Biomedical subjects
Publications and source records attributed to J D Bunce.
Comparative Molecular Field Analysis (CoMFA) has shown predictive performance and versatility that appear to be unprecedented among computer-based techniques for aiding molecular design.
A number of tertiary and secondary homoallylic amines, i.e. (Z)- and (E)-4-(4-bromophenyl)-4-(3-pyridyl)-3-buten-1-ylamines, were synthesized in diastereomerically pure forms. The compounds were evaluated as neuronal norepinephrine (NE) and serotonin (5-HT) uptake inhibitors under in vitro and ex vivo conditions and compared with the tricyclics amitriptyline and nortriptyline having homoallylic side chains and with the corresponding diastereomers in the zimeldine series having allylic side chains. The Z isomers of the new homoallylic derivatives (3Z, 4Z) were specific 5-HT uptake inhibitors in analogy with the corresponding allylic derivatives zimeldine (1Z) and norzimeldine (2Z). Likewise, the selectivity profile of the homoallylic (3E, 4E) and the allylic (1E, 2E) derivatives was comparable. In general, the homoallylic compounds were less potent inhibitors than their allylic counterparts. The similarities and discrepancies were evaluated in terms of conformational preferences determined by CAMSEQ molecular mechanics calculations. Homonorzimeldine (4Z) can accommodate energetically favored, but less populated, conformations having amino nitrogen atom to aromatic ring center distances comparable to those in norzimeldine. These facts correlate to retained 5-HT selectivity but diminished potency of 4Z compared to 2Z.
We use molecular mechanics to calculate the conformational properties of a cyclic urea mimetic of alpha-chymotrypsin proposed, but not yet synthesized, by Cram and co-workers. We find that, in order to bring the structural elements of the catalytic triad into a spatial orientation suitable for proton transfer, the proposed enzyme mimetic must adopt a highly strained conformation. We redesign that part of the molecular architecture holding the catalytic triad in position and suggest two alternative enzyme mimetics. Of these, we find that the mimetic containing a fused ring structure positions the components of the catalytic triad at reasonable distances for proton transfer. We study the effect of these structural alterations on the recognition pattern presented by the enzyme mimetic to the substrate, as illustrated by the molecular electrostatic potential of the artificial enzyme.
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