Synthesis of the three isomeric mono-2-, 3-, or 6-hydroxy permethylated beta-cyclodextrins and unambiguous high field NMR characterisation

The three isomeric mono-2-, 3- or 6-hydroxy permethylated beta-cyclodextrin s are goad precursors for a wide variety of mono functionalised 'permethyl' beta -cyclodextrins. In this work, we describe the selective access to mon o-6-hydroxy (via the mono-6-tertbutyldimethylsilyl derivative), mono-2-hydr oxy (via the mono-2-benzyl derivative) and mono-3-hydroxypermethylated-beta -cyclodextrins (by under-methylation of heptakis (2,6-di-O-methyl)-beta -c yclodextrin). These derivatives were characterised by high field H-1 and C- 13 NMR spectroscopy. The position of the free hydroxyl group was confirmed unambiguously by C-13 NMR after methylation with C-13-labelled methyl iodid e. (C) 2001 Elsevier Science Ltd. All rights reserved.