In this paper, we report efficient cyanation of various peptides containing the α-bromocarbonyl moiety using a Cucatalyzed radical-based methodology employing zinc cyanide as the cyanide source. Mechanistic studies revealed that in situ formed CuCN was a key intermediate during the catalytic cycle. Our method could be useful for the synthesis of modified peptides containing quaternary carbons.
A regioselective radical C-H trifluoromethylation of aromatic compounds was developed using cyclodextrins (CDs) as additives. The C-H trifluoromethylation proceeded with high regioselectivity to afford the product in good yield, even on the gram scale. In the presence of CDs, some substrates underwent a single trifluoromethylation selectively, whereas mixtures of single-and double-trifluoromethylated products were formed in the absence of the CD. 1 H NMR experiments indicated that the regioselectivity was controlled by the inclusion of a substrate inside the CD cavity.
The decatungstate photocatalyst [W10O32]4– efficiently promoted the C(sp3)–H
alkylation of the trifluoroacetic acid salt of valine methyl ester
(H-Val-OMe·TFA) with electron-deficient alkenes under UV irradiation.
The electrostatic interaction between the cationic ammonium group
(+NH3) of the main chain and anionic [W10O32]4– played an important role
in this reaction. The influence of various protected amino acids in
the C(sp3)–H alkylation was investigated as the
model reaction for the alkylation of Val-containing peptides. The
introduction of an alkyne moiety into Val through this alkylation
was successful, and successive copper-catalyzed azide–alkyne
cycloaddition (CuAAC) was demonstrated. The C(sp3)–H
bond of a Val residue located at the second from the N-terminus was
also successfully converted. C(sp3)–H alkylation
of oligopeptides containing two Val residues selectively proceeded
proximally to the N-terminus.
A regioselective radical C–H trifluoromethylation of aromatic compounds was developed using cyclodextrins (CDs) as
additives. The C–H trifluoromethylation
proceeded with high regioselectivity to afford the product in good yield, even
on the gram
scale. In the presence of CDs, some substrates underwent a single
trifluoromethylation selectively, whereas mixtures of
single- and double-trifluoromethylated
products were formed in the absence of the CD. <sup>1</sup>H NMR experiments
indicated that the regioselectivity was controlled by the inclusion of a
substrate inside the CD cavity.
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