Structure-Based Design of a General Class of Mechanism-Based Inhibitors of the Serine Proteinases Employing a Novel Amino Acid-Derived Heterocyclic Scaffold

Abstract

We describe in this paper the structure-based design of a general class of heterocyclic mechanism-based inhibitors of the serine proteinases that embody in their structure a novel peptidomimetic scaffold (1,2,5-thiadiazolidin-3-one 1,1-dioxide). Sulfone derivatives of this class (I) were found to be time-dependent, potent, and highly efficient irreversible inhibitors of human leukocyte elastase, cathepsin G, and proteinase 3. The partition ratios for a select number of inhibitors were found to range between 0 and 1. We furthermore demonstrate that these inhibitors exhibit remarkable enzyme selectivity that is dictated by the nature of the P1 residue and is consistent with the known substrate specificity reported for these enzymes. Thus, inhibitors with small hydrophobic side chains were found to be effective inhibitors of elastase, those with aromatic side chains of cathepsin G, and those with a basic side chain of bovine trypsin. Taken together, the findings cited herein reveal the emergence of a general class of stable mechanism-based inhibitors of the serine proteinases which can be readily synthesized using amino acid precursors. Biochemical and high-field NMR studies show that the interaction of this class of inhibitors with a serine proteinase results in the formation of a stable acyl complex(es) and the release of benzenesulfinate, formaldehyde, and a low molecular weight heterocycle. The data are consistent with initial formation of a Michaelis-Menten complex, acylation of Ser195, and tandem loss of the leaving group. The initial HLE-inhibitor complex reacts with water generating formaldehyde and a stable HLE-inhibitor complex. Whether the initial HLE-inhibitor complex also reacts with His57 to form a third complex is not known at this point. The desirable salient parameters associated with this class of inhibitors, including the expeditious generation of structurally diverse libraries of inhibitors based on I, suggest that this class of mechanism-based inhibitors is of general applicability and can be used in the development of inhibitors of human and viral serine proteinases of clinical relevance.

Coumarinic derivatives as mechanism-based inhibitors of α-chymotrypsin and human leukocyte elastase

“…These include halo enol lactones, 9À11 b-lactams, 12À16 saccharin derivatives, 17,18 benzoxazinones, 19,20 substituted isocoumarins, 21À23 halomethyldihydrocoumarins 24,25 and thiadiazolidinones. 26,27 We previously described the development of coumarinic derivatives 28 characterized by an alkyl, aryl ester (1) or amide (2) function in the position 3 ( Fig. 1).…”

Synthesis, stability, biochemical and pharmacokinetic properties of a new potent and selective 4-oxo-β-lactam inhibitor of human leukocyte elastase

“…We therefore turned our attention to the more polar sulphone counterparts. Aryl sulphonylmethyl moieties have been successfully incorporated into the design of mechanism-based HLE inhibitors, examples of which are the 1,2-benzisothiazol-3(2H)-one 1,1-dioxide [16] and 1,2,5-thiadiazolidin-3-one 1,1-dioxide scaffolds [17][18][19][20][21]. For example, Groutas et al suggested that the latter inactivates HLE via a mechanism involving the departure of the corresponding sulphinic acid to form an electrophilic imine, while the less potent sulphide counterpart leads to acylation of the enzyme without loss of the leaving group [18].…”

Formation of an unusual product in the reaction of a 1,2,5‐thiadiazolidine 1,1‐dioxide‐derived thioether with sulfuryl chloride

“…We have previously described the design, synthesis, and in vitro biochemical evaluation of a new and general class of mechanism-based inhibitors of serine proteases (structure (I), Figure 1) [17,18], and have recently demonstrated that the time-dependent inactivation of these enzymes by (I) proceeds through the initial formation of a Michael acceptor (a sulfonyl imine), ultimately leading to the formation of an inactive enzyme-inhibitor complex (or complexes) [19]. A key step in the multistep synthesis of (I) was the synthesis of a substituted N-chloromethyl sulfohydantoin via a sulfuryl chloride-mediated cleavage of a phenylthiomethyl ether (Scheme 1).…”