Remote substituent effects and regioselective enhancement of electrophilic substitutions in helical aromatic oligoamides.
The bromination of helically folded oligoamides of 8-amino-4-isobutoxy-2-quinolinecarboxylic acid by N-bromosuccinimide has been investigated. Bromination occurs preferentially if not exclusively at one position in the sequence despite the presence of multiple, up to seven, a priori comparable, reaction sites. Reactions are up to 2 orders of magnitude faster in a folded octamer than in a short nonhelical dimer, despite the steric hindrance that is expected in a compact folded conformation. The presence of substituents remote from the reaction site have considerable influence, resulting in the loss of regioselectivity, or in the slowing down of the reaction by several orders of magnitude.
Srinivas
Kolupula
K
Institut Européen de Chimie et Biologie, Université de Bordeaux-CNRS UMR 5248 and UMS3033, 2 rue Robert Escarpit, 33607 Pessac Cedex, France.
Kauffmann
Brice
B
Dolain
Christel
C
Léger
Jean-Michel
JM
Ghosez
Léon
L
Huc
Ivan
I
D000577:Amides / Q000737:chemistry*; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D015363:Quinolones / Q000737:chemistry
D000577:Amides; D015363:Quinolones