Microwave-Assisted Regioselective Suzuki Coupling of 2,4-Dichloropyrimidines with Aryl and Heteroaryl Boronic Acids

SNAr Reactions on 2-Amino-4,6-dichloropyrimidine-5-carbaldehyde

We report the experimental results of unexpected aromatic nucleophilic substitution reaction products on 2-amino-4,6-dichloropyrimidine-5-carbaldehyde. The isolated compounds are products of amination, solvolysis, and condensation processes under mild and environmentally friendly conditions, due to the influence of structural factors of the starting pyrimidine and a high concentration of alkoxide ions. This method allows the building of pyrimidine-based compound precursors of N-heterocyclic systems.

Further hit optimization of 6-(trifluoromethyl)pyrimidin-2-amine based TLR8 modulators: Synthesis, biological evaluation and structure-activity relationships

Toll-like receptor 8 (TLR8) is an endosomal TLR that has an important role in the innate human immune system, which is involved in numerous pathological conditions. Excessive activation of TLR8 can lead to inflammatory and autoimmune diseases, which highlights the need for development of TLR8 modulators. However, only a few small-molecule modulators that selectively target TLR8 have been developed. Here, we report the synthesis and systematic investigation of the structure-activity relationships of a series of novel TLR8 negative modulators based on previously reported 6-(trifluoromethyl)pyrimidin-2-amine derivatives. Four compounds showed low-micromolar concentration-dependent inhibition of TLR8-mediated signaling in HEK293 cells. These data confirm that the 6-trifluoromethyl group and two other substituents on positions 2 and 4 are important structural elements of pyrimidine-based TLR8 modulators. Substitution of the main scaffold at position 2 with a methylsulfonyl group or para hydroxy/hydroxymethyl substituted benzylamine is essential for potent negative modulation of TLR8. Our best-in-class TLR8-selective modulator 53 with IC₅₀ value of 6.2 μM represents a promising small-molecule chemical probe for further optimization to a lead compound with potent immunomodulatory properties.