The conformation of a tetratritylated alpha-cyclodextrin with unusual proton NMR.

Tetratritylation of alpha-cyclodextrin (CD) and subsequent peracetylation of the partially tritylated mixture allowed the preparation and isolation of the symmetrical 6(A),6(B),6(D),6(E)-tetratritylated alpha-CD in pure form. The (1)H NMR spectra of the compound showed abnormal behaviour with the anomeric proton of one of the glycopyranosyl systems resonating below 3.0 ppm, which is exceptionally unusual. To understand this anomaly in the (1)H NMR data, we performed a complete NMR analysis and using molecular modelling as a tool, we were able to obtain a conformation that can explain the observed NMR phenomenon.