TABLE 2.

Effect of isopropyl ether content on regioselective acylation of arbutin with vinyl vanillic acid catalyzed by immobilized PEL.

Solvent	Time (h)	Conversion (%)	6′-Regioselectivity (%)
THF-Isopropyl ether (5%, v/v)	1	4.8	>99
	92	45	>99
THF-Isopropyl ether (10%, v/v)	1	7.2	>99
	80	60	>99
THF-Isopropyl ether (15%, v/v)	1	11.4	>99
	76	69	>99
THF-Isopropyl ether (20%, v/v)	1	13.2	>99
	72	73	>99
THF-Isopropyl ether (25%, v/v)	1	10.8	>99
	76	70	>99
THF-Isopropyl ether (30%, v/v)	1	7.6	>99
	80	64	>99

Reaction conditions: 0.04 mmol arbutin, 0.20 mmol vinyl vanillic acid, 50 U/mL immobilized PEL, 2 mL anhydrous solvent mixtures, 50°C, 200 r/min.