Thalidomide -4-O-CH2-COO(t-Bu) is t-Bu modified Thalidomide , which is the final step intermediate in the synthesis of Thalidomide -4-OH. Thalidomide -4-O-CH2-COO(t-Bu) acts as a Cereblon ligand to recruit CRBN proteins. The t-Bu protecting group at the end of Thalidomide -4-O-CH2-COO(t-Bu) can be removed under acidic conditions to participate in the synthesis of PROTAC molecules. Thalidomide -4-O-CH2-COO(t-Bu) is a key intermediate in the synthesis of CRBN-based designed PROTAC molecules.