Role of structure and pH in cyclization of allene oxide fatty acids: Implications for the reaction mechanism
作者:Alexander N Grechkin、Ivan R Chechetkin、Lucia S Mukhtarova、Mats Hamberg
DOI:10.1016/s0009-3084(02)00107-x
日期:2002.12
electrocyclization of 18:2-allene oxides and thus the yield of cyclopentenones. The well-known cyclization of the homoallylic allene oxide (12,13-EOT) derived from alpha-linolenic acid 13-hydroperoxide (E,Z-13-HPOT) into cis-12-oxo-10,15-phytodienoic acid was suppressed at pH below neutral and was not observable at pH 4.5. In contrast, cyclization of the allene oxide ((9E)-12,13-EOD) derived from (E
在pH 7.5下,亚麻或玉米的氧化烯合成酶与亚油酸的13-氢过氧化物和9-氢过氧化物的E,E-异构体(分别为E,E-13-和E,E-9-HPOD)一起孵育反式二取代的环戊烯酮的产率。在使用的条件下,(Z,E)-HPODs主要转化为α-酮醇,仅提供痕量的环戊烯酮。这些发现表明,将双键的几何形状从Z改变为E显着增加了18:2-丙二烯氧化物电环化所需的环戊二烯基阳离子中间体的形成速率,从而提高了环戊烯酮的收率。众所周知,将α-亚麻酸13-氢过氧化物(E,Z-13-HPOT)衍生的均烯丙基氧化烯(12,13-EOT)环化为cis-12-oxo-10,在低于中性的pH值下15-植物二烯酸被抑制,在pH 4.5上不能观察到。相反,在低pH条件下,偏向于衍生自(E,E)-13-HPOD的氧化烯((9E)-12,13-EOD)的环化作用略微有利。pH值变化对12,13-EOT和(9E)-12,13-EOD