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Solid‐Phase Development of Chiral Phosphoramidite Ligands for Enantioselective Conjugate Addition Reactions
Author(s) -
Huttenloch Oliver,
Laxman Eltepu,
Waldmann Herbert
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20021018)8:20<4767::aid-chem4767>3.0.co;2-o
Subject(s) - enantioselective synthesis , phosphoramidite , conjugate , combinatorial chemistry , solid phase synthesis , ligand (biochemistry) , chemistry , chiral ligand , cyclohexenone , steric effects , catalysis , stereochemistry , organic chemistry , mathematics , peptide , oligonucleotide , receptor , dna , mathematical analysis , biochemistry
The development of a method for the optimization of chiral ligands for the steric steering of enantioselective Cu‐catalyzed conjugate additions of Zn‐alkyls to enones is described. The method is based on combinatorial principles and solid‐phase techniques. It includes the combinatorial synthesis of chiral bispidine‐derived ligands embodying a phosphoramidite group on the solid phase and their investigation in immobilized form in the conjugate addition of ZnEt 2 to cyclohexenone as test reaction. The best identified ligands were also synthesized separately and investigated in its soluble form. The results obtained for the polymer‐bound ligands correctly mirrored the performance of the soluble ligands. The library embodied members giving ee values varying between 3 and 67 %. The “positional scanning” approach proved to be invalid for the study of the ligand system, indicating that this approach in general should be applied with care. Taken together, the method allowed for rapid and efficient optimization of the ligands and led to the development of the first enantioselective, Cu‐catalyzed conjugate addition reaction with a polymer‐bound ligand.