Deacylation of 4-nitrophenyl acetate by 6(A)-(omega-aminoalkyl)amino-6(A)-deoxy-beta-cyclodextrins

The deacylation of 4-nitrophenyl acetate (pNPA) in aqueous solution to give 4-nitrophenolate is significantly accelerated by the 6(A)-(omega-aminoalky l)amino-6(A)-deoxy-beta-cyclodextrins [beta CDNH(CH2)(n)NH2] which are them selves acylated to give predominantly beta CDNH(CH2)(n)NHCOCH3. The deacyla tion is characterised by k(d)K = 27.4, 35.5, 24.5 and 16.0 dm(3) mol(-1) s( -1) at 298.2 K in aqueous 0.05 mol dm(-3) borate buffer and I = 0.10 mol dm (-3) (NaClO4) when n = 2, 3, 4 and 6, respectively, where k(d) (s(-1)) is t he rate constant for pNPA deacylation through a beta CDNH(CH2)(n)NH2. pNPA complex characterised by a stability constant K (dm(3) mol(-1)). The inhibi tion of the deacylation by adamantane-1-carboxylate (AC(-)) is consistent w ith a mechanism where AC(-) competes with pNPA in entering the beta CDNH(CH 2)(n)NH2 annulus through the formation of a beta CDNH(CH2)(n)NH2. AC(-) com plex. The latter complex has been qualitatively studied by H-1 NMR ROESY me thods, and its structure and that of beta CDNH(CH2)(n)NH2. pNPA have also b een force-field modelled. The possibility of the operation of an S(N)2 mech anism as an alternative explanation for the deacylation data is also consid ered.