Hydroxyl-Substituted Ladder Polyethers via Selective Tandem Epoxidation/Cyclization Sequence

A new and highly selective method for the synthesis of hydroxyl-substituted tetrahydropyrans is described. This method utilizes titanium(IV) isopropoxide and diethyl tartrate to perform a diastereoselective epoxidation followed by in situ epoxide activation and highly selective endo-cyclization to form the desired tetrahydropyran ring. The HIJ ring fragment of the marine ladder polyether yessotoxin was synthesized using this two-stage tactic that proceeds with high efficiency and excellent regioselectivity.National Institute of General Medical Sciences (U.S.) (GM72566)National Science Foundation (U.S.) (CHE-0234877)National Science Foundation (U.S.) (CHE-9808061

Hydroxyl-Substituted Ladder Polyethers via Selective Tandem Epoxidation/Cyclization Sequence

A new and highly selective method for the synthesis of hydroxyl-substituted tetrahydropyrans is described. This method utilizes titanium­(IV) isopropoxide and diethyl tartrate to perform a diastereoselective epoxidation followed by in situ epoxide activation and highly selective <i>endo</i>-cyclization to form the desired tetrahydropyran ring. The <i>HIJ</i> ring fragment of the marine ladder polyether yessotoxin was synthesized using this two-stage tactic that proceeds with high efficiency and excellent regioselectivity

Benzylic Phosphates as Electrophiles in the Palladium-Catalyzed Asymmetric Benzylation of Azlactones

Palladium-catalyzed asymmetric benzylation has been demonstrated with azlactones as prochiral nucleophiles in the presence of chiral bisphosphine ligands. Benzylic electrophiles are utilized under two sets of reaction conditions to construct a new tetrasubstituted stereocenter. Electron density of the phenyl ring dictates the reaction conditions, including the leaving group. The reported methodology represents a novel asymmetric carbon–carbon bond formation in an amino acid precursor