Strategy for designing selective α-l-rhamnosidase inhibitors: Synthesis and biological evaluation of l-DMDP cyclic isothioureas.

This study shows that the cyclization of l-DMDP thioureas to bicyclic l-DMDP isothioureas improved α-l-rhamnosidase inhibition which was further enhanced by increasing the length of the alkyl chain. The addition of a long alkyl chain, such as decyl or dodecyl, to the nitrogen led to the production of highly potent inhibitors of α-l-rhamnosidase; it also caused broad inhibition spectrum against ß-glucosidase and ß-galactosidase. In contrast, the corresponding N-benzyl-l-DMDP cyclic isothioureas display selective inhibition of α-l-rhamnosidase; 3',4'-dichlorobenzyl-l-DMDP cyclic isothiourea (3r) was found to display the most potent and selective inhibition of α-l-rhamnosidase, with IC50 value of 0.22µM, about 46-fold better than the positive control 5-epi-deoxyrhamnojirimycin (5-epi-DRJ; IC50=10µM) and occupied the active-site of this enzyme (Ki=0.11µM). Bicyclic isothioureas of ido-l-DMDP did not inhibit α-l-rhamnosidase. These new mimics of l-rhamnose may affect other enzymes associated with the biochemistry of rhamnose including enzymes involved in progression of tuberculosis.

Synthesis of new tricyclic thiolactams as potent antitumor agent for pancreatic cancer.

We synthesized the novel tricyclic thiolactams 2a-d, 3d-k, having a benzyl or substituted benzyl substituent on the nitrogen of indole subunit, and their preferential cytotoxicity under both nutrient-deprived medium (NDM) and Dulbecco's modified Eagle's medium (DMEM) was evaluated against a human pancreatic cancer cell line PANC-1. Among the tested compounds, the 4'-hydroxy derivative 3d showed the most potent cytotoxicity in NDM (PC50 1.68µM) although the moderate preferential cytotoxicity (PC50 1.68µM in NDM vs PC50 20µM in DMEM). The 3'-hydroxy derivative 3e exhibited the most preferential cytotoxicity (PC50 1.96µM in NDM vs less than 50% inhibition at 30µM in DMEM). The benzyl 2a and halogenated benzyl derivatives 2b,c showed no cytotoxicity in NDM. In addition, the indole (10, PC50 173.7µM), lactone (11, PC50 131.7µM), and lactam (12, PC50 44.8µM) derivatives showed week or moderate cytotoxicity in NDM. These results indicated that the hydroxy group on the benzyl substituent and tricyclic thiolactam ring were essential for the cytotoxicity in NDM against PANC-1 cell line. Moreover, 3'-hydroxy derivative 3e compound exhibited antitumor activity against the pancreatic ductal adenocarcinoma (PDAC) xenograft model in vivo.

Design, synthesis, and biological evaluation of novel (1-thioxo-1,2,3,4-tetrahydro-ß-carbolin-9-yl)acetic acids as selective inhibitors for AKR1B1.

New substituted (1-thioxo-1,2,3,4-tetrahydro-ß-carbolin-9-yl)acetic acids were designed as the inhibitor of AKR1B1 based upon the structure of rhetsinine, a minor alkaloidal component of Evodia rutaecarpa, and twenty derivatives were synthesized and evaluated. The most active compound of the series was (2-benzyl-6-methoxy-1-thioxo-1,2,3,4-tetrahydro-ß-carbolin-9-yl)acetic acid (7m), which showed comparable inhibitory activity for AKR1B1 (IC(50)=0.15µM) with clinically used epalrestat (IC(50)=0.1µM). In the view of activity and selectivity, the most potent compound was (2-benzyl-6-carboxy-1-thioxo-1,2,3,4-tetrahydro-ß-carbolin-9-yl)acetic acid (7t), which showed strong inhibitory effect (IC(50)=0.17µM) and very high selectivity for AKR1B1 against AKR1A1 (311:1) and AKR1B10 (253:1) compared with epalrestat.