Synthesis and Enzymatic Evaluation of a Small Library of Substituted Phenylsulfonamido-Alkyl Sulfamates towards Carbonic Anhydrase II

Abstract

A small library of 79 substituted phenylsulfonamidoalkyl sulfamates, 1b-79b, was synthesized starting from arylsulfonyl chlorides and amino alcohols with different numbers of methylene groups between the hydroxyl and amino moieties yielding intermediates 1a-79a, followed by the reaction of the latter with sulfamoyl chloride. All compounds were screened for their inhibitory activity on bovine carbonic anhydrase II. Compounds 1a-79a showed no inhibition of the enzyme, in contrast to sulfamates 1b-79b. Thus, the inhibitory potential of compounds 1b-79b towards this enzyme depends on the substituent and the substitution pattern of the phenyl group as well as the length of the spacer. Bulkier substituents in the para position proved to be better for inhibiting CAII than compounds with the same substituent in the meta or ortho position. For many substitution patterns, compounds with shorter spacer lengths were superior to those with long chain spacers. Compounds with shorter spacer lengths performed better than those with longer chain spacers for a variety of substitution patterns. The most active compound held inhibition constant as low as K_i = 0.67 μM (for 49b) and a tert-butyl substituent in para position and acted as a competitive inhibitor of the enzyme.

Keywords: carbonic anhydrase II; inhibitor; sulfamates.

Figure 1

Structures of established CA inhibitors acetazolamide, dorzolamide, and brinzolamide.

Figure 2

Zn(II) ion coordination in the CA II active site.

Scheme 1

Synthesis of target sulfamates (structure B) from arylsulfonylchlorides via precursors A; (a) CH₂Cl₂, NEt₃, 20 °C 3–24 h; (b) CH₂Cl₂, NEt₃, sulfamoyl chloride, 0 °C → 20 °C, 3–24 h.

Figure 3

Structure of compounds 1a–79a and 79b–79b.

Figure 4

Inhibition (in %) of ortho-substituted compounds 26b–32b (methyl), 47b–48b (iso-propyl) and 65b–67b (tert-butyl), respectively.

Figure 5

Inhibition (in %) of meta-substituted compounds 19b–25b (methyl), 40b–46b (iso-propyl), and 58b–64b (tert-butyl), respectively.

Figure 6

Inhibition (in %) of para-substituted compounds 12b–18b (methyl), 33b–39b (iso-propyl), and 49b–57b (tert-butyl), respectively.

Figure 7

Inhibition (in %) of compounds holding the bulkiest substituents in the para position (^tbutyl (orange), cyclohexyl (green), adamantyl (violet)).

Figure 8

Inhibition (in %) of ^tbutyl-substituted compounds 49b–67b.

Figure 9

Inhibition (in %) of ^tbutyl-substituted compounds depends on position of the ^tBu group and on the chain length of the alkyl spacer.

Figure 10

Inhibition (in %) of isopropyl-substituted compounds.

Figure 11

Inhibition (in %) of methyl-substituted compounds 12b–32b.

Figure 12

Inhibition (in %) of unsubstituted compounds 1b–11b.

Figure 13

Modeling scores of the methyl-substituted compounds 12b–32b.

Figure 14

Dixon plots for compounds 12b, 26b, 30b, 33b, 40b, and 49b, respectively. The concentration of the inhibitor: for 12b: 0.1, 03, 0.5 μM; for 26b: 0.1, 0.3, 0.5 μM; for 30b: 0.1, 0.3 0.5 μM; for 33b: 0.2, 0.4, 0.6 μM; for 40b: 0.1, 0.3, 0.5 μM; for 49b: 0.2, 0.3, 0.4 μM.

Figure 14

Dixon plots for compounds 12b, 26b, 30b, 33b, 40b, and 49b, respectively. The concentration of the inhibitor: for 12b: 0.1, 03, 0.5 μM; for 26b: 0.1, 0.3, 0.5 μM; for 30b: 0.1, 0.3 0.5 μM; for 33b: 0.2, 0.4, 0.6 μM; for 40b: 0.1, 0.3, 0.5 μM; for 49b: 0.2, 0.3, 0.4 μM.