The effect of substrate structure to the enzymatic synthesis of coumarin carboxamide derivatives under continuous-flow conditions^a.

Entry	Methyl nicotinate	R 2	Method	Time	Product	Yieldb (%)
1		CH(CH3)2	A	35 min	3a	86.2 ± 1.5
			B	24 h		67.1 ± 0.8
2			A	35 min	3b	68.5 ± 0.8
			B	24 h		54.2 ± 0.9
3			A	35 min	3c	65.2 ± 1.5
			B	24 h		54.3 ± 1.2
4			A	35 min	3d	71.2 ± 0.8
			B	24 h		62.8 ± 0.9
5		H	A	35 min	3e	86.8 ± 0.4
			B	24 h		68.7 ± 0.9
6		CH3	A	35 min	3f	83.3 ± 0.9
			B	24 h		75.9 ± 1.2
7		CH(CH3)2	A	35 min	3g	88.5 ± 0.7
			B	24 h		77.4 ± 1.5
8			A	35 min	3h	69.4 ± 1.8
			B	24 h		58.5 ± 0.7
9			A	35 min	3i	65.4 ± 0.5
			B	24 h		55.9 ± 0.8
10			A	35 min	3j	72.5 ± 0.7
			B	24 h		61.5 ± 0.5
11		H	A	35 min	3k	81.6 ± 0.7
			B	24 h		67.5 ± 0.7
12		CH3	A	35 min	3l	85.6 ± 1.5
			B	24 h		65.9 ± 0.7
13		CH(CH3)2	A	35 min	3m	85.1 ± 1.2
			B	24 h		69.8 ± 0.7
14			A	35 min	3n	75.5 ± 0.7
			B	24 h		57.8 ± 0.5
15			A	35 min	3o	73.8 ± 0.9
			B	24 h		52.5 ± 0.6
16			A	35 min	3p	75.4 ± 1.5
			B	24 h		58.6 ± 0.8
17		H	A	35 min	3q	81.6 ± 1.2
			B	24 h		66.5 ± 0.7
18		CH3	A	35 min	3r	82.2 ± 0.7
			B	24 h		62.3 ± 0.6

^aGeneral experimental conditions: Method A: continuous flow reactors, feed 1, dissolve 5 mmol of methyl nicotinate derivatives in 10 mL tert-amyl alcohol; feed 2, dissolve 10 mmol of amines in 10 mL tert-amyl alcohol, flow rate 17.8 μL min⁻¹, residence time 35 min, enzyme 870 mg, 50 °C. Method B: shaker reactors, add 5 mmol of methyl nicotinate derivatives, 10 mmol of amines and 20 mL tert-amyl alcohol to a 50 mL Erlenmeyer flask, enzyme 870 mg, 160 rpm, 50 °C, 24 h.

^bIsolated yield. Yield: 100 × (actually obtained amount/calculated amount). The data are presented as average ± SD of triplicate experiments.