International Union of Pure and Applied Chemistry

Development of synergistic NMR and molecular mechanics - Strategies for determining natural product stereochemistry*

Thomas R. Hoye,² Seif-Eldin N. Ayyad,¹ Andrew S. Judd,² Dmitry O. Koltun,² and Matthew K. Renner²1. Chemistry Department, Faculty of Science, Mansoura University, New Dammiatta, Egypt
2. Department of Chemistry, University of Minnesota, Minneapolis, MN 55455
E-mail: [email protected]

Abstract: Techniques that exploit straightforward aspects of NMR spectroscopy combined with conformational analysis are being developed in our laboratory. These studies are often driven by a need for new methods for determination of stereochemistry in various natural products. Both coupling constant-based and chemical shift-based NMR methods are interpreted with the help of a thorough analysis of families of conformations identified by appropriate molecular mechanics treatments. This often results in solutions to structure assignment problems that are not addressable by multi-dimensional NMR approaches.

Selected examples of this strategy, such as those outlined below, will be described:

a study of the relative configuration of two, isomeric, 4-methylene-2-cyclohex-enones of constitution 1, isolated from Ottelia alismoides found in the delta region of the Nile River.

a general method for the assignment of absolute configuration of b -chiral carboxylic acids (2).
a general method for the determination of absolute configuration of substituted, cyclic amines (cf., 3).

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* Invited lecture presented at the International Conference on Bioversity and Bioresources: Conservation and Utilization, 23-37 November 1997, Phuket, Thailand.

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