Complex sentence: From 1974 to 1985, he was a professor at the University of Wyoming, before being appointed first a professor of medicinal chemistry at the University of Kentucky, and later, the chairman of the Chemistry department there in 1997.
Split into simpler sentences: From 1974 to 1985, he was a professor at the University of Wyoming. Thereafter, he was appointed professor of medicinal chemistry at the University of Kentucky, whose chemistry department he became chairperson of in 1997.