Synthesis of 13C-labelled (all-E,3R,3′R)-β,β-carotene-3,3′-diol (zeaxanthin) at C(12), C(13), C(12′), and C(13′) via all-E-2,7-dimethylocta-2,4,6-triene-1,8-dial-13C4
作者:Frederick Khachik、Gary R. Beecher、Betty W. Li、Gerhard Englert
DOI:10.1002/jlcr.2580361206
日期:1995.12
The title compound (10) has been synthesized from all-E-2,7- dimethylocta-2,4,6-triene-1,8-dial (C10-dialdehyde, 8) labelled with four 13C from commercially available and relatively inexpensive starting materials. The key starting material in this synthesis, (EtO)2P(O)13CHMe13CO2Et (2), has been prepared from triethyl phosphonoacetate-13C2. The sodium salt of 2 reacted with fumarylaldehyde dimethylacetal to give ethyl 6,6-dimethoxy-2-methyl-E, E-2,4-hexadienoate (4) which was converted to 8 in four steps [(1) acid hydrolysis, (2) 2/NaH, (3) LiAlH4 reduction, (4) MnO2 oxidation]. The overall yield of 8 based on phosphonate 1 is 43-46%. The double Wittig reaction of 8 with [(3R-3-hydroxy-β-ionylidene)ethyl]triphenylphosphonium chloride afforded 10 also known as (all-E,3R,3′R)-zeaxanthin-13C4 (39% based on phosphonate 1) in high purity. This synthetic method may be extended to prepare other 13C-labelled carotenoids.
标题化合物 (10) 是由全-E-2,7-二甲基辛-2,4,6-三烯-1,8-二(C10-二醛,8)标记了 4 个 13C 的全-E-2,7-二甲基辛-2,4,6-三烯-1,8-二(C10-二醛,8)从市面上相对便宜的起始材料合成的。本合成中的关键起始材料 (EtO)2P(O)13CHMe13CO2Et (2) 是由磷酰乙酸三乙酯-13C2 制备的。2 的钠盐与富马酸醛二甲基乙缩醛反应生成 6,6-二甲氧基-2-甲基-E,E-2,4-己二烯酸乙酯 (4),该乙酯通过四个步骤转化为 8 [(1)酸水解,(2)2/NaH,(3)LiAlH4 还原,(4)MnO2 氧化]。基于膦酸盐 1 的 8 的总产率为 43-46%。将 8 与[(3R-3-羟基-β-亚氮基)乙基]三苯基氯化鏻进行双威蒂希反应,可得到高纯度的 10,也称为 (all-E,3R,3′R)-玉米黄质-13C4(39%,基于膦酸盐 1)。这种合成方法可扩展用于制备其他 13C 标记的类胡萝卜素。