A synthesis of the spiroacetal moiety of milbemycin β<sub>3</sub>
作者:Philip Kocienski、Stephen D. A. Street
DOI:10.1039/c39840000571
日期:——
Intramolecular reaction of an enol silylether with a dioxonium ion generated by treatment of the 1,5,7-trioxaspiro[5.5]undecane (5b) with BF3·Et2O was the key step in a synthesis of the 1,7-dioxaspiro[5.5]undecane moiety (2) of Milbemycin β3(1).
Stereoselective Aldol-Type Cyclization Reaction Mediated by Dibutylboron Triflate/Diisopropylethylamine
作者:Sanjib Das、Lian-Sheng Li、Subhash C. Sinha
DOI:10.1021/ol036229b
日期:2004.1.1
[reaction: see text] Dibutylboron triflate/diisopropylethylamine mediated aldol-type cyclization provides an expedient route for the stereoselective synthesis of cyclic ethers in a single step. The method is highly efficient for the stereoselective synthesis of 4-cis-tetrahydropyranones. The reaction is proposed to proceed via an S(N)1-type mechanism through a chair-like transition state, in which