Enantioselective Cyclization of Racemic Supramolecular Polymers

Abstract

Homochiral hydrogen-bonded cyclic assemblies are formed in dilute solutions of racemic supramolecular polymers based on the quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidinone unit, as observed by 1H NMR and SEC experiments. Preorganization of the monomers and the combined binding strength of the eight hydrogen bonds result in a very high stability of the cyclic aggregates with pronounced selectivity between homochiral and heterochiral cyclic species, usually only observed in crystalline or liquid crystalline phases.

Convenient Solid‐Phase Synthesis of Ureido‐Pyrimidinone Modified Peptides

“…2‐(1‐Imidazolylcarbonylamino)‐6‐methyl‐4(1 H )‐pyrimidinone (11) (CDI‐activated methyl‐isocytosine): 2‐Amino‐4‐hydroxy‐6‐methylpyrimidine was activated with 1,1‐carbonyldiimidazole (CDI) in a similar way as shown before 27,28. 2‐amino‐4‐hydroxy‐6‐methylpyrimidine (4.0 mmol, 0.5 g) and CDI (5.2 mmol, 0.84 g) were suspended in DMSO and stirred for 1 h at 80 °C.…”

“…Two different UPy synthons were designed for this convenient solid‐phase synthesis approach; based on a carbonyldiimidazole‐activated amine precursor UPy27 11 – 12 or on an isocyanate functionality18 13 (Figure 2). The carbonyldiimidazole‐activated amine precursor UPy was used with two different substituents at the 6‐position of the pyrimidinone moiety; a methyl group28 11 or an ethylpentyl27 substituent 12 . Both types of UPy synthons 11 – 13 were used in both coupling methods, that comprise of either N‐terminal UPy functionalization of the peptide (method 1; see example Figure 1, B) or UPy coupling to the ϵ‐position of the lysine next to the C‐terminal glycine (method 2; see example Figure 1, C).…”

Perspectives on main‐chain hydrogen bonded supramolecular polymers

“…Harnessing this responsive nature while controlling their stability for practical applications will be challenging. Hybrid materials that combine supramolecular monomers with traditional systems are already under investigation 119–124. For example, traditional telechelic polymers have been functionalized with hydrogen bonding arrays.…”

Tuning the size of supramolecular single‐chain polymer nanoparticles

“…1‐(6‐Isocyanato‐hexyl)‐3‐(6‐methyl‐4‐oxo‐1,4‐dihydro‐pyrimidin‐2‐yl)‐urea was prepared according to previously reported methods 27. N‐(6‐methyl‐4‐oxo‐1,4‐dihydropyrimidin‐2‐yl)‐1H‐imidazole‐1‐carboxamide was prepared from 6‐methyl‐isocytosine and carbonyldiimidazole as published previously 28…”