A series of six methyl enol ether analogs 8-13 of geraniol, (E,E)-farnesol, and (E,E,E)-geranylgeraniol was synthesized from a group of three allylic methyl ethers and three allylic chlorides. Lithiation of the 1-methyl-, or 1-alkenylvinyl ethers with sec-butyllithium at -78 °C followed by alkylations of the resulting (Z)-(3-methoxyallyl)lithium reagents afforded the six possible Z-configured(trans) methoxynor polyprenyl benzyl ethers bearing the methoxy substituent at the internal and terminal double bonds with high Z/E ratios (5 : 1-31 : 1) and 47-80% yields. Reductive cleavage of the benzyl groups with lithium in liquid ammonia gave the corresponding methoxynor polyprenols. 11-Methoxy-18-nor and 7-methoxy-19-nor geranylgeraniols (13 and 12) were converted to the corresponding diphosphates, 7 and 32, by the Poulter displacement method. The stability of the enol ether in 7 in aqueous solution at pH 8 was verified by NMR analyses. The diphosphates of the methoxynor polyprenols may prove useful as substrate analogs for terpene synthases to capture transient intermediates in cyclization reactions catalyzed by these enzymes.
一系列六种甲基烯醇醚类似物8-13,包括香叶醇、(E,E)-法尼醇和(E,E,E)-戊二烯醇的合成,从三种烯丙基甲基醚和三种烯丙基氯化物开始。在-78°C下用sec丁基锂对1-甲基或1-烯基乙烯醚进行锂化,然后通过烷基化反应得到(Z)-(3-甲氧基烯丙基)锂试剂,合成了可能的Z-构型(反式)甲氧基聚戊二烯苄醚,其在内部和末端双键处带有甲氧基取代基,Z/E比例高(5:1-31:1),产率为47-80%。在液氨中用锂对苄基进行还原解离,得到相应的甲氧基聚戊二烯醇。11-甲氧基-18-去和7-甲氧基-19-去戊二烯醇(13和12)通过Poulter位移法转化为相应的二磷酸酯7和32。通过NMR分析验证了在pH 8水溶液中7中烯醇醚的稳定性。这些甲氧基聚戊二烯醇的二磷酸酯可能作为萜类合酶的底物类似物,用于捕获这些酶催化的环化反应中的瞬态中间体。