Electronic Finetuning of 8‐Methoxy Psoralens by Palladium‐Catalyzed Coupling: Acidochromicity and Solvatochromicity

Abstract

Differently 5‐substituted 8‐methoxypsoralens can be synthesized by an efficient synthetic route with various cross‐coupling methodologies, such as Suzuki, Sonogashira and Heck reaction. Compared to previously synthesized psoralens, thereby promising daylight absorbing compounds as potentially active agents against certain skin diseases can be readily accessed. Extensive investigations of all synthesized psoralen derivatives reveal fluorescence in the solid state as well as several distinctly emissive derivatives in solution. Donor‐substituted psoralens exhibit remarkable photophysical properties, such as high fluorescence quantum yields and pronounced emission solvatochromicity and acidochromicity, which were scrutinized by Lippert–Mataga and Stern–Volmer plots. The results indicate that the compounds exceed the limit of visible light, a significant factor for potential applications as an active agent. In addition, (TD)DFT calculations were performed to elucidate the underlying electronic structure and to assign experimentally obtained data.

Reversal of ABCG2/BCRP-Mediated Multidrug Resistance by 5,3′,5′-Trihydroxy-3,6,7,4′-Tetramethoxyflavone Isolated from the Australian Desert Plant Eremophila galeata Chinnock

“…Based on these criteria and a comparison with previously published data, compound 2 was identified as 5,3 ,5 -trihydroxy-3,6,7,4 -tetramethoxyflavone (Table 1), which is also in agreement with previously published UV maxima and MS data for this compound [30]. No previously published NMR data of 5,3′,5′-trihydroxy-3,6,7,4′-tetramethoxyflavone were found, but the NMR data of 2 were in agreement with previously published NMR data of a flavone with an identical C5-C10 A-ring structure [31] and with that of 2methoxybenzene-1,3-diol with an identical B-ring structure [32], further confirming the structure of 2.…”

“…The resistant HT29SN38 and non-resistant HT29par cells were pre-treated with 50 µg/mL of 2 or 1 µM of Ko143, and then 5 µg/mL H33342 was added to each well followed No previously published NMR data of 5,3 ,5 -trihydroxy-3,6,7,4 -tetramethoxyflavone were found, but the NMR data of 2 were in agreement with previously published NMR data of a flavone with an identical C5-C10 A-ring structure [31] and with that of 2-methoxybenzene-1,3-diol with an identical B-ring structure [32], further confirming the structure of 2.…”

Fluorescent Donor–Acceptor Psoralen Cruciforms by Consecutive Suzuki–Suzuki and Sonogashira–Sonogashira One-Pot Syntheses

“…Recently, starting from 5-bromo-8-methoxypsoralen, we successfully disclosed diversity-oriented cross-coupling reactions to 5-arylated, 5-styrylated, and 5-arylalkynylated 8-methoxypsoralens with fine-tunable absorption and emission maxima (Scheme ). Due to the inherent donor–acceptor chromophore structure of psoralen, we reasoned that placing donor and acceptor moieties at positions 8 and 5 could result in orthogonal bis­(donor–acceptor) cruciforms. These X-shaped chromophores presumably will possess distinct spatially separated frontier molecular orbitals (FMO). , These features are particularly interesting beyond psoralen-typical applications as absorbers or emitters in molecular photonics. , …”

Synthesis and Photophysics of Water‐Soluble Psoralens with Red‐Shifted Absorption

“…Upon treatment of compounds 1 and 2 (17) with trimethyloxonium tetrafluoroborate (Meerwein's salt) (25) in dichloromethane at 0°C for 15 min and at room temperature for 24–48 h, the quaternized derivatives were obtained in 62–67% yield as crystalline solids (Scheme 2).…”

“…The solution was heated in a water bath up to 93°C and cooled down to room temperature within several hours. Psoralen precursors 1 and 2 for quaternization were synthesized by Suzuki or Sonogashira coupling from 5‐bromo‐8‐methoxy psoralen according to our previously published protocol (17) and 4‐ethynyl‐1‐methylpyridinium triflate (MPE triflate) was synthesized according to literature (18). All measurements were performed at room temperature (˜ 20°C).…”