Synthesis and Application of D- and C-Labelled tert-Butyl Hoechst Dye.

Herein, the successful syntheses of D- and C-N-methyl and D-tert-butyl Hoechst dyes are presented. This includes the preparation of the labelled D- and C-N-methyl piperazines and D-tert-butylated hydroxytoluene precursors. The tert-butyl Hoechst dye is known to bind a specific RNA aptamer.

Biophysical characterization and design of a minimal version of the Hoechst RNA aptamer.

RNA aptamers are oligonucleotides, selected through Systematic Evolution of Ligands by EXponential Enrichment (SELEX), that can bind to specific target molecules with high affinity. One such molecule is the RNA aptamer that binds to a blue-fluorescent Hoechst dye that was modified with bulky t-Bu groups to prevent non-specific binding to DNA. This aptamer has potential for biosensor applications; however, limited information is available regarding its conformation, molecular interactions with the ligand, and binding mechanism.

Difluorinative ring expansions of benzo-fused carbocycles and heterocycles are achieved with p-(difluoroiodo)toluene.

A chemoselective fluorinative ring expansion has been realized using the hypervalent iodine (HVI) reagent p-TolIF2, which delivers β,β-difluoroalkyl arenes in yields up to 89% and allylic gem-difluorides in yields up to 78%. This rapid reaction exploits the ambiphilic nature of alkenes and allenes, and incorporates both fluorine atoms of the (difluoroiodo)arene in the products. The mechanism involves a 1,2-phenyl shift, which provides access in one step to important fluorinated building blocks for bioactive molecule synthesis.