Coumarin Photocaging Groups Modified with an Electron‐Rich Styryl Moiety at the 3‐Position: Long‐Wavelength Excitation, Rapid Photolysis, and Photobleaching

Abstract

A new class of coumarin photocaging groups modified with an electron-rich styryl moiety at the 3-position was constructed. The large π-conjugated structure and stabilization of the carbocation intermediates by electron donors endowed the new photocaging groups with excellent long-wavelength absorption, large two-photon absorption cross-sections, and high uncaging quantum yields. Moreover, the new photocaging groups displayed unique photobleaching properties after photocleavage as a result of the intramolecular cyclization rearrangement of a carbocation intermediate to form five-membered ring byproducts and block the styryl conjugation at the 3-position. These superior properties of the new photocaging groups are extremely beneficial for high-concentration samples and thick specimens, thus extending the application of photocaging groups in many fields.

The Role of Photochemical Reactions in the Development of Advanced Soft Materials for Biomedical Applications

“…This reaction can be adapted to the fabrication of hydrogels via crosslinking of adequately functionalized polymers and several examples were described using violet light photocleavable groups, such as DEAC, or bimane . Recently, bathochromic modifications in the DEAC molecules provided additional derivatives that can be cleaved using wavelengths ranging from 428 to 515 nm . These developments could be potentially used in combination with the previous described approach to provide hydrogels with crosslinking and degrading capabilities.…”

Dual-wavelength efficient two-photon photorelease of glycine by π-extended dipolar coumarins

“…Until recently, the use of most cages described in the literature was somewhat limited for in vivo applications due to their low 2PU cross-sections (with δ maxu values below 1 GM) 1,15. To overcome this limitation and avoid the use of deleterious excitation powers, two main engineering strategies have been developed in the last decade: the modification of the π-conjugated backbone of known cages16–18 or the design of 2P sensitized tandem systems 19,20. Both strategies led in several cases to innovative PPGs with δ u values over a dozen GM.…”

Coumarins and P450s, Studies Reported to-Date

“…One of the main limitations of such strategy is the toxicity/drug interactions of the coumarins and the products of metabolism of the released coumarins by cytochrome P450 enzymes. Figure 6 shows the coumarin structures that have shown promise in photo-caging [68,70].…”