Efficient Conditions for Conversion of 2-Substituted Furans into 4-Oxygenated 2-Enoic Acids and Its Application to Synthesis of (+)-Aspicilin, (+)-Patulolide A, and (−)-Pyrenophorin
作者:Yuichi Kobayashi、Miwa Nakano、G. Biju Kumar、Kiyonobu Kishihara
DOI:10.1021/jo980942a
日期:1998.10.1
the ester 6. Stereocontrolled reduction of 6 followed by deprotection and the Yamaguchi macrocyclization furnished (+)-aspicilin. For the synthesis of (+)-patulolide (Scheme 3) and (-)-pyrenophorin (Scheme 4), the intermediates are the furans 38 and 44, which were prepared easily by the classical methods using furyllithium 33. The furan ring oxidations proceeded as well, furnishing acids 40 and 46 in
通过在THF-丙酮-H(2)O中使用NBS /吡啶,发现2-取代的呋喃1a,b,c可以方便地转化为反式4-氧-2-烯醛2a,b,c,产率为62-87% (<-15摄氏度,然后室温)或NBS / NaHCO(3)在丙酮-H(2)O中的溶液(<-15摄氏度,然后在添加吡啶后室温)。使用NaClO(2)进一步氧化烯类2a-c导致反式4-氧代-2-烯酸3a-c的产率很高。考虑到这种转变,我们设计了(+)-aspicilin,(+)-patulolide和(-)-pyrenophorin的合成。如路线1和2所示,在合成(+)-阿斯匹林林中,关键中间体6由其中连接有2-呋喃基的烯烃7制备。7的AD反应确保了Aspicilin的C(5)和C(6)立体化学,随后使用上述方案进行的转化获得了酯6。立体控制还原6,然后脱保护并由Yamaguchi大环化提供(+)-aspicilin。对于合成(+)-巴特洛利德