Versatilechiralbuildingblocks for the construction of chiral natural products bearing a secondarymethylgroup have been efficiently prepared from (S)-O-benzylglycidol.
New asymmetricconjugatereduction of beta,beta-disubstituted alpha,beta-unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6-bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)-4-Phenyl-3-penten-2-one and (E)-4-phenyl-4-isopropyl-3-penten-2-one were readily reduced at 60 degrees C in 95 % ee and 98 % ee, respectively
Chiral rhodium(bisoxazolinylphenyl) complexes reduced α,β-unsaturatedesters in high enantioselectivity up to 97-98% ee in the combination of alkoxyhydrosilanes.
Azabis(oxazolines) prove to be superior ligands for the enantioselective, cobalt(II)-catalyzed conjugatereduction of α,β-unsaturated carbonylcompounds with sodium borohydride. β-Trisubstituted α,β-unsaturated esters and amides as well as γ-butenolides are readily converted to their corresponding saturated counterparts with enantioselectivities up to 97% ee.
SYNTHESIS OF THE SEX-ATTRACTANT OF PINE SAWFLIES (DIPRION SPECIES); (2<i>S</i>,3<i>R</i>,7<i>R</i>)- AND (2<i>S</i>,3<i>R</i>,7<i>S</i>)-3,7-DIMETHYLPENTADECAN-2-OL
作者:Tadashi Kikukawa、Motomasa Imaida、Akira Tai
DOI:10.1246/cl.1982.1799
日期:1982.11.5
candidate epimers, (2S,3R,7R)-and (2S,3R,7S)-3,7-dimethylpentadecan-2-ol were synthesized by the coupling reaction of optically active C5 and C12 units. The C12 units, (R)-(−)-and (S)-(+)-1-bromo-2-methyludecane were preparedfrom (R)-(+)-pulegone. The C5 unit, (2R,3S)-2-methyl-3-tetrahydropyranoxy-1-tosyloxybutane was derived from (2S,3S)-2-methyl-3-hydroxybutyric acid prepared by the reported prodedure