engleski

New chiral stationary phases based on (R)-1- naphthylethylamine bound to 2,4,5,6-tetrachloro- 1,3-dicyanobenzene

Chiral functionalization of 2, 4, 5, 6-tetrachloro- 1, 3-dicyanobenzene (1) by regioselective nucleophilic substitution of one or two chlorine atoms by optically pure (R)-(+)-1- naphthylethylamine (NEA), or by a glycine unit as a spacer to (R)-NEA, enables the preparation of brush-type chiral selectors (2, 3, 9, 13). By the introduction of the 3-aminopropyltriethoxysilyl (APTES) group, reactive intermediates 4a/b, 5, 10a/b, and 14a/b are obtained (a/b indicate a mixture of regioisomers with APTES in 6- and 2- position). Binding of these to silica gel afforded four novel chiral stationary phases (CSPs) 6, 7, 15, and 16. HPLC columns containing CSPs with (R)- NEA directly linked to polysubstituted aromatic ring (6, 7) are not very effective in resolution of most of the 23 racemic analytes, whereas the columns with distant π-basic subunits (15, 16) exhibited higher resolving efficacy, in particular towards the isopropyl esters of racemic N-3, 5- dinitrobenzoyl-α-amino acids. Effective resolution of test racemates reveals the importance of the presence of the hydrogen bond donor amido group and the distance between the persubstituted benzene ring in 1 and the π-basic naphthalene ring of (R)-NEA.

chiral selector ; silica-bound brush-type CSP ; HPLC resolution of enantio-mers

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