https://doi.org/10.15255/KUI.2002.028
Published: Kem. Ind. 52 (6) (2003) 251–272
Paper reference number: KUI-28/2002
Paper type: Review
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DRAGUTIN FLEŠ – Member of Croatian Academy of Sciences and Arts. Autobiographic Review of the Research in Chemistry 1946-2002

D. Fleš+

Abstract

Dragutin Fles born in 1921 in Vukovar, Croatia, studied chemistry at the Technical Faculty, University of Zagreb, where he obtained the engineering degree in 1946. During the second part of 1946 he was employed in PLIVA, Pharmaceutical and Chemical Company in Zagreb, in the Department of Chemotherapeutical Drugs Production. For two years he worked on the production of neoarsphenamine and on the synthesis and tuberculostatic activity of pyrrol-azo-phenylarsonic acids and pyrrol-azo-benzoic acid. By means of toxicological and spectroscopic methods he proved, with Nikola Muic, the existence of cis-trans isomers of 3,3´-diamino-4,4´-dihydroxyarsenobenzene. In 1950 he worked as a member of "Foreign Student Summer Project" at Masachusetts Institute of Technology, Cambridge, Mas, on the synthesis of β-carotene in the laboratory of Profesor Nicholas A. Milas. During the academic year 1952/53 he continued the work on the synthesis of polyenes in MIT, Cambridge. He obtained his Ph. D. degree under the supervision of Profesor Kresimir Balenovic in 1952, with whom he worked on the stereochemistry of sulfur containing β-amino acids: L-β-methionine, L-β-cystine and L-β-homodjenkolic acid, and several dipeptides and tripeptides of β-amino acids containing sulfur. Of interest are his works on the stereochemistry of chloramphenicol, β-nor-pseudo-ephedrine and a series of β-propiothiolactones and poly-propiothiolactones. The absolute configuration of chloramphenicol was determined by the synthesis of natural antibiotic from D-serine. Attempts to prepare mercaptochloramphenicol in which -CH2OH group was substituted with -CH2SH, has shown that S-benzyl-N-phthaloyl-L-cysteinyl chloride with two moles of AlCl3 gave β-phthalimido-β-propiothiolactone, while with 1 mole of AlCl3 poly(N-phthaloyl-cysteine) was obtained. The synthesis of 15,15´-dihydro-β-carotene in 1960 was of considerable interest, since at that time it was considered that this compound during the synthesis undergoes a double allylic shift, thus being rearranged to 7,7´-dihydro-β-carotene. The synthesis performed in PLIVA was the first succesful synthetic preparation of 15,15´-dihydro-β-carotene. The academic year 1957/58 he spent as a fellow of Alfred P. Sloan Foundation in Urbana, Ill., working with Profesor Roger Adams on the configuration of C1 and C8 atoms of pyrrolizidine moieties of Senecio alkaloids. The configuration was determined by chemical interconversion of optically active compounds of known configuration by means of stereospecific reactions. Soon after he returned from the University of Illinois, Urbana, he became engaged in the organization of development of petrochemical industry in Zagreb. As newly appointed Research Director of OKI he organized the first modern equipped research institute actively engaged in the development of new polymeric material and petrochemicals of commercial interest. Research activities were mostly devoted to the synthesis and stereochemistry of optically active and specialty polymers like polyamides, substituted butadienes, β-substituted styrenes and propiothiolactones. Of interest is to mention his contributions to the studies of the mechanism of alternating copolymerization of donor-acceptor monomers which form charge-transfer complexes. On the bases of a large number of alternating copolymerizations described in published papers and reviews, it was found that the values of complexation constants do not depend on steric factors, while the rates of complexation are significantly dependent on steric factors. It was further found that alternating copolymerization via the charge-transfer monomer copolymerization, follows the concerted mechanism under the simultaneous crospropagation of monomers and addition of complexes during the propagation. The work which is still under investigation is a synthesis of croslinked polymers and copolymers which contain selectively imprinted regions. As visiting profesor he presented lectures at the University of Merseburg, in Max Planck Institute in Mainz, University of Ann Arbour, Michigan, University of Arizona, and as lecturer he participated in Summer Schools on Optically Active Polymers at Forge-les-Eaux in France. During the summer periods of 1980 and 1990 he participated as lecturer in Summer Schools on Polymers, NATO Institute of Science, Tirrenia, Italy. With his coworkers he presented a large number of plenary lectures and reports on various IUPAC Symposia: Madrid, Budapest, Amhest, Mainz, Helsinki, Strasbourgh, Paris, Louvain, Bruxelles, and in 1977 he presented an introductory lecture concerning the mechanism of alternating copolymerization at the Gordon Conference in New London, NH. He also participated as lecturer at the international conferences on development of petrochemistry in Baghdad and Abu Dhabi. He spent his entire profesional life in industrial organizations: PLIVA, OKI, INA where he worked as production engineer, research director and finally as member of management board until the retirement in 1985. At the same time he was full profesor (h.c.) at the Faculty of Natural Sciences and Matematics, University of Zagreb, for many years teaching courses of stereochemistry and synthetic organic chemistry in graduate and postgraduate studies. He was one of initiators of the organization of postgraduate courses in the field of macromolecular science in Zagreb. With his coworkers he published more than 200 scientific papers, mostly in leading international journals, 70 profesional and review articles, 31 patents and more than 100 scientific and review articles published in proceedings of international and domestic conferences and symposia. Studies on synthesis and stereochemistry of polymers which are of interest as new materials in technical fields, specially as materials of importance in petroleum and petrochemical industry, are continued after the retirement through the collaboration with scientists from INA.

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Keywords

autobiography, studies at the University of Zagreb, postgraduate studies at MIT and University of Illinois, associate member of Academy, 1981., full member 1992., stereochemistry, macromolecular sciences, petrochemistry