title: Homochiral supramolecular polymerization of an "S"-shaped chiral monomer: translation of optical purity into molecular weight distribution.
abstract: An "S"-shaped chiral motif of a p-xylylene-bridged bis(cyclic dipeptide) (1), having four hydrogen-bonding amide functionalities, formed a homochiral supramolecular polymer in solution. X-ray crystallography of a slightly modified version of 1 for an enhanced crystallinity showed one-dimensional columnar assemblies via four double hydrogen-bonding interactions. Model studies with half-protected analogues of 1 indicated a nearly perfect enantioselectivity in hydrogen-bonding dimerization. When 1 was not racemic but enriched in either of the enantiomers, a supramolecular polymer with a bimodal molecular weight distribution resulted, due to the formation of two homochiral polymers with different molecular weights. By taking advantage of this, separation of optically pure 1 from an enantiomerically unbalanced mixture was possible by means of size-exclusion chromatography.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering,The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. ishida@chiral.t.u-tokyo.ac.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishida
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida
mesh_terms: D002850:Chromatography, Gel; D002942:Circular Dichroism; D004151:Dipeptides / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D014633:Valine / Q000737:chemistry*
chemical_list: D004151:Dipeptides; D010455:Peptides; D014633:Valine