CHIRAL STATIONARY-PHASE DESIGN - A STUDY IN OPTIMIZATION

A pi-basic, brush-type chiral stationary phase (CSP) derived from (S)- N-(1-naphthyl)leucine undecenyl ester has been shown to effectively se parate the enantiomers of a broad array of pi-acidic analytes. Armed w ith a mechanistic hypothesis as to how this CSP differentiates between the enantiomers of pi-acidic derivatives of alpha-amino acids, the st ructure of this CSP was modified in a series of steps, each intended t o enhance the enantioselectivity of the CSP. Specifically, brush-type CSPs were prepared from N-(1-naphthyl)leucine di-n-propyl amide and fr om N-(5-acenaphthyl)leucine di-n-propyl amide. The latter selector was also incorporated into a polysiloxane, then coated and bonded to sili ca. The rationale for each of the structural changes, and its effect o n the enantioselectivity of the resulting CSP is described.