were dissolved in 50 g
toluene. A solution of triethylamine (0.081 g, 0.8 mmol) as catalyst
in 10 g toluene was added dropwise to the above solution at 50 C.
The mixture was kept stirring for 5 h, and then purified by rotary
evaporation under reduced pressure at 90 C for the removal of
solvent, catalyst and excess 2-mercaptoethanol. After cooled to
room temperature, white GM-ME was collected.