Herein we report the first example of a strategy for peptide functionalization through the generation of selenocysteine electrophile in 5‐ and 6‐endo‐dig cyclization reactions. This simple approach allows bio‐conjugation of selenocystine‐based peptides. The developed protocol is based on copper(II) bromide mediated reactions of selenocystine with either 2‐propargyl N‐heterocycles through 5‐endo‐dig closure or with 2‐ethynylbiaryls through 6‐endo‐dig closure. It allows construction of indolizinium moiety on selenocysteine residue as well as formation of polyaromatic fragment bonded to selenium in a simple one‐pot process under mild reaction conditions.
A straightforward and atom‐economic method for the functionalization of short selenocystine‐containing peptides is presented. This method is shown to be tolerant to unprotected peptides. The detailed protocol is based on the generation of a selenium radical via visible light‐initiated reaction in the presence of transition metal‐free photocatalyst. The selenium radical is further oxidized to an electrophile and trapped by N‐heterocycles. The mechanism is confirmed by NMR, HRMS, UV, EPR and cyclic voltammetry (CV) experiments and photocatalyst emission quenching studies. A visible light‐initiated reaction is employed for the synthesis of selenocysteine‐containing indole‐based macrocycles via intramolecular Se−C bond formation.
Herein, we present methods for the generation of selenocysteinyl electrophile by weak Lewis acids or oxidants. The electrophilic selenium species were further utilized in 5‐endo‐dig cyclization reactions with 2‐ethynyl phenols, anisoles, and anilines, yielding substituted benzo[b]furans and indoles bearing short selenocysteine‐containing peptides. Copper(II) bromide promoted 5‐endo‐dig cyclization can be successfully applied for protected and unprotected peptides in high yields. Elaborated protocol allows the construction of phenylindeno[1,2‐c]chromene moiety in 5‐endo‐dig/6‐endo‐dig cascade reactions.
We describe the proof of concept of a portable testing setup for the detection of triacetone triperoxide (TATP), a common component in improvised explosive devices, which will allow for field-testing...
A mild and efficient method for preparation of 3-sulfenyl
and 3-selenyl
coumarins and quinolinones mediated by artificial light or sunlight
is presented. The elaborated protocol highlights the use of nonyl
acridine orange as a photocatalyst to generate a sulfenyl radical
from thiols that is further trapped by a heterocycle. The utility
of the protocol is justified by a diverse scope of thiols, including
short cysteine-containing peptides. The same reaction conditions can
be applied for preparation of 3-selenyl coumarins and quinolinones.
Various protected and unprotected selenocysteine-containing peptides
were successfully utilized demonstrating high tolerance for amino
acids with sensitive groups (Arg, Lys, Trp, His, and Tyr).
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