摘要
在宿主-客体化学中,环糊精(CD)是受到最广泛研究的宿主之一.近年来,糖淀粉(A)及其衍生物也已被确认为一类新的宿主化合物.由于A和CD分子都由C椅式构型的D-葡萄糖残基所组成,A的螺旋内穴应与CD的环状内穴相当类似.因此,比较同一反
Both amylose(A)and cyclodextrin(CD)were found to be able to catalyze the deprotonation ofβ-keyoesters via formation of host-guest complexes in which the ionized hydroxyl groups of host molecules acted as general base.For methyl 3-oxo-dodecanoate(1),the bimolecular catalytic rate constants of the complexes forα-CD,β-CD,and A are 3.9×10^(3),1.2×10^(3),and 1.7×10^(3) M.srespectively,in contrast to that with glucose as the catalyst,0.93 M^(-1).s^(-1).This observation could be a reflection of the excellence of mutual-fit between the host and guest,and might imply that each loop of the helical inclusion complexes formed by A and 1 is probably composed of 6~7 glucose residues,with comparable snugness of binding by A or byβ-CD.A“location effect”in the amylose system was first observed:when the reacting site lay in the inner cavities of A,the efficiencies of the attack by hydroxyl groups of A or by the buffer ions were disfavorably affected in comparison with the case in which the reacting site was located in the proximity of the hydroxyl groups on the lip or the opening edge of the helical A-substrate complexes.
出处
《化学学报》
SCIE
CAS
1985年第1期99-102,共4页
Acta Chimica Sinica
