作者:Hiromi Nakashima、Masayuki Sato、Takahiko Taniguchi、Kunio Ogasawara
DOI:10.1055/s-2000-6271
日期:——
A series of polyoxygenated cyclopentanoids, including 2,2-dimethyl-3a,6a-dihydro-4H-cyclopenta[d][1,3]dioxol-4-one, has been prepared in both enantiomeric forms from cyclopentadiene by employing lipase-mediated kinetic resolution as the key step. Thus, cyclopentadiene is first transformed into racemic cis-4-cumyloxycyclopent-2-en-1-ol which is resolved under transesterification conditions in the presence of lipase PS. After transformation into the corresponding tert-butyldimethylsilyl (TBS) ethers, each of the enantiomers is cis-dihydroxylated diastereoselectively from the less hindered face which is transformed into the 2,3-O-isopropylidene-1,4-di-O-protected (trans-1,2 : cis-2,3 : trans-3,4)-1,2,3,4-cyclopentanetetraol. Selective removal of the 1,4-protecting group gives the corresponding 2,3,4-O-protected cyclopentanols which are further transformed into the 2,3,4-O-protected cyclopentanones on oxidation without suffering β-elimination. Exposure of the cyclopentanones to warm acetic acid allows β-elimination to give rise to the dehydration product 2,2-dimethyl-3a,6a-dihydro-4H-cyclopenta[d][1,3]dioxol-4-one having the corresponding chirality without losing their original chiral integrity.
一系列多氧化环戊烷类化合物,包括2,2-二甲基-3a,6a-二氢-4H-环戊烯基[d][1,3]二氧杂环-4-酮,已通过使用脂肪酶介导的动力学分离从环戊二烯中制备成两种对映异构体。因此,环戊二烯首先转化为外消旋cis-4-香草基氧环戊-2-烯-1-醇,该化合物在脂肪酶PS的存在下在转酯化条件下被分离。经过转化成相应的叔丁基二甲基硅基(TBS)醚后,每个对映体都从较少阻碍的面选择性地进行cis-二羟基化,转化为2,3-O-异丙缩酮-1,4-二-O-保护的(trans-1,2 : cis-2,3 : trans-3,4)-1,2,3,4-环戊烷四醇。选择性去除1,4-保护基团得到相应的2,3,4-O-保护环戊醇,这些化合物在氧化过程中进一步转化为2,3,4-O-保护的环戊酮而不发生β-消除。将环戊酮暴露在温热的醋酸中,可以使β-消除反应发生,从而得到脱水产物2,2-二甲基-3a,6a-二氢-4H-环戊烯基[d][1,3]二氧杂环-4-酮,具有相应的手性且不失去其原有的手性完整性。