Chitinase inhibitors: extraction of the active framework from natural argifin and use of in situ click chemistry

Abstract

In situ click chemistry is a target-guided synthesis technique for discovering potent protein ligands by assembling azides and alkynes into triazoles inside the affinity site of a target protein. We report the rapid discovery of a new and potent inhibitor of bacterial chitinases by the use of in situ click chemistry. We observed a target-templated formation of a potent triazole inhibitor of the chitinase-catalyzed chitin hydrolysis, through in situ click chemistry between a biologically active azide-containing scaffold and structurally unrelated alkyne fragments. Chitinase inhibitors have chemotherapeutic potential as fungicides, pesticides and antiasthmatics. Argifin, which has been isolated and characterized as a cyclopentapeptide natural product by our research group, shows strong inhibitory activity against chitinases. As a result of our efforts at developing a chitinase inhibitor from an azide-bearing argifin fragment and the application of the chitinase template and a library of alkynes, we rapidly obtained a very potent and new 1,5-disubstituted triazole inhibitor against Serratia marcescens chitinase (SmChi) B. The new inhibitor expressed 300-fold increase in the inhibitory activity against SmChiB compared with that of argifin. To the best of our knowledge, our finding of an enzyme-made 1,5-disubstituted triazole, using in situ click chemistry is the second example reported in the literature.

Rapid Identification via <i>In Situ</i> Click Chemistry of a Novel Chitinase Inhibitor

“…39 We thus focused on simpli cation of the N ω methylcarbamoyl L Arg substrate, as a smaller analog of 2, and the use of in situ click chemistry. 18,19 Firstly, in order to drive in situ click chemistry, an anchor molecule with an azide or acetylene group needed to be prepared based on the structure of N ω methylcarbamoyl L Arg. Preparation of the azide bearing N ω methylcarbamoyl L Arg inhibitor 11, a representative and a most potent Chi inhibitor among Arg derivatives, commenced with the condensation between commercially available Fmoc L Orn(Boc) OH 3 and dibenzyl amine, followed by Fmoc deprotection to afford amine 4 (Scheme 1).…”

“…In situ click chemistry research to date has garnered success in inhibitor explorations where acetylcholinesterase, 10 12 carbonic anhydrase, 13 16 HIV 1 protease, 17 chitinase (Chi), 18,19 EthR protein as a mycobacterial transcriptional regulator,…”

<i>In Situ</i> Click Chemistry for the Identification of a Potent D-Amino Acid Oxidase Inhibitor

“…ase, [14][15][16][17] carbonic anhydrase, [18][19][20][21] human immunodeficiency virus (HIV)-1 protease, 22) Serratia marcescens chitinase (SmChi), [23][24][25] Mycobacterium tuberculosis EthR protein, 26) Akt1, 27) acetylcholine binding protein, 28) G-Quadruplex 29) and biotin protein ligase inhibitors 30) have served as templates. Here, we report in situ click chemistry approaches, focusing on hDAO as the target enzyme to generate novel hDAO inhibitors.…”

Solid-phase total synthesis of the chitinase inhibitor Argadin using a supported acetal resin

“…We have also evaluated acyclic peptide analogs of 2 20 and have investigated the application of in situ click chemistry with SmChi to swiftly generate more potent chitinase inhibitors using the simplified structure of natural 2. 21 In this study, we describe our efficient solid-phase total synthesis of 1 using glycerol polystyrene resin along with only one-time HPLC separation at the final step.…”