For every left hand, there is a matching right hand, and for every l-isomer, a d-isomer. So goes the mirror-image rule of chirality. Most molecules in nature exist in either of two chiral enantiomers, forms that mirror each other in structure. In chemistry, chiral molecules are important because one enantiomer of a given compound may be biologically active, whereas its mirror-image enantiomer is inactive. For example, the common amino acid alanine has two chiral forms—S-alanine and R-alanine—but only S-alanine is prevalent in proteins.
Enriching only the bioactive chiral forms of a compound has been a major focus among chemists for decades, and William S. Knowles is one of the founding pioneers of the field of chiral chemistry. Retired after more than 40 years at Monsanto (St. Louis, MO), Knowles was elected to the National Academy of Sciences (NAS) in 2004. Together with Ryoji Noyori and K. Barry Sharpless, Knowles was awarded the Nobel Prize in Chemistry in 2001 for his lifetime of trailblazing work in catalytic asymmetric synthesis, specifically in the area of hydrogenation (1, 2). Catalytic asymmetric synthesis is an enzyme-like process that can rapidly produce an excess of one chiral compound form, a process with numerous practical applications, such as production of industrial biomaterials and pharmaceuticals.
Born in 1917 in Taunton, MA, Knowles grew up in nearby New Bedford where his family was involved in business and maritime activities. He attended boarding school at Berkshire School (Sheffield, MA) in western Massachusetts and excelled in mathematics and science. “I was terrible at athletics and never made a team but quite easily led my class in academics,” says Knowles in his Nobel Prize autobiography. Studying in the Northeast provided Knowles with “a good lesson in New England thrift,” he says. “To get free …
