Process or synthesis of (3S)- and (3R)-3-hydroxy-beta-ionone, and their transformation to zeaxanthin and beta-cryptoxanthin
申请人:University of Maryland, College Park
公开号:US08222458B2
公开(公告)日:2012-07-17
Disclosed is a process for the synthesis of (3R)-3-hydroxy-β-ionone and its (3S)-enantiomer in high optical purity from commercially available (rac)-α-ionone. The key intermediate for the synthesis of these hydroxyionones is 3-keto-α-ionone ketal that was prepared from (rac)-α-ionone after protection of this ketone as a 1,3-dioxolane. Reduction of 3-keto-α-ionone ketal followed by deprotection, lead to 3-hydroxy-α-ionone that was transformed into (rac)-3-hydrox-β-ionone by base-catalyzed double bond isomerization in 46% overall yield from (rac)-α-ionone. The racemic mixture of these hydroxyionones was then resolved by enzyme-mediated acylation in 96% ee. (3R)-3-Hydroxy-β-ionone and its (3S)-enantiomer were respectively transformed to (3R)-3-hydroxy-(β-ionylideneethyl)triphenylphosphonium chloride [(3R)-C15-Wittig salt] and its (3S)-enantiomer [(3S)-C15-Wittig salt] according to known procedures. Double Wittig condensation of these Wittig salts with commercial available 2,5- dimethtylocta-2,4,6-triene-1,8-dial provided all 3 stereoisomers of zeaxanthin. Similarly, (3R)-C15-Wittig and its (3S)-enantiomer were each coupled with β-apo-12′-carotenal.
本文披露了一种从商业可获得的(rac)-α-离子酮合成(3R)-3-羟基-β-离子酮及其(3S)对映体的高光学纯度的过程。合成这些羟基离子酮的关键中间体是从(rac)-α-离子酮制备的3-酮-α-离子酮缩酮,经过将该酮保护为1,3-二氧杂环后得到。还原3-酮-α-离子酮缩酮,然后去保护,得到3-羟基-α-离子酮,通过碱催化的双键异构化,从(rac)-α-离子酮中总产率为46%转化为(rac)-3-羟基-β-离子酮。这些羟基离子酮的混合物随后通过酶介导的酰化在96%的ee下分离。(3R)-3-羟基-β-离子酮及其(3S)对映体分别按照已知程序转化为(3R)-3-羟基-(β-离子基乙基)三苯基膦盐[(3R)-C15-Wittig盐]和其(3S)对映体[(3S)-C15-Wittig盐]。将这些Wittig盐与商业可获得的2,5-二甲基辛二烯-1,8-二醛进行双Wittig缩合,得到所有3种类脂黄素的立体异构体。类似地,(3R)-C15-Wittig及其(3S)对映体分别与β-脱氧-12'-类胡萝卜素醛偶联。