Amide derivatives with pyrazole carboxylic acids of 5-amino-1,3,4-thiadiazole 2-sulfonamide as new carbonic anhydrase inhibitors: synthesis and investigation of inhibitory effects

Pyrazole carboxylic acid amides of 5-amino-1,3,4-thiadiazole-2-sulfonamide were synthesized from 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carbonyl chloride and 4-benzoyl-1-(3-nitrophenyl)-5-phenyl-1H-pyrazole-3-carbonyl chloride. Carbonic anhydrase isoenzymes (hCA-I and hCA-II) were purified from human erythrocyte cells by the affinity chromatography method. The inhibitory effects of 5-amino-1,3,4-thiadiazole-2-sulfonamide 1, acetazolamide 2 and new synthesized amides on these isozymes have been studied in vitro. The I(50) concentrations (the concentration of inhibitor producing a 50% inhibition of CA activity) against hydratase activity ranged from 1.2 to 2.2 nM for hCA-I and from 0.4 to 2 nM for hCA-II. The I(50) values against esterase activity ranged from 1.4 to 8 nM for hCA-I and from 1.3 to 6 nM for hCA-II. The K(i) values were observed between 8.2 x 10(- 5) to 6.2 x 10(- 4) M for hCA-I and between 2.9 x 10(- 4) to 8.2 x 10(- 4) M for hCA-II. The comparison of new synthesized amides to 5-amino-1,3,4-thiadiazole-2-sulfonamide 1, acetazolamide 2 indicated that the new synthesized compounds (18-23) inhibit CA activity more potently than the parent compounds.     

Carbonic Anhydrase Inhibitors. Synthesis of Topically Effective Intraocular Pressure Lowering Agents Derived from 5-(omega-Amino- alkylcarboxamido)-1,3,4-Thia- diazole-2-Sulfonamide

Reaction of the acyl chlorides of phthalimido-glycine or phthalimido-beta-alanine with 5-amino-1,3,4-thiadiazole-2-sulfonamide afforded after hydrazinolysis and deprotection of the phthalimido group the corresponding 5-(omega-aminoalkylcarboxamido)-1,3,4-thiadiazole-2-sulfonamides. Reaction of 5-(beta-aminoethylcarboxamido)-1,3,4-thiadiazole-2-sulfonamide with sulfonyl halides or acyl halides afforded a series of compounds possessing beta-alkyl/arylsulfonyl/carbonylamidoethylcarboxamido moieties in the 5 position of the thiadiazole-2-sulfonamide ring. The new derivatives were efficient inhibitors of three carbonic anhydrase (CA) isozymes, CA I, II (cytosolic forms) and IV (membrane-bound form), but especially against CA II and CA IV (in nanomolar range), the two isozymes known to play an important role in aqueous humor secretion within the ciliary processes of the eye. Some of the synthesized inhibitors possessed good water solubility (as hydrochlorides or sodium salts) and were applied as 2% solutions directly into the eye of normotensive or glaucomatous albino rabbits. Very strong intraocular pressure (IOP) lowering was observed for many of them for prolonged periods of 1-2 h, and the active drug was detected in eye tissues and fluids indicating that the antiglaucoma effect is due to CA inhibition within the eye.     

Carbonic anhydrase inhibitors. Synthesis of topically effective intraocular pressure lowering agents derived from 5-(omega-aminoalkylcarboxamido)-1,3,4-thiadiazole-2-sulfonamide

Reaction of the acyl chlorides of phthalimido-glycine or phthalimido-beta-alanine with 5-amino-1,3,4-thiadiazole-2-sulfonamide afforded after hydrazinolysis and deprotection of the phthalimido group the corresponding 5-(omega-aminoalkylcarboxamido)-1,3,4-thiadiazole-2-sulfonamides. Reaction of 5-(beta-aminoethylcarboxamido)-1,3,4-thiadiazole-2-sulfonamide with sulfonyl halides or acyl halides afforded a series of compounds possessing beta-alkyl/arylsulfonyl/carbonylamidoethylcarboxamido moieties in the 5 position of the thiadiazole-2-sulfonamide ring. The new derivatives were efficient inhibitors of three carbonic anhydrase (CA) isozymes, CA I, II (cytosolic forms) and IV (membrane-bound form), but especially against CA II and CA IV (in nanomolar range), the two isozymes known to play an important role in aqueous humor secretion within the ciliary processes of the eye. Some of the synthesized inhibitors possessed good water solubility (as hydrochlorides or sodium salts) and were applied as 2% solutions directly into the eye of normotensive or glaucomatous albino rabbits. Very strong intraocular pressure (IOP) lowering was observed for many of them for prolonged periods of 1-2 h, and the active drug was detected in eye tissues and fluids indicating that the antiglaucoma effect is due to CA inhibition within the eye.     

In vitro inhibition effects of some new sulfonamide inhibitors on human carbonic anhydrase I and II

A new series of aromatic and heterocyclic sulfonamides, including six new derivatives, 2-(3-cyclohexene-1-carbamido)-1,3,4-thiadiazole-5-sulfonamide (CCTS), 4-(3-cyclohexene-1-carbamido) methyl-benzenesulfonamide (CCBS), 2-(9-octadecenoylamido)-1,3,4-thiadiazole-5-sulfonamide (ODTS), 2-(4,7,10-trioxa-tetradecanoylamido)-1,3,4-thiadiazole-5-sulfonamide (TDTS), 2-(coumarine-3-carbamido)-1,3,4-thiadiazole-5-sulfonamide (COTS) and 2-(8-methoxycoumarine-3-carbamido)-1,3,4-thiadiazole-5-sulfonamide (MCTS), has been investigated. These sulfonamides were assayed for inhibition of human carbonic anhydrase I (hCA-I) and human carbonic anhydrase II (hCA-II) which were purified by affinity chromatography.     

The in vitro and in vivo inhibitory effects of some sulfonamide derivatives on rainbow trout (Oncorhynchus mykiss) erythrocyte carbonic anhydrase activity

The in vitro and in vivo inhibitory effects of 5-(3alpha, 12alpha-dihydroxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (1), 5-(3alpha, 7alpha, 12alpha-trihydroxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (2), 5-(3alpha, 7alpha, 12alpha-triacetoxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (3) and acetazolamide on rainbow trout (Oncorhynchus mykiss) (RT) erythrocyte carbonic anhydrase (CA) were investigated. The RT erythrocyte CA was obtained by affinity chromatography with a yield of 20.9%, a specific activity of 422.5EU/mg protein and a purification of 222.4-fold. The purity of the enzyme was confirmed by SDS-PAGE. Inhibitory effects of the sulfonamides and acetazolamide on the RT erythrocyte CA were determined using the CO2-Hydratase method in vitro and in vivo studies. From in vitro studies, it was found that all the compounds inhibited CA. The obtained I50 value for the sulfonamides (1), (2) and (3) and acetazolamide were 0.83, 0.049, 0.82 and 0.052 microM, respectively. From in vivo studies, it was observed that CA was inhibited by the sulfonamides (1), (2) and (3) and acetazolamide.     

Investigation of the effects of some sulfonamide derivatives on the activities of glucose-6-phosphate dehydrogenase, 6-phospho gluconate dehydrogenase and glutathione reductase from human erythrocytes

In this study, the in vitro effects of some sulfonamide derivatives, which are carbonic anhydrase inhibitors, on the enzymes activities of glucose-6-phosphate dehydrogenase, 6-phospho gluconate dehydrogenase and glutathione reductase were investigated. For this purpose, these three enzymes were purified from human erythrocytes. Purification procedure composed of four steps; preparation of the hemolysate, ammonium sulfate precipitation, 2',5'-ADP Sepharose 4B affinity chromatography, and gel filtration chromatography on Sephadex G-200. 5-(3alpha-Hydroxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (1), 5-(3alpha,12alpha-Dihydroxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (2), 5-(3alpha,7alpha,12alpha-Trihydroxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (3), 5-(3alpha,Acetoxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (4), 5-(3alpha,7alpha,12alpha-Triacetoxy-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (5), 5-(3,7,12-Trioxo-5-beta-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (6), acetazolamide, and dorzolamide were tested in this experiment. Compounds 3, 5, and dorzolamide showed inhibitory effects on the activity of 6-phosphogluconate dehydrogenase, and I(50) values and K(i) constants were calculated as 0.0601 mM, 0.00253 mM, and 1.41 mM and 0.0878 +/- 0.0274 mM, 0.0042 +/- 0.0009 mM, and 3.1446 +/- 0.2081 mM, respectively. Glutathione reductase was also inhibited by 1 and 2. I(50) values and K(i) constants were 0.0471 mM and 0.0723 +/- 0.0388 mM for 1 and 0.0045 mM and 0.0061 +/- 0.0014 mM, for 2. If these sulfonamide derivatives are proposed as drugs, some of which are being used in glaucoma treatment such as acetazolamide and dorzolamide, these results should be taken into consideration concerning via these enzymes.     

Inhibition of Bovine Carbonic Anhydrase by New Sulfonamide Compounds

Inhibitory effects of three new derivatives of 2-acetylamino-1,3,4-thiadiazole-5-sulfonamide on bovine carbonic anhydrase have been investigated. The new compounds are 2-(3-chloropropionylamino)-1,3,4-thiadiazole-5-sulfonamide, 2-(2,2-dichloroacetylamino)-1,3,4-thiadiazole-5-sulfonamide, and 2-(3-phenylpropionylamino)-1,3,4-thiadiazole-5-sulfonamide. The new compounds inhibit the esterase activity of carbonic anhydrase noncompetitively and have inhibition constants and I ₅₀ values very similar to those for 2-acetylamino-1,3,4-thiadiazole-5-sulfonamide, the latter being clinically used in the treatment of glaucoma.     

Carbonic anhydrase inhibitors. The X-ray crystal structure of human isoform II in adduct with an adamantyl analogue of acetazolamide resides in a less utilized binding pocket than most hydrophobic inhibitors

We investigated the inhibitory activity of several 1,3,4-thiadiazole-sulfonamides against all catalytically active CA (EC 4.2.1.1), CA I–XV. The tail derivatizing the 5-position in the 1,3,4-thiadiazole-2-sulfonamide scaffold was observed to be critical as an inhibitory determinant of these compounds. The high resolution X-ray crystal structure of hCA II in complex with 5-(1-adamantylcarboxamido)-1,3,4-thiadiazole-2-sulfonamide, showed the adamantyl moiety of the inhibitor residing in a less utilized binding pocket than that of most hydrophobic inhibitors, lined by the amino acid residues Ile91, Val121 and Phe131. This binding site may explain the diverse inhibition profiles of 5-carboxamide- and sufonamide-derivatized 1,3,4-thiadiazole-2-sulfonamides and offers a hot spot for designing isoform selective inhibitors, considering that residues 91 and 131 are highly variable among the 13 catalytically active isoforms.     

Purification of carbonic anhydrase from dog erythrocytes and investigation of in vitro inhibition by various compounds

The enzyme carbonic anhydrase (E.C. 4.2.1.1) has a stimulatory effect on glaucoma, an eye disease that has a risk to dogs, which are models for the human eye disease, that is similar to that in humans.

In this study, some sulfonamide derivatives, 2-(3-cyclohexene-1-carbamido)-1,3,4-thiadiazole-5-sulfonamide (CCTS), 4-(3-cyclohexene-1-carbamido) methyl-benzenesulfonamide (CCBS), 2-(9-octadecenoylamido)-1,3,4-thiadiazole-5-sulfonamide (ODTS), 2-(4,7,10-trioxa-tetradecanoylamido)-1,3,4-thiadiazole-5-sulfonamide (TDTS), and 2-(8-methoxycoumarine-3-carbamido)-1,3,4-thiadiazole-5-sulfonamide (MCTS), as well as some anionic compounds (perchlorate and chloride) and existing medicines (dorzolamide-HCl, gentamicine sulphate, tropicamide, and procaine-HCl) were assayed for their inhibition of dog carbonic anhydrase (dCA), which was purified from erythrocytes on an affinity gel of L-tyrosine-sulfonamide-Sepharose 4B. ODTS showed the highest potency amongst the synthetic compounds with IC₅₀ value 1.18 × 10^{? 5} M. Amongst the medicines tested, only dorzolamide showed inhibition with IC₅₀ value 5.05 × 10^{? 4} M. Procaine and tropicamide actually showed an activatory effect, whereas gentamicine sulfate had no significant effect. The inhibitory effects of anionic compounds such as perchlorate and chloride were also investigated; whereas perchlorate showed inhibition, chloride did not.     

Purification of carbonic anhydrase from dog erythrocytes and investigation of in vitro inhibition by various compounds

The enzyme carbonic anhydrase (E.C. 4.2.1.1) has a stimulatory effect on glaucoma, an eye disease that has a risk to dogs, which are models for the human eye disease, that is similar to that in humans. In this study, some sulfonamide derivatives, 2-(3-cyclohexene-1-carbamido)-1,3,4-thiadiazole-5-sulfonamide (CCTS), 4-(3-cyclohexene-1-carbamido) methyl-benzenesulfonamide (CCBS), 2-(9-octadecenoylamido)-1,3,4-thiadiazole-5-sulfonamide (ODTS), 2-(4,7,10-trioxa-tetradecanoylamido)-1,3,4-thiadiazole-5-sulfonamide (TDTS), and 2-(8-methoxycoumarine-3-carbamido)-1,3,4-thiadiazole-5-sulfonamide (MCTS), as well as some anionic compounds (perchlorate and chloride) and existing medicines (dorzolamide-HCl, gentamicine sulphate, tropicamide, and procaine-HCl) were assayed for their inhibition of dog carbonic anhydrase (dCA), which was purified from erythrocytes on an affinity gel of L-tyrosine-sulfonamide-Sepharose 4B. ODTS showed the highest potency amongst the synthetic compounds with IC50 value 1.18 x 10(-5) M. Amongst the medicines tested, only dorzolamide showed inhibition with IC50 value 5.05 x 10(-4) M. Procaine and tropicamide actually showed an activatory effect, whereas gentamicine sulfate had no significant effect. The inhibitory effects of anionic compounds such as perchlorate and chloride were also investigated; whereas perchlorate showed inhibition, chloride did not.     

Carbonic anhydrase inhibitors: X-ray crystallographic studies for the binding of 5-amino-1,3,4-thiadiazole-2-sulfonamide and 5-(4-amino-3-chloro-5-fluorophenylsulfonamido)-1,3,4-thiadiazole-2-sulfonamide to human isoform II

The X-ray crystal structures of 5-amino-1,3,4-thiadiazole-2-sulfonamide (the acetazolamide precursor) and 5-(4-amino-3-chloro-5-fluorophenylsulfonamido)-1,3,4-thiadiazole-2-sulfonamide in complex with the human isozyme II of carbonic anhydrase (CA, EC 4.2.1.1) are reported. The thiadiazole-sulfonamide moiety of the two compounds binds in the canonic manner to the zinc ion and interacts with Thr199, Glu106, and Thr200. The substituted phenyl tail of the second inhibitor was positioned in the hydrophobic part of the binding pocket, at van der Waals distance from Phe131, Val 135, Val141, Leu198, Pro202, and Leu204. These structures may help in the design of better inhibitors of these widespread zinc-containing enzymes.     

Investigation of the effects of some sulfonamide derivatives on the activities of glucose-6-phosphate dehydrogenase, 6-phospho gluconate dehydrogenase and glutathione reductase from human erythrocytes

In this study, the in vitro effects of some sulfonamide derivatives, which are carbonic anhydrase inhibitors, on the enzymes activities of glucose-6-phosphate dehydrogenase, 6-phospho gluconate dehydrogenase and glutathione reductase were investigated. For this purpose, these three enzymes were purified from human erythrocytes. Purification procedure composed of four steps; preparation of the hemolysate, ammonium sulfate precipitation, 2′,5′-ADP Sepharose 4B affinity chromatography, and gel filtration chromatography on Sephadex G-200. 5-(3α-Hydroxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (1), 5-(3α,12α-Dihydroxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (2), 5-(3α,7α,12α-Trihydroxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (3), 5-(3α,Acetoxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (4), 5-(3α,7α,12α-Triacetoxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (5), 5-(3,7,12-Trioxo-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (6), acetazolamide, and dorzolamide were tested in this experiment. Compounds 3, 5, and dorzolamide showed inhibitory effects on the activity of 6-phosphogluconate dehydrogenase, and I₅₀ values and K_i constants were calculated as 0.0601 mM, 0.00253 mM, and 1.41 mM and 0.0878 ± 0.0274 mM, 0.0042 ± 0.0009 mM, and 3.1446 ± 0.2081 mM, respectively. Glutathione reductase was also inhibited by 1 and 2. I₅₀ values and K_i constants were 0.0471 mM and 0.0723 ± 0.0388 mM for 1 and 0.0045 mM and 0.0061 ± 0.0014 mM, for 2. If these sulfonamide derivatives are proposed as drugs, some of which are being used in glaucoma treatment such as acetazolamide and dorzolamide, these results should be taken into consideration concerning via these enzymes.     

Amide derivatives with pyrazole carboxylic acids of 5-amino-1,3,4-thiadiazole 2-sulfonamide as new carbonic anhydrase inhibitors: Synthesis and investigation of inhibitory effects

Pyrazole carboxylic acid amides of 5-amino-1,3,4-thiadiazole-2-sulfonamide were synthesized from 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carbonyl chloride and 4-benzoyl-1-(3-nitrophenyl)-5-phenyl-1H-pyrazole-3-carbonyl chloride. Carbonic anhydrase isoenzymes (hCA-I and hCA-II) were purified from human erythrocyte cells by the affinity chromatography method. The inhibitory effects of 5-amino-1,3,4-thiadiazole-2-sulfonamide 1, acetazolamide 2 and new synthesized amides on these isozymes have been studied in vitro. The I₅₀ concentrations (the concentration of inhibitor producing a 50% inhibition of CA activity) against hydratase activity ranged from 1.2 to 2.2 nM for hCA-I and from 0.4 to 2 nM for hCA-II. The I₅₀ values against esterase activity ranged from 1.4 to 8 nM for hCA-I and from 1.3 to 6 nM for hCA-II. The K_i values were observed between 8.2·10^{? 5} to 6.2·10^{? 4} M for hCA-I and between 2.9·10^{? 4} to 8.2·10^{? 4} M for hCA-II. The comparison of new synthesized amides to 5-amino-1,3,4-thiadiazole-2-sulfonamide 1, acetazolamide 2 indicated that the new synthesized compounds (18–23) inhibit CA activity more potently than the parent compounds.     

The In Vitro and In Vivo Inhibitory Effects of Some Sulfonamide Derivatives on Rainbow Trout (Oncorhynchus Mykiss) Erythrocyte Carbonic Anhydrase Activity

The in vitro and in vivo inhibitory effects of 5-(3α, 12α-dihydroxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (1), 5-(3α, 7α, 12α-trihydroxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (2), 5-(3α, 7α, 12α-triacetoxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (3) and acetazolamide on rainbow trout (Oncorhynchus mykiss) (RT) erythrocyte carbonic anhydrase (CA) were investigated. The RT erythrocyte CA was obtained by affinity chromatography with a yield of 20.9%, a specific activity of 422.5?EU/mg protein and a purification of 222.4-fold. The purity of the enzyme was confirmed by SDS-PAGE. Inhibitory effects of the sulfonamides and acetazolamide on the RT erythrocyte CA were determined using the CO₂-Hydratase method in vitro and in vivo studies. From in vitro studies, it was found that all the compounds inhibited CA. The obtained I₅₀ value for the sulfonamides (1), (2) and (3) and acetazolamide were 0.83, 0.049, 0.82 and 0.052?μM, respectively. From in vivo studies, it was observed that CA was inhibited by the sulfonamides (1), (2) and (3) and acetazolamide.     

Carbonic anhydrase inhibitors. Biphenylsulfonamides with inhibitory action towards the transmembrane, tumor-associated isozymes IX possess cytotoxic activity against human colon, lung and breast cancer cell lines

Reaction of 4,4-biphenyl-disulfonyl chloride with aromatic/heterocyclic sulfonamides also incorporating a free amino group, such as 4-aminobenzenesulfonamide, 4-aminoethyl-benzenesulfonamide, 6-chloro-4-aminobenzene-1,3-disulfonamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide afforded bis-sulfonamides which have been tested as inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4..2.1.1). The compounds were rather modest inhibitors of isozymes CA I and XII, but were more efficient as inhibitors of the cytosolic CA II and transmembrane, tumor-associated CA IX (inhibition constants in the range of 21-129 nM gainst hCA II, and 23-79 nM against hCA IX, respectively). The new bis-sulfonamides also showed inhibition of growth of several tumor cell lines (ex vivo), with GI(50) values in the range of 0.74-10.0 microg/mL against the human colon cancer cell line HCT116, the human lung cancer cell line H460 and the human breast cancer cell line MCF-7.     

Carbonic anhydrase inhibitors: Schiff's bases of aromatic and heterocyclic sulfonamides and their metal complexes

Schiff's bases were obtained from aromatic/heterocyclic sulfonamides and amino-sulfonamide derivatives, such as sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide and 5-amino-1,3,4-thiadiazole-2-sulfonamide. Metal complexes of some of these Schiff's bases, incorporating Zn(II), Co(lI), Ni(II) and Cu(II) ions, were also prepared and tested as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more specifically the red blood cell isozymes I and II. The Schiff's bases behaved as medium potency CA I and CA II inhibitors, whereas their metal complexes showed a highly enhanced potency, with several low nanomolar CA II inhibitors detected.     

Carbonic Anhydrase Inhibitors: Schiff's Bases of Aromatic and Heterocyclic Sulfonamides and their Metal Complexes

Schiff's bases were obtained from aromatic/heterocyclic sulfonamides and amino-sulfonamide derivatives, such as sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide and 5-amino-1,3,4-thiadiazole-2-sulfonamide. Metal complexes of some of these Schiff's bases, incorporating Zn(II), Co(II), Ni(II) and Cu(II) ions, were also prepared and tested as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more specifically the red blood cell isozymes I and II. The Schiff's bases behaved as medium potency CA I and CA II inhibitors, whereas their metal complexes showed a highly enhanced potency, with several low nanomolar CA II inhibitors detected.     

Carbonic anhydrase inhibitors: inhibition of the human transmembrane isozyme XIV with a library of aromatic/heterocyclic sulfonamides

The first inhibition study of the transmembrane carbonic anhydrase (CA, EC 4.2.1.1) isozymes hCA XIV with a library of aromatic and heteroaromatic sulfonamides synthesized earlier is reported. Most of the inhibitors were sulfanilamide, homosulfanilamide and 4-aminoethyl-benzenesulfonamide derivatives, to which tails that would induce diverse physicochemical properties have been attached at the amino moiety. Several of these compounds were metanilamide, benzene-1,3-disulfonamide or the 1,3,4-thiadiazole/thiadiazoline-2-sulfonamide derivatives. The tails incorporated in these molecules were of the alkyl/aryl-carboxamido/ sulfonamido-, ureido- or thioureido-types. The sulfanilamides acylated at the 4-amino group with short aliphatic/aromatic moieties incorporating 2-6 carbon atoms showed modest hCA XIV inhibitory activity (K(I)-s in the range of 1.25-4.2 microM) which were anyhow better than that of sulfanilamide (K(I) of 5.4 microM). Better activity showed the homosulfanilamide and 4-aminoethyl-benzenesulfonamide derivatives bearing arylsulfonamido/ureido and thioureido moieties, with K(I)'s in the range of 203-935 nM. The best activity was observed for the heteroaromatic compounds incorporating 1,3,4-thiadiazole/thiadiazoline-2-sulfonamide and 5-arylcarboxamido/sulfonamido moieties, with K(I)'s in the range of 10-85 nM. All these compounds were generally also much better inhibitors of the other two transmembrane CA isozyme, hCA IX and XII. Thus, highly potent hCA XIV inhibitors were detected, but isozyme-specific inhibitors were not discovered for the moment.     

Carbonic anhydrase inhibitors. Preparation of potent sulfonamides inhibitors incorporating bile acid tails

Reaction of TBDMS-protected bile acids (cholic, chenodeoxycholic, deoxycholic, lithocholic, ursodeoxycholic acids) or dehydrocholic acid with aromatic/heterocyclic sulfonamides possessing free amino/hydroxy moieties, in the presence of carbodiimides, afforded after deprotection of the OTBDMS ethers, a series of sulfonamides incorporating bile acid moieties in their molecules. Many such derivatives showed strong inhibitory properties against three isozymes of carbonic anhydrase (CA, EC 4.2.1.1), that is CA I, II and IV, zinc enzymes playing critical roles in many pathologies, and which represent interesting targets for developing diverse pharmacological agents. Some of the most active derivatives, incorporating 1,3,4-thiadiazole-2-sulfonamide or benzothiazole-2-sulfonamide functionalities in their molecules, showed low nanomolar affinity for CA II and CAIV. Furthermore, the bioavailability of these derivatives in rabbits is comparable to that of acetazolamide, being in the range of 85-90%, showing them as promising candidates for systemically acting CA inhibitors.     

Carbonic anhydrase inhibitors. Novel sulfanilamide/acetazolamide derivatives obtained by the tail approach and their interaction with the cytosolic isozymes I and II, and the tumor-associated isozyme IX

A series of sulfonamides has been obtained by reacting sulfanilamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide with omega-chloroalkanoyl chlorides, followed by replacement of the omega-chlorine atom with secondary amines. Tails incorporating heterocyclic amines belonging to the morpholine, piperidine and piperazine ring systems have been attached to these sulfonamides, by means of an alkanoyl-carboxamido linker containing from two to five carbon atoms. The new derivatives prepared in this way were tested as inhibitors of three carbonic anhydrase (CA, EC 4.2.1.1) isozymes, the cytosolic isozymes CA I and II, and the catalytic domain of the transmembrane, tumor-associated isozyme CA IX. Several low nanomolar CA I and CA II inhibitors were detected both in the aromatic and heterocyclic sulfonamide series, whereas the best hCA IX inhibitors (inhibition constants in the range of 22-35 nM) all belonged to the acetazolamide-like derivatives.