Simple synthesis of carbon-11 labeled styryl dyes as new potential PET RNA-specific, living cell imaging probes

Abstract

A new type of styryl dyes have been developed as RNA-specific, live cell imaging probes for fluorescent microscopy technology to study nuclear structure and function. This study was designed to develop carbon-11 labeled styryl dyes as new probes for biomedical imaging technique positron emission tomography (PET) imaging of RNA in living cells. Precursors ( E)-2-(2-(1-(triisopropylsilyl)-1 H-indol-3-yl)vinyl)quinoline ( 2), ( E)-2-(2,4,6-trimethoxystyryl)quinoline ( 3) and ( E)-4-(2-(6-methoxyquinolin-2-yl)vinyl)- N, N-diemthylaniline ( 4), and standards styryl dyes E36 ( 6), E144 ( 7) and F22 ( 9) were synthesized in multiple steps with moderate to high chemical yields. Precursor 2 was labeled by [ 11C]CH 3OTf, trapped on a cation-exchange CM Sep-Pak cartridge following a quick deprotecting reaction by addition of ( n-Bu) 4NF in THF, and isolated by solid-phase extraction (SPE) purification to provide target tracer [ 11C]E36 ([ 11C] 6) in 40–50% radiochemical yields, decay corrected to end of bombardment (EOB), based on [ 11C]CO 2. The target tracers [ 11C]E144 ([ 11C] 7) and [ 11C]F22 ([ 11C] 9) were prepared by N-[ 11C]methylation of the precursors 3 and 4, respectively, using [ 11C]CH 3OTf and isolated by SPE method in 50–70% radiochemical yields at EOB. The specific activity of the target tracers [ 11C] 6, [ 11C] 7 and [ 11C] 9 was in a range of 74–111 GBq/μmol at the end of synthesis (EOS).