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用 MNDO方法对磷酰化丝氨酸仿生化反应机理中所形成的六配位磷中间体 ( 3 )可能的 3个异构体的结构及其反应活性进行了研究 .在六配位磷中间体 3的 6根键中 ,丝氨酸的羧基氧 O3与磷之间的键最弱 ,最易断裂生成新的五配位磷中间体 4 ,4的 P_ N键断裂得到磷酰基的 N→ O转位反应产物 5.对于六配位磷中间体 3中的两个异丙氧基 ,位于丝氨酸侧链羟基 O6对面的异丙氧基较另一个易于离去 (约低 3 7k J/mol)并得到中间体 6,接着甲醇从 O6对面新产生的空隙进攻中间体 6中的磷 ,生成磷上酯交换产物 9.六配位磷中间体机理比较好地解释了实验中所发现的磷酰化丝、苏氨酸仿生化反应的多样性和复杂性
The structure and reactivity of three possible isomers of hexa-coordinated phosphorus intermediate (3) formed by the mechanism of phosphorylation serine biomimerization were studied by MNDO method. Of the 6 keys, the bond between the carboxyl oxygen O3 and phosphorus of serine is the weakest, and the most vulnerable to cleavage leads to the cleavage of the P_N bond of the new pentacoordinated phosphorus 4, 4, resulting in the N → O translocation reaction of phosphoryl Product 5. For two isopropoxy groups in the hexacoordinated phosphorus intermediate 3, the isopropoxy group located opposite the serine side-chain hydroxyl O6 is easier to leave (about 37 kJ / mol lower) than the other and gives the middle Body 6, followed by freshly generated methanol across O6, intercepts the phosphorus in intermediate 6 to form phosphorus-on-phosphorus transesterification product 9. The mechanism of hexacoordination phosphorus intermediates explains well the phosphorylated filaments found in experiments, The diversity and complexity of threonine biomimetic reactions