Corwin Hansch and Toshio Fujita

The Hansch-Fujita Foundation recognizes the pioneering publications of these two scientists [1, 2, 3]. Although both were mature researchers at the time of their short collaboration in the early 1960s, together their invention of QSAR provided timeless guidelines as to how to translate differences in chemical structures into those properties that relate to differences in their biological properties.

Toshio Fujita (L) and Corwin Hansch (R).

Toshio Fujita (L) and Corwin Hansch (R).

The formulation of QSAR provided six key insights that remain relevant to this day: (1) Usually differences in more than one molecular property are required to understand the basis of differences in the biological properties of molecules. (2) Hydrophobicity as quantified by the logarithm of the octanol-water partition coefficient (log P) is key to understanding structure-activity relationships, (3) There is frequently an optimum log P associated with a particular biological response. (4) It is possible to estimate log P from a chemical structure. (5) A mathematical analysis, multiple regression analysis in their case, is necessary to identify correct relationships between molecular and biological properties. (6) A digital computer is necessary to explore the possible relationships. According to Google Scholar, their initial formulation of QSAR has been cited more than 2000 times (search: May 31, 2014) and their insights into the calculation of log P more than 1300 times. Both have been identified as citation classics.

Professor Hansch

After their collaboration, Professor Hansch continued teaching organic chemistry as Professor of Chemistry at Pomona College, teaching there from 1946 to 1988 and mentoring many undergraduate students and more than 40 visiting scientists and postdoctoral scholars. Importantly, he continued pursuing QSAR research until 2010 and published numerous books and more than 400 journal and review articles. He was the recipient of many awards, including the Smissman-Bristol Award in Medicinal Chemistry from the American Chemical Society in 1976, an honorary professorship from the University of Beijing, two Wig Awards for excellence in teaching at Pomona College, a Guggenheim Fellowship and numerous accolades from the American, Italian, and Japanese Chemical Societies. He was elected to the Royal Society of Chemistry in 1990 and inducted into the American Chemical Society Medicinal Chemistry Hall of Fame in 2007. 

Professor Hansch collected all of the QSAR equations that his group derived in a searchable database; in addition, he and Albert Leo collected a database of octanol-water partition coefficients that they measured or found in the literature. These databases, plus the CLOGP program developed by David Weininger, form the basic offerings of the BioByte Corporation that Professor Hansch and Albert Leo founded in 1995.

Professor Fujita

Professor Fujita returned to Kyoto University after their collaboration, where he became Professor of Pesticide and Bioregulation Chemistry (Professor Emeritus since 1992). He also continued to pursue QSAR, publishing approximately 290 original papers and review articles and editing four books. His work on QSAR was recognized by the Award for Research Achievement from the Pesticide Science Society of Japan, March 1979; the Award for Research Achievement from the Agricultural Chemical Society of Japan, March 1989; Recognition for Research Performance from the Division of Agrochemicals of the American Chemical Society, August 1992; and the International Award in Pesticide Chemistry from the American Chemical Society, August 1994. Professor Fujita´s academic activities include being president of the Pesticide Science Society of Japan from 1984 to 1986 and chairman of the Kansai Regional Section of Biotechnology and Agrochemistry between 1988 and 1990. 

Professor Fujita is inventor and chief developer of EMIL (Example-Mediated Innovation for Lead Evolution) software that contains a database of bioisosteric transformations (structural transformations of drugs and pesticides that retain the biological properties of the original). 

[1] Correlation of Biological Activity of Phenoxyacetic Acids with Hammett Substituent Constants and Partition Coefficients. 
Corwin Hansch, Peyton P. Maloney, Toshio Fujita, Robert M. Muir
Nature 194, 178 - 180 (14 April 1962);

[2] ρ-σ-π Analysis. A Method for the Correlation of Biological Activity and Chemical Structure
Corwin Hansch, Toshio Fujita 
J. Am. Chem. Soc., 1964, 86 (8), pp 1616–1626
DOI: 10.1021/ja01062a035
Publication Date: April 1964

[3] A New Substituent Constant, π, Derived from from Partition Coefficients
Toshio Fujita, Junkichi Iwasa, Corwin Hansch 
J. Am. Chem. Soc., 1964, 86 (23), pp 5175–5180
DOI: 10.1021/ja01077a028
Publication Date: December 1964