Esters and Amides of 6-(Chloromethyl)-2-oxo-2H-1-benzopyran-3-carboxylic Acid as Inhibitors of α-Chymotrypsin:  Significance of the “Aromatic” Nature of the Novel Ester-Type Coumarin for Strong Inhibitory Activity

Abstract

A series of esters and amides of 6-(chloromethyl)-2-oxo-2H-1-benzopyran-3-carboxylic acid were synthesized and evaluated in vitro for their inhibitory activity toward bovine alpha-chymotrypsin and human leukocyte elastase. Both series behaved as time-dependent inhibitors of alpha-chymotrypsin, but ester-type coumarins were clearly more efficient than the corresponding amides in inactivating the serine proteinase. The best inactivations were observed with "aromatic" esters, in particular with meta-substituted phenyl esters such as m-chlorophenyl 6-(chloromethyl)-2-oxo-2H-1-benzopyran-3-carboxylate, which appears to be one of the most powerful inactivators of alpha-chymotrypsin yet reported (kinact/KI = 760,000 M-1 S-1 at pH 7.5 and 25 degrees C). Usually, the coumarin derivatives failed to inhibit significantly human leukocyte elastase. As a result, the reported series of aromatic coumarinic esters behaves as a new chemical family of selective alpha-chymotrypsin inhibitors.

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

“…These results con®rm the in¯uence on the inactivation process of the nature of the substituent at the C-3 position; the presence of an aromatic moiety strongly improves the inhibition. 28 Consequently, we focused our works on aryl ester derivatives by analyzing the e ect on inhibition of substituent on the aromatic moiety. The compounds 26±34 and 36 behaved as time-dependent inhibitors of a-CT and HLE, whereas 35 was found to be inactive (Table 2).…”

“…The residue reacted with the appropriate alcohol (1.1 equiv), amine (1.1 equiv) or thiol (1.1 equiv) in the presence of anhydrous pyridine as previously described. 28 Cyclohexyl 6-(chloromethyl)-2-oxo-2H-1-benzopyran-3-carboxylate (11 Hydroxylamine reactivation assays were performed by treating inactivated a-CT solutions with 0.5 M hydroxylamine at pH 7.5 and 25 C during 30 min. Enzyme activity of aliquots was monitored and compared to a control.…”

“…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).…”

6-Substituted 2-oxo-2H-1-benzopyran-3-carboxylic acid derivatives in a new approach of the treatment of cancer cell invasion and metastasis

“…Compound 12 obtained from 11 by acetylation was converted into the corresponding acid chloride 13 as previously described [21,23]. The acyl chloride intermediate 13 then reacted with appropriate thiophenols and anilines to provide the thioesters 14, the secondary amides 15 and the tertiary amides 16 (Scheme 1).…”

“…Compounds 25 previously described [23] reacted with hexamethylenetetramine to give the hexaminium salts 26. The 'Delepine' reaction conditions of hydrolysis were then used to convert the hexaminium salts into the corresponding primary amines 27.…”