Rather than trying to redesign the force field from scratch, we decided to add a simple filter to the existing force field. The conformation search was performed as before, but all the Chair and Boat B structures that were generated were discarded. This filtering process is the simplest method of emphasising the importance of the boat transition structures. However, we are interested in producing useful tools for organic chemists as rapidly as possible, and this filtering approach enabled us to obtain such a tool very quickly. The new protocol was applied to a range of ketones and the two different chiral ligands.
Experimental results are available for the reaction of the chiral enol borinates with methacrolein.
The experimental and the computational results for the face selectivity on the methacrolein are listed in Table 1 . The right hand column of the table allows you to view the global minimum structure for each diastereomeric transition structure. The new protocol accounts for the reversal in selectivity observed in changing from Z enol borinates to unsubstituted enol borinates. It also mirrors the trends in changing the size of the group opposite to the side of enolisation. It appears to be a useful tool, therefore, for the chiral ligands that have been tested.