NAD(P)H辅酶模型物结构与反应性关系的研究──3-位酰基的电子效应

合成了一系列3酰胺基氮取代的NAD(P)H模型物,测定了其与5硝基异喹啉正离子的二级反应速率常数,并与模型物的氧化还原电势进行了比较.实验结果表明,模型物3位酰基氧一方面可离域二氢吡啶环上N的电子;另一方面负电性的3位酰基氧在反应过渡态中又可引起分子内和分子间的两种静电作用;3位酰基的电子效应对模型物动力学反应性的影响是这两种效应综合作用的结果.

Studies on Structure reactivity Relationship for NAD(P)H Model Compounds-Electronic Effectof the 3Acyls

Aseries of 3-N-substituted 1, 4-dihydronicotinamide model compounds(1_4)were synthesized.The second order rate const ants of The apparent hydride transfer reactions of these NAD (P)Hmodels with 5-nit roisoquinolinium ion were measured.The redox pot entials were also determined.The results show ed that The 3-acyl group of The dihydropy ridine ring could on one hand delocalize The electrons on The ring nit rogen, and on The other hand the part ially negat ively charged 3-acy loxygen could cause two types of Electrostatic stabilization to the reaction transition state, i.e.electrostatic stabilizing interaction with the partialy positively charged 4 carbon with in The model molecule, and intermolecular electrostatic stabilizing interaction with The positively charged subst rate.The Electronic ef fectof The 3carbonyl group on The kinetic reactivities of The NAD(P)Hmodels in relation to their respective Thermodynamic parameters is rationalized by combination of Both effects.