Host-guest complexations of local anaesthetics by cucurbit[7]uril in aqueous solution.
The cucurbit[7]uril (CB[7]) host molecule forms very stable host-guest complexes with the local anaesthetics procaine (K(CB[7]) = (3.5 +/- 0.7) x 10(4) dm(3) mol(-1)), tetracaine (K(CB[7]) = (1.5 +/- 0.4) x 10(4) dm(3) mol(-1)), procainamide (K(CB[7]) = (7.8 +/- 1.6) x 10(4) dm(3) mol(-1)), dibucaine (K(CB[7]) = (1.8 +/- 0.4) x 10(5) dm(3) mol(-1)) and prilocaine (K(CB[7]) = (2.6 +/- 0.6) x 10(4) dm(3) mol(-1)) in aqueous solution (pD = 4.75). The stability constants are 2-3 orders of magnitude greater than the values reported for binding by the comparably sized beta-cyclodextrin host molecule. The inclusion by CB[7] raises the first pK(a) values of the anaesthetics by 0.5-1.9 pK units, as the protonated forms are bound more strongly in acidic solution. The complexation-induced chemical shift changes in the guest proton resonances provide an indication of the site(s) of binding and the effects of protonation on the location of the binding sites.
Wyman
Ian W
IW
Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada.
Macartney
Donal H
DH
D000779:Anesthetics, Local / Q000737:chemistry*; D001665:Binding Sites; D001952:Bridged-Ring Compounds / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
D000779:Anesthetics, Local; D001952:Bridged-Ring Compounds; D007093:Imidazoles; D012996:Solutions; D014867:Water; C456276:cucurbit(7)uril; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils