Conformational Analysis of Longifolene

Subramaniam, G.; Patel, Varsha; Karimi, Sasan

doi:10.1080/00387010802371528

“…Thus, they have been used by Guo and co-workers 194 197 from Lactuca triangulata, and the tricyclic sesquiterpenoid longifolene studied by Subramaniam. 198 It has been shown by the authors in the latter case that the flexible seven-membered ring of longifolene adopts a twist-chair conformation. Complete spectral assignments including three-bond proton-proton couplings have been made by Diniz et al 199 for two novel cordiaquinones from the roots of Cordia leucocephala; by Chen et al 200 Experimental and theoretical 3 J HH couplings have been extensively used by Mendoza-Espinoza et al 214 to establish the absolute configuration and conformation of hypurticin, hyptolide and spicigerolide, representatives of polyacyloxy-6-heptenyl-5,6-dihydro-2H-pyran-2-ones, natural products occurring in several members of the mint family (Lamiaceae).…”

Section: Three-bond Hydrogen-hydrogen Couplingsmentioning

confidence: 97%

Applications of spin-spin couplings

Trela¹

1994

Nuclear Magnetic Resonance

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“…184,185 Coupling constant calculations have also been reported to assist determining the relative configuration of various natural molecules. 186,187 1.4 Conformational Analysis for Assigning Absolute Configurations Assigning absolute configuration to flexible organic molecules through comparison of experimental spectral data with quantum chemically calculated data has also been becoming more and more practical. 188 The use of quantum chemical calculations for predicting NMR, electronic circular dichroism (ECD), vibrational circular dichroism (VCD) spectra, optical rotatory dispersion (ORD), and optical rotation and their comparison with the experimental data to assign absolute configuration has become a common tool for organic, especially natural product, chemists.…”

Section: Conformational Analysis For the Prediction Of Nmr Datamentioning

confidence: 99%

MICE-PES: An Algorithm for Accurate Conformational Analysis and its Implementation to Natural Products

Hashmı¹

0

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<p>Secondary metabolites from natural sources have revolutionized the modern drug industry by acting as lead compounds. Many commercial drugs have evolved originally from natural molecules before being synthesized in the laboratory for commercialization. Because of the importance of natural molecules, it is crucial to determine their structural properties carefully as it is essential for their synthesis and studying their pharmacological behaviour. Many natural molecules have flexible structures and can adopt many different conformations in solution at room temperature. Hence, the determination of their relative configuration is a challenging task with the available experimental techniques. For structural analysis of natural molecules and to study their properties, all conformers which might be responsible for their chemical properties have to be considered. Theoretical chemistry has been very helpful in absolute structure determination of complex and conformationally flexible natural molecules by calculating their theoretical nuclear magnetic resonance, ultraviolet, infra red, and circular dichroism spectra etc. There are a number of software tools that offer conformational analysis by utilizing different molecular mechanics approaches. They produce a large number of possible conformers and are not general purpose, thus compromising accuracy. Apart from that, different force fields available for conformational analysis and minimization have been designed for specific molecular classes and do not produce good results beyond their scope. In the past, there have been reports about a “build-up procedure” for predicting the low energy conformations of peptides by optimising smaller fragments of the molecule under study and then joining them while minimizing their energies using force fields. Later on, this method was extended to predict the structure of DNA from sequences. This method used force field methods and did not gain much popularity due to its various limitations. Here, MICE-PES (Method for the Incremental Construction and Exploration of the Potential Energy Surface) is presented, an algorithm which performs a conformational analysis using high level quantum chemical calculations by building the molecule incrementally from its smallest possible analogue whose conformational degrees of freedom are very well separated than the rest of the molecule. MICE-PES has been validated through studies on known biomolecule 3-epi-xestoaminol whose absolute configuration has been determined already by experimental and theoretical methods. MICE-PES has also been used to assign the relative configuration of a natural product (meroterphenol C) whose configuration could not be established experimentally. Overall, the development of MICE-PES will be very helpful in solving problems in the study of conformationally flexible systems, in all aspects of organic chemistry.</p>

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“…184,185 Coupling constant calculations have also been reported to assist determining the relative configuration of various natural molecules. 186,187 1.4 Conformational Analysis for Assigning Absolute Configurations Assigning absolute configuration to flexible organic molecules through comparison of experimental spectral data with quantum chemically calculated data has also been becoming more and more practical. 188 The use of quantum chemical calculations for predicting NMR, electronic circular dichroism (ECD), vibrational circular dichroism (VCD) spectra, optical rotatory dispersion (ORD), and optical rotation and their comparison with the experimental data to assign absolute configuration has become a common tool for organic, especially natural product, chemists.…”

Section: Conformational Analysis For the Prediction Of Nmr Datamentioning

confidence: 99%

MICE-PES: An Algorithm for Accurate Conformational Analysis and its Implementation to Natural Products

Hashmı¹

0

View full text Add to dashboard Cite

<p>Secondary metabolites from natural sources have revolutionized the modern drug industry by acting as lead compounds. Many commercial drugs have evolved originally from natural molecules before being synthesized in the laboratory for commercialization. Because of the importance of natural molecules, it is crucial to determine their structural properties carefully as it is essential for their synthesis and studying their pharmacological behaviour. Many natural molecules have flexible structures and can adopt many different conformations in solution at room temperature. Hence, the determination of their relative configuration is a challenging task with the available experimental techniques. For structural analysis of natural molecules and to study their properties, all conformers which might be responsible for their chemical properties have to be considered. Theoretical chemistry has been very helpful in absolute structure determination of complex and conformationally flexible natural molecules by calculating their theoretical nuclear magnetic resonance, ultraviolet, infra red, and circular dichroism spectra etc. There are a number of software tools that offer conformational analysis by utilizing different molecular mechanics approaches. They produce a large number of possible conformers and are not general purpose, thus compromising accuracy. Apart from that, different force fields available for conformational analysis and minimization have been designed for specific molecular classes and do not produce good results beyond their scope. In the past, there have been reports about a “build-up procedure” for predicting the low energy conformations of peptides by optimising smaller fragments of the molecule under study and then joining them while minimizing their energies using force fields. Later on, this method was extended to predict the structure of DNA from sequences. This method used force field methods and did not gain much popularity due to its various limitations. Here, MICE-PES (Method for the Incremental Construction and Exploration of the Potential Energy Surface) is presented, an algorithm which performs a conformational analysis using high level quantum chemical calculations by building the molecule incrementally from its smallest possible analogue whose conformational degrees of freedom are very well separated than the rest of the molecule. MICE-PES has been validated through studies on known biomolecule 3-epi-xestoaminol whose absolute configuration has been determined already by experimental and theoretical methods. MICE-PES has also been used to assign the relative configuration of a natural product (meroterphenol C) whose configuration could not be established experimentally. Overall, the development of MICE-PES will be very helpful in solving problems in the study of conformationally flexible systems, in all aspects of organic chemistry.</p>

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Conformational Analysis of Longifolene

Cited by 3 publications

References 21 publications

Applications of spin-spin couplings

Applications of spin-spin couplings

MICE-PES: An Algorithm for Accurate Conformational Analysis and its Implementation to Natural Products

MICE-PES: An Algorithm for Accurate Conformational Analysis and its Implementation to Natural Products

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