Alkyl Groups Fold to Fit within a Water-Soluble Cavitand

We report here a widened, deep cavitand host that binds hydrophobic and amphiphilic guests in D2O. Small alkanes (C-6 to C-11) are bound in compressed conformations and tumble rapidly within the space. Longer n-alkanes (C-13 to C-14), n-alcohols, and alpha,omega-diols are taken up in folded conformations. The guests' termini are exposed to solvent while atoms near the alkane's center are buried and protected. The cavitand acts as a concave template that pushes terminal atoms of the guest closer together. The unexpected binding modes are interpreted in terms of the size and shape of the space accessible in the new cavitand.