ABSTRACT
A visible-light-enabled, photocatalyst-free conjugate addition reaction of dehydroamino acids is disclosed. Employing 4-acyl-1,4-dihydropyridines as both a radical reservoir and reductant, various ß-acyl α-amino acids and their deuterated analogues were obtained in good results. Both late-stage peptide modification and stereoselective synthesis of chiral oxazolidinones are successfully achieved. The protocol is characterized by mild conditions and efficient derivatization, thus unlocking a novel blueprint to access unnatural amino acid derivatives, important building blocks with potential application in the peptidomimetic toolbox.
ABSTRACT
Herein we report a protocol for the visible-light-mediated alkylation/acylation reaction of benzothiazoles. Alkyl/acyl substituted Hantzsch esters are easily prepared and rationally used as radical precursors. In the presence of BF3·Et2O and Na2S2O8, various benzothiazole derivatives were readily obtained in good yields. Our user-friendly protocol can proceed by simple irradiation with blue LEDs (λ = 465 nm) and without the assistance of external photocatalysts. The reaction is also characterized by mild conditions and scalability, thus offering an alternative and efficient tool for the synthesis of 2-functionalized benzothiazoles.
