A slow rate exchange process allows the detection of both carbonyl (C=O) and hydroxyl (-OH) O-17 nuclear magnetic resonances of the carboxylic group
Φόρτωση...
Ημερομηνία
Συγγραφείς
Tsikaris, V.
Moussis, V.
Sakarellos-Daitsiotis, M.
Sakarellos, C.
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
Elsevier
Περίληψη
Τύπος
Είδος δημοσίευσης σε συνέδριο
Είδος περιοδικού
peer reviewed
Είδος εκπαιδευτικού υλικού
Όνομα συνεδρίου
Όνομα περιοδικού
Tetrahedron Lett
Όνομα βιβλίου
Σειρά βιβλίου
Έκδοση βιβλίου
Συμπληρωματικός/δευτερεύων τίτλος
Περιγραφή
In this study we report, for the first time, on the detection of both the carbonyl (-C=O) and the hydroxyl (-OH) O-17 resonances of the carboxylic group by O-17 NMR spectroscopy. Two well separated peaks, at 340.3 and 175 ppm, were detected for the -C=O and -OH groups, respectively, of Boc[O-17]Tyr(2,6-diClBzl)-OH in DMSO-d(6). This finding is attributed to the participation of the carboxylic group in a rather strong hydrogen-bonded interaction. These resonances disappeared in the presence of a small quantity of TFA (trifluoroacetic acid), which, however, did not cleave the Boc-group and a broad resonance was detected for both oxygens. In fact, this result indicates that the proposed hydrogen-bonded interaction is not stabilized in the presence of TFA, which is a very strong hydrogen bond breaker. Only one broad signal was observed for both carboxylic oxygens at 251.8 ppm for the HCl[O-17]Tyr(2,6-diClBzl)-OH in DMSO-d(6) solution, suggesting that the carbonyl oxygen of the Boc-group is probably the proton acceptor group of the carboxylic hydrogen, stabilizing a gamma -turn like structure. A single relatively sharp resonance appearing in chloroform, (247.5 ppm) upheld shifted by similar to 14.5 ppm, compared to the resonance found in DMSO-d(6) for Boc-[17(O)]Tyr(2,6-ClBzl)-OH in the presence of TFA, is attributed to a gamma -turn fraction being in a fast exchange with the open form. (C) 2000 Elsevier Science Ltd. All rights reserved.
Περιγραφή
Λέξεις-κλειδιά
Θεματική κατηγορία
Παραπομπή
Σύνδεσμος
<Go to ISI>://000165150200050
http://ac.els-cdn.com/S004040390001515X/1-s2.0-S004040390001515X-main.pdf?_tid=02daadba0ca44bcfbbbe6b5ea2112cc2&acdnat=1333038891_3a537d369afcdd02499e87ac76a3742c
http://ac.els-cdn.com/S004040390001515X/1-s2.0-S004040390001515X-main.pdf?_tid=02daadba0ca44bcfbbbe6b5ea2112cc2&acdnat=1333038891_3a537d369afcdd02499e87ac76a3742c
Γλώσσα
en
Εκδίδον τμήμα/τομέας
Όνομα επιβλέποντος
Εξεταστική επιτροπή
Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας