ABSTRACT
By the beginning of the 20th century, it was recognized that many diseases were caused by microorganisms. A scientist called Paul Ehrlich proposed the principle of chemotherapy, which stated that poisons might be developed that were selectively toxic to microorganisms rather than humans, and would thus prove useful medicines. Ehrlich investigated arsenic-based structures that would be less toxic than arsenic itself, and eventually developed salvarsan, which was introduced in 1907. At the beginning of the 20th century, two important groups of synthetic drugs were discovered – barbiturates and local anesthetics. Barbiturates were used as hypnotics or sedatives, and remained unchallenged in this role until the 1950s. The success of the local anesthetics established one of the important strategies used in medicinal chemistry – the simplification of complex natural products.
