We also evaluated the internal olefin presented in Table , conscious of the possible impact of trisubstitution on the reaction selectivity. Gratifyingly, we observed a significant level of enantioselectivity (25:75 er) for the hydrogenation upon changing the ligand from acacH to dibmH. This further supports the hypothesis that iron is present in the enantiodetermining step (H-atom transfer from an iron(II) thiol complex). In addition, a change of the solvent system to 95:5 MTBE:EtOH led to a shorter reaction time and higher er, the latter of which is consistent with our spectroscopic studies indicating that iron(II) thiol binding may be more favorable in less polar solvents. Additionally, we screened the alternate carbohydrate-derived thiols using the internal olefin and found similar trends, with the highest er still provided by C1 (see SI).