title: Absolute structure determination as a reference for the enantiomeric resolution of racemic mixtures of cyclophosphazenes via chiral high-performance liquid chromatography.
abstract: Reversed-phase chiral high-performance liquid chromatography (HPLC) is a potentially powerful technique for the enantiomeric resolution of racemic mixtures, although the elution order of enantiomers is only relative and it is necessary to fully characterize reference systems for this method to provide absolute configurational information. The enantiomeric resolution of a series of racemic di-spiro cyclotriphosphazene derivatives, N3P3X2[O(CH2)(3)NH]2 (X = Cl, Ph, SPh, NHPh, OPh) [(1)-(5), respectively] was carried out by reversed-phase chiral HPLC on a commercially available Pirkle-type chiral stationary phase (R,R)-Whelk-01 using 85:15 (v/v) hexane-thf as the mobile phase. The absolute configurations of the resulting enantiomers of compounds (3) (X = SPh) and (5) (X = OPh) were determined unambiguously by X-ray crystallography. For both (3) and (5) it was found that the SS enantiomer eluted before the RR enantiomer, indicating a convenient method to determine the absolute configurations of enantiomers of this series of cyclophosphazene derivatives and providing the first set of enantiomeric reference compounds for cyclophosphazene derivatives. These structures demonstrate an interesting anomaly in that the pair of enantiomers of (3) crystallize in enantiomorphically paired space groups whilst, under the same conditions, the solid-state forms of the enantiomers of (5) form structures in Sohncke space groups that are not enantiomorphous.
authors.affiliation: Department of Chemistry, University of Southampton, Southampton SO17 1BJ, England. s.j.coles@soton.ac.uk
authors.forename: Simon
authors.initials: S
authors.lastname: Coles
authors.forename: David
authors.initials: D
authors.lastname: Davies
authors.forename: Michael
authors.initials: M
authors.lastname: Hursthouse
authors.forename: Serkan
authors.initials: S
authors.lastname: Yeşilot
authors.forename: Bünyemin
authors.initials: B
authors.lastname: Coşut
authors.forename: Adem
authors.initials: A
authors.lastname: Kiliç
mesh_terms: D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry* / Q000302:isolation & purification*; D013237:Stereoisomerism
chemical_list: D009943:Organophosphorus Compounds