Born in Bavaria, Germany, Ralph Hirschmann came to the US in his teens. He graduated from Oberlin College before serving in the US Army for three years. He resumed his education at the University of Wisconsin (Madison) with W. S. Johnson as the Sterling Winthrop Fellow (1950). That year he was recruited by M. Tishler to join Process Research at Merck. He discovered the first rearrangement under stereoelectronic control, studied later in detail by E. J. Corey. With R. G. Denkenwalter he directed the first solution synthesis of an enzyme, announced jointly with Merrifield's solid phase synthesis in 1969.

Becoming increasingly interested in medicinal and bio-organic chemistry, he was appointed Executive Director of Medicinal Chemistry at Merck, West Point (PA) in 1974 and Vice President/Senior Vice President of Basic Research (Rahway) in 1976/1978, respectively.

Professional activities included serving on the NIH Medicinal Chemistry A Study Section, on several committees of the NSF, NRC and ACS, on over a dozen Editorial and Advisory Boards, and on the Boards of Trustees of Oberlin College, the Gordon Research Conferences, and others.

He holds three honorary Doctor of Science degrees and was elected member of the American Academy of Arts and Sciences and of the National Academy of Sciences. During his tenure as Merck's Head of Basic Research, his colleagues discovered and/or studied such blockbuster drugs as Mevacor, Vasotec, Primaxin and Ivermectin.

In 1988 he was invited to join the Department of Chemistry of the University of Pennsylvania as the first Research Professor in Chemistry. In 1994 he was appointed the Rao Makineni Professor of Bioorganic Chemistry.