Summary.
2H-Pyran-2-ones 1 were transformed with various hydrazines into (E)- or (Z)-α,β-didehydro-α-amino acid (DDAA) derivatives 4 (and 7) containing a highly substituted pyrazolyl moiety attached at the β-position. With heterocyclic hydrazines, the products 4 were accompanied also by decarboxylated enamines E-6. In order to separate (E/Z)-mixtures of acids, they were transformed to the corresponding methyl esters 9 and 10 by the application of diazomethane. Catalytic hydrogenation under high pressures with Pd/C as a catalyst resulted in the formation of racemic alanine derivatives 11.
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Received January 29, 2002 Accepted May 27, 2002 Published online December 18, 2002
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ID="*" Dedicated with deep respect to Professor Waldemar Adam on the occasion of his 65th birthday.
Acknowledgements We thank the Ministry of Education, Science and Sport of the Republic of Slovenia for the financial support (P0-0503-103). Dr. B. Kralj and Dr. D. Žigon (Center for Mass Spectroscopy, “Jožef Stefan” Institute, Ljubljana, Slovenia) are gratefully acknowledged for the mass measurements.
Authors' address: Prof. Marijan Kočevar, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia, E-mail: marijan.kocevar@uni-lj.si
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Vraničar, L., Požgan, F., Polanc, S. et al. Synthesis and transformations of a pyrazole containing α,β-didehydro-α-amino acid derivatives. Amino Acids 24, 273–280 (2003). https://doi.org/10.1007/s00726-002-0406-5
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DOI: https://doi.org/10.1007/s00726-002-0406-5