title: Synthesis and Rotational Isomerism of 1-Substituted Methyl (S)-[5-(2-Nitrophenyl)-1H-pyrazole-4-carbonyl]alaninates.
abstract: Seven title compounds 12a-g and the (S)-prolinate analogue 13 were prepared in five steps from 2-nitrobenzoic acid (7). Reduction of the nitro group followed by derivatization of the so formed anilines 14 gave the N-alkyl-(15a-c), N-acyl-(16a,b and 19), and N-vinyl derivative 20. NMR spectra of (S)-alanine and (S)-proline derived compounds 12, 13, 14-16, 19, and 20 exhibited two sets of signals corresponding to pairs of conformational diastereomers. The free energy barriers of rotation, ΔG(‡)298 = 82-86 kJ mol(-1), were determined by (1)H NMR for 12a, 12d, 12f, and 12g and evaluated by DFT calculations.
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Luka
authors.initials: L
authors.lastname: Šenica
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Karmen
authors.initials: K
authors.lastname: Stopar
authors.affiliation: Centre of Excellence EN-FIST , Trg Osvobodilne fronte 13, SI-1000 Ljubljana, Slovenia.|National Institute of Chemistry , Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
authors.forename: Miha
authors.initials: M
authors.lastname: Friedrich
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Uroš
authors.initials: U
authors.lastname: Grošelj
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.|Centre of Excellence EN-FIST , Trg Osvobodilne fronte 13, SI-1000 Ljubljana, Slovenia.|National Institute of Chemistry , Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
authors.forename: Janez
authors.initials: J
authors.lastname: Plavec
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Marta
authors.initials: M
authors.lastname: Počkaj
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Črtomir
authors.initials: Č
authors.lastname: Podlipnik
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.|Centre of Excellence EN-FIST , Trg Osvobodilne fronte 13, SI-1000 Ljubljana, Slovenia.
authors.forename: Bogdan
authors.initials: B
authors.lastname: Štefane
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.|Centre of Excellence EN-FIST , Trg Osvobodilne fronte 13, SI-1000 Ljubljana, Slovenia.
authors.forename: Jurij
authors.initials: J
authors.lastname: Svete