Lemieux, Raymond Urgel
LEMIEUX, RAYMOND URGEL
(b. Lac La Biche, Alberta, Canada, 16 June, 1920; d. Edmonton, Alberta, Canada, 22 July 2000),
carbohydrate chemistry, synthesis, conformational analysis, NMR coupling constants, stereoelectronic effects, molecular recognition, glycobiology.
Lemieux was one of the outstanding chemists of the second half of the twentieth century. His contributions spanned a wide area that included stereochemistry, nuclear magnetic resonance (NMR)-based methods for structural and configurational assignments, synthetic methods and molecular recognition. Lemieux’s insight into chemical problems resulted in numerous seminal discoveries such as the first synthesis of sucrose, the correlation of vicinal coupling constants with configuration, the anomeric effect, the first chemical synthesis of the human blood group substances, and numerous contributions to molecular modeling and molecular recognition of carbohydrates by proteins. His work influenced organic chemistry extensively, and was a determining factor in converting carbohydrate chemistry from an academic specialization to one of great practical importance in chemistry, biology and medicine. Lemieux’s influential role was recognized when, with twenty-one world-renowned chemists, he was invited by the American Chemical Society to contribute to the autobiographical series, “Profiles, Pathways and Dreams,” which documents the development of modern organic chemistry through the research careers of chemists who made seminal contributions to the field. Lemieux’s contribution, Explorations with Sugars, How Sweet It Was, is an excellent account of his research from 1946–1990.
Lemieux was widely recognized for his scientific achievements. Amongst his most notable awards were the Gairdner Foundation International Award (1985), the Rhône-Poulenc Award of the Royal Society of Chemistry (1989), the King Faisal International Prize in Science (1990), and the Wolf Prize for Chemistry (1999).
Family Background and Formative Development . Raymond Urgel Lemieux was born on 16 June 1920, in the small prairie community of Lac La Biche (population 75– 300 during the 1921–1931 period), two hundred kilometers northeast of Edmonton, Alberta. Both his parents traced their roots to France. His mother died when he was seven and sometime later the family moved from Lac La Biche to Edmonton (the provincial capital of Alberta, with a population in 1935 of about 80,000). Lemieux was a good student and began his education in the fall of 1939 at the University of Alberta, Edmonton. In the spring of 1943 he graduated and later the same year he left Edmonton for Montreal, Quebec (a three-day train trip) and McGill University, where he registered for graduate studies with Clifford Purves at the Pulp and Paper Research Institute of Canada.
By 1946 Lemieux had completed studies for his doctoral dissertation and the possibility of postdoctoral studies attracted him. He had become completely entranced by stereochemistry and the discovery that the antibiotic streptomycin was a carbohydrate was of great interest. When he discovered that research on streptomycin was going on in the laboratory of Melville Wolfrom, Lemieux applied for postdoctoral studies in the famous carbohydrate group at Columbus, Ohio. The move to Ohio held far greater significance, as it was at Ohio State University that Raymond met Virginia McConaghie, who was studying for her PhD degree in high-resolution infrared spectroscopy. They were married in New York City in 1948, and over the ensuing years in locations from Saskatoon, Saskatchewan to Ottawa, Ontario and back to Edmonton, they raised five daughters and one son.
Early Research . At Ohio State University Lemieux was involved in the structural elucidation of streptomycin. He also became fascinated by the configurational correlation of sugars and amino acids. Techniques he was using to elucidate the structure of streptomycin appeared to be well suited to the controlled degradation of D-glucosamine to give L-alanine thereby providing a correlation with the relative configuration of D-glyceraldehyde (Figure 1).
This work served as a milestone in stereochemistry by linking the stereochemical notation for amino acids with that for sugars.
In 1947 Lemieux became an assistant professor at the University of Saskatchewan, and two years later he joined the National Research Council’s (NRC) Prairie Regional Laboratory, also in Saskatchewan. During this period he attracted considerable public and scientific attention with the first rational synthesis of sucrose. During the 1947–1954 period he began his studies and lifelong interest in the chemistry of the anomeric center (the aldehyde or ketone carbon atom of a sugar that is the most reactive and the atom through which one sugar is joined to another to create oligosaccharides and polysaccharides). During this period he attracted considerable public and scientific attention with the first rational synthesis of sucrose.
It was obvious that the methods available at the time for determination of the stereochemistry at the anomeric center were certainly laborious and left a great deal of uncertainty. It was also clear to him that there were special effects in play when it came to the conformational preference of certain pyranose derivatives. These caused large electronegative substituents at C-1 of the pyranose ring to occupy the sterically crowded axial orientation rather than the expected equatorial position (Figure 2). In 1953, however, there was no way to obtain direct evidence for the preferred conformations of such molecules in solution. The resolution of this problem coincided with his move to the University of Ottawa, Ontario in 1954.
The president of the National Research Council of Canada, Edgar W. R. Steacie had strongly urged the young Lemieux to consider a move to Ottawa to help build the faculty and an “atmosphere of research.” Lemieux became professor and chairman of the Department of Chemistry at the University of Ottawa in 1954, and served as the vice-dean of the Faculty of Pure and Applied Science. During his tenure he established a flourishing research environment.
Conformational Analysis by NMR Spectroscopy . When Lemieux first heard a presentation on NMR at the National Research Council (NRC) he immediately began to speculate on the steric effects that might influence the chemical shifts of protons attached to the carbon atoms of the pyranose ring. With Rudolf Kullnig (a graduate student in his group) and under the guidance of Harold Bernstein (NRC), the first NMR spectra of sugar acetates were obtained at 40 MHz. The work provided the long-sought definitive assessment of the preferred conformations of the sugar acetates in solution. Expansion of the approach led to the first application of proton NMR (1HNMR) spectroscopy for the establishment of the relative configurations of chiral centers in organic compounds and thus the foundation of the Karplus relationship. In 1958, Lemieux presented this work, prior to publication, in the Karl Folkers lectures at the University of Illinois, where Martin Karplus was in the audience. It was his equations that provided a theoretical basis for the quantitative correlation of three bond coupling constants with torsional angle, one of organic chemistry’s most potent stereochemical probes. Karplus later wrote, “Just as I finished the work on vicinal coupling constants, I heard a lecture by R. U. Lemieux on the conformations of acetylated sugars. I do not remember why I went to the talk because it was on organic chemistry. Lemieux reported results for vicinal coupling constants and noted that there appeared to be dihedral angle dependence, although the details of the behavior were not clear. However, it was evident that these experimental results confirmed the theory even before it was published” (Karplus, 1996).
In the same year Lemieux discovered the anomeric effect, the preference of large electronegative constituents at C-1 of the pyranose ring to preferentially adopt the
axial orientation, now recognized as a fundamental stereoelectronic phenomenon. The phenomenon extends to acetals in general and to electronegative substituents at the C-2 position of saturated heterocycles. However, it was not until 1971 that Lemieux made a formal publication on this topic in a paper entitled, “Effects of Unshared Pairs of Electrons and Their Solvation on Conformational Equilibria.”
In 1961 Lemieux received an offer of a professorship from the University of Alberta in Edmonton. His group in Alberta in the early 1960s undoubtedly represented one of the high points of his career. Several outstanding PhD students and postdoctoral fellows during the 1961–1973 period helped him consolidate an undisputed reputation as a world leader in his field. Key advances in the chemistry of orthoesters, glycals and their nitrosyl chloride adducts represented major contributions during this period. (For details and references to the primary publications, see Lemieux, 1990, and the biographical essay by Bundle, 2003). Against this backdrop of new synthetic chemistry and an increasing understanding of the anomeric effects, the exploitation of 1 H NMR spectroscopy to solve conformational and configurational questions was now routinely applied in his group. During this period further studies of conformational equilibria in solution, using both NMR and chiroptical approaches, added to the appreciation of the importance of the anomeric effect in dictating not only the anomeric preference of electronegative substituents, but also the conformation of glycosides (exo-anomeric effect).
Rationale Synthesis of Complex Oligosaccharides . With the increasingly sophisticated understanding of reactions at the anomeric center and the capability to contemplate synthetic targets that few others could consider in the late 1960s, Lemieux turned his attention to the selection of challenging targets. He felt the oligosaccharide chains of glycoproteins and glycolipids could no longer be ignored as these structures carry messages essential for the control of many crucial cellular functions. The study of these new phenomena was critically hampered by the enormous difficulties encountered in trying to obtain even milligram quantities of structurally well-characterized carbohydrates.
The most direct solution was to synthesize the required complex oligosaccharides, but this had not been attempted because of the difficulties involved. In the late 1960s, the synthesis of a disaccharide was considered a major undertaking, and the preparation of more elaborate oligosaccharides must have appeared as an unrealistic project. The successful completion of such a program required at a minimum the development of new glycosylation methods. The controlled synthesis of a glycosidic bond between two sugars was especially challenging at this time, particularly for the stereochemical arrangement where, for glucose and galactose, the two most frequently encountered hexoses, the hydroxyl group at C-2 and the newly formed bond at C-1 are in a 1,2- cis relationship. For all practical purposes there was no reliable method to achieve this outcome in reliable yield and high stereoselctivity. In order to be able to follow the outcome of such reactions new methods for the structural analysis of both protected oligosaccharide intermediates and of the final synthetic products were required.
Intrigued by the biological activities of natural occurring glycoconjugates such as the glycolipids and glycoproteins, Lemieux set himself the formidable goal of achieving the synthesis of the human blood groups. This required mastery of reactions at the anomeric center of hexoses. Because the challenges of stereocontrolled glyco-side synthesis had been a continuing interest since the synthesis of sucrose in 1953 it was not surprising that Lemieux’s laboratory would develop novel methodologies for the stereospecific formation of the glycosidic linkage. These discoveries and advances came to a climax in the early 1970s. For the first time, the synthesis of oligosaccharides with the complexity of the naturally occurring
structures could be accomplished and their structures confidently confirmed by NMR spectroscopy. These new synthetic reactions included a method for the preparation of α-linked 2-amino-2-deoxy glycosides and later a procedure for the preparation of β-linked 2-amino-2-deoxy glycosides (Lemieux, 1990). Most importantly, the development of the halide-ion glycosylation reaction permitted the synthesis of the hitherto elusive α-glycosidic linkage (Lemieux, Henricks, et al., 1975a). These achievements were reported in four publications (Lemieux et al., 1975a–1975d) dealing with the syntheses of the trisaccharide antigenic determinants of the B and Lewis-a human blood groups (Figure 3).
Synthetic Antigens and Immunoadsorbents . In itself, the laboratory preparation of these antigenic determinants would have been a remarkable achievement. However, Lemieux’s insight into the potential utility of these compounds was of such clarity that he foresaw their use as artificial antigens. His syntheses were conducted in such a way that the completed oligosaccharides incorporated a tether to allow covalent attachment to appropriate carrier molecules. He also recognized that attachment to solid supports would provide biospecific adsorbents that would be of exceptional value in medical research. Ideas began to take root for the formation of what would later be called a biomedical start-up or spin-off company. However, Lemieux’s conception of a company that combined leading edge chemistry with immunological applications was years ahead of its time, although subsequent and comparable ventures would later emerge in the financially more adventurous climate of the United States. In 1979 the new company, ChemBiomed, was formed but after approximately ten years in search of viable markets it ceased business.
Determination of Oligosaccharide Conformation . The exploitation of NMR to answer stereochemical problems had become a hallmark of Lemieux’s publications and with the advent of the pulsed, Fourier-transform technique, fast digital computers and cryomagnets in the mid 1970s, the capabilities of the technique again offered unique opportunities. It was evident that measurement of inter-proton distances by either T1 measurements or nuclear Overhauser (nOe) experiments was now relatively straightforward and in combination with the estimation of torsional angles, conformational analysis of oligosaccharides was a tangible objective. Lemieux began a collaboration with Klaus Bock (Technical University, Lyngby, Denmark) that laid the foundations for a large body of pioneering studies on the determination of oligosaccharide solution conformation using NMR methods and semi-empirical calculations, based on the HSEA (Hard-Sphere-Exo-Anomeric) algorithm. Lemieux had anticipated that the relative orientation of contiguous sugar residues in oligomeric structures was governed by the exoanomeric effect. Confirmation of this idea was achieved through the observation of near-invariant vicinal coupling constants between the anomeric hydrogen and aglyconic carbon atoms in the nuclear magnetic resonance spectra of appropriately C-13 enriched synthetic model glycosides (Lemieux et al., 1979). The development of a molecular modeling program, the HSEA forcefield, was basically an extension of this work. These calculations were subsequently refined into a computer program that was made widely available during the 1980s. The initial work was largely completed by 1980 and published in a comprehensive paper describing the three dimensional properties of the human blood group oligosaccharides.
Molecular Recognition in Sugar-Protein Complexes . Knowledge of the three-dimensional shapes of oligosaccharides was a prerequisite for appreciation of their biological activities and the availability of these oligosaccharides in quantities sufficient for systematic study was an essential component in the successful research program that evolved during the 1980–1990 decade. These developments allowed Lemieux to apply his discoveries to the human blood-group specific oligosaccharide determinants, including those with specificities designated
serologically as A, B, O(H), Lewis-a, Lewis-b, Lewis-X, Lewis-Y and related antigens (Figure 4). With knowledge of the three-dimensional shapes and flexibility of these important biologically active oligosaccharides, their binding to antibodies, lectins and enzymes could, for the first time, be examined in solution at the molecular level.
A strategy based on functional group replacement was developed to dissect the contribution of individual hydroxyl groups to the free energy of binding. Lemieux initiated a vigorous synthetic program that produced more than one hundred tri- and tetrasaccharide structures. These synthetic oligosaccharides were all analogs of the natural blood group determinants, which had been modified, either through removal of hydroxyl groups or by their replacement with other substituents. The specific alterations permitted the highly specific recognition of oligosaccharides by protein receptors to be dissected in molecular detail. During this period two research associates played leading roles in the molecular recognition studies. Beginning late in 1981, Ole Hindsgaul helped lead Lemieux’s group until 1986 in studies on the lectins, Ulex europaeus and Griffonia simplicifolia IV, as well as Lewis-b and blood group B monoclonal antibodies. Ulrike Spohr, who had joined Lemieux’s group as a postdoctoral fellow in 1982, became his research associate from 1985 until he closed his research laboratory in 1995 and led in depth studies of Griffonia simplicifolia IV and other lectins that recognized the Lewis or H-type antigens.
Through a systematic study of the binding of these analogs Lemieux was able to define the precise molecular features required for the specific recognition of complex carbohydrate determinants by these proteins. An account of this work summarizes the development of his thinking during the 1975–1996 period, beginning with the “hydrated polar-group gate effect” as the key to the specificity in the recognition of complex carbohydrates through to the idea of water reorganization as a major driving force for complexation. The work culminated in the high resolution crystal structure of the lectin Griffonia simplicifolia complexed with the human Lewis b tetrasaccharide, data that substantiated the crucial inferences that had been drawn from congener mapping of the binding site. The most important was the confirmation, for this and several other systems, that only a very limited number of hydroxyl groups—often 2–3 out of some 10–12 present in an oligosaccharide epitope (the part of an antigen recognized by an antibody)—are essential for acceptor recognition and biological activity.
Water in Sugar-Protein Complexes . The results of Monte Carlo calculations on the hydration of oligosaccharide surfaces led Lemieux to conclude that the principle source of binding energy between protein receptor and oligosaccharide epitope derived not from polar interactions between solutes but from the collapse of perturbed water about the interacting, and polyamphiphilic surfaces. The return of these energetically disadvantaged water molecules from the closest hydration layers to bulk water would then provide a large source of free energy change. These controversial ideas were refined over several years, and about the time Lemieux was closing his laboratory supporting experimental evidence for this interpretation appeared. Calorimetric studies showed that 25–100 percent of the observed binding enthalpy could arise from solvent reorganization.
Industrial Activities . Lemieux founded three companies: R&L Molecular Research, Raylo Chemicals, and Chembiomed Ltd., which sought to apply the creativity of his university-based research on antibiotics and complex carbohydrates. Several practical applications arose from this work. One intriguing idea at Chembiomed was the development of immunoabsorbents to remove ABO iso-antibodies from a patients blood, thereby permitting organ transplantation in spite of the ABO histocompatibility barrier. From the mid 1980s into the early 2000s, the shortage of organs for transplant and the increasing attention being given to xenotransplants suggests that the Lemieux technology or its subsequent embodiments may find expanded application. Much of the subsequent activity in the search for carbohydrate based therapeutics, in laboratories around the world, had its origin in his pioneering work.
Lemieux’s profound influence on organic chemistry derived in large part from his enduring interest in the basic physical characteristics of molecules. Theoretical support for the concept of the anomeric effect followed many years after their recognition and acceptance as general, stereoelectronic effects in organic chemistry. This fundamental understanding of the chemistry of the anomeric centre paved the way for new methods of 1,2-cis-glycoside synthesis, a career-long interest. These major creative steps first generated methods for assignment of structural details, then provided tools for the assembly of complex structures, and finally placed him in a position to explore the subtleties of carbohydrate recognition phenomena.
Awards . Lemieux’s academic and research accomplishments have been recognized in Canada, the United States, and Europe through honorary degrees and numerous awards: the American Chemical Society’s Claude S. Hudson Award in 1966; fellowship in the Royal Society of London in 1967; and the Haworth Memorial Medal of the Chemical Society of London in 1978. In Canada, he was appointed an Officer of the Order of Canada in 1968, and in 1996 was elevated to the highest level of recognition, Companion of the Order of Canada. He was the first recipient of the Izaak Walton Killam Memorial Prize and of the Science and Engineering Research Council’s Canada Gold Medal for Science and Engineering. Among his many awards, Lemieux was especially proud of his highest Canadian honors, the Companion of the Order of Canada and the Canada Gold Medal for Science and Engineering. In order to perpetuate and nurture the research Lemieux began, the University of Alberta established an endowed chair in his name of which he and Mrs. Lemieux where major benefactors.
In his early years Lemieux had a reputation as a demanding, tough supervisor and lecturer. He had intense drive, did not tolerate nonsense, and always came to the point quickly, even at times brusquely. He was committed to excellence in himself and from those around him and he did not hesitate to let his coworkers know if they were wrong about something. However, his criticism was given without rancor or harshness. Lemieux was an unassuming individual who was devoid of pretensions and was regarded by colleagues from around the world as good-humored and fun to be around, especially when he was relaxing at the pub or bar.
Although formally retired, Lemieux maintained his research group well into the 1990s, and despite an ongoing battle with failing eyesight caused by macular degeneration, he maintained his interest in carbohydrate-protein recognition until his death in July 2000. He was without doubt one of the most outstanding Canadian chemists of the twentieth century, whose contributions to organic chemistry profoundly influenced the development of the discipline in the second half of the century.
WORKS BY LEMIEUX
With Melville L. Wolfrom and S. M. Olin. “Configurational Correlation of L-(levo)-Glyceraldehyde with Natural (dextro)Alanine by a Direct Chemical Method.” Journal of the American Chemical Society 71 (1949): 2870–2873.
With Georg Huber. “A Chemical Synthesis of Sucrose.” Journal of the American Chemical Society 75 (1953): 4118.
With Rudolf K. Kullnig, Harold J. Bernstein, and William G. Schneider. “Configurational Effects in the Proton Magnetic Resonance Spectra of Acetylated Carbohydrates.” Journal of the American Chemical Society 79 (1957): 1005–1006.
With Rudolf K. Kullnig, Harold J. Bernstein, and William G. Schneider. “Configurational Effects on the Proton Magnetic Resonance Spectra of Six-Membered Ring Compounds.” Journal of the American Chemical Society 80 (1958): 6098–6105.
“Rearrangements and Isomerizations in Carbohydrate Chemistry.” In Molecular Rearrangements, edited by Paul de Mayo, Interscience, 1964.
“Effects of Unshared Pairs of Electrons and Their Solvation on Conformational Equilibria.” Pure and Applied Chemistry 25 (1971): 527–548.
With Shinkiti Koto. “The Conformational Properties of Glycosidic Linkages.” Tetrahedron 30 (1974): 1933–1944.
With K. B. Hendriks, Robert V. Stick, and Kenneth James. “Halide-Ion Catalyzed Glycosidation Reactions. Syntheses of α-Linked Disaccharides.” Journal of the American Chemical Society 97 (1975a): 4056–4062.
With Hughes Driguez. “The Chemical Synthesis of 2-Acetamido-2-deoxy-4-O-(α-L-fucopyranosyl)-3-O-(β-Dgalactopyranosyl)-D-glucose. The Lewis a Blood-Group Antigenic Determinant.” Journal of the American Chemical Society 97 (1975b): 4063–4069.
With Hughes Driguez. “The Chemical Synthesis of 2-O-(α-Lfucopyranosyl)-3-O-(α-D-galactopyranosyl)-D-galactose. The Terminal Structure of the Blood-Group B Antigenic Determinant.” Journal of the American Chemical Society 97 (1975c): 4069–4075.
With David R. Bundle and Donald A. Baker. “The Properties of a ‘Synthetic’ Antigen Related to the Human Blood-group Lewis a.” Journal of the American Chemical Society 97 (1975d): 4076–4083.
“Human Blood Groups and Carbohydrate Chemistry.” Chemical Society Review 7 (1978): 423–452.
With Shinkiti Koto and D. Voisin. “The Exo-Anomeric Effect.” In Origin and Consequence of the Anomeric Effect, American Chemical Society Symposium Series, No. 87. Washington, DC: American Chemical Society, 1979.
With Klaus Bock, Louis T. J. Delbaere, Shinkiti Koto and V. S. Rao. “The Conformations of Oligosaccharides Related to the ABH and Lewis Human Blood Group Determinants.” Canadian Journal of Chemistry 58, (1980): 631–653.
Explorations with Sugars. How Sweet It Was. Profiles, Pathways and Dreams. Autobiographies of Eminent Chemists, Jeffrey I. Seeman, series editor. Washington, DC: American Chemical Society, 1990.
With Louis T. J. Delbaere, Margaret Vandonselaar, Lata Prasad, et al. “Molecular Recognition of a Human Blood Group Determinant by a Plant Lectin.” Canadian Journal of Chemistry, 68 (1990): 1116–1121.
With Pandurang V. Nikrad and Herman Beierbeck. “Molecular Recognition X. A Novel Procedure for the Detection of the Intermolecular Hydrogen Bonds Present in a Protein Oligosaccharide Complex.” Canadian Journal of Chemistry 70 (1992): 241–253.
“How Water Provides the Impetus for Molecular Recognition in Aqueous Solution.” Accounts of Chemical Research 29 (1996): 373–380.
Bannett, A. D., William I. Bensinger, R. Raja, et al. “Immunoadsorption and Renal Transplant in Two Patients with a Major ABO Incompatibility.” Transplantation 43 (1987): 909–911.
Bundle, David R. “Raymond Urgel Lemieux 16 June 1920–22 July 2000.” Biographical Memoirs of Fellows of the Royal Society 48 (2002) 251–273. Contains a complete list of Lemieux’s publications.
———. Advances in Carbohydrate Chemistry and Biochemistry 58 (2003): 1–33. Contains a complete list of Lemieux’s publications.
David R. Bundle
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