Cyclodextrin derivatives in GC separation of racemates of different volatility Part XVIII: 2-methyl-3-acetyl- and 2-acetyl-3-methyl-6-O-t-hexyldimethylsilyl--cyclodextrin derivatives

The 2-O-methyl-3-O-acetyl- and 2-O-acetyl-3-O-methyl-derivatives of 6-O-t-hexyldimethylsilyl-(lambda)-cyclodextrins (THDMS--CDs) were synthesised and tested as GC stationary phases for enantiomer GC separation. The performance of columns prepared with these CD derivatives diluted in OV-1701 was evaluated with several series of racemates having different structures and volatilities; they were compared with those of 2,3-di-O-methyl- and 2,3-di-O-acetyl-6-t-hexyldimethylsilyl--cyclodextrins. The comparison aimed to evaluate the influence on enantioselectivity of the substituents in positions 2 and 3 of the sugar units of the cyclodextrin ring. On the basis of the results obtained to date, 2-O-methyl-3-O-acetyl-6-O-THDMS--CD showed the highest enantioselectivity among the four CDs investigated, while evidence of a direct connection between their enantioselectivity and the nature of the substituents in positions 2 and 3 of the CD ring is rather limited.