The first step was to protect the amino group of Tris by using t-butyloxycarbonyl anhydride((Boc)2O),then mPEG was activated by changing hydroxide terminal into acid chloride and carboxylation of mPEG was fulfilled before.

• 利用叔丁氧羰基酸酐((Boc)2O)对Tris上的氨基进行保护,对mPEG端羟基依次进行羧基化、酰氯化等活化处理,通过酰氯与羟基的官能团反应合成出目标分子。