Diastereoselective Synthesis of Merucathin: The Singlet Oxygen Ene Reaction (Schenck Reaction) as a Key Step Towards an E-Configured β-Amino Allylic Alcohol
作者:Waldemar Adam、Hans-Günter Brünker
DOI:10.1055/s-1995-4071
日期:1995.9
An enantio- and diastereoselective synthesis of the naturally occuring merucathin is reported. The singlet oxygen ene reaction of the bis-Boc-protected allylic amine 3, which was prepared from L-alanine, was employed as key step for this regio- and diastereoselective synthesis. The ene reaction is highly erythro-selective and the newly formed double bond in the allylic hydroperoxide 5 is exclusively E-configured. Reduction of the allylic hydroperoxide 5 and base-catalyzed deprotection provides a convenient and unprecedented synthesis of the optically active E-configured β-amino allylic alcohol merucathin from the corresponding acylated allylic amine 3.
报道了天然存在的merucathin的对映选择性和非对映选择性合成。由L-丙氨酸制备的双Boc保护的烯丙胺3的单线态氧烯反应被用作该区域和非对映选择性合成的关键步骤。烯反应具有高度的红选择性,烯丙基氢过氧化物 5 中新形成的双键完全是 E 构型。烯丙基氢过氧化物 5 的还原和碱催化的脱保护提供了从相应的酰化烯丙胺 3 合成光学活性 E 构型 β-氨基烯丙醇 merucathin 的便捷且前所未有的合成方法。
作者:Waldemar Adam、Chantu R. Saha-Möller、Simon B. Schambony、Katharina S. Schmid、Thomas Wirth
DOI:10.1111/j.1751-1097.1999.tb08241.x
日期:1999.10
preference of the singlet‐oxygen attack. Depending on the electronic properties of the double bond and the nature of the allylic substituent, threo or erythro selectivity may be imposed through hydrogen bonding, electrostatic and stericeffects and stereoelectronic alignment. Such directing properties, especially that of the hydroxy group, were also confirmed in the other reaction modes of singlet oxygen
如果在底物构象固定(1,3-烯丙基应变)中,与攻击性氧亲烯体相互作用的烯丙基取代基对齐,则可以控制单线态氧与无环烯烃反应的立体化学过程。选择了各种底物来阐明控制单线态氧攻击的感觉(苏式与赤式)和 ii 面部偏好程度所必需的烯烃特征。根据双键的电子特性和烯丙基取代基的性质,可以通过氢键、静电和空间效应以及立体电子排列来施加苏式或赤式选择性。这种导向性质,尤其是羟基的导向性质,在单线态氧的其他反应模式中也得到了证实,即手性萘醇的 [4+2] 环加成和金刚烷基取代的烯丙醇的 [2+2] 环加成。天然产物 Merucathin 和 Iso-dihydromahubanolide B 的合成是两个例子,其中这种立体控制的光氧化作用已被用作关键步骤,以选择性地建立所需的手性非对映体。