Samuel J. Danishefsky
Wolf Prize Laureate in Chemistry 1995/6
Samuel J. Danishefsky
Affiliation at the time of the award:
Memorial Sloan-Kettering Cancer Center, USA
Columbia University, USA
“for designing and developing novel chemical reactions which have opened new avenues to the synthesis of the synthesis of complex molecules, particularly polysaccharides and many other biologically and medicinally important compounds.”
Over almost five decades, Professor Gilbert Stork has changed the face of organic chemistry , and organic synthesis in particular. Stork´s contributions to the development of theories of stereoelectronic control over chemical reactions, include the SN2´ reaction, polyene cyclizations, alkylation reactions with enolates and enolate equivalents, reactions involving enamines and metalloenamines, the paradigm of trapping kinetic enolates, and various annulation reactions. Stork´s pioneering studies into free radical cyclizations have been recognized as one of the most powerful and concise strategies for assembling polycyclic natural products. Once considered the least tractable of synthetic intermediates, free radical chemistry is now routinely practiced in synthetic laboratories throughout the world.
Professor Samuel J. Danishefsky has developed a number of new concepts in organic reactivity, thoroughly investigated the relevant stereochemical and mechanistic issues and subsequently provided new solutions to demanding problems in natural product synthesis. Examples include his polyannulating reagents in steroid synthesis, his now routinely employed dienes for Diels-Alder and hetero-Diels-Alder reactions, and more recently, his use of glycals for the synthesis of oligosaccharides. The capacity that these methodologies bring to the synthesis of complex structures which bear multiple asymmetric centers is a major triumph in chemistry.
The synthesis of complex polysaccharides has been one of the long-standing problems in synthesis. Such compounds play a crucial role in many biologically important phenomena, including cell adhesion, enzyme inhibition, determination of blood groups, immune response and cancer. Polysaccharides represent one of the three most important classes of biopolymers. While the synthesis of the other two – polynucleotides and polypeptides – has reached a satisfactory level of maturity with an immense impact on the study of biology and on medicine, the synthesis of polysaccharides has remained a formidable challenge.
In 1993 Danishefsky announced a highly efficient synthesis of oligosaccharides on a polymer support using same of the mutually developed tools. More recently, he has extended the method to the solid-phase synthesis of glycopeptides. This work has brought us to the threshold of a new era where complex carbohydrates can be assembled with an unprecedented selectivity and efficiency. Some of these fully synthetic compounds, such as the human breast cancer tumor antigen, are now being evaluated with respect to anticancer vaccines.
The influence of this mentor/disciple couple on several generations of chemists in organic synthesis and related bioorganic areas has been immense. Their noncompromising commitment to academic excellence has produced hundreds of top-class organic chemists, many of which are now university professors and key scientists in the chemical and bio-medical industries around the world.