García-Río L, Hervés P, Leis J R, Mejuto J C, Pérez-Juste J, Rodríguez-Dafonte P
Departamento de Química Física, Facultad de Química, Universidad de Santiago, 15782, Santiago, Spain.
Org Biomol Chem. 2006 Mar 21;4(6):1038-48. doi: 10.1039/b513214b. Epub 2006 Jan 30.
The influence of the organic solvent on the acid and basic hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) in the presence of alpha- and beta-cyclodextrins has been studied. The observed rate constant was found to decrease through the formation of an unreactive complex between MNTS and the cyclodextrins. In the presence of dioxane, acetonitrile or DMSO, the inhibitory effect of beta-CD decreased on increasing the proportion of organic cosolvent as a result of a competitive reaction involving the formation of an inclusion complex between beta-CD and the cosolvent. The disparate size of the organic solvent molecules resulted in stoichiometric differences between the complexes; the beta-CD-dioxane and beta-CD-DMSO complexes were 1 : 1 whereas the beta-CD-acetonitrile complex was 1 : 2. The basic and acid hydrolysis of MNTS in the presence of alpha-CD showed a different behavior; thus, the reaction gave both 1 : 1 and 2 : 1 alpha-CD-MNTS complexes, of which only the former was reactive. This result was due to the smaller cavity size of alpha-CD and the consequent decreased penetration of MNTS into the cavity in comparison to beta-CD. The acid hydrolysis of MNTS in the presence of alpha-CD also revealed decreased penetration of MNTS into the cyclodextrin cavity, as evidenced by the bound substrate undergoing acid hydrolysis. In addition, the acid hydrolysis of MNTS in the presence of acetonitrile containing alpha-CD gave 1 : 1 alpha-CD-acetonitrile inclusion complexes, which is consistent with a both a reduced cavity size and previously reported data.
研究了在α-和β-环糊精存在下，有机溶剂对N-甲基-N-亚硝基对甲苯磺酰胺（MNTS）酸水解和碱水解的影响。观察到的速率常数因MNTS与环糊精之间形成无反应性的络合物而降低。在二氧六环、乙腈或二甲基亚砜存在下，由于β-环糊精与助溶剂之间形成包合物的竞争反应，随着有机助溶剂比例的增加，β-环糊精的抑制作用减弱。有机溶剂分子大小不同导致络合物之间化学计量存在差异；β-环糊精-二氧六环和β-环糊精-二甲基亚砜络合物为1:1，而β-环糊精-乙腈络合物为1:2。在α-环糊精存在下MNTS的碱水解和酸水解表现出不同的行为；因此，反应生成了1:1和2:1的α-环糊精-MNTS络合物，其中只有前者具有反应性。这一结果是由于α-环糊精的空腔尺寸较小，与β-环糊精相比，MNTS进入空腔的渗透率降低。在α-环糊精存在下MNTS的酸水解也表明MNTS进入环糊精空腔的渗透率降低，这由结合的底物发生酸水解证明。此外，在含有α-环糊精的乙腈存在下MNTS的酸水解生成了1:1的α-环糊精-乙腈包合物，这与空腔尺寸减小以及先前报道的数据一致。
