Enantiomer separation on novel cellulose derivatives bearing regioselective phenylcarbamate groups

Four novel regioselectively carbamoylated cellulose derivatives with two types of substituents, one being a 3-chloro-4-methylphenylcarbamate group and the other being a phenylcarbamate, a 3,5-dichlorophenylcarbamate or a 4-methylphenylcarbamate group, at the 2-, 3-positions and 6-position were synthesized and utilized as chiral stationary phases in high-performance liquid chromatography. The obtained derivatives exhibited characteristic chiral recognition abilities which were significantly affected by the nature and arrangement of the groups at the 2-, 3-positions and 6-position. Compared with cellulose tris(3-chloro-4-methylphenylcarbamate) and Chiralcel OD columns, several racemates were better resolved on these new phases. With all six racemates resolved on cellulose 2,3-bis(4-methylphenylcarbamate)-6-(3-chloro-4-methylphenylcarbamate), it appears to be a potential useful chiral stationary phase in the future. Also, the influence of mobile phase on chiral recognition was investigated. Better resolutions were generally obtained with decreased amount of 2-propanol with a mixture of hexane/2-propanol as the mobile phase. Moreover, when ethanol was used instead of 2-propanol as the mobile phase modifier, poorer enantioseparations were often achieved.