Chiral auxiliaries , The New Age of Organic SynthesisJuan Camilo OspinaJuan.camilo.ospina@correounivalle.edu.co Facultad De Ciencias Naturales Y Exactas, Universidad Del ValleSantiago De Cali - Valle

Chiral molecules and compounds play an important and decisive role in the current science and technology. Especially, life itself depends on these, many biological functions require precise intrinsic stereochemistry, many of the physical phenomena of the universe are determined by highly precise molecular interactions. When performing organic synthesis, its very important to control the stereochemistry of the compound to synthesize, because if the compound has isomers, can be harmful if synthesize the two. A major example of this is the well-known synthesis of Contergan, which had a sleeping pill drug thalidomide as active substance, which is synthesized with its two enantiomers, R-isomer Thalidomide, sedative had the desired property, but its enantiomer S-Thalidomide was teratogenic and produced malformations in fetuses. However, throughout history, control the stereochemistry of the synthesis, has not been entirely easy. Noyori[footnoteRef:1], verify that in the mid-90s, 90% of the drugs produced by humanity, were racemic. That is why the Chiral auxiliaries or chiral catalysts, are a great tool for the synthesis of drugs, since these chemical compounds bind a temporary synthesis to control the stereochemistry of the reaction, thus making it easier to obtain desired stereoisomer. [1: Noyori, Ryoji. Asymmetric catalysis: science and opportunities (Nobel lecture). Angewandte Chemie International Edition, 2002, vol 41. 2008.]

The pioneering research of Chiral catalysts, specifically in the hydrogenation reaction was Dr. William S. Knowles, born in the city of Taunton, Massachusetts, on June 1, 1917, who studied at Harvard University, then graduation he went to work at Columbia University, where he worked until his retirement in 1986. In 1968, Knowless found that rhodium element, can be used as a chiral compound to catalyze the asymmetric hydrogenation. Also, developed amino acid synthesis L-DOPA, which was very important for the treatment of Parkinson's disease.

Later, The Japanese chemist Ryoji Noyori, born in the city of Kobe in 1938, studied at Kyoto University and then completed his doctorate at Harvard University. Dr. Noyori, development Ru-BINAP compound, which is widely used for the synthesis of R-1,2-propansdiol. Active Compound antibiotic levofloxacin.

Both, won the Nobel Prize in Chemistry in 2001 for their joint work on the hydrogenation reaction using Chiral catalysts. But the 2001 award must be shared with another person, Dr. K. Barry Sharpless, who also performed great advances in chiral catalysis, but this time focused on oxidation reactions.

Dr. Sharpless was born in Philadelphia in the year 1941. He did his doctoral studies at Stanford University. He has professor at Harvard, MIT, and is currently a professor at the Scripps Research Institute in La Jolla in California. Dr. Sharpless, in a homologue and parallel way with colleagues, development progress in asymmetric catalytic reactions. He made many advances and discoveries in chemical oxidations, such as titanium, used as a molecular chiral to develop many important synthesis of drugs, including drugs to lower blood pressure.

These 3 great scientists have shown the scientific community and the world the importance of chiral auxiliaries as a sophisticated tool to obtain the proper synthesis of compounds necessary for every commitment. The need to improve the synthesis of chemicals, invites a scientist to motivated for develop new forms of asymmetric synthesis (or chiral synthesis) to increase the quality of life of mankind and also find ways to avoid damaging the planet.

References:

- Knowles, William. " Asymmetric Hydrogenations (Nobel Lecture) Angewandte Chemie International Edition. 2002. Vol 41 . 1998 2007.

- Noyori, Ryoji. Asymmetric catalysis: science and opportunities (Nobel lecture). Angewandte Chemie International Edition, 2002, vol 41. 2008-2022.

- Sharpless, K. Barry. Searching for new reactivity (Nobel lecture). Angewandte Chemie International Edition, 2002, vol 41. 2024-2032.

- Nozaki, H., et al. Homogeneous catalysis in the decomposition of diazo compounds by copper chelates: Asymmetric carbenoid reactions. Tetrahedron, 1968, vol. 24, no 9, p. 3655-3669.

- en.wikipedia.org/wiki/Chiral_auxiliary (Revisado: 15 de marzo de 2015).