By carefully choosing acidic additives and reaction media they can switch the enforced sense of diastereo-induction of the catalyst, in this case a cinchona-based primary amine, to obtain either the syn or anti product with high enantioselectivity. Find out how to ‘control’ the stereochemistry of the products here:
Diastereodivergent Asymmetric Sulfa-Michael Additions of α-Branched Enones using a Single Chiral Organic Catalyst
Xu Tian, Carlo Cassani, Yankai Liu, Antonio Moran, Atsushi Urakawa, Patrizia Galzerano, Elena Arceo, and Paolo Melchiorre*
J. Am. Chem. Soc., 2011, 133 (44), pp 17934–17941
This way they synthesised 100 new bidentate chiral diphosphines. The chirality stems from the chiral diol at the top of the molecule and it is transduced all the way down the molecule over 10 bonds or more.
They use this library of diphosphines for Rh-catalysed asymmetric hydrogenation obtaining ee’s of up to 92%.Enantioselective Supramolecular Catalysis Induced by Remote Chiral Diols
Piet W. N. M. van Leeuwen*, David Rivillo, Matthieu Raynal, and Zoraida Freixa
J. Am. Chem. Soc., Article ASAP