Stereochemical basis for the anti-chlamydial activity of the phosphonate protease inhibitor JO146

Abstract

JO146, a mixture of two diastereomers of a peptidic phosphonate inhibitor for Chlamydial HtrA (CtHtrA), has reported activity against Chlamydia species in both human and koala. In this study we isolated the individual diastereomers JO146-D1 and JO146-D2 (in  90% purity) and assessed their individual inhibitory activity against the serine protease human neutrophil elastase (HNE) which is structurally related to CtHtrA, as well as in Chlamydia trachomatis cell culture. JO146-D2 [S,S,R-Boc-Val-Pro-Val P (OPh)2], the isomer with the physiologically relevant valine at P1, had an approximate 2.5fold increase in in vitro HNE inhibition potency over JO146-D1 [S,S,S-Boc-Val-Pro-Val P (OPh)2] and greater than 100fold increase in cellular anti-chlamydial activity compared to JO146-D1 which possesses the unnatural valine at P1. JO146 and the individual diastereomers had excellent selectivity for the serine protease HNE over the potential off-target serine proteases trypsin and chymotrypsin. Docking studies supported the biological data with a geometrically unfavoured interaction observed between the P1 valine residue of JO146-D1 and the enzyme S1 sub-pocket.

Broad-spectrum coronavirus 3C-like protease peptidomimetic inhibitors effectively block SARS-CoV-2 replication in cells: Design, synthesis, biological evaluation, and X-ray structure determination

“…The dipeptide intermediates 20 and 21 were functionalized at the C-4 hydroxyl group of the P2 proline residue by reaction with di- tert -butyl dicarbonate under Lewis acid promoted conditions in presence of ytterbium (III) trifluoromethanesulfonate, as reported in literature for the synthesis of other tert -butyl ethers [ 25 ], in order to afford the corresponding tert -butyl ether intermediates 22d , e with around 45% yield. Alkaline hydrolysis of the ester derivatives 22a-f gave the correspondent carboxylic acids 23a-f in quantitative yields, which together with the dipeptide carboxylic acids 23g - i [ 26 ] were reacted under coupling conditions, using EDCI in presence of HOBt and DIPEA, with the commercial P1 amine 24 to afford the tripeptides 25a-i in yields ranging from 37 to 71%. Then, the ester derivatives 25a-i were reduced into the alcohol intermediates 27a-i , which were finally oxidized by Parikh-Doering reaction to obtain the final aldehydes 6–14 , while hydrolysis of the ester intermediate 25g afforded the corresponding acid 26 .…”

Structure-activity analysis of peptidic Chlamydia HtrA inhibitors

“…We have previously reported the full NMR and mass spectrometric characterization of JO146 1, as part of the stereochemical investigation of its two diastereomers. 36 The analogues 8a-h are characterized as follows with 13 C-31 P J values reported where clearly evident.…”

Recent Developments in Peptidyl Diaryl Phoshonates as Inhibitors and Activity-Based Probes for Serine Proteases

“…Tripeptide analog Boc-Val-Pro-ValP(OPh) 2 was recently reported to alter virulence of another species of pathogenic bacteria. Significant loss of Chlamydia trachomatis infectious progeny was observed when the cell culture was treated with 10 µM of the phosphonate in the mid-replicative phase [35]. Antichlamydial activity was measured to be 100-fold higher for the lll diastereoisomer compared to the epimer bearing the d -ValP(OPh) 2 fragment.…”