The """"""""shikimic acid pathway"""""""" is one of the key assembly lines in cellular metabolism, occupying a pivotal position between primary and secondary metabolism. In the former, it is responsible for the biosynthesis of the aromatic amino acids, and in the latter, it is the originating point for most classes of alkaloids as well as several other groups of natural products having mixed biosynthetic origins. The fundamental importance of the shikimic acid pathway in biochemistry would, in itself, justify further study of the individual reactions involved. The particular reaction we have chosen to investigate is especially useful and interesting to study as it is the only example known to us of a 1,6-hydride shift occurring in nature. The currently accepted mechanism for this transformation is a direct, one- step transfer of hydride. Examination of molecular models shows this to be highly unfavorable at best. We propose to show that a two-step mechanism (a 1,7-hydride shift followed by a 1,2-hydride shift) is the correct explanation. Our approach will be to examine a series of model compounds. Simple product analysis should give an unambiguous confirmation of one of these two mechanisms. Our initial plan has been to synthesize the required model compounds from the known compound, 10-phenylanthrone. All should be accessible via synthetic sequences ranging from three to five steps. Study of this unusual reaction is of broad significance beyond the specific problem itself. There is a growing awareness amongst organic chemists that the three-dimensional disposition of interacting orbitals is of prime importance in predicting which intramolecular reactions occur readily and which will be so slow as to be insignificant. We have begun parallel studies in simpler systems in order to test the generality of our ideas about stereoelectronic control of intramolecular hydride transfers. Additionally, we feel that our approach to this specific problem will yield results of wide synthetic utility. We have developed new strategies for preparing anthrones substituted in the 10-position and will continue efforts in this area as well. The close resemblance which anthrones bears to many pharmaceutically useful drugs, in particular the anthracyclines, warrants a renewal of synthetic interest in this class of compounds.
Showing the most recent 10 out of 47 publications
