Enantiospecific syntheses of pseudopterosin aglycones. Part 2. Synthesis of pseudopterosin K–L aglycone and pseudopterosin A–F aglycone via a B→BA→BAC annulation strategy
作者:Philip J. Kocienski、Alessandro Pontiroli、Liu Qun
DOI:10.1039/b102961b
日期:——
The enantiomeric aglycones of pseudopterosins KâL and AâF are synthesised from (â)- and (+)-isopulegol respectively. Key features are (a) the construction of the C3 stereogenic centre by a directed epoxidationâreduction sequence (KâL); (b) the creation of the C3 stereogenic centre by a Pfaltz asymmetric conjugate reduction (AâF); (c) benzannulation of a cyclic ketone starting with an α-oxoketene-S,S-acetal to give a tetrahydronaphthol ether; and (d) a diastereoselective intramolecular electrophilic aromatic substitution using an allylic sulfone as the electrophilic trigger to complete the hexahydro-1H-phenalene core. An X-ray structure of compound 50 was determined.
假矮伞素K‒L和A‒F的对映体苷元分别由(−)-异胡薄荷醇和(+)-异胡薄荷醇合成。关键特征包括:(a)通过定向环氧化‒还原序列构建C3手性中心(假矮伞素K‒L);(b)通过Pfaltz不对称共轭还原创建C3手性中心(假矮伞素A‒F);(c)从α-氧代烯酮-S,S-缩酮开始,环酮进行苯并环合反应生成四氢萘酚醚;以及(d)以内烯基砜为亲电触发剂,通过非对映选择性分子内亲电芳香取代反应完成六氢-1H-菲啶核的构建。化合物50的X射线结构已被确定。