Ascorbigen A-NMR identification

J 2019

Ascorbigen A-NMR identification

SYCHROVSKY, V., D. SAMAN, Radovan FIALA, Otakar HUMPA, J. SYKORA et. al.

Basic information

Original name

Ascorbigen A-NMR identification

Authors

SYCHROVSKY, V. (203 Czech Republic), D. SAMAN (203 Czech Republic), Radovan FIALA (203 Czech Republic, guarantor, belonging to the institution), Otakar HUMPA (203 Czech Republic, belonging to the institution), J. SYKORA (203 Czech Republic), P. KESSLER (276 Germany), V. BLECHTA (203 Czech Republic), P. DOBREV (203 Czech Republic) and J. SCHRAML (203 Czech Republic)

Edition

Magnetic Resonance in Chemistry, HOBOKEN, John Wiley & Sons, 2019, 0749-1581

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10402 Inorganic and nuclear chemistry

Country of publisher

United States of America

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

URL

Impact factor

Impact factor: 2.035

RIV identification code

RIV/00216224:14740/19:00111526

Organization unit

Central European Institute of Technology

DOI

http://dx.doi.org/10.1002/mrc.4890

UT WoS

000473987100001

Keywords in English

C-13 NMR; C-13-C-13 coupling constants; C-13-H-1 coupling constants; H-1 NMR; H-1-H-1 coupling constants; natural product; NMR; NOE; rotamers; stereochemistry

Abstract

V originále

The connectivities of all atoms in ascorbigen A, an important metabolite, were determined unambiguously for the first time. The connectivity between carbon atoms was established by 2D INADEQUATE, and one-bond C-13-C-13 coupling constants were determined for all pairs of directly connected carbon atoms except for two strongly coupled carbon pairs. The C-13-C-13 coupling in one of the pairs was proved by a modification of standard INADEQUATE; however, the signals from the other pair were too weak to be observed. The connectivity within the two strongly coupled C-C pairs was confirmed by a combination of COSY and gHSQC; the latter experiment also identified all C-H bonds. The proton nuclear magnetic resonance (H-1 NMR) spectra in dry dimethyl sulfoxide allowed identification and assignment of the signals due to NH and OH protons. The derived structure, 3-((1H-indol-3-yl)methyl)-3,3a,6-trihydroxytetrahydrofuro[3,2-b]furan-2(5H)-one, agrees with the structure suggested for ascorbigen A in 1966. The density functional theory (DFT) calculations showed that among 16 possible stereoisomers, only two complied with the almost zero value of the measured (3)J(H6-H6a). Of the two stereoisomers, 3S,3aS,6S,6aR and 3R,3aR,6R,6aS, the latter was excluded on synthetic grounds. The nuclear Overhauser effect measurements unveiled close proximity between H2 ' proton of the indole and the H6a proton of the tetrahydrofuro[3,2-b]furan part. Detailed structural interpretation of the measured NMR parameters by means of DFT NMR was hampered by rotational flexibility of the indole and tetrahydrofuro[3,2-b]furan parts and inadequacy of Polarizable Continuum Model (PCM) solvent model.

Links

90043, large research infrastructures

Name: CIISB

Citovat

SYCHROVSKY, V., D. SAMAN, Radovan FIALA, Otakar HUMPA, J. SYKORA, P. KESSLER, V. BLECHTA, P. DOBREV and J. SCHRAML. Ascorbigen A-NMR identification. Magnetic Resonance in Chemistry. HOBOKEN: John Wiley & Sons, 2019, vol. 57, No 12, p. 1084-1096. ISSN 0749-1581. Available from: https://dx.doi.org/10.1002/mrc.4890.

@article{1585757,
   author = {Sychrovsky, V. and Saman, D. and Fiala, Radovan and Humpa, Otakar and Sykora, J. and Kessler, P. and Blechta, V. and Dobrev, P. and Schraml, J.},
   article_location = {HOBOKEN},
   article_number = {12},
   doi = {http://dx.doi.org/10.1002/mrc.4890},
   keywords = {C-13 NMR; C-13-C-13 coupling constants; C-13-H-1 coupling constants; H-1 NMR; H-1-H-1 coupling constants; natural product; NMR; NOE; rotamers; stereochemistry},
   language = {eng},
   issn = {0749-1581},
   journal = {Magnetic Resonance in Chemistry},
   title = {Ascorbigen A-NMR identification},
   url = {http://dx.doi.org/10.1002/mrc.4890},
   volume = {57},
   year = {2019}
}

TY  - JOUR
ID  - 1585757
AU  - Sychrovsky, V. - Saman, D. - Fiala, Radovan - Humpa, Otakar - Sykora, J. - Kessler, P. - Blechta, V. - Dobrev, P. - Schraml, J.
PY  - 2019
TI  - Ascorbigen A-NMR identification
JF  - Magnetic Resonance in Chemistry
VL  - 57
IS  - 12
SP  - 1084-1096
EP  - 1084-1096
PB  - John Wiley & Sons
SN  - 07491581
KW  - C-13 NMR
KW  - C-13-C-13 coupling constants
KW  - C-13-H-1 coupling constants
KW  - H-1 NMR
KW  - H-1-H-1 coupling constants
KW  - natural product
KW  - NMR
KW  - NOE
KW  - rotamers
KW  - stereochemistry
UR  - http://dx.doi.org/10.1002/mrc.4890
L2  - http://dx.doi.org/10.1002/mrc.4890
N2  - The connectivities of all atoms in ascorbigen A, an important metabolite, were determined unambiguously for the first time. The connectivity between carbon atoms was established by 2D INADEQUATE, and one-bond C-13-C-13 coupling constants were determined for all pairs of directly connected carbon atoms except for two strongly coupled carbon pairs. The C-13-C-13 coupling in one of the pairs was proved by a modification of standard INADEQUATE; however, the signals from the other pair were too weak to be observed. The connectivity within the two strongly coupled C-C pairs was confirmed by a combination of COSY and gHSQC; the latter experiment also identified all C-H bonds. The proton nuclear magnetic resonance (H-1 NMR) spectra in dry dimethyl sulfoxide allowed identification and assignment of the signals due to NH and OH protons. The derived structure, 3-((1H-indol-3-yl)methyl)-3,3a,6-trihydroxytetrahydrofuro[3,2-b]furan-2(5H)-one, agrees with the structure suggested for ascorbigen A in 1966. The density functional theory (DFT) calculations showed that among 16 possible stereoisomers, only two complied with the almost zero value of the measured (3)J(H6-H6a). Of the two stereoisomers, 3S,3aS,6S,6aR and 3R,3aR,6R,6aS, the latter was excluded on synthetic grounds. The nuclear Overhauser effect measurements unveiled close proximity between H2 ' proton of the indole and the H6a proton of the tetrahydrofuro[3,2-b]furan part. Detailed structural interpretation of the measured NMR parameters by means of DFT NMR was hampered by rotational flexibility of the indole and tetrahydrofuro[3,2-b]furan parts and inadequacy of Polarizable Continuum Model (PCM) solvent model.
ER  -

SYCHROVSKY, V., D. SAMAN, Radovan FIALA, Otakar HUMPA, J. SYKORA, P. KESSLER, V. BLECHTA, P. DOBREV and J. SCHRAML. Ascorbigen A-NMR identification. \textit{Magnetic Resonance in Chemistry}. HOBOKEN: John Wiley \&{} Sons, 2019, vol.~57, No~12, p.~1084-1096. ISSN~0749-1581. Available from: https://dx.doi.org/10.1002/mrc.4890.

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