Synthesis of Thiazoloindole α-Amino Acids: Chromophores Amenable to One- and Two-Photon Induced Fluorescence

Abstract

Thiazoloindole α-amino acids have been synthesized in four steps from tryptophan using a dual-catalytic thiolation reaction and a copper-mediated intramolecular N-arylation process. Late-stage diversification of the thiazoloindole core with electron-deficient aryl substituents produced chromophores that on one-photon excitation displayed blue-green emission, mega-Stokes shifts, and high quantum yields. The thiazoloindole amino acids could also be excited via two-photon absorption in the near-infrared, demonstrating their potential for biomedical imaging applications.

Fluorescent carbazole-derived α-amino acids: structural mimics of tryptophan

“…1a ). 11 While these have useful fluorescent properties compared to l -tryptophan, unnatural amino acids that act as a close structural analogue of l -tryptophan in proteins but with brighter fluorescence for more general biology applications are still required. In designing a novel amino acid side chain, we proposed that the insertion of an aromatic ring between the amino acid core and indole ring to give a carbazole moiety ( Fig.…”

Synthesis of β-Pyridyl α-Amino Acids: Conformationally Sensitive Charge Transfer-Based Fluorophores

“… 7 These include julolidine-based molecular rotors such as 9-(2-carboxy-2-cyanovinyl)julolidine 3 , 8 that on incorporation into a peptide to form fluorescent probes such as 4 , have been used to investigate protein–protein interactions ( Figure 1 b). 9 We have reported various novel classes of unnatural α-amino acids that can act as fluorescent probes for chemical biology applications, 10 including benzotriazinone-derived α-amino acids, which were found to exist as planar and twisted rotamers, resulting in dual emission fluorescent properties. 11 Based on this work, we proposed that a fluorescent α-amino acid bearing a poly aromatic side-chain with multiple rotation sites, which can adopt planar and twisted conformations could act as a viscosity probe.…”