Total Synthesis of (−)- and (+)-Decarbamoyloxysaxitoxin and (+)-Saxitoxin
作者:Osamu Iwamoto、Ryoko Shinohara、Kazuo Nagasawa
DOI:10.1002/asia.200800382
日期:2009.2.2
AbstractPlaying the sax: The enantioselective total syntheses of (−)‐ and (+)‐decarbamoyloxysaxitoxin (doSTX) and (+)‐saxitoxin (STX) are reported. A new methodology was developed for the synthesis of STXs, featuring discriminative reduction of the nitro group and NO bond in nitroisoxazolidine.magnified imageEnantioselective total syntheses of (−)‐ and (+)‐decarbamoyloxysaxitoxin (doSTX) and (+)‐saxitoxin (STX) were achieved. The characteristic spiro‐fused cyclic guanidine structure of STX was constructed by oxidation at the C4 position with IBX via an α‐iminium carbonyl intermediate and acid‐promoted cyclization of guanidine at the C5 position. A second‐generation methodology was developed for the synthesis of STX, featuring discriminative reduction of the nitro group and NO bond in nitroisoxazolidine. This approach provides efficient access to the key diamine intermediate for STXs.