Abstract
Two α‐aminoisobutyric acid (Aib) foldamers bearing Zn(II)‐chelating N‐termini have been synthesized and compared with a reported Aib foldamer that has a bis(quinolinyl)/mono(pyridyl) cap (BQPA group). Replacement of the quinolinyl arms of the BQPA‐capped foldamer with pyridyl gave a BPPA‐capped foldamer, then further replacement of the linking pyridyl with a 1,2,3‐triazole gave a BPTA‐capped foldamer. Their ability to relay chiral information from carboxylate bound to Zn(II) at the N‐terminus to a glycinamide‐based NMR reporter of conformational preference at the C‐terminus was measured. The importance of the quinolinyl arms became readily apparent, as the foldamers with pyridyl arms were unable to report on the presence of chiral carboxylate in acetonitrile. Low solubility, X‐ray crystallography and 1H NMR spectroscopy suggested that interfoldamer interactions inhibited carboxylate binding. However changing solvent to methanol revealed that the end‐to‐end relay of chiral information could be observed for the Zn(II) complex of the BPTA‐capped foldamer at low temperature.
Highlights
Two α-aminoisobutyric acid (Aib) foldamers bearing Zn(II)chelating N-termini have been synthesized and compared with a reported Aib foldamer that has a bis(quinolinyl)/mono(pyridyl) cap (BQPA group)
The importance of the quinolinyl arms became readily apparent, as the foldamers with pyridyl arms were unable to report on the presence of chiral carboxylate in acetonitrile
Foldamer 2 was synthesized in four steps from N3Aib4GlyNH2 5, with commercially available di-(2-picolyl)amine 4 and 6(bromomethyl)nicotinate (Scheme 1)
Summary
Two α-aminoisobutyric acid (Aib) foldamers bearing Zn(II)chelating N-termini have been synthesized and compared with a reported Aib foldamer that has a bis(quinolinyl)/mono(pyridyl) cap (BQPA group). Their ability to relay chiral information from carboxylate bound to Zn(II) at the. We have used the BQPA motif as a ligand recognition domain on the N-terminus of a 310 helical α-aminoisobutyric acid (Aib) foldamer. Metal complexes of these BQPA-capped Aib foldamers have been used to relay chemical information through the length of Aib foldamers to a reporter group, information that is encoded either in ligand shape (chiral ligands)[8] or in the e.e. of a scalemic mixture of carboxylates.[9]
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