Browsing by Author "Shetty, N.S."

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Design, synthesis and antimicrobial activities of some new quinoline derivatives carrying 1,2,3-triazole moiety
(2010) Thomas, K.D.; Adhikari, A.V.; Shetty, N.S.
A new series of [1-(6-methoxy-2-methylquinolin-4-yl)-1H-1,2,3-triazol-4-yl] methanamine derivatives were synthesized starting from 4-methoxyaniline through multi-step reactions. The title compounds 5a-y were prepared by treating the azide intermediate 4 with propargyl bromide and different alkyl/heterocyclic amines in a sequential three component synthesis. All the new compounds were characterized by spectral and elemental analyses. The newly synthesized final compounds were evaluated for their in vitro antibacterial and antifungal activities against pathogenic strains. The preliminary screening results indicated that most of the compounds demonstrated moderate to very good antibacterial and antifungal activities, comparable to the first-line drugs. Twenty five new derivatives of [1-(6-methoxy-2-methylquinolin-4-yl)-1H-1,2,3- triazol-4-yl] methanamine have been synthesized and the most effective compounds have MIC of 6.25 ?g/mL, which are in comparable with present antibiotics. 2010 Elsevier Masson SAS. All rights reserved.
Design, synthesis and antimicrobial activities of some new quinoline derivatives carrying 1,2,3-triazole moiety
(2010) Thomas, K.D.; Vasudeva Adhikari, A.V.; Shetty, N.S.
A new series of [1-(6-methoxy-2-methylquinolin-4-yl)-1H-1,2,3-triazol-4-yl] methanamine derivatives were synthesized starting from 4-methoxyaniline through multi-step reactions. The title compounds 5a-y were prepared by treating the azide intermediate 4 with propargyl bromide and different alkyl/heterocyclic amines in a sequential three component synthesis. All the new compounds were characterized by spectral and elemental analyses. The newly synthesized final compounds were evaluated for their in vitro antibacterial and antifungal activities against pathogenic strains. The preliminary screening results indicated that most of the compounds demonstrated moderate to very good antibacterial and antifungal activities, comparable to the first-line drugs. Twenty five new derivatives of [1-(6-methoxy-2-methylquinolin-4-yl)-1H-1,2,3- triazol-4-yl] methanamine have been synthesized and the most effective compounds have MIC of 6.25 ?g/mL, which are in comparable with present antibiotics. © 2010 Elsevier Masson SAS. All rights reserved.
Synthesis and antimicrobial activities of novel quinoline derivatives carrying 1,2,4-triazole moiety
(2009) Eswaran, S.; Adhikari, A.V.; Shetty, N.S.
A new class of quinoline derivatives containing 1,2,4-triazole moiety were synthesized from derivatives of 4-hydroxy-8-(trifluoromethyl)quinoline-3-carbohydrazide 4 through multi-step reactions. The compound 4, on treatment with substituted Isothiocyanates yielded quinoline-thiosemicarbazides 5a-c, which were conveniently cyclized to (5-mercapto-4H-triazol-3-yl)-quinolin-4-ols 6a-c in basic medium. These intermediates were then transformed to their respective chloro derivatives 7a-c by treatment with phosphorus oxychloride, which on further reaction with different biologically active rare amines yielded the target compounds 8a-g, 9a-h and 10a-h in good yield. The ultimate step, involving nucleophilic substitution reaction was achieved by microwave-induced technique, which has reduced the reaction time drastically as well as improved the yield when compared to conventional heating. The newly synthesized final compounds were evaluated for their in vitro antibacterial and antifungal activities against four strains each. Preliminary results indicated that most of the compounds demonstrated very good antimicrobial activity, comparable to the first line standard drugs. The most effective compounds have exhibited activity at MIC of 6.25 ?g/mL. 2009 Elsevier Masson SAS. All rights reserved.
Synthesis and antimicrobial activities of novel quinoline derivatives carrying 1,2,4-triazole moiety
(2009) Eswaran, S.; Vasudeva Adhikari, A.V.; Shetty, N.S.
A new class of quinoline derivatives containing 1,2,4-triazole moiety were synthesized from derivatives of 4-hydroxy-8-(trifluoromethyl)quinoline-3-carbohydrazide 4 through multi-step reactions. The compound 4, on treatment with substituted Isothiocyanates yielded quinoline-thiosemicarbazides 5a-c, which were conveniently cyclized to (5-mercapto-4H-triazol-3-yl)-quinolin-4-ols 6a-c in basic medium. These intermediates were then transformed to their respective chloro derivatives 7a-c by treatment with phosphorus oxychloride, which on further reaction with different biologically active rare amines yielded the target compounds 8a-g, 9a-h and 10a-h in good yield. The ultimate step, involving nucleophilic substitution reaction was achieved by microwave-induced technique, which has reduced the reaction time drastically as well as improved the yield when compared to conventional heating. The newly synthesized final compounds were evaluated for their in vitro antibacterial and antifungal activities against four strains each. Preliminary results indicated that most of the compounds demonstrated very good antimicrobial activity, comparable to the first line standard drugs. The most effective compounds have exhibited activity at MIC of 6.25 ?g/mL. © 2009 Elsevier Masson SAS. All rights reserved.
Synthesis and antimicrobial activities of some novel 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles and 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines carrying thioalkyl and sulphonyl phenoxy moieties
(2007) Karabasanagouda, T.; Adhikari, A.V.; Shetty, N.S.
Thirty one new 6-aryl-3-{(4-substituted phenoxy) methyl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles (6a-s) and 6-aryl-3-{(4-substituted phenoxy methyl}-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines (7a-l) have been synthesized from 4-thioalkyl phenols (1a-b) through a multi-step reaction sequence. Compounds 1a-b reacted with ethyl chloroacetate in presence of acetone and potassium carbonate to give ethyl [4-(thioalkyl) phenoxy] acetates (2a-b). Further, 2a was oxidized to [4-(methyl sulphonyl) phenoxy] acetate (2c) using hydrogen peroxide in acetic acid. Reactions of (2a-c) with hydrazine hydrate in alcoholic medium furnished 2-[4-thiosubstituted phenoxy] acetohydrazides (3a-b) and 2-[4-methyl sulphonyl phenoxy] acetohydrazide (3c) which on treatment with carbon disulphide and methanolic potassium hydroxide yielded corresponding potassium dithiocarbazates (4a-c). They were then converted to 4-amino-5-{(4-thioalkyl phenoxy) methyl}-4H-1,2,4-triazole-3-thiols (5a-b) and 4-amino-5-{(4-methyl sulphonyl phenoxy) methyl}-4H-1,2,4-triazole-3-thiol (5c) by refluxing them with aqueous hydrazine hydrate. The title compounds 6a-s were prepared by condensing 5a-c with various aromatic carboxylic acids in presence of phosphorus oxychloride. The intermediates 5a-c, on condensation with various substituted phenacyl bromides afforded a series of title compounds (7a-l). The structures of new compounds 2a-7l were established on the basis of their elemental analysis, IR, 1H NMR, 13C NMR and mass spectral data. All the title compounds were subjected to in vitro antibacterial testing against four pathogenic strains and antifungal screening against three fungi. Preliminary results indicate that some of them exhibited promising activities and they deserve more consideration as potential antimicrobials. 2006 Elsevier Masson SAS. All rights reserved.
Synthesis and antimicrobial activities of some novel 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles and 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines carrying thioalkyl and sulphonyl phenoxy moieties
(2007) Karabasanagouda, T.; Vasudeva Adhikari, A.V.; Shetty, N.S.
Thirty one new 6-aryl-3-{(4-substituted phenoxy) methyl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles (6a-s) and 6-aryl-3-{(4-substituted phenoxy methyl}-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines (7a-l) have been synthesized from 4-thioalkyl phenols (1a-b) through a multi-step reaction sequence. Compounds 1a-b reacted with ethyl chloroacetate in presence of acetone and potassium carbonate to give ethyl [4-(thioalkyl) phenoxy] acetates (2a-b). Further, 2a was oxidized to [4-(methyl sulphonyl) phenoxy] acetate (2c) using hydrogen peroxide in acetic acid. Reactions of (2a-c) with hydrazine hydrate in alcoholic medium furnished 2-[4-thiosubstituted phenoxy] acetohydrazides (3a-b) and 2-[4-methyl sulphonyl phenoxy] acetohydrazide (3c) which on treatment with carbon disulphide and methanolic potassium hydroxide yielded corresponding potassium dithiocarbazates (4a-c). They were then converted to 4-amino-5-{(4-thioalkyl phenoxy) methyl}-4H-1,2,4-triazole-3-thiols (5a-b) and 4-amino-5-{(4-methyl sulphonyl phenoxy) methyl}-4H-1,2,4-triazole-3-thiol (5c) by refluxing them with aqueous hydrazine hydrate. The title compounds 6a-s were prepared by condensing 5a-c with various aromatic carboxylic acids in presence of phosphorus oxychloride. The intermediates 5a-c, on condensation with various substituted phenacyl bromides afforded a series of title compounds (7a-l). The structures of new compounds 2a-7l were established on the basis of their elemental analysis, IR, 1H NMR, 13C NMR and mass spectral data. All the title compounds were subjected to in vitro antibacterial testing against four pathogenic strains and antifungal screening against three fungi. Preliminary results indicate that some of them exhibited promising activities and they deserve more consideration as potential antimicrobials. © 2006 Elsevier Masson SAS. All rights reserved.
Synthesis and antimicrobial activities of some novel 1,3,4-oxadiazoles carrying alkylthio and alkylsulphonyl phenoxy moieties
(2007) Karabasanagouda, T.; Adhikari, A.V.; Shetty, N.S.
A series of new 2-[(4-alkylthio/alkylsulfonyl phenoxy) methyl]-5- substituted-1,3,4-oxadiazoles 4a-y, 5a-h) have been synthesized from 4-alkylthio phenol (1a-b) through a multi-step reaction sequence. Compounds 1a-b reacted with ethyl chloroacetate to give ethyl [4-(alkylthio) phenoxy] acetate (2a-b) which on oxidation yielded ethyl [4-(alkylsulfonyl)phenoxy]acetate (2c-d). They were readily converted to the corresponding hydrazides 3a-d, and then cyclized to the title compounds 2-{[4-(alkylthio/alkylsulfonyl) phenoxy] methyl}-5-aryl-1,3,4-oxadiazoles (4a-y) by condensing with aromatic carboxylic acids. Further, 3a-b, on condensation with carbon disulphide afforded the title compounds 2-{[4-(alkylthio) phenoxy]methyl}-1,3,4-oxadiazole-5-thiols(5a-b), which on alkylation yielded the title compounds 2-[(4-alkylthio phenoxy) methyl]-1,3,4-oxadiazole-5-alkyl thiols (5c-f), while with chloroacetic acid gave the target compounds 2-[(4-alkylthio phenoxy) methyl]-1,3,4-oxadiazole-5- thioacetic acid (5g-h). The structures of new compounds 4a-5h were established on the basis of their elemental analysis and IR, 1H NMR, 13C NMR MASS spectral data. All the title compounds were subjected to in vitro antibacterial testing against four pathogenic strains and antifungal screening against three fungi. Preliminary results indicate some of them exhibited promising activities and they deserve more consideration as potential antimicrobials. Copyright Taylor & Francis Group, LLC.
Synthesis and antimicrobial activities of some novel 1,3,4-oxadiazoles carrying alkylthio and alkylsulphonyl phenoxy moieties
(2007) Karabasanagouda, T.; Vasudeva Adhikari, A.V.; Shetty, N.S.
A series of new 2-[(4-alkylthio/alkylsulfonyl phenoxy) methyl]-5- substituted-1,3,4-oxadiazoles 4a-y, 5a-h) have been synthesized from 4-alkylthio phenol (1a-b) through a multi-step reaction sequence. Compounds 1a-b reacted with ethyl chloroacetate to give ethyl [4-(alkylthio) phenoxy] acetate (2a-b) which on oxidation yielded ethyl [4-(alkylsulfonyl)phenoxy]acetate (2c-d). They were readily converted to the corresponding hydrazides 3a-d, and then cyclized to the title compounds 2-{[4-(alkylthio/alkylsulfonyl) phenoxy] methyl}-5-aryl-1,3,4-oxadiazoles (4a-y) by condensing with aromatic carboxylic acids. Further, 3a-b, on condensation with carbon disulphide afforded the title compounds 2-{[4-(alkylthio) phenoxy]methyl}-1,3,4-oxadiazole-5-thiols(5a-b), which on alkylation yielded the title compounds 2-[(4-alkylthio phenoxy) methyl]-1,3,4-oxadiazole-5-alkyl thiols (5c-f), while with chloroacetic acid gave the target compounds 2-[(4-alkylthio phenoxy) methyl]-1,3,4-oxadiazole-5- thioacetic acid (5g-h). The structures of new compounds 4a-5h were established on the basis of their elemental analysis and IR, 1H NMR, 13C NMR MASS spectral data. All the title compounds were subjected to in vitro antibacterial testing against four pathogenic strains and antifungal screening against three fungi. Preliminary results indicate some of them exhibited promising activities and they deserve more consideration as potential antimicrobials. Copyright © Taylor & Francis Group, LLC.