Stereoselective total syntheses of the (±)-di-O-methyl ethers of agatharesinol, sesquirin-A, and hinokiresinol, and of (±)-tri-O-methylsequirin-E, characteristic norlignans of coniferae
Stereoselective total syntheses of the (±)-di-O-methyl ethers of agatharesinol, sesquirin-A, and hinokiresinol, and of (±)-tri-O-methylsequirin-E, characteristic norlignans of coniferae
复制标题
琼脂树脂醇、倍半香素-A 和扁柏树脂醇的 (±)-二-O-甲基醚以及松柏科特征性正木脂素 (±)-三-O-甲基倍半香素-E 的立体选择性全合成
DOI：
10.1039/p19780001257
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
D. Whiting
中科院分区：
文献类型：
--
作者：
A. P. Beracierta;D. Whiting
本文报道了去甲木脂素Sequirin-A，Agatharesinol和Hinokiresinol的（±）-二-O-甲基醚和（±）-三-O-甲基Sequirin-E的全合成。将对甲氧基苯乙酮转化为对甲氧基苯甲酰基乙烯，然后转化为4-（对甲氧基苯甲酰基）-2，2-二甲基-1，3-二氧戊环（13）。缩水甘油酸（15）是由（13）通过与氯乙酸苄酯的Darlene缩合和所得酯的氢解得到的。缩水甘油酸在热丙酮中的脱羧-重排是立体选择性的，得到所需的2，2-二甲基-1，3-二氧戊环-4-基-（对甲氧基苯基）乙醛的非对映异构体（17）（>80%）。（17）与对甲氧基苯亚甲基三苯基膦反应，得到反式和顺式-（±）-二甲基沉香树脂酚丙酮化合物。反式-丙酮化合物（19）水解为（±）-二甲基沉香树脂酚（21），后者的混合原甲酸酯热解得到（±）-二甲基扁柏树脂酚。顺式异构体（18）经水解和环化得到（±）-二甲基奎宁-A。醛（17）与3，4-二甲氧基亚苄基三苯基膦反应，然后经酸催化环化，通过丙酮化合物（20）得到（±）-三甲基Sequirin-E。另一种方法来二甲基沉香树脂酚进行了讨论。
Total syntheses of the (±)-di-O-methyl ethers of the norlignans sequirin-A, agatharesinol, and hinokiresinol, and of (±)-Tri-O-methyl sequirin-E are described. p-Methoxyacetophenone was converted into p-methoxybenzoylethylene and thence into 4-(p-methoxybenzoyl)-2,2-dimethyl-1,3-dioxolan (13). The glycidic acid (15) was obtained from (13) by Darzens condensation with benzyl chloroacetate and hydrogenolysis of the resulting ester. Decarboxylation–rearrangement in hot acetone of the glycidic acid was stereoselective providing the desired diastereoisomer (17)(>80%) of 2,2-dimethyl-1,3-dioxolan-4-yl-(p-methoxyphenyl)acetaldehyde. Reaction of (17) with p-methoxybenzylidenetriphenylphosphorane gave trans- and cis-(±)-dimethylagatharesinol acetonides The trans-acetonide (19) was hydrolysed to (±)-dimethylagatharesinol (21); pyrolysis of the mixed orthoformate of the latter provided (±)-dimethylhinokiresinol. The cis-isomer (18) was hydrolysed and cyclised to yield (±)-dimethylsequirin-A. Reaction of the aldehyde (17) with 3,4-dimethoxybenzylidenetriphenylphosphorane, followed by acid-catalysed cyclisation, afforded (±)-trimethylsequirin-E, via the acetonide (20). An alternative approach to dimethylagatharesinol is discussed.