In(OTf)3 promoted sonochemical approach to 3-(2-chloropyrimidin-4-yl)indoles: their in silico and in vitro evaluation against SIRT1

We report exploring the 3-(2-chloropyrimidin-4-yl)indole framework for the identification of new inhibitors of SIRT1. A library of compounds based on this framework was synthesized via an ultrasound assisted heteroarylation approach. The methodology involved In(OTf)3 mediated C-C bond forming reaction between 2,4-dichloropyrimidine and indoles to give the desired products in good to acceptable yields. The regioselectivity of this approach appeared to be a key feature as the methodology involved sonochemical replacement of the (i) C-3 hydrogen of indole and (ii) C-4 chloro group of the pyrimidine ring at the same time. Its synthetic application was demonstrated by converting one of the synthesized compounds into the naturally occurring alkaloid Meridianin G. The in silico docking of 3-(2-chloropyrimidin-4-yl)indoles prepared showed promising interactions with SIRT1 in addition to probable selectivity towards this protein over SIRT2. A majority of compounds participated in H-bond interaction with GLN345 residue mainly through their indole “NH” moiety. However, higher binding affinities were observed for compounds possessing a sulfonamide moiety at C-5 position of the indole ring. Correlating the findings of in silico studies a number of synthesized compounds showed inhibition of SIRT1 in vitro. With the inhibition > 70% the compound 3e, 3o and 3p were identified as initial hit molecules when 3p emerged as most promising among them. The SAR (Structure-Activity-Relationship) analysis also suggested that a sulfonamide moiety at C-5 position was beneficial for the high SIRT1 inhibition whereas a free NH moiety of the indole ring was essential for activity. Based on in silico and in vitro studies including ADME predictions the compound 3p appeared as a key agent for further pharmacological evaluation.