Complexes of 6(A)-(2-aminoethylamino)-6(A)-deoxy- beta-cyclodextrin and 6(A)-[bis(carboxylatomethyl)amino]-6(A)-deoxy-beta-cyclodextrin with (R)- and(S)-tryptophanate and (R)- and (S)-phenylalaninate in aqueous solution. A pH titrimetric and NMR spectroscopic study

The 1:1 host-guest complexes formed by 6(A)-(2-aminoethylamino)-6(A)-deoxy- beta-cyclodextrin and (R)- and (S)-tryptophanate are characterized by log(K /dm(3) mol(-1)) = 4.83+/-0.02 and 4.72+/-0.03, respectively, and for those formed with (R)- and (S)-phenylalaninate log(K/dm(3) mol(-1)) = 3.82+/-0.05 and 4.12+/-0.02, respectively, in aqueous solution at 298.2 K and I = 0.10 mol dm(-3) (NaClO4), where K is the stability constant. The corresponding values for the analogous complexes formed by 6(A)-[bis(carboxylatomethyl)am ino]-6(A)-deoxy-beta-cyclodextrin are 3.4+/-0.1, 3.3+/-0.1, 4.02+/-0.06 and 4.00+/-0.06, respectively. Host-guest complexes are also formed by the mon oprotonated substituted beta-cyclodextrins. H-1 n.m.r. spectroscopy (ROESY) indicates that the guests are complexed with their indole and phenyl entit ies inside the annuli of the substituted beta-cyclodextrin hosts.