2^A,6^A-F-Hepta-O-tert-butyldimethylsilyl α-cyclodextrin - A carbohydrate undecaol with all OH groups visible in NMR indicative of a partially disrupted hydrogen bond network

During a synthesis of the well-known and useful building block 6^A-F-hexa-O-tert-butyldimethylsilyl α-cyclodextrin (2) by silylation of α-cyclodextrin (1) we isolated as a byproduct the oversilylated 2^A,6^A-F-hepta-O-tert-butyldimethylsilyl α-cyclodextrin (3) where one 2-OH group has also been silylated. This unsymmetrical new compound has a remarkable ¹H NMR spectrum in CDCl₃ where all 11 alcohol groups are visible. We have analyzed the spectrum of 3 using 1D and 2D 800 MHz NMR and are able to assign all the 11 alcohol protons. The remarkable chemical shifts of these protons are interpreted as being due to a partial disruption of an otherwise efficient hydrogen bond network.