General procedure: Tetraethylene glycol monomethyl ether was synthesized from the compound (CAS: 727986-31-4). This was done as follows: to a solution of 2-(2,5,8,11-tetraoxatridecan-13-yloxy)tetrahydro-2H-pyran (280 mg, 0.96 mmol) in methanol (5 mL) was added pyridinium salt of p-toluenesulfonate (PPTS, 24 mg, 0.096 mmol) at 0 °C. The reaction mixture was slowly warmed from 0 °C to room temperature and stirred for 16 hours. Upon completion of the reaction, the solvent was removed by concentration under reduced pressure to give the crude product. Subsequently, the crude product was purified using silica gel column chromatography with an eluent of 5% methanol/dichloromethane (v/v), resulting in the target compound 5-2A (180 mg, 0.87 mmol, 90% yield) as a pale yellow liquid.
