Caging of Carbonyl Compounds as Photolabile (2,5-Dihydroxyphenyl)ethylene Glycol Acetals

Abstract

Aldehydes and ketones caged as 4-(2,5-dihydroxyphenyl)-1,3-dioxolanes are efficiently (Phi = 0.1-0.2) released in a good to excellent chemical yield upon irradiation with 300 nm light. Caged carbonyl compounds are prepared by their acetalization with (2,5-dimethoxyphenyl)ethylene glycol followed by oxidative demethylation to produce corresponding (1,3-dioxolane-4-yl)-1,4-benzoquinones. The latter acetals are photochemically inert but can be converted into photolabile hydroquinones by mild reduction in situ.

Photoremovable Protecting Groups in Chemistry and Biology: Reaction Mechanisms and Efficacy

“…Irradiation of the latter with 300-nm light results in the efficient photocleavage of the acetals, releasing carbonyl compounds in 88–100% chemical yields. 341 …”

Recent advances in 1,4-benzoquinone chemistry

“…Oxidative demethylation was also achieved using silver oxide/ nitric acid reagent. 181 Recently Popik and co-workers 182 synthesized (1,3-dioxolane-4-yl)-1,4-benzoquinones (130) from their dimethoxy precursors (129) using silver oxide/ nitric acid reagent in good yield (Scheme 25).…”

“…Among the possible isomers of pyridoquinones the 2,5-isomer was calculated to be the most stable. Apart from pyridoquinones, Yavari et al 213 also modelled another interesting group of quinones, pentaloquinones (PQ) (179)(180)(181)(182)(183)(184).…”

Photoactivatable Fluorescein Derivatives Caged with a (3-Hydroxy-2-naphthalenyl)methyl Group

“…In this report, we describe the use of recently developed (3-hydroxyl-2-naphthyl)methyl (NQMP) 17 photolabile protecting group for the caging of fluorescein-based dyes. Irradiation of NQMP ethers or esters 1 with 300 – 350 nm light results in the efficient cleavage of the benzylic C-O bond and the release of a substrate (Scheme 1).…”

“…Use of 350 nm lamps requires four times longer exposure, apparently due to lower extinction coefficient of NQMP chromophore at this wavelength. 17 Upon 460 nm excitation, the photolysate is intensely fluorescent (λ max = 515 nm, Φ FL = 0.22–25, Figure 3). The absorbance spectrum shows two maxima, which also suggests the presence of tautomeric forms of uncaged dye 21 , typical of fluorescein derivatives.…”