Total Synthesis of (−)-Neplanocin A by Using Lithium Thiolate-Initiated Michael−Aldol Tandem Cyclization Reaction
作者:Masashi Ono、Katsumi Nishimura、Hiroshi Tsubouchi、Yasuo Nagaoka、Kiyoshi Tomioka
DOI:10.1021/jo016090n
日期:2001.11.1
of this synthesis is a stereoselective construction of five-membered ring of neplanocin A by intramolecular aldol reaction of the lithium enolate that was generated by conjugate addition of lithium thiolate. TBS-protected chiral omega-oxo-alpha,beta-unsaturated ester 16, which was prepared from D-mannitol, was treated with 1.2 equiv of lithium benzylthiolate in THF at -20 degrees C to give three separable
合成(-)-Neplanocin A(1),S-腺苷同型半胱氨酸水解酶抑制剂。该合成的特征是通过烯醇锂的分子内醇醛羟醛缩合反应的分子内醛醇缩合反应,形成的新霉素A的五元环的立体选择性构建,该烯醇式锂通过共轭加成硫醇锂而产生。由D-甘露糖醇制备的TBS保护的手性ω-氧代-α,β-不饱和酯16在-20℃下用1.2当量苄基硫醇锂的THF溶液处理,得到三种可分离的环化产物,收率和立体选择性好。在保护基团转化之后,通过氧化成亚砜并随后热消除,除去21的苄基硫烷基部分,得到所需的双键。通过30的官能团转化,完成了(-)-neplanocin A(1)的全合成。