The Ir(I) complexes of chiral spiro phosphinoâoxazoline ligands (SpinPhox) have demonstrated good to excellent enantioselectivity in the asymmetric hydrogenation (AH) of a variety of (E)-β,β-disubstituted α,β-unsaturated N-methoxy-N-methylamides, affording the corresponding optically active Weinreb amides with up to 97% ee.
Rhodium/diene-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated Weinreb amides
作者:Ryo Shintani、Takahiro Kimura、Tamio Hayashi
DOI:10.1039/b502921j
日期:——
Rhodium/chiral diene (S,S)-3b complex has been found to effectively catalyze the 1,4-addition of arylboronic acids to α,β-unsaturated Weinreb amides, furnishing useful β-chiral Weinreb amides in high enantioselectivity.
Synthesis of (R)-ar-turmerone and its conversion to (R)-ar-himachalene, a pheromone component of the flea beetle: (R)-ar-himachalene is dextrorotatory in hexane, while levorotatory in chloroform
作者:Kenji Mori
DOI:10.1016/j.tetasy.2004.11.077
日期:2005.2
(R)-ar-Turmerone was synthesized from (4-methylphenyl)acetic acid by employing Evans asymmetric alkylation as the key step. (R)-ar-Turmerone was converted to (R)-ar-himachalene, which was dextrorotatory in hexane while levorotatory in chloroform. Enantiomerically impure (75% ee) (R)-3-(4-methylphenyl)butanoic acid crystallized more readily than the enantiomerically pure one.
Examples are given to illustrate the use of chemical and/or enzymatic asymmetric reactions in the synthesis of the new pheromones of the broad-horned flour beetle, flea beetle, currant stem girdler and Colorado potato beetle. The relationships between stereochemistry and bioactivity among pheromones are summarized to emphasize biodiversity as revealed in pheromone perception.