Table 2. Selected results for the genetic optimization of the performance of [η⁶-(arene)Ru(Biot-p-L)CI]⊂(strept)avidin as an artificial metalloenzyme for the transfer hydrogenation of acetophenone 2a by using formate·boric acid as a reducing agent.

Entry	Ligand	η6-arene	Protein	Conversion, %	ee, %
1	Biot-p-L	p-cymene	r-GAvi	40	22 (R)
2	Biot-p-L	p-cymene	S112G Sav	90	28 (R)
3	Biot-p-L	p-cymene	V47G Sav	42	68 (R)
4	Biot-p-L	p-cymene	K80G Sav	54	65 (R)
5	Biot-p-L	p-cymene	P64G Sav	54	72 (R)
6	Biot-p-L	p-cymene	P64G S112G Sav	95	58 (R)
7	Biot-p-L	Benzene	S112G Sav	42	8 (S)
8	Biot-p-L	Benzene	V47G Sav	8	56 (S)
9	Biot-p-L	Benzene	K80G Sav	31	51 (S)
10	Biot-p-L	Benzene	P64G Sav	30	58 (S)

All catalytic runs were carried out at 45°C for 40 h at pH_initial = 6.25, using a Ru/acetophenone 2a/formate ratio of 1:100:4,200, by using the mixed buffer HCO₂Na(0.5M)+B(OH)₃ (0.47 M) as a formate source. Conversions and enantioselectivities were determined by HPLC on Chiralcel OB-H.