The complexation and chiral selectivity of 2-hydroxypropyl-β-cyclodextrin with guest molecules as studied by electrospray mass spectrometry

Electrospray mass spectrometry has been used to study the complexation of ‘guest’ molecules with a mixture of hydroxypropyl‐substituted β‐cyclodextrin derivatives. In all cases studied, the predominant derivative was shown to contain a maximum of seven hydroxypropyl groups, most probably related to alkylation of each of the seven glucose units of the parent β‐cyclodextrin. Chiral selectivity was not observed for D‐ and L‐phenylalanine methyl esters. In contrast D‐propranolol and L‐tryptophan methyl ester formed stronger complexes than the corresponding L‐ and D‐enantiomers, respectively. Molecular modelling studies were also carried out, in an attempt to identify the factors that can play a part in determining the mechanism of the observed non‐covalent interactions.