title: Mechanism and Scope of Preferential Enrichment, a Symmetry-Breaking Enantiomeric Resolution Phenomenon.
abstract: The mechanism of "preferential enrichment", an unusually symmetry-breaking enantiomericresolution phenomenon that is observed upon simple recrystallization of a certain kind of organic racemiccrystal from the usual organic solvents without any external chiral element, has been rationalized in termsof a complexity system involving multistage processes that affect each other. These processes comprise:(1) preferential homochiral molecular association to give one-dimensional (1D) R andS chains in solution; (2) formation of γ-form prenucleationaggregates consisting of the same homochiral 1D chains; (3) nucleation and crystal growth of the metastableγ-form crystal composed of irregular alignment of the homochiral 1D R andS chains; (4) the solvent-assisted solid-to-solid type of polymorphictransition of the incipient γ-form crystal into the more stable polymorphic form, such as the α-,δ-, or ε-form; and (5) partial crystal disintegration in the transformed crystal to releaseexcess R or S moleculesinto solution. Based on this mechanism, both induction and inhibition of preferential enrichment have beenachieved by controlling the mode of polymorphic transition during crystallization with appropriate seedcrystals. We call this forced polymorphic transition on the surface of a seed crystal "epitaxialtransition".
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, 606-8501, Kyoto, Japan, tamura-r@mbox.kudpc.kyoto-u.ac.jp.
authors.forename: Rui
authors.initials: R
authors.lastname: Tamura
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Fujimoto
authors.forename: Takanori
authors.initials: T
authors.lastname: Ushio