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.
Synthesis of<i>cis</i>-Fused Bicyclic Systems by Radical Cyclization Approach: Formal Synthesis of Ethisolide and<i>iso</i>-Avenaciolide
作者:Gangavaram V. M. Sharma、Devoju Harinada Chary
DOI:10.1080/00397911.2013.871562
日期:2014.6.18
iso-avenaciolide was achieved using furanoid glycal-vinyl radical intermediates. The vinyl radical cyclization by 5-exo-dig mode gave the cis-fused bicyclic systems with an efficient introduction of the exo-methylene group, besides helping in the inversion of the adjacent stereocentre. Further, the study describes the synthesis of cis-fused bicyclic systems from L-arabinose and D-xylose for the creation