Versatile Diazomethane Sulfonamide for Expedited Exploration of Azole-Based Carbonic Anhydrase Inhibitors via [3+2] Cycloaddition.

A newly introduced diazo reagent, 1-diazo-N,N-bis(4-methoxybenzyl)methanesulfonamide, enables access to a range of azole-based primary sulfonamides via [3+2] cycloaddition followed by protecting group removal. Such compounds are representative of the sulfonamide chemical space highly relevant but hitherto not investigated in the context of inhibition of therapeutically relevant isoforms of carbonic anhydrase enzyme. Using this reagent, three sets of primary sulfonamides based on pyrazole, 1,2,3-triazole and tetrazole cores were synthesized and profiled for inhibition of tumor-associated hCA IX and XII isoforms as well as abundant cytosolic hCA I and II isoforms. Using virtual library design and docking prioritization tool of the Schrödinger suite, one of the promising leads was evolved into a dual hCA IX/XII inhibitor with excellent selectivity over off-target hCA I and II. The new synthetic strategy to access azole-based primary sulfonamides will support the discovery of novel, isoform-selective inhibitors of carbonic anhydrase within the poorly explored azole chemical space.

Carbonic Anhydrase Glycoinhibitors belonging to the Aminoxysulfonamide Series.

A general approach for the synthesis of carbonic anhydrases glycoinhibitors belonging to an aminoxysulfonamide series is presented using a Ferrier sulfonamidoglycosylation reaction on glycals. All the compounds showed good in vitro inhibitory activity against four human carbonic anhydrase isoforms, with selectivity against the cytosolic (hCA II) vs the tumor associated (hCA IX and XII) enzymes.

Carbonic anhydrase inhibitors. Inhibition of human cytosolic isoforms I and II with (reduced) Schiff's bases incorporating sulfonamide, carboxylate and carboxymethyl moieties.

A library of Schiff bases was synthesized by condensation of aromatic amines incorporating sulfonamide, carboxylic acid or carboxymethyl functionalities as Zn(2+)-binding groups, with aromatic aldehydes incorporating tert-butyl, hydroxy and/or methoxy groups. The corresponding amines were thereafter obtained by reduction of the imines. These compounds were assayed for the inhibition of two cytosolic human carbonic anhydrase (hCA, EC 4.2.1.1) isoenzymes, hCA I and II. The Ki values of the Schiff bases were in the range of 7.0-21,400nM against hCA II and of 52-8600nM against hCA I, respectively. The corresponding amines showed Ki values in the range of 8.6nM-5.3µM against hCA II, and of 18.7-251nM against hCA I, respectively. Unlike the imines, the reduced Schiff bases are stable to hydrolysis and several low-nanomolar inhibitors were detected, most of them incorporating sulfonamide groups. Some carboxylates also showed interesting CA inhibitory properties. Such hydrosoluble derivatives may show pharmacologic applications.

Superacid synthesized tertiary benzenesulfonamides and benzofuzed sultams act as selective hCA IX inhibitors: toward understanding a new mode of inhibition by tertiary sulfonamides.

A series of tertiary (fluorinated) benzenesulfonamides was synthesized in superacid HF-SbF5. To circumvent the problem of the in situ iminium ion formation, proved by low temperature NMR experiments, a tandem superacid catalysed cross-coupling reaction was employed to synthesize the benzofuzed sultams analogues. These tertiary benzenesulfonamides were tested as inhibitors of human carbonic anhydrases (hCAs, EC 4.2.1.1). These compounds did not inhibit the widespread off target hCA II isoform and showed strong selectivity toward tumor-associated carbonic anhydrase isoform IX. A dramatic effect of the electronic and structural shape of the inhibitors on selectivity was demonstrated, confirming the non-zinc-bonding mode of inhibition of this class of sulfonamides. This work allowed identifying a highly selective hCA IX inhibitor lead in this series.

Carbonic anhydrase inhibitors: synthesis and inhibition of the human carbonic anhydrase isoforms I, II, VII, IX and XII with benzene sulfonamides incorporating 4,5,6,7-tetrabromophthalimide moiety.

A series of 4,5,6,7-tetrabromo-1,3-dioxoisoindolin-2-yl benzenesulfonamide derivatives (compounds 1-8) was synthesized by reaction of benzene sulfonamide derivatives with 4,5,6,7-tetrabromophthalic anhydride moiety. These new sulfonamides were investigated as inhibitors of the zinc metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) and more specifically against the human (h) cytosolic isoforms hCA I, II and VII and the transmembrane tumor-associated isoform hCA IX and XII. The new compounds were good hCA I inhibitors (Kis in the range of 143 to >10,000nM), but were moderately effective, as hCA II inhibitors (Kis of 47-190nM) and poor hCA VII inhibitors (Kis in the range of 54-175nM) compared to acetazolamide. The tumor-associated hCA IX was effectively inhibited with Kis ranging between 8.5 and 234nM and hCA XII with inhibition constants in the range of 6.1-197nM with high selectivity ratio. The structure-activity relationship (SAR) with this series of sulfonamides is straightforward, with the main features leading to good activity for each isoforms being established. The high sequence hCA alignment homology and molecular docking study of compounds was performed to rationalize the SAR reported over here.

Natural product hybrid and its superacid synthesized analogues: dodoneine and its derivatives show selective inhibition of carbonic anhydrase isoforms I, III, XIII and XIV.

The natural product dodoneine (a dihydropyranone phenolic compound), extracted from African mistletoe Agelanthus dodoneifolius, has been investigated as inhibitor of several human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms. By using superacid chemistry, analogues of the lactone phenolic hybrid lead compound have been synthesized and tested as CA inhibitors. Small chemical modifications of the basic scaffold revealed strong changes in the selectivity profile against different CA isoforms. These new compounds selectively inhibited isoforms CA I (K(I)s in the range of 0.13-0.76 µM), III (K(I)s in the range of 5.13-10.80 µM), XIII (K(I)s in the range of 0.34-0.96 µM) and XIV (K(I)s in the range of 2.44-7.24 µM), and can be considered as new leads, probably acting as non-zinc-binders, similar to other phenols/lactones investigated earlier.

New superacid synthesized (fluorinated) tertiary benzenesulfonamides acting as selective hCA IX inhibitors: toward a new mode of carbonic anhydrase inhibition by sulfonamides.

Tertiary substituted (fluorinated) benzenesulfonamides were synthesized in superacid HF/SbF5 and tested as inhibitors of human carbonic anhydrases (hCAs, EC 4.2.1.1). Strong selectivity toward tumor-associated hCA IX, without inhibiting the offtarget hCA II, was observed, pointing out to a new mechanism of action compared to classical sulfonamides.