Synthesis and high field NMR study of a new cyclodipeptide–β-cyclodextrin derivative

Abstract

The synthesis and high field NMR study of a new cyclopeptide functionalized-β-cyclodextrin β-CDen-c(Glu-Glu)(3) in aqueous solution are reported. This compound has been synthesized by condensation of the ethylendiamine-β-cyclodextrin derivative β-CDen (1) with the cyclo-(glutamyl-glutamyl)[c-(Glu-Glu)](2). The NMR analysis has been carried out on 500, 600 and 750 MHz instruments and has been largely based on advanced two-dimensional NMR experiments, i.e. DQF-COSY, TOCSY, HMQC and HMBC. The selective excitation technique (1D TOCSY) has also been applied. The study has led to a complete ¹H and ¹³C NMR assignment of the pendant moiety and the modified glucopyranose unit (A), and a detailed assignment of the unmodified glucopyranose units (B–G). Data about the preferred conformation of 3 are also acquired by means of ROESY experiments.