Cyclodextrin derivatives in enantiomer GC separation of volatiles. Part XXI: Complexation of some terpenoids with 2-O-acetyl-3-O-methyl- and 2-O-methyl-3-O-acetyl-6-O-t-hexyldimethylsilyl-γ-cyclodextrins: Molecular Mechanics and Molecular Dynamics

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Abstract

Molecular Mechanics and Molecular Dynamics calculations were performed to simulate the 1 : 1 complex formation of 2-O-acetyl-3-O-methyl- and 2-O-methyl-3-O-acetyl-6-O-t-hexyldimethylsilyl-γ-cyclodextrins with a group of monoterpenoids having the p-menthane skeleton (menthol, i-menthol, neo-menthol, neo-i-menthol, menthone, i-menthone, and 3-oxo-1,8-cineole) using nitrogen as simulated gas carrier. 1 : 1 complexes of the terpenoids studied are stable and non-bonded van der Waals interactions are mainly responsible for complexation. The results suggest that the nature of the substituent (hydroxyl or oxo groups) at C3 on the cyclohexane ring, and its configuration for hydroxylated racemates, are responsible for the differences in complexation energies between the two investigated CD derivatives. This is in agreement with considerations of the difference in the experimental values of thermodynamic parameters, reported elsewhere, and may explain the difference in the enantioselectivity of the two CD derivatives for the terpenoids investigated. The substituents in position 1 are less involved in the chiral recognition process.

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