7 research outputs found
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