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Enantioselective preparative HPLC separation of the HBCD—Stereoisomers from the technical product and their absolute structure elucidation using X‐ray crystallography

2007; Wiley; Volume: 19; Issue: 3 Linguagem: Inglês

10.1002/chir.20366

1520-636X

Robert Koeppen, Roland Becker, Franziska Emmerling, Christian Jung, Irene Nehls,

Toxic Organic Pollutants Impact

Abstract 1,2,5,6,9,10‐Hexabromocyclododecane (HBCD) is a widely used flame retardant, which tends to persist in the environment and accumulates in biota. The six stereoisomers (three racemates named α‐, β‐, and γ‐HBCD) of the technical mixture were isolated with high‐performance liquid chromatography (HPLC). Direct separations were performed on a chiral stationary phase containing permethylated β‐cyclodextrin (NUCLEODEX β‐PM column) and the pure enantiomers of α‐, β‐, and γ‐HBCD were physically characterized for the first time. The absolute configurations of all six isomers were determined by anomalous dispersion using single crystal X‐ray crystallography. Optical rotations αD in tetrahydrofuran were +4.2/−4.0 (α‐HBCD), +26.1/−27.5 (β‐HBCD), and +68.0/−66.3 (γ‐HBCD). The sense of rotation could be correlated with the absolute configurations of α‐, β‐, and γ‐HBCD enantiomers and their order of elution on a chiral permethylated β‐cyclodextrin‐bonded stationary phase. The diastereomersα‐, β‐, and γ‐HBCD displayed distinctly different melting points as well as 1 H‐, 13 C NMR, and IR spectra. Chirality, 2007. © 2007 Wiley‐Liss, Inc.