Stereoselective synthesis of freelingyne and related γ-alkylidenebutenolides via vinylogous Mukaiyama aldol additions
作者:Frank von der Ohe、Reinhard Brückner
DOI:10.1039/b002903n
日期:——
Following the strategy of Scheme 1, a Mukaiyama aldol addition/anti-elimination route to stereopure γ-alkylidenebutenolides 4 was established. The addition giving 27 was only moderately diastereoselective but the products lk- and ul-27 were chromatographically separable (Scheme 4). They underwent highly selective anti-eliminations in the presence of triflic anhydride–pyridine or Burgess' reagent, furnishing
遵循的策略 方案1,建立了向立体纯γ-亚烷基丁烯内酯4的Mukaiyama醛加成/抗消除途径 。给出的加成27仅具有中等非对映选择性,但产物lk-和ul - 27在色谱上是可分离的(方案4)。他们在三氟甲磺酸酐-吡啶或伯吉斯试剂的存在下进行了高度选择性的抗消除作用,分别提供了含噻吩的丁烯内酯Z-和E - 28(方案5)。的向山羟醛反应导致化合物29 100% LK -选择性时由BF介导的3醚合物和87:13微升-选择性在ZnBr存在2(方案6)。所产生的丁烯羟的斯蒂芬-卡斯特罗接头LK -和UL - 29与3-ethynylfuran与立体化学完整性的完整保护(进行方案7)。随后的抗水-eliminations物最好通过与DEAD-PPH治疗实现3。它们提供freelingyne(ž - 9)配有DS = 92:8及其异构体ë - 9与DS = 98:2(方案8)。类似地,不同取代的(三甲