Double Intramolecular S<sub>N</sub>‘ <i>O</i>-Cyclization for Stereoselective Synthesis of Bistetrahydrofuran Core of Acetogenins
作者:Pan Li、Jiong Yang、Kang Zhao
DOI:10.1021/jo981771c
日期:1999.4.1
A C-2-symmetric bistetrahydrofuran core of acetogenins has been prepared via double intramolecular S-N' O-cyclization reactions. Approaches using readily prepared both E- and Z-olefin substrates are investigated. The cyclization of E-olefins gave a mixture of two diastereomers with low selectivity, while the corresponding Z-olefins predominantly provided a desired trans,trans-bistetrahydrofuran product. The high diastereoselectivity is presumably controlled by a hydrogen-bonding transition state. An efficient enantioselective synthesis of this C-2-symmetric bistetrahydrofuran is also described. Sharpless asymmetric dihydroxylation was used for this approach.