Discovery of 3H-imidazo[4,5-c]quinolin-4(5H)-ones as potent and selective dipeptidyl peptidase IV (DPP-4) inhibitors: use of a carboxylate prodrug to improve bioavailability

We have previously reported a novel series of 3H-imidazo[4,5-c]quinolin-4(5H)-ones with potent dipeptidyl peptidase IV (DPP-4) inhibitory activity. However, these compounds showed poor oral absorption. We attempted in this study esterification of the carboxylic acid moiety to improve the compounds 1-4 plasma concentrations. Our efforts yielded 10h with a 5-methyl-2-oxo-1,3-dioxol-4-yl methyl ester as an S9/plasma-cleavable functionality. Compound 10h showed significantly high oral absorption and potent DPP-4 inhibition in vivo and decreased Zucker fatty rats glucose levels in the oral glucose tolerance test. Optimization of the ester moiety revealed that rapid conversion to the carboxyl form in both liver S9 fractions and serum was important for prodrugs not to be detected in the plasma after oral administration. In particular, lability in the serum was found to be an important characteristic. Through our investigation, we were able to develop a novel efficient synthetic method for construction of 3H-imidazo[4,5-c]quinolin-4(5H)-ones using intramolecular radical cyclization.

Fabrication of visible-light-driven N-doped ordered mesoporous TiO2 photocatalysts and their photocatalytic applications

Herein we report a facile method for the synthesis of N-doped crystalline mesoporous titanium dioxide (NMT) with ordered structure. Structural characterization and HR-TEM studies revealed that NMT exhibits pure anatase phase with highly crystalline ordered mesoporous structure in NMT. The N2 isotherms are of type IV with an H1 hysteresis loop and a pronounced capillary condensation step at high relative pressure for NMT, suggesting the presence of well-ordered mesoporous structure. The reflectance spectrum of NMT shows stronger absorption in the visible region above 400 nm, owing to the substitution of the lattice oxygen by nitrogen. XPS results proved the doping of nitrogen in to oxygen in TiO2 lattice, which confirmed by the presence of peak at 401 eV for N1s. The efficiency of photocatalyst was evaluated by the degradation of Rhodamine-B and antibacterial activity against E. coli under visible-light irradiation. N-doped mesoporous TiO2 shows superior photocatalytic and anti-bacterial activity compared to pure TiO2 under visible-light irradiation. The enhanced photocatalytic activity of NMT is attributed to synergistic effect of NMT that is N-doping and well ordered crystalline mesoporous structure with high surface area of NMT. These findings suggest that N-doped mesoporous TiO2 has potential application in many areas such as degradation of hazardous pollutants, anti-bacterial agents, fuel cells, battery electrode, sensors, opto electronic devices, photo active self-cleaning surfaces.

Studies aimed at the total synthesis of azadirachtin. A modeled connection of C-8 and C-14 in azadirachtin

[reaction: see text] Studies on the connection between the right and left segments of azadirachtin are described. The Ireland-Claisen rearrangement of Li-enolate of the modeled ester with dichlorodimethylsilane in toluene afforded the desired limonoid framework stereoselectively in good yield.