Total synthesis of siphonazole and its O-methyl derivative, structurally unusual bis-oxazole natural products
作者:Jörg Linder、Alexander J. Blake、Christopher J. Moody
DOI:10.1039/b810855b
日期:——
The details of the first syntheses of the unusual bis-oxazole natural products siphonazole and its O-methyl derivative are reported. The cinnamyl substituted oxazole was constructed using diazocarbonyl chemistry, whereby the cinnamamide was reacted with the rhodium carbene derived from methyl 2-diazo-3-oxobutanoate to give a β-ketoamide that was cyclodehydrated to the corresponding oxazole-4-ester. Reduction to the corresponding aldehyde was followed by coupling with a zinc reagent derived from methyl 2-iodomethyl-5-methyloxazole-4-carboxylate, also prepared using rhodium carbene chemistry, to give, after oxidation of the resulting secondary alcohol, the desired bis-oxazole ketone. The syntheses were completed by hydrolysis of the ester and coupling of the 2,4-pentadienylamine side chain.
报道了不寻常的双噁唑天然产物siphonazole及其O-甲基衍生物的首次合成细节。采用重氮羰基化学构建了肉桂基取代的噁唑,将肉桂酰胺与来自甲基2-重氮-3-氧代丁酸酯的铑卡宾反应,生成β-酮酰胺,随后环脱水生成相应的噁唑-4-酯。将其还原为相应的醛后,与来自甲基2-碘甲基-5-甲基噁唑-4-羧酸酯的锌试剂耦合,同样使用铑卡宾化学进行合成,得到的次级醇经过氧化后,得到所需的双噁唑酮。合成通过水解酯和耦合2,4-戊二烯基胺侧链完成。