Solid-phase synthesis of chiral stationary phases based on 2,4,5,6-tetrachloro-1,3-dicyanobenzene derivatives spaced from N-3,5-dinitrobenzoyl alpha-amino acids: Comparative study of their resolution efficacy

Two new chiral stationary phases, 3-[5-chloro-1,3-dicyano-2,4-[2'-(N'-1,3-d initrobenzoyl-D-phenylglycinyl) aminoethyl]aminophen-1-yl] aminopropyl sili ca (CSP-I) and 3-[5-chloro-1,3-dicyano-2,4-[2'- (N'-1,3-dinitrobenzoyl-L-le ucinyl) aminoethyl] aminophen-1-yl] aminopropyl silica (CSP-S), were prepar ed by solid-phase synthesis. They comprise chiral unit, 3,5-dinitrobenzoyl derivative of the amino acid, D-PhGly or L-Leu, bound via spacer 1,2-diamin oethane to 2,4-positions of the persubstituted benzene ring, derived from c ompound 1, and possess pseudo-C-2 symmetry. Preparation of model compounds 6 and 7 confirmed the structure of chiral selectors, which comprise pi -don or persubsituted aromatic ring and two strong ii-acceptor 3,5-dinitrobenzoy l amido units. CD spectra of model selectors 6 and 7, run in DMSO above 250 nm, exhibit negative exciton coupling CEC) between pi -acceptor and pi -do nor chromophores, C-1 symmetric model compound 8 exhibited much weaker EC a nd 9, devoid of rr-donor unit, does not exhibit any significant CD. Combine d pi -donor and pi -acceptor properties enable the new CSPs to separate a b road range of racemates. The columns with CSP-1 and CSP-2 were tested for t he separation of 22 racemates by HPLC with two different mobile phase syste ms and the results are compared with those obtained by using a structurally related commercial column. Chirality 13.294-301, 2001. (C) 2001 Wiley-Liss , Inc.