Cytosporacin, a Highly Unsaturated Polyketide:  Application of the ACCORD-ADEQUATE Experiment to the Structural Determination of Natural Products

2003 ◽  
Vol 68 (16) ◽  
pp. 6079-6082 ◽  
Author(s):  
Haiyin He ◽  
Jeffrey E. Janso ◽  
R. Thomas Williamson ◽  
Hui Y. Yang ◽  
Guy T. Carter
Keyword(s):  
Natural Products ◽  
Structural Determination

Cytosporacin (I), a Highly Unsaturated Polyketide: Application of the ACCORD-ADEQUATE Experiment to the Structural Determination of Natural Products.

ChemInform ◽  
2003 ◽  
Vol 34 (49) ◽  
Author(s):  
Haiyin He ◽  
Jeffrey E. Janso ◽  
R. Thomas Williamson ◽  
Hui Y. Yang ◽  
Guy T. Carter
Keyword(s):  
Natural Products ◽  
Structural Determination

Tropical Marine Algae. VIII. The Structural Determination of Novel Sesquiterpenoid Metabolites From the Red Alga .Laurencia majuscula

1992 ◽  
Vol 45 (10) ◽  
pp. 1611 ◽  
Author(s):  
R Denys ◽  
JC Coll ◽  
BF Bowden
Keyword(s):  
Natural Products ◽  
Great Barrier Reef ◽  
Marine Algae ◽  
Structural Type ◽  
Red Alga ◽  
Structural Determination ◽  
Barrier Reef ◽  
Natural Products Chemistry ◽  
Laurencia Majuscula

An investigation of the natural products chemistry of the red alga Laurencia mujuscula from the Great Barrier Reef yielded three novel metabolites, (1), (2) and (3a), possessing a new sesquiterpenoid structural type. Known metabolites (6)-(11) were also isolated and the reassignment of n.m.r. spectral values for (11) is reported.

Single crystal x-ray structural determination of natural products

2012 ◽  
Author(s):  
Hoong-Kun Fun ◽  
Nawong Boonnak ◽  
Suchada Chantrapromma
Keyword(s):  
Natural Products ◽  
Single Crystal ◽  
Structural Determination ◽  
X Ray

The Structural Determination of a New Steroidal Metabolite from the Brown Alga Sargassum asperifolium

2003 ◽  
Vol 58 (5-6) ◽  
pp. 333-336 ◽  
Author(s):  
Seif-Eldin N. Ayyad ◽  
Salah Z. A Sowellim ◽  
Mohamed S. El-Hosini ◽  
Amal Abo-Atia
Keyword(s):  
Natural Products ◽  
Chemical Transformation ◽  
Red Sea ◽  
Spectral Methods ◽  
Brown Alga ◽  
Structural Determination ◽  
Natural Products Chemistry

Abstract An investigation of the natural products chemistry of the brown alga Sargassum asperifolium from the red sea yielded a new steroidal metabolite, 24-vinyl cholest -4-ene -24- ol -3 one, saringosterone (3), a known steroidal metabolite, 24-vinyl cholest -5-ene -3b, 24-diol, saringosterol (4), and known diterpene with a hydroazulene skeleton, dictyone (1). The identification of the isolated metabolites was established mainly by spectral methods and chemical transformation of the dictyone (1) to its acetate (2).

Carbon-13 Nuclear Magnetic Resonance Chemical Shift Calculation Protocol Applied to Rigid Triterpenes Molecules

2020 ◽  
Vol 12 (8) ◽  
pp. 995-1001
Author(s):  
Rênica Alves de Morais Rocha ◽  
Thaís Forest Giacomello ◽  
Antonio Maia de Jesus Chaves Neto ◽  
Gunar Vingre Da Silva Mota ◽  
Fabio Luiz Paranhos Costa
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Natural Products ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Scaling Factor ◽  
Resonance Spectroscopy ◽  
Theoretical Point ◽  
Structural Determination ◽  
Nuclear Magnetic

Nuclear magnetic resonance spectroscopy is one of the most powerful experimental techniques for obtaining three-dimensional structures of complex molecules, mainly for the analysis of the relative and absolute configurations of organic compounds. For this reason, this has become one of the most promising tools in the field of chemistry. From the theoretical point of view, advanced computational protocols have been developed for calculating nuclear magnetic resonance, mainly hydrogen-1 and carbon-13, parameters of isolated molecules, in which the environmental effects are neglected. These effects are predominantly related to the inherently large size of such systems, making conventional ab initio theories either very computationally demanding or even prohibitive. Despite the current advances in spectroscopic techniques, instances of revision of structures erroneously established for natural products are still common in the literature. Therefore, it is still necessary the development of quantum-chemical protocols that may assist in the correct structural determination of these compounds. This work aimed to test a universal scaling factor, based on a linear regression, for the calculation of carbon-13 nuclear magnetic resonance chemical shifts for rigid molecules, which has low computational cost and great accuracy to aid in the structural determination of natural products. The carbon-13 chemical shifts were calculated using the mPW1PW91/3-21G level of theory. Scaled chemical shifts were obtained according to the relation: 1.14x(calculated chemical shifts)–4.71. To test the application of the created scaling factor to problems related to stereochemistry, we investigated its ability to differentiate pentacyclic triterpenes regioisomers. Our results show that the mPW1PW91/3-21G//PM7 level of theory applied to the calculations, together with the use of the scaling factor, is an efficient and low-cost tool as an alternative to computational requirement approaches, usually applied to the calculation of carbon-13 nuclear magnetic resonance chemical shifts.

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