Table 3. Selected results for the optimization of the performance of [η⁶-(arene)Ru(Biot-p-L)Cl]⊂(strept)avidin as an artificial metalloenzyme for the transfer hydrogenation of acetophenone derivatives 2a-c by using formate·boric acid as a reducing agent in 0.15 M Mops buffer.

Entry	Ligand	η6-arene	Protein	Substrate	Temperature, °C	Time, h	Conversion, %	ee, %
1	Biot-p-L	p-cymene	Sav	2a	45	40	40	66 (R)
2	Biot-p-L	Benzene	Sav	2a	45	40	30	63 (S)
3	Biot-p-L	p-cymene	Sav	2a	55	64	82	68 (R)
4	Biot-p-L	p-cymene	P64G Sav	2a	55	64	90	85 (R)
5	Biot-p-L	p-cymene	P64G Sav	2b	55	64	97	89 (R)
6	Biot-p-L	p-cymene	P64G Sav	2c	55	64	92	94 (R)
7	Biot-p-L	p-cymene	P64G S112 G Sav	2a	55	40	Quantitative	67 (R)
8	Biot-p-L	p-cymene	P64G S112 G Sav	2b	55	40	Quantitative	88 (R)
9	Biot-p-L	p-cymene	P64G S112 G Sav	2c	55	40	Quantitative	90 (R)
10	Biot-p-L	Benzene	P64G Sav	2c	45	64	34	57 (S)
11	Biot-p-L	Benzene	P64G Sav	2c	55	64	44	44 (S)

All catalytic runs were carried out at pH_initial = 6.25 by using the mixed buffer HCO₂Na (0.5 M) + B(OH)₃ (0.47 M) combined with Mops (0.15 M) with a Ru/substrate 2 a-c/formate ratio of 1:100:4,500. Conversions and enantioselectivity were determined by HPLC on Chiralcel OB-H.