ABSTRACT A highly diastereoselective synthesis of cationic permethylated α‐ and β‐cyclodextrins (α‐CDs and β‐CDs), incorporating a quaternary ammonium unit bridging two adjacent glucose units, has been developed. This novel methodology provides access to amphipathic α‐CDs equipped with an outward‐facing alkyl chain, which self‐assemble in water to form linear, head‐to‐tail supramolecular oligomers (DP up to five CD units) when the alkyl chain is sufficiently short (C8 and C12), and larger nano‐objects with a longer C16 chain. Alternatively, permethylated β‐CD analogs bearing an alkyl chain terminated by an adamantyl unit have also been prepared and shown to form similar linear oligomeric material. As a result of the fixed stereochemistry of the quaternary ammonium nitrogen and the blocked narrow opening of the CD, these amphiphilic cationic host molecules are prevented from undergoing self‐inclusion or forming head‐to‐head dimers in water.
Kolb et al. (Mon,) studied this question.