Thalidomide -NH-(CH2)3-NH-Boc is a Boc-modified Thalidomide , which acts as a Cereblon ligand to recruit CRBN protein. The Boc protecting group at the end of Thalidomide -NH-(CH2)3-NH-Boc can be removed under acidic conditions to participate in the synthesis of PROTAC molecules. Thalidomide -NH-(CH2)3-NH-Boc is a key intermediate in the synthesis of CRBN-based designed PROTAC molecules targeting 11β-substituted estradiol.