(a) Orientation of 24(R), for which the NH group of the ligand is hydrogen-bonded with the calcium coordinating residues N224 or D269. In the latter case, this could interfere with a potential catalytic dyad. (b) The alkyl side chain was often observed to be facing H285, and the oxygen of the aryloxy and alkoxy group is often hydrogen-bonded to N168, which, in turn, is hydrogen-bonded to D183.