ma7b00343_si_001.pdf (1.29 MB)
Induction of Chirality in β‑Turn Mimetic Polymer Conjugates via Postpolymerization “Click” Coupling
journal contribution
posted on 2017-03-23, 19:18 authored by Stefanie Deike, Wolfgang H. BinderChiral
and achiral β-turn mimetic polymer conjugates were
synthesized, and their chiroptical properties were investigated. Chiral
helical poly(n-hexyl isocyanate)s (PHICs) with alkyne
functional end groups (4.0–5.4 kDa) were synthesized via coordination
polymerization using either a chiral or an achiral alkyne-functional
organotitanium catalyst. The obtained helical polymers were coupled
with a chiral β-turn mimetic structure using the copper-catalyzed
azide/alkyne cycloaddition (CuAAC) reaction, in turn allowing to tune
the distance between the PHIC-helix and the chiral center from 7 to
14 Å. The successful linkage of the PHIC-helix to the β-turn
mimetic was confirmed by size exclusion chromatography (SEC), high
performance liquid chromatography (HPLC), 1H NMR spectroscopy,
and MALDI-ToF mass spectrometry, proving the attachment of either
one or two PHIC-helices to the central β-turn. Circular dichroism
(CD) spectra confirmed chirality induction from the chiral β-turn
mimetic structure to the polymer backbone of the achiral PHIC over
five chemical bonds via postpolymerization modification, and revealed
a distance-dependent effect for the transmission of stereochemical
information. In contrast, a linkage effect leading to reduced chirality
was observed when an additional linker unit was incorporated in-between
the β-turn mimetic structure and the polymer backbone. The reported
data do show that transfer of chirality is possible after polymerization
over a relatively short distance of atoms.