The tamoxifen carbocation (Ph(Ar)C=CPh-CH+-CH3, Ar = 4-Me2NCH2CH2OC6H4) is generated from acetate and sulfate precursors by SN1 ionization in water. The cation exists in (E) and (Z) forms which equilibrate before reaction. The major products are the α-hydroxytamoxifens Ph(Ar)C=CPh-CHOH-CH3, both (E) 64% and (Z) 29%, with the ratio independent of the configuration of the starting ester. Two minor products with a total yield of 7% account for the rest of the products. These have been characterized as indenes derived from intramolecular cyclization, a 4.5% yield of the indene derived from cyclization into the Ar ring with 2.5% due to cyclization into the phenyl ring. Experiments in acid solutions (0.01-0.1 M HCl) starting with pure (E)- or (Z)-α-hydroxytamoxifen reveal that the two alcohols equilibrate. This occurs by H+-catalyzed formation of the carbocation followed by water capture. Occurring about 10-fold slower than this isomerization is an irreversible process resulting in the two indenes. This cyclization will result in the destruction of the α-hydroxytamoxifens upon exposure to acidic conditions and also makes the direct observation of the tamoxifen carbocation under super-acid conditions difficult, if not impossible. The indenes do form in low yield whenever the tamoxifen carbocation is generated from an SN1 precursor. Thus these products could serve as markers for the formation of the tamoxifen carbocation in cellular systems or in in vivo experiments.Key words: carbocation, indene, allylic cation, isomerization.
他莫昔芬卡阳离子(Ph(Ar)C=CPh-CH
+-CH
3,Ar = 4-Me
2NCH
2CH
2OC
6H
4)是由
乙酸盐和
硫酸盐前体在
水中通过S
N1电离生成的。这个阳离子存在(E)和(Z)形式,在反应前平衡。主要产物是α-羟基
他莫昔芬Ph(Ar)C=CPh-CHOH-CH
3,分别为(E)64%和(Z)29%,比例与起始酯的构型无关。两种产物的总产率为7%,其余的产品为两种次要产物。这些次要产物已被确定为由分子内环化衍生的
茚烯,其中4.5%的产率来自于环化成Ar环的
茚烯,2.5%来自于环化成苯环的
茚烯。在酸性溶液(0.01-0.1 M HCl)中进行的实验,从纯(E)或(Z)-α-羟基
他莫昔芬开始,显示这两种醇会平衡。这是通过H
+催化形成卡阳离子,然后被
水捕获来实现的。比这种异构化慢大约10倍的是一个不可逆过程,导致两种
茚烯的形成。这种环化将导致α-羟基
他莫昔芬在酸性条件下暴露时被破坏,并且使在超酸条件下直接观察
他莫昔芬卡阳离子变得困难,甚至不可能。每当
他莫昔芬卡阳离子由S
N1前体生成时,
茚烯都会以低产率形成。因此,这些产物可以作为
细胞系统或体内实验中
他莫昔芬卡阳离子形成的标志。关键词:卡阳离子,
茚烯,烯丙基阳离子,异构化。