DIRECT CHIRAL HPLC SEPARATION OF SEVERAL BARBITURATES ON A CHIRALCEL(R) OJ COLUMN - SUBSTITUENT EFFECTS ON THE ENANTIOSELECTIVITY

The enantioselectivity and enantiomeric separation of 15 racemic barbi turate analogs with various substitutions on C-5, on cellulose tris (4 -methyl benzoate) chiral stationary phase known as Chiralcel(R) OJ-CSP were investigated under the same chromatographic conditions. The resu lts revealed that a better resolution was achieved for barbiturates wi th one cyclic substituent at C-5 while no separation was achieved with analogs having two aliphatic chain substituents at C-5. Also, increas ed chain length did not enhance resolution. Both steric and electronic effects are involved in the resolution of barbiturates on Chiralcel O J-CSP. Possible chiral recognition mechanisms for these barbiturates a nd the CSP are discussed.