Total Synthesis and Structure Assignment of (+)‐Hexacyclinol

Porco, John A.; Su, Shun; Lei, Xiaoguang; Bardhan, Sujata; Rychnovsky, Scott D.

doi:10.1002/anie.200602854

Cited by 76 publications

(51 citation statements)

References 20 publications

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“…[61] An analysis of the original report [62] suggests that at least three errors were made: H (12) is located at δ = 3.62 ppm, not 3.55 pm; H (12) is directly attached to a carbon atom at δ = 41.0 ppm, not 40.4 ppm; and H(19) is directly attached to a carbon atom at δ = 40.6 ppm, not 40.9 ppm. These errors likely resulted from insufficient carbon resolution in the original heteronuclear correlation spectra.…”

Section: Verifying Proposed Structuresmentioning

confidence: 97%

Structural Elucidation with NMR Spectroscopy: Practical Strategies for Organic Chemists

2008

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Practical strategies for the structural elucidation of small organic molecules are described for typical organic chemists. The analysis of an unknown is divided into three stages. First, structural connectivity is deduced from through‐bond correlation experiments. Next, the relative stereochemistry is determined from NOE correlations and coupling constants (both proton–proton and proton–carbon). Finally, the proposed structure is verified by a careful inspection of all of the observed data. Tactics for the management of overlapping peaks, low sample concentrations, and high molecular weights are also described. This approach is illustrated by the step‐by‐step analyses of a simple test compound, menthol, and a complex polycyclic natural product, salvinorin A. Detailed procedures and sample data for menthol are provided as a practical tutorial. This will enable organic chemists to elucidate a wide range of complex structures by using modern NMR spectroscopic experiments.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Section: Verifying Proposed Structuresmentioning

confidence: 97%

Structural Elucidation with NMR Spectroscopy: Practical Strategies for Organic Chemists

2008

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“…One of the most recent and striking examples of the successful application of the QM approach was described by Rychnovsky [26] who refuted the incorrect structure of hexacyclinol proposed by Grafe et al [27] and suggested another structure which was then unambiguously proved by synthesis and X-ray analysis. [28] A systematic method to confirm the structure of hexacyclinol using Structure Elucidator was also described elsewhere. [29] QM chemical shift prediction is rather time consuming relative to other approaches.…”

Section: Introductionmentioning

confidence: 99%

A systematic approach for the generation and verification of structural hypotheses

Elyashberg¹,

Blinov²,

Williams³

2009

Magnetic Reson in Chemistry

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During the process of molecular structure elucidation the selection of the most probable structural hypothesis may be based on chemical shift prediction. The prediction is carried out using either empirical or quantum-mechanical (QM) methods. When QM methods are used, NMR prediction commonly utilizes the GIAO option of the DFT approximation. In this approach the structural hypotheses are expected to be investigated by scientist. In this article we hope to show that the most rational manner by which to create structural hypotheses is actually by the application of an expert system capable of deducing all potential structures consistent with the experimental spectral data and specifically using 2D NMR data. When an expert system is used the best structure(s) can be distinguished using chemical shift prediction, which is best performed either by an incremental or neural net algorithm. The time-consuming QM calculations can then be applied, if necessary, to one or more of the 'best' structures to confirm the suggested solution.

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“…The intriguing story about the structure elucidation of hexacyclinol was described in a series of publications. [61][62][63][64][65] 13 C chemical shift calculation should be considered as the most severe filter to reject all invalid structures and to select the most probable one. However, the average deviations between experimental and predicted spectra that serve as effective criteria for structure assessment are calculable only if chemical shift assignment is completed.…”

Section: Discussionmentioning

confidence: 99%

Structural Revisions of Natural Products with the Aid of the Structure Elucidator System

2011

Contemporary Computer-Assisted Approaches to Molecular Structure Elucidation

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Every year a number of articles are published that contain incorrectly elucidated structures. Based on our experience with the application of CASE systems it is expected that such software and algorithms can help the chemist in the elucidation process or can at least provide warnings for structures suggested by scientists. This chapter therefore reviews the application of CASE to a series of examples for which the original structures were later revised. It is demonstrated that the chemical structure can be correctly elucidated if 2D NMR data were available and the expert system Structure Elucidator is employed. It is also shown that if only 1D NMR spectra from the original articles were used then simply the calculation of the 13C chemical shifts for the hypothetical structures frequently allows a scientist to realize that the structural hypothesis is likely incorrect.

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Total Synthesis and Structure Assignment of (+)‐Hexacyclinol

Cited by 76 publications

References 20 publications

Structural Elucidation with NMR Spectroscopy: Practical Strategies for Organic Chemists

Structural Elucidation with NMR Spectroscopy: Practical Strategies for Organic Chemists

A systematic approach for the generation and verification of structural hypotheses

Structural Revisions of Natural Products with the Aid of the Structure Elucidator System

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