DESIGN, SYNTHESIS, AND PHOTOCHEMICAL PROPERTIES OF A PHOTORELEASABLE UBIQUINOL-2 - A NOVEL COMPOUND FOR STUDYING RAPID ELECTRON-TRANSFER KINETICS IN UBIQUINOL-OXIDIZING ENZYMES

The design and multistep convergent synthesis of the novel photoactive ubiquinol-benzoin adduct 1a,b has been accomplished. Optical spectra of the steady-state photolysis reactions showed a smooth conversion fr om 1a,b to 5,7-dimethoxy-2-phenylbenzofuran (13) and ubiquinol-2 with an isobestic point at 258 nm. HPLC analysis of the photoproducts was a lso consistent with the clean formation of the desired ubiquinol-2 (3) and the expected 5,7-dimethoxy-2-phenylbenzofuran (2). Transient phot olysis at 355 nm was consistent with a rapid photolysis rate that exce eded the instrument response time (>10(6) s(-1)). Accordingly, the stu dy of rapid electron-transfer events in ubiquinol oxidizing enzymes is now feasible. Furthermore, the synthetic methods developed herein wil l be of general application for the facile synthesis of a variety of p hotoreleasable substrates for studying rapid kinetic events in enzymat ic reactions.