Structure of a new usnic acid derivative from a deacylating Mannich reaction

NMR studies supported by theoretical calculations of chemical shifts

Huong Giang Thi Nguyen, Vinh Ngoc Nguyen, Fadhil S. Kamounah, Poul Erik Hansen

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Resumé

In a conventional Mannich reaction using piperidine, hydroxypiperidines, morpholine, and N‐methylpiperazine with usnic acid, a deacetylation was observed resulting in a substitution at C‐2, a loss of an acetyl group, and a Mannich base with a stabilized enol. The enol has a hydrogen bond to the nitrogen of the secondary amine. The structure was investigated by nuclear magnetic resonance and deuterium isotope effects on 13C chemical shifts as well as with density functional theory calculations to study the changed hydrogen bond pattern. It was found that the hydrogen bond involving the OH‐9 group in chloroform forms a strong hydrogen bond than in usnic acid itself and that this hydrogen bond becomes even stronger in the more polar solvent, dimethylsulfoxide. Tautomerism was observed in the Mannich base as demonstrated by deuterium isotope effects on chemical shifts. The position of the tautomeric equilibrium depends on the solvent, and the position of the equilibrium governs the strength of the OH‐9…O═C hydrogen bond.
OriginalsprogEngelsk
TidsskriftMagnetic Resonance in Chemistry
Vol/bind56
Udgave nummer11
Sider (fra-til)1094-1100
Antal sider7
ISSN0749-1581
DOI
StatusUdgivet - 20 aug. 2018

Bibliografisk note

Important note from the Publisher regarding the attached document:
"This is the peer reviewed version of the following article: Nguyen HGT, Nguyen VN, Kamounah FS, Hansen PE. Structure of a new usnic acid derivative from a deacylating Mannich reaction: NMR studies supported by theoretical calculations of chemical shifts. Magn Reson Chem. 2018;56:1094–1100. https://doi.org/10.1002/mrc.4760, which has been published in final form at https://doi.org/10.1002/mrc.4760. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions."

Emneord

  • deacetylation
  • Mannich reaction
  • usnic acid
  • hydrogen bonding

Citer dette

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title = "Structure of a new usnic acid derivative from a deacylating Mannich reaction: NMR studies supported by theoretical calculations of chemical shifts",
abstract = "In a conventional Mannich reaction using piperidine, hydroxypiperidines, morpholine, and N‐methylpiperazine with usnic acid, a deacetylation was observed resulting in a substitution at C‐2, a loss of an acetyl group, and a Mannich base with a stabilized enol. The enol has a hydrogen bond to the nitrogen of the secondary amine. The structure was investigated by nuclear magnetic resonance and deuterium isotope effects on 13C chemical shifts as well as with density functional theory calculations to study the changed hydrogen bond pattern. It was found that the hydrogen bond involving the OH‐9 group in chloroform forms a strong hydrogen bond than in usnic acid itself and that this hydrogen bond becomes even stronger in the more polar solvent, dimethylsulfoxide. Tautomerism was observed in the Mannich base as demonstrated by deuterium isotope effects on chemical shifts. The position of the tautomeric equilibrium depends on the solvent, and the position of the equilibrium governs the strength of the OH‐9…O═C hydrogen bond.",
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Structure of a new usnic acid derivative from a deacylating Mannich reaction : NMR studies supported by theoretical calculations of chemical shifts. / Nguyen, Huong Giang Thi ; Nguyen, Vinh Ngoc ; Kamounah, Fadhil S.; Hansen, Poul Erik.

I: Magnetic Resonance in Chemistry, Bind 56, Nr. 11, 20.08.2018, s. 1094-1100.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Structure of a new usnic acid derivative from a deacylating Mannich reaction

T2 - NMR studies supported by theoretical calculations of chemical shifts

AU - Nguyen, Huong Giang Thi

AU - Nguyen, Vinh Ngoc

AU - Kamounah, Fadhil S.

AU - Hansen, Poul Erik

N1 - Important note from the Publisher regarding the attached document: "This is the peer reviewed version of the following article: Nguyen HGT, Nguyen VN, Kamounah FS, Hansen PE. Structure of a new usnic acid derivative from a deacylating Mannich reaction: NMR studies supported by theoretical calculations of chemical shifts. Magn Reson Chem. 2018;56:1094–1100. https://doi.org/10.1002/mrc.4760, which has been published in final form at https://doi.org/10.1002/mrc.4760. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions."

PY - 2018/8/20

Y1 - 2018/8/20

N2 - In a conventional Mannich reaction using piperidine, hydroxypiperidines, morpholine, and N‐methylpiperazine with usnic acid, a deacetylation was observed resulting in a substitution at C‐2, a loss of an acetyl group, and a Mannich base with a stabilized enol. The enol has a hydrogen bond to the nitrogen of the secondary amine. The structure was investigated by nuclear magnetic resonance and deuterium isotope effects on 13C chemical shifts as well as with density functional theory calculations to study the changed hydrogen bond pattern. It was found that the hydrogen bond involving the OH‐9 group in chloroform forms a strong hydrogen bond than in usnic acid itself and that this hydrogen bond becomes even stronger in the more polar solvent, dimethylsulfoxide. Tautomerism was observed in the Mannich base as demonstrated by deuterium isotope effects on chemical shifts. The position of the tautomeric equilibrium depends on the solvent, and the position of the equilibrium governs the strength of the OH‐9…O═C hydrogen bond.

AB - In a conventional Mannich reaction using piperidine, hydroxypiperidines, morpholine, and N‐methylpiperazine with usnic acid, a deacetylation was observed resulting in a substitution at C‐2, a loss of an acetyl group, and a Mannich base with a stabilized enol. The enol has a hydrogen bond to the nitrogen of the secondary amine. The structure was investigated by nuclear magnetic resonance and deuterium isotope effects on 13C chemical shifts as well as with density functional theory calculations to study the changed hydrogen bond pattern. It was found that the hydrogen bond involving the OH‐9 group in chloroform forms a strong hydrogen bond than in usnic acid itself and that this hydrogen bond becomes even stronger in the more polar solvent, dimethylsulfoxide. Tautomerism was observed in the Mannich base as demonstrated by deuterium isotope effects on chemical shifts. The position of the tautomeric equilibrium depends on the solvent, and the position of the equilibrium governs the strength of the OH‐9…O═C hydrogen bond.

KW - deacetylation

KW - Mannich reaction

KW - usnic acid

KW - hydrogen bonding

KW - deacylation

KW - Mannich base

KW - usnic acid

KW - DFT calculations

KW - isotope effects

U2 - 10.1002/mrc.4760

DO - 10.1002/mrc.4760

M3 - Journal article

VL - 56

SP - 1094

EP - 1100

JO - Magnetic Resonance in Chemistry

JF - Magnetic Resonance in Chemistry

SN - 0749-1581

IS - 11

ER -