The potential of new natural products as an important source for the exploration and development of new drugs and crop protection products is a long way from being exhausted. The statistical analysis of the structures of the natural and synthetically derived compounds has shown conspicuous variations in structural types in the natural products derived from different natural sources, which can be utilized in the search for individual active substances. The occasionally voiced prepossession that natural products have already been sufficiently examined and therefore no more innovations are to be expected can definitely be rejected.

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We describe a new penalty function for use in restrained molecular dynamics simulations which allows experimental J-coupling information to be enforced as a time-averaged, rather than instantaneous, quantity. The pseudo-energy term has been formulated in terms of a calculated J value (a measured quantity) rather than the relevant dihedral angle (a derived quantity). This accounts for the distinct non-linearity of the coupling constant with respect to either Cartesian coordinates or dihedral angles. Example simulations of the cyclic decapeptide antamanide show the procedure's ability to enforce experimental restraints while exploring a large region of conformational space and producing a relatively small disturbance of the physical force field.

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