Prins cyclization to tetrahydrofuran units of polyether antibiotics: Remarkable siloxy effect for stereocontrolled cyclization
作者:Koichi Mikami、Masaki Shimizu
DOI:10.1016/s0040-4039(00)60962-0
日期:1992.10
A novel route to substituted tetrahydrofurans is described, which is based on the Lewis acid-promoted Prins cyclization with side chain formation of CC bond. Bishomoallylic silyl ethers, rather than the (chloro)benzyl ethers and esters, provide selectively tetrahydrofurans, indicating the siloxy effect for facilitating the cyclization.
Remote asymmetric induction based on carbonyl-ene reactions with bishomoallylic silyl ethers: dramatic changeover of regioselectivity by the remarkable siloxy effect
作者:Masaki Shimizu、Koichi Mikami
DOI:10.1021/jo00049a011
日期:1992.11
A new approach to remote asymmetric induction is described for not only a 1,4- but also a 1,5-relationship, which is based on the carbonyl-ene reactions with chiral bishomoallylic silyl ethers. Silyl ethers, rather than alkyl ethers, exhibit beta-regiospecificity. Remarkably high levels of remote asymmetric induction can then be established with chiral bishomoallylic ethers to provide eventually a simple and efficient method for asymmetric induction.