Fig 1.
General synthesis of compounds 6–19.
Reagents and conditions: a) HATU, DIPEA, 1-amino-1-cyclopropanecarbonitrile, DMF, rt, 18 h; b) formic acid, rt, 18 h; c) HATU or TBTU, DIPEA, carboxylic acid, DMF, rt, 18 h; d) DDQ, CH2Cl2, rt, 3–5 days.
Fig 2.
General synthesis of compounds 50–60, 65–69.
Reagents and conditions: a) Isobutyl chloroformate, NH4Cl 2 M, DIPEA, DMF, 0 °C to rt, 20 h; b) TFA, CH2Cl2, 0 °C to rt, 2 h; c) HATU, DIPEA, Boc-AA-OH, DMF, rt, 18 h; d) TFA, CH2Cl2, 0 °C to rt, 2 h; e)TBTU, DIPEA, 3-(tert-butyl)-1-methyl-1H-pyrazole-5-carboxylic acid, DMF/CH2Cl2, rt, 18 h; f) Cyanuric chloride, DMF, 0 °C to rt, 0.5 h; g) H2 (1 atm), Pd/C, rt, 18 h; h) DDQ, CH2Cl2, rt, 3–5 days; i) TFAA, DIPEA, THF, 0 °C to rt, 2 h.
Fig 3.
Crystal structures of vinyl sulfone derivative K777 and dipeptidyl nitrile 33L covalently bound to cruzain.
Left. K777 in the active site of cruzain (PDB-ID: 1F2B). Right 33L in the active site of cruzain (PDB-ID 4QH6).
Fig 4.
The putative orientation of P1 moieties in compounds 50, 52, 56, and 58.
Fig 5.
Structure representation of compounds 6–19.
Fig 6.
Structure of compounds 50–60 and 65–69.
Fig 7.
Change in stereochemistry for compounds bearing Thr or Thr-O-Bzl group in P1.
Table 1.
Number identification, pKi values for CatB, CatK, CatL, CatS, Cz and LmCPB.
Fig 8.
SAR summary for P1-S1/S1´ interactions.
Values are reported as differences in pKi and are color-coded as red (negative), green (positive), grey (no significant difference, ΔpKi < 0.2).
Fig 9.
SAR summary starting from compound 11.
Values are reported as differences in pKi and are color-coded as red (negative), green (positive), grey (no significant difference, ΔpKi < 0.2).
Fig 10.
Values are reported as differences in pKi and are color-coded as red (negative), green (positive), grey (no significant difference, ΔpKi< 0.2).
Fig 11.
Values are given in pKi. The X-axis represents the difference in pKi for the same inhibitor for a pair of CPs. Y-axis represents the mean value of pKi for the same inhibitor for a pair of CPs. The black dashed line highlights no selectivity. The magenta dashed line highlights a significant selectivity. Positive differences correspond to Cz pKi values that are greater than those for CatB, CatK, CatL or CatS.
Table 2.
Biological data for trypanocidal activity (EC50), cytotoxicity (CC50), and selective index (SI) for the series of dipeptidyl nitriles.
Fig 12.
Schematic representation of physicochemical properties and SARs for trypanocidal activity.
EC50 calculated for amastigote forms of T. cruzi (Tuhaluen strain). CC50 calculated for the LLCMK2 strain (host cell). Green areas highlight biochemical results. TPSA, ilogP, and Ali_Logs have been calculated with the swissADME online service [35]. pKi values are referring to Cz inhibition.
Fig 13.
Schematic representation for non-additivity of SARs for trypanocidal activity.
EC50 calculated for amastigote forms of T.cruzi (Tuhaluen strain). CC50 calculated for the LLCMK2 strain (host cell). Green areas highlight biochemical results. TPSA, ilogP, and Ali_Logs have been calculated with the swissADME online service [29]. pKi values are referring to Cz inhibition.
Fig 14.
Schematic representation for non-additivity of SARs for compounds 58, 59, 67 and 68.
EC50 calculated for amastigote forms of T.cruzi (Tuhaluen strain). CC50 calculated for the LLCMK2 strain (host cell). Green areas highlight biochemical results. TPSA, ilogP, and Ali_Logs have been calculated with the swissADME online service [35]. pKi values are referring to Cz inhibition.