Louis Pasteur,Chemist: An Account of His Studies of Cinchona Alkaloids

Pasteur carried out pioneering work on cinchona alkaloids and their derivatives and his studies led to important discoveries. He examined crystals of cinchona alkaloids for his correlation of crystal hemihedrism with molecular chirality, studies that led Pasteur to the discovery of physicochemical differences between diastereoisomeric salts of tartaric acids with optically active cinchona bases, an important insight into fundamentals of molecular chirality. These physicochemical differences also led to Pasteur’s invention of the vital method of racemate resolution through diastereoisomeric derivatives. Pasteur clarified the confusion around the cinchona alkaloids by elucidating their identities and relations. He discovered the conversion of the major cinchona alkaloids to quinicine and cinchonicine, a finding subsequently of considerable importance in studies of the structure and synthesis of the major cinchona alkaloids. The reaction producing quinicine and cinchonicine led Pasteur to the discovery of the racemization of tartaric acid and the finding of meso‐tartaric acid, fundamental breakthroughs in the development of stereochemistry.