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.