Free radical 5-exo-dig cyclization as the key step in the synthesis of bis-butyrolactone natural products: experimental and theoretical studies
作者:Gangavaram V. M. Sharma、Devoju Harinada Chary、Nagula Chandramouli、Florian Achrainer、Sateesh Patrudu、Hendrik Zipse
DOI:10.1039/c1ob00019e
日期:——
Radical cyclization reactions were performed by 5-exo-dig mode to yield cis-fused bicyclic systems, leading to the synthesis of bis-butyrolactone class of natural products. The study was aimed at understanding the impact of alkyl side chains of furanoside ring systems in L-ara configuration on the radical cyclization. It was amply demonstrated by experimental studies that the increase in the length of the alkyl side chain has an effect on the cyclization: while efficient cyclization reactions could be realized with methyl and ethyl side chains, the yields were significantly reduced in the case of n-pentyl side chain. Theoretical studies using DFT and (RO)MP2 methods were carried out to analyze the influence of the substitution pattern on the cyclization barriers.
采用5-exo-dig模式进行自由基环化反应,以获得顺式融合的双环系统,从而合成了双丁内酯类自然产物。本研究旨在了解L-ara构型的呋喃苷环系统中的烷基侧链对自由基环化反应的影响。实验研究充分表明,烷基侧链长度的增加对环化反应有影响:在甲基和乙基侧链的情况下可以实现高效的环化反应,而在正戊基侧链的情况下,产率显著降低。使用DFT和(RO)MP2方法进行了理论研究,以分析取代模式对环化势垒的影响。