Multicomponent synthesis and photophysical study of novel α,β-unsaturated carbonyl depsipeptides and peptoids.

Multicomponent reactions were performed to develop novel α,β-unsaturated carbonyl depsipeptides and peptoids incorporating various chromophores such as cinnamic, coumarin, and quinolines. Thus, through the Passerini and Ugi multicomponent reactions (P-3CR and U-4CR), we obtained thirteen depsipeptides and peptoids in moderate to high yield following the established protocol and fundamentally varying the electron-rich carboxylic acid as reactants. UV/Vis spectroscopy was utilized to study the photophysical properties of the newly synthesized compounds. Differences between the carbonyl-substituted chromophores cause differences in electron delocalization that can be captured in the spectra. The near UV regions of all the compounds exhibited strong absorption bands. Compounds , , , , and displayed absorption bands in the range of 250-350 nm, absorbing radiation in this broad region of the electromagnetic spectrum. A photostability study for showed that its molecular structure does not change after exposure to UV radiation. Fluorescence analysis showed an incipient emission of , while showed blue fluorescence under UV radiation. The photophysical properties and electronic structure were also determined by TD-DFT theoretical study.