ACD/Structure Elucidator

To use Structure Elucidator, you require a set of 2D NMR spectra and a molecular formula or a ¹³C NMR spectrum. It is helpful (but not necessary) to have carbon multiplicity information (available from experiments such as APT, DEPT, etc.), and ¹H NMR, MS, Chrom, and IR spectral data.

A Detailed Look at ACD/Structure Elucidator Features:

Spectral Data Import

• Allow the Elucidation Wizard to guide you through the process of Structure Elucidation with step-by-step file import and structure generation.
• Transfer processed data from ACD/1D NMR Manager, ACD/NMR Workbook, ACD/UV-IR Manager, ACD/ChromManager, and ACD/MS Manager directly to the ACD/Structure Elucidator interface:
  • Transfer partially assigned spectra to Structure Elucidator. The software will use these assignments when generating possible structures.
  • Import multiplet information.
• Enter any compositional information such as MS data, known Molecular Formula, etc.
• Automatically generate a mass value from MS data (when available).
• Automatically generate Molecular Formula from MS data, and NMR spectral information.
• Use DEPT-edited NMR spectra to automatically determine ¹³C multiplicity.
• Create Good or Bad lists to provide the software with any structural knowledge that may be known prior to elucidation (i.e., include or exclude known structure fragments, functional groups, ring sizes, etc.).

Database Searching (Dereplication Stage)

• Automatically search ACD/Structure Elucidator's internal library of over 410,000 compounds from the spectral data provided.
• If no structures are found in the initial database search, the software can search through its internal library of over 2,000,000 structural fragments. Any found structural fragments can be used in the ensuing elucidation process or can be used for substructure searches in in-house or commercial libraries.

Structure Elucidation (Structure Generation Phase)

• Generate a 2D connectivity map (Molecular Connectivity Diagram, MCD) and then draw in carbonyl, carboxyl, or other obvious features from IR knowledge or synthetic pathways. A molecular connectivity diagram (MCD) is a map of atoms and correlations between atoms that is automatically built by the software from 2D NMR spectral inputs and used as a starting point for structure generation.
• The Molecular Connectivity diagram can be viewed and edited within the software. Different bond correlations are denoted in color.
• The user can edit the MCDs to draw forbidden and obligatory bonds based on their own knowledge of the chemical structure and substance.

Structure Identification (Compound Evaluation Phase)

• Following structure elucidation, the software compiles all possible structures based on the spectral, MF, and mass data provided, along with their correspondence with the proposed MCD.
• View the generated structures in a tile, table or one record mode.
• Calculate the deviation statistic for each proposed structure. The deviation statistic is a value that determines agreement between the experimental ¹³C NMR data and predicted ¹³C NMR data. The lower the match, the better the correspondence the proposed structure has with the experimental data.
• Sort the generated structures based on the deviation statistic to determine which compounds best match the experimental 1D and 2D NMR data provided.
• Interactively select only the chemically relevant structures from the proposed list and create a new list of structures in Table or Tile mode. For example, a spectroscopist can browse all of the proposed structures provided by the software and quickly eliminate any structures that are irrelevant based on their biosynthetic pathways, etc.
• Automatically remove any structures from consideration based on a deviation statistic threshold. A general rule of thumb is to reject any proposed structures with an average shift deviation of greater than 5.5 ppm. It is important to note that ranking structures with match factors less than 5.5 ppm should be done with extreme care and the user should evaluate the suggested fragments very carefully.
• If proposed structures have several stereoisomers, the software can use NOESY and ROESY data to determine the relative stereochemistry of the proposed compounds.

Statistics

Structure Elucidator 8.0 was tested with the spectra of more than 250 novel compounds. The 1D and 2D NMR spectra of these structures were published in the Journal of Natural Products between 2000 and 2005 as well as obtained directly from different chemists. Molecules containing between 20 and 90 skeletal atoms and having molecular masses ranging from 200 to 1285 a.m.u. were used. Approximately 70% of the problems were solved with default options. The rest of the problems were solved after a small amount of user intervention (automatic or manual determination of ^4-5J correlations, verification of different variants of atom property, etc.). In all, 50% of the analyses required less than 1 min and 95% of the analyses required no more than 30 min of computation time (including all spectrum predictions). This test clearly demonstrates the utility of Structure Elucidator for the elucidation of novel natural product structures with up to 90 skeletal atoms. For examples of chemical structures which have been elucidated with ACD/Structure Elucidator, please review the publication.

Examples of Solutions

Click here to view a review of structures that have been elucidated to date using ACD/Structure Elucidator.