D. A. Evans Diastereoselective Peracid Epoxidation Chem 206 Stereoelectronic Implications of intramolecular Peracid Epoxidation The Directed Peracid Epoxidation a Transition State Hydrogen Bonding: Substrate as H-bond donor(Henbest I Per-arachidonic acid Epoxidation: Corey, JACS 101, 1586(1979) a Transition State Hydrogen Bonding: Peracid as H-bond donor(Ganem R-O require more acidic peracid both allylic alcohols and ethers OK 50:1 5:1 OTBS 1:8 OTBS 1:4 Me,C Ganem Tet. Let. 1985. 26. 4895O R O O H O C H C H2 O C H R R O H O R O C C C H2 H R H R O CF3 O O H O C H C H2 O R C H R O O H O CF3 C H2 R O C H C H R •• •• R O O O H O O H O H C R R C H C H2 O C R C R H C H2 O H O H O CF3 OH OTBS OH Me3C Me3C OTBS O H O O Me3C OH OTBS Me3C ● ● 1 : 7 5 : 1 1 : 8 12 : 1 100 : 1 1 : 4 1 : 6 24 : 1 100 : 1 5 : 1 24 : 1 50 : 1 Syn : Anti (CF3CO3H) Syn : Anti (m-CPBA) Syn : Anti (m-CPBA) Syn : Anti (CF3CO3H) Ganem Tet. Let. 1985, 26, 4895 require more acidic peracid both allylic alcohols and ethers OK require allylic or homoallylic alcohol ■ Transition State Hydrogen Bonding: Peracid as H-bond donor (Ganem) ‡ ‡ ■ Transition State Hydrogen Bonding: Substrate as H-bond donor (Henbest) The Directed Peracid Epoxidation D. A. Evans Diastereoselective Peracid Epoxidation Chem 206 ■ Per-arachidonic acid Epoxidation: Corey, JACS 101, 1586 (1979) Stereoelectronic Implications of intramolecular Peracid Epoxidation ● ● ● ●