activity with an IC(50 )value of 2.0 6 10(-4 )M.

Synthesis and potent antimicrobial activities of some novel retinoidal monocationic benzimidazoles.

Several 2-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-1H-benzimidazole-5-carboxamidine analogues were synthesized for their antibacterial and antifungal activities against S. aureus, Methicillin-resistant S. aureus (MRSA), C. albicans, and C. krusei. MIC values of the targeted compounds 43-58 are comparable to those of Fluconazole and Sultamicillin. The most potent compounds, 51 and 53, showed MIC values as 0.78 and 1.56 microg/mL against S. aureus and C. albicans, respectively.

Synthesis, antioxidant and radical scavenging activities of novel benzimidazoles.

The synthesis and antioxidant evaluation of some novel benzimidazole derivatives (10-24) are described. Antioxidant properties of the compounds were investigated employing various in vitro systems viz., microsomal NADPH-dependent inhibition of lipid peroxidation (LP), interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and scavenging of superoxide anion radical. Compounds 12 and 13 showed very good antioxidant capacity and were 17-18-fold more potent than BHT (IC50 2.3 x 10(-4) M) with 1.3 x 10(-5) M and 1.2 x 10(-5) M IC50 values, respectively, by interaction of the stable DPPH free radical.

Synthesis and antioxidant properties of novel benzimidazoles containing substituted indole or 1,1,4,4-tetramethyl-1,2,3,4-tetrahydro-naphthalene fragments.

Some 6-fluoro-5-substituted-benzimidazole derivatives in which indole and 1,1,4,4-tetramethyl-1,2,3,4-tetrahydro-naphthalene groups were attached to the 2-position of the benzimidazole ring were synthesized and tested for antioxidant properties in vitro. Almost all the synthesized compounds at the 10(-3) M concentrations showed superoxide anion scavenging activity. Compounds 5, 3, 9, 4, 17 and 13 have strong inhibitory effects on superoxide anion formation (98%, 93%, 91%, 88%, 85% and 81%, respectively) at 10(-3) M concentration and these results are better than 30 IU of superoxide dismutase (SOD) (76%). Compound 11 is the most effective scavenger of 2,2-diphenyl-1-picrylhydrazyl (DPPH) stable free radical at 10(-3)M (61%) concentration.

Synthesis and antioxidant properties of novel benzimidazole derivatives.

Some novel benzimidazole derivatives carrying thiosemicarbazide and triazole moieties at the N1 position were synthesized and their in vitro effects on rat liver microsomal NADPH-dependent lipid peroxidation (LP) levels determined by measuring the formation of 2-thiobarbituric acid reactive substance. The free radical scavenging properties of the compounds were also examined in vitro by determining the capacity to scavenge superoxide anion formation and the interaction with the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The compounds showed a significant effect in the above tests except to scavenge superoxide anion formation.

Synthesis and antioxidant properties of some novel benzimidazole derivatives on lipid peroxidation in the rat liver.

Some benzimidazole derivatives namely 1-[(substituted thiocarbamoylhydrazine carbonyl) methyl]-2-phenyl-1H-benzimidazoles (1a-13a), N-[(2-phenylbenzimidazol-1-yl methyl)-[1,3,4]-thiadiazole-2-yl]-substituted phenyl amines (1b-13b) and 5-(2-phenyl benzimidazol-1-yl-methyl)-4-substituted phenyl-4H-1,2,4-triazole-3-thiones (1c-13c) were synthesized, and their in vitro effects on the rat liver microsomal NADPH-dependent lipid peroxidation (LP) levels were determined. The most active compound 10a caused an 84% inhibition of LP at 10(-3) M, which is better than that of butylated hydroxytoluene (BHT) (65%).

Synthesis of some new 2-substituted-phenyl-1H-benzimidazole-5-carbonitriles and their potent activity against Candida species.

New 2-substituted-phenyl-1H-benzimidazole-5-carboxylic acids (35, 38), ethyl-5-carboxylate (36), -5-carboxamides (37, 39),-5-carboxaldehyde (42), -5-chloro (40), -5-trifluoromethyl (41), and -5-carbonitriles (44-53, 55-67), -6-carbonitrile (54) were prepared and evaluated in vitro against Candida species. The cyano substituted compounds 53, 57, 58 and 61 exhibited the greatest activity with MIC values of 3.12 microg/mL, values similar to that of fluconazole.