Search

Abstract: A series of 1,4- and 1,5-diaryl substituted 1,2,3-triazoles was synthesized by either Cu(I)-catalyzed or Ru(II)-catalyzed 1,3-dipolar cycloaddition reactions between 1-azido-4-methane-sulfonylbenzene 9 and a panel of various para-substituted phenyl acetylenes (4-H, 4-Me, 4-OMe, 4-NMe2, 4-Cl, 4-F). All compounds were used in in vitro cyclooxygenase (COX) assays to determine the combined electronic and steric effects upon COX-1 and COX-2 inhibitory potency and selectivity. Structure-activity relationship studies showed that compounds having a vicinal diaryl substitution pattern showed more potent COX-2 inhibition (IC50 =0.03–0.36μM) compared to their corresponding 1,3-diaryl-substituted counterparts (IC50 =0.15 to >10.0μM). In both series, compounds possessing an electron-withdrawing group (Cl and F) at the para-position of one of the aryl rings displayed higher COX-2 inhibition potency and selectivity as determined for compounds containing electron-donating groups (Me, OMe, NMe2). The obtained data show, that the central carbocyclic or heterocyclic ring system as found in many COX-2 inhibitors can be replaced by a central 1,2,3-triazole unit without losing COX-2 inhibition potency and selectivity. The high COX-2 inhibition potency of some 1,2,3-triazoles having a vicinal diaryl substitution pattern along with their ease in synthesis through versatile Ru(II)-catalyzed click chemistry make this class of compounds interesting candidates for further design and synthesis of highly selective and potent COX-2 inhibitors. [Copyright &y& Elsevier]

Abstract: The radiosynthesis of 3-(4-[18F]fluorophenyl)-2-(4-methylsulfonylphenyl)-1H-indole [18F]-3 as potential PET radiotracer for functional characterization of cyclooxygenase-2 (COX-2) in vitro and in vivo is described. [18F]-3 was prepared by McMurry cyclization of a 18F-labeled intermediate with low valent titanium and zinc via a two-step procedure in a remote controlled synthesizer unit including HPLC purification and solid phase extraction. In this way [18F]-3 was synthesized in 80min synthesis time in 10% total decay corrected yield from [18F]fluoride in radiochemical purity >98% and a specific activity of 74–91GBq/μmol (EOS). [18F]-3 was evaluated in vitro using pro-inflammatory stimulated THP-1 and COX-2 expressing tumor cell lines (FaDu, A2058, HT-29), where the radiotracer uptake was shown to be consistent with up regulated COX-2 expression. The stability of [18F]-3 was determined by incubation in rat whole blood and plasma in vitro and by metabolite analysis of arterial blood samples in vivo, showing with 75% of original compound after 60min an acceptable high metabolic stability. However, no substantial tumor accumulation of [18F]-3 could be observed by dynamic small animal PET studies on HT-29 tumor-bearing mice in vivo. This may be due to the only moderate COX-1/COX-2 selectivity of 3 as demonstrated by both cellular and enzymatic cyclooxygenase inhibition assay in vitro. Nevertheless, the new approach first using McMurry cyclization in 18F-chemistry gives access to 18F-labeled diarylsubstituted heterocycles that hold promise as radiolabeled COX-2 inhibitors. [Copyright &y& Elsevier]