Bulk electrolysis and chemical oxidation with FeCl3 of
all-trans canthaxanthin (I) and
8′-apo-β-caroten-8′-al (II) gave primarily the 9- and
13-cis-isomers, which were separated by HPLC and
identified by 1H NMR spectroscopy. Optical absorption
measurements showed that the 15-cis,
9,13-di-cis isomers of I are also formed by these
methods. In the case of the unsymmetrical compound II, additional
isomers were formed. The cis isomers account for about
40–60% of products formed. Formation of the isomers is believed to
occur by rotation about certain bonds in the cation radicals or
dications, which are formed in the oxidation processes. The neutral
cis species are then formed by an electron exchange
reaction of the cis-cation radicals with neutral
all-trans carotenoids in solution. The electrochemical
and iron(III) chloride oxidation induced isomerization are shown to be
efficient and improved methods for forming selected carotenoid
isomers.
大规模电解和
氯化
铁(FeCl3)
化学氧化全反式的卡餐黄素(I)和8'-阿波-
β-胡萝卜素-8'-醛(II)主要生成9-和13-顺式异构体,这些异构体通过高效
液相色谱法(HPLC)分离,并通过1H NMR光谱鉴定。光学吸收测量表明,这些方法还形成了15-顺式和9,13-双顺式异构体I。在不对称化合物II的情况下,形成了额外的异构体。顺式异构体占生成的产品约40-60%。异构体的形成被认为是通过氧化过程生成的阳离子自由基或二阳离子在某些键周围的旋转而发生。随后,顺式中性物种通过顺式阳离子自由基与溶液中的中性全反式
胡萝卜素之间的电子交换反应生成。电
化学和
铁(III)
氯化物氧化诱导的异构化被证明是形成选定
胡萝卜素异构体的有效且改进的方法。