ORGN 380 |
| Many biological systems use the hydrophobic effect to modulate guest binding and reactivity. Study of the properties of synthetic water-soluble receptors can give insight into some of these processes. Here we show that deep cavitands act as water-soluble synthetic receptors, and can extract hydrophobic species into aqueous solution. Binding of n-alkanes causes the guest to assume a coiled, helical conformation to maximize favorable interactions with the cavity. The alkanes also tumble rapidly on the NMR timescale. Derivatization of the cavitand rim provides an increased selectivity for small hydrophobic guests, and slows the in/out exchange rate of guests with the bulk solvent. This very strong hydrophobic binding can be exploited to allow control of reactivity. The cavitand can extract into solution reactive guests with a large hydrophobic “handle” for binding. If a water-soluble reactive partner is present, reaction occurs, conferring water-solubility on the product and drastically reducing its binding affinity. Turnover is then possible, allowing the receptor to act as a phase-transfer catalyst with little to no product inhibition observed.
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Molecular Recognition and Self-Assembly
8:00 AM-12:00 PM, Tuesday, 12 September 2006 Moscone Center -- Room 132, Oral
Division of Organic Chemistry |
