Ординатура / Офтальмология / Английские материалы / Carbonic Anhydrase Its Inhibitors and Activators_Supuran, Scozzafava, Conway_2004

TABLE 4.5 (continued)

CA Inhibition Data with 4-Isothiocyanatobenzenesulfonamide 4.37 and the Thioureas 4.38

aHuman (cloned) isozymes.

bFrom bovine lung microsomes by the esterase method.

Source: Reported from Casini, A. et al. (2000) Journal of Medicinal Chemistry 43, 4884–4892. With permission.

CI2, AcOH

R SH

4.41

SCHEME 4.5

4.46. Compound 4.44, acetazolamide, proved to possess excellent pharmacological properties (low toxicity, very good CA inhibitory action, excellent bioavailability) and was shortly thereafter introduced into clinical medicine as the first nonmercurial diuretic (Maren, 1967). Since 1954, acetazolamide, has been continuously used to manage glaucoma, gastroduodenal ulcers and many other disorders (Maren 1967; Supuran and Scozzafava 2000a, 2002a).

The clinical success of acetazolamide fostered a further search for active structures in this ring system. Thus, Vaughan et al. (1956) and Young et al. (1956) prepared and assayed many acetazolamide-like sulfonamides 4.47 possessing 5-acylamido and 5-arylsulfonamido moieties, as well as 2-sulfonamido- 5-1,3,4- thiadiazoline derivatives of type 4.46. Some of the most active inhibitors are presented in Table 4.6 (thiadiazoles) and Table 4.7 (thiadiazolines), with structurally related compounds investigated subsequently by other groups.

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Data in Table 4.6 show that the acylation of amine 4.43 led to inhibitors with enhanced efficiency; acylamidoand alkyl/aryl-sulfonamido groups were equally useful in inducing this effect. CA inhibitory action is particularly higher in derivatives bearing lipophilic moieties (4.47f, g, m, o). On the other hand, compounds substituted with arylamidoand arylsulfonamidogroups are stronger acids than the other derivatives, which was also correlated with increased CA inhibition. (Thio)ureidosubstituted derivatives 4.47p–s recently reported are hydrosoluble, but were unfortunately not active by the topical route for the management of glaucoma (Supuran 1994).

Methazolamide (4.48), already reported in 1956, has been used in clinical medicine for more than 35 years. Although it has a structure similar to that of acetazolamide (4.44), methazolamide is more liposoluble, possesses only one acidic proton and is more diffusible in body fluids than is acetazolamide (Maren 1967). As methazolamide is relatively nontoxic and because of its pharmacological properties the same physiological responses being achieved at only one third the dose of acetazolamide, it is not surprising that many derivatives related to methazolamide, of type 4.46, have been investigated (Table 4.7). Generally, the activity was influenced in the same way as for compounds 4.47 by changing the group in position 5 of the heterocyclic ring (Supuran 1994; see Table 4.7). The same is true for the moiety substituting the N-4 atom (although the greater majority of these compounds bear an N-Me group). Importantly, this research line led to the discovery topically active inhibitors in glaucoma. Compound 4.46g, trifluoromethazolamide, was the first inhibitor possessing such properties (see later).

Recently, 1,3,4-thiadiazole-2-sulfonamide and the corresponding thiadiazolines bearing 5-alkyl/arylsulfonamido moieties, of types 4.49 and 4.50, respectively, have

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TABLE 4.6

Inhibition Data for hCA II with 1,3,4-Thiadiazole-2-Sulfonamide Derivatives 4.47

Source: From Roblin, R.O., Jr., and Clapp, J.W. (1950) Journal of the American Chemical Society 72, 4890–4892 and Supuran, C.T. (1994) In Carbonic Anhydrase and Modulation of Physiologic and Pathologic Processes in the Organism, Puscas, I., Ed., Helicon Press, Timisoara, Romania, pp. 29–111. With permission.

been investigated in detail (Table 4.8 and Table 4.9; Supuran et al. 1998a). Derivatives 4.49 and 4.50 contained alkylsulfonyl-, dimethylaminosulfamoylor halogeno-, alkyl-, methoxy-, aminoand nitrosubstituted phenylsulfonyl moieties, and were chosen to obtain compounds with different physicochemical properties (e.g., enhanced lipophilicity, or, conversely, enhanced hydrosolubility) and also those

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TABLE 4.7

CA II Inhibition with 5-1,3,4-Thiadiazoline-2-

Sulfonamide Derivatives 4.46

Source: From Vaughan, J.R. et al. (1956) Journal of Organic Chemistry 21, 700–771 and Supuran, C.T. (1994) In Carbonic Anhydrase and Modulation of Physiologic and Pathologic Processes in the Organism, Puscas, I., Ed., Helicon Press, Timisoara, Romania, pp. 29–111. With permission.

containing groups that would allow an easy derivatization, which can be exploited to prepare isotopically labeled compounds, envisaging a possible application of such inhibitors in PET imaging (Supuran et al. 1998a). As seen from the data in Table 4.8 and Table 4.9, most of these sulfonamides are very effective inhibitors of isozymes I, II and IV. Some 1,3,4-thiadiazole-5-sulfonamides incorporating 2-aminoacyl moieties were reported by Jayaweera et al. (1991).

Derivatives of thiophene-2-sulfonamide of the types 4.52 to 4.55 that possess different substitution patterns, such as 5-arylthio, 5-arylsulfinyl and 5-arylsulfonyl moieties, were prepared in the search for anticonvulsant and cerebrovasodilator agents (Scheme 4.6; Barnish et al. 1981). Sulfones 4.55 were generally more active

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TABLE 4.8

Compounds of Type 4.49: Inhibition Data (KI) toward hCA I, hCA II and bCA IV, Chloroform–Buffer Partition Coefficients and Solubility Data

aHuman (cloned) isozymes.

bFrom bovine lung microsomes.

cChloroform–buffer partition coefficient.

dSolubility in pH 7.40 buffer at 25°C.

eAs perchlorate salt.

fAs tetrafluoroborate salt.

Source: From Supuran, C.T. et al. (1998a). With permission.

than sulfoxides 4.54, which in turn were more active than sulfides 4.53 (IC50 values 10–8 to10–9 M). More recently, Chow et al. (1996) reported a series of 5-substituted- 3-thiophenesulfonamides with good inhibitory properties.

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TABLE 4.9

Compounds of Type 4.50: Inhibition toward hCA I, hCA II and bCA IV, Partition Coefficient and Solubility Data

O N N

aHuman (cloned) isozymes.

bFrom bovine lung microsomes.

cChloroform–buffer partition coefficient.

dSolubility in pH 7.40 buffer at 25°C.

eAs perchlorate salt.

fAs tetrafluoroborate salt.

Source: From Supuran, C.T. et al. (1998a). With permission

Other approaches were designed to obtain bicyclic inhibitors commencing from 5-amino-1,3,4-thiadiazole-2-sulfonamide 4.43 or 2-amino-thiazole-5-sulfonamide, which were annulated with α-bromoketones, phosgene, carbonsuboxide, ethenesulfonylchloride and chlorosulfonyl isocyanate (Scheme 4.7; Barnish et al. 1980;

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4-halogeno; 4-OMe; 4-SMe; 4-NH2

SCHEME 4.6

Katritzky et al. 1987). The imidazo[2,1-b]thiadiazole-5-sulfonamides (4.56) as well as the thiadiazolo[3,2-a]pyrimidinesulfonamides (4.58 to 4.61) and thiadiazolo[3,2- a]triazinesulfonamides (4.62) thus obtained were very effective inhibitors, with IC50 values of 10–8 to 10–9 M (Katritzky et al. 1987).

Some thieno[2,3-b]pyrrole-5-sulfonamides of types 4.68 and 4.69 were prepared as outlined in Scheme 4.8, but no data have been published on their inhibitory properties toward CAs (Hartman and Halczenko 1989).

Annulation of thiophene-3-carbaldehyde with methyloxycarbonylazide afforded the thieno[2,3-b]pyrrole 4.64, which was protected at the NH group by treatment with benzenesulfonyl chloride. After chlorosulfonation, amidation and conversion of the carboxymethyl group to a secondary amine, inhibitors of types 4.68 and 4.69 were obtained.

4.2.3 Bis-sulfonamides

Compounds that possess more than one sulfonamide group in their molecule were tested as CAIs in the search for either more active structures or to design compounds with a different biological activity, e.g., saluretics and high-ceiling diuretics (the CA inhibitory effect being subsidiary in the latter cases; Beasley et al. 1958; Maren 1967). Thus, 1,3,4-thiadiazole-2,5-disulfonamide 4.70, already reported by Roblin and Clapp (1950), was reported to be a stronger inhibitor than acetazolamide 4.44, but this finding was later revealed to be incorrect (Supuran et al. 1996a). This compound had constituted the lead molecule for designing important classes of other pharmacological agents, such as benzothiadiazine diuretics and high-ceiling diuretics (Maren 1967). It was then proved that 4.70 is actually quite a weak CAI (KI = 10 μM against hCA II), whereas 1,3-disulfamoylbenzenes of type 4.71, prepared from it as

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lead, ironically, are potent CAIs. Indeed, dichlorophenamide 4.71 has an IC50 of 3 ∞ 10–8 M and is still used clinically as a diuretic, antiglaucoma and antihypertensive drug (Maren 1967; Supuran and Scozzafava 2000a, 2001).

Bis-sulfonamides derived from biphenyl, biphenylether, biphenylsulfide, biphenylmethane or containing urea or guanidine moieties as spacers, of types 4.72, reported by Beasley et al. (1958) were generally more active than the corresponding compounds containing only one SO2NH2 group and possessed IC50 values of 1–7 ∞ 10–7 M (against unpurified blood CA, i.e., a mixture of isozymes I and II). Derivatives 4.73 containing thiophene instead of phenylene moieties, reported by Buzas et al. (1961), were again prepared in the search for more potent diuretics and possess CA inhibitory effects (IC50 values not specified).

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4.69 (R = Me, i-Bu)

SCHEME 4.8

Bis-sulfonamides of type 4.75, containing the classical 2-sulfonamido-1,3,4- thiadiazole-moieties were prepared by Supuran et al. (1991) as outlined in Scheme 4.9 by the bisacylation of amine 4.43 with diacyl halides (Table 4.10).

Compounds containing aliphatic, aromatic or heterocyclic groups as spacers between the two thiadiazolic moieties were very effective as CAIs, in contrast to derivatives possessing bulky spacers (such as 2,2′-biphenyl-carboxamido in 4.75e or the macrocyclic ring in 4.75i) which showed poor activities, probably because of the hindered access of the latter ones to the active site of the enzyme. Some of these compounds might possess a depot effect (in vivo) as CAIs, because of their very low solubilities in most solvents and water (Supuran et al. 1991).

The reaction of sulfanilamide 4.1 with potassium thiocyanate in the presence of hydrochloric acid, affording the corresponding thiourea 4.76 (A = 1,4-phenylene; Scheme 4.10) was described by Beasley et al. (1958). They also oxidized this thiourea with iodine but could not establish the structure of the oxidation product. By reinvestigating this reaction, it was found out that a new route to 2,5-disubstituted thiadiazoles is readily available (Scozzafava and Supuran 1998a). Reaction of several aromatic sulfonamides containing a free amino group with cyanate or thiocyanate in the presence of acid afforded the corresponding urea/thiourea derivatives, which were assayed as inhibitors of three isozymes, CA I, II and IV. Oxidation of the obtained thioureas 4.76 with iodine/KI in an acidic medium afforded symmetrical

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SCHEME 4.9

2,5-bis-(substituted-phenyl)-1,3,4-thiadiazole derivatives that possessed sulfonamido groups on the aromatic ring (4.78) via a new synthesis of the heterocyclic moiety (Scheme 4.10). Good inhibition of all three CA isozymes was observed with the new compounds 4.78, but the exciting finding was that the ureas/thioureas reported here have an increased affinity to the slow-reacting isozyme CA I, generally more insensitive to inhibition by sulfonamides as compared to the rapid-reacting isozymes CA II and CA IV (Scozzafava and Supuran 1998a).

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