Prins cyclization to tetrahydrofuran units of polyether antibiotics: Remarkable siloxy effect for stereocontrolled cyclization
作者:Koichi Mikami、Masaki Shimizu
DOI:10.1016/0040-4020(96)00252-9
日期:1996.5
A novel route to substituted tetrahydrofurans is described, which is based on the Lewis acid-promoted Prins cyclization with side chain formation of carbon-carbonbond. Bishomoallylic silyl ethers, rather than the (chloro)benzyl ethers and esters, provide selectivity 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.