The new compound Thalidomide was developed in the laboratories of Grünenthal under the authority of Dr. Heinrich Mückter, Grünenthal’s research director at the time. While trying to synthesize new substances, Mückter and his team managed to create Phthalimidoglutarimid (internal name: K 17, later called Thalidomide) in early 1954. They soon realized their new compound had a sedative effect. Mückter was later credited with being the inventor of Thalidomide.
Source: Anklageschrift (indictment) from 1967, today archived at the National Archives of North Rhine-Westphalia in Duisburg, Germany (Rheinland Division, Gerichte Rep. 139, No. 1–396), p. 45.