作者:Renzo Rossi
DOI:10.1055/s-1997-1299
日期:1997.9
A concise stereocontrolled synthesis of the racemic forms of two naturally occurring lignans, savinin (5) and gadain (6), is described. The reaction sequences used for the preparation of these lignans involve: (i) a regioselective and stereospecific Pd-mediated reaction between (3,4-methylenedioxy)phenylzinc chloride (15a) and the easily available methyl (Z)- and (E)-2,3-dibromopropenoate [(Z)- and (E)-(14)], respectively; (ii) a Pd-mediated reaction between the 3-aryl substituted 2-propenylzinc chloride (17) and the stereoisomerically pure 3-aryl-2-bromopropenoates (Z)- and (E)-16, respectively, so obtained; and (iii) treatment of the resulting dienyl esters (E)- and (Z)-18, with dicyclohexylborane followed by oxidation with 30% H2O2 in the presence of alkali and subsequent lactonization.
本文描述了两种天然存在的木脂素(savinin (5)和gadain (6))外消旋形式的简明立体控制合成。制备这些木脂素所用的反应序列包括:(i) (3,4-亚甲基二氧基)苯基氯化锌(15a)与容易获得的(Z)-和(E)-2,3-二溴丙烯酸甲酯[(Z)-和(E)-(14)]分别发生Pd介导的位点选择性和立体选择性反应;(ii) 3-芳基取代的2-丙烯基氯化锌(17)与分别由此获得的立体异构体纯的3-芳基-2-溴丙烯酸酯(Z)-和(E)-16发生Pd介导的反应;以及(iii) 用二环己基硼烷处理所得的二烯酯(E)-和(Z)-18,然后在碱存在下用30%的H2O2氧化,最后进行内酯化。