INFORMATION-THEORY DESCRIPTION OF SYNTHETIC STRATEGIES IN THE POLYQUINANE SERIES - THE HOLOSYNTHON CONCEPT

Information theory makes it possible to give a semiquantitative graphi cal representation of the various strategies used to reach a given syn thetic target. Skeletal complexity and similarity of the precursors wi th respect to the target structure provide figures which monitor the p rogress made from the starting material en route toward the target. Ex amples selected from the triquinane family are used to illustrate the benefits but also the present limits of such an approach. Whereas for silphinene and hirsutene various synthetic strategies appear in a clea r graphical form when treated within this framework, coriolin shows th at the skeleton-only approach provides graphics which can be misleadin g. To improve this limitation, progress will have to be made in the tr eatment of functional complexity from a synthetic point of view. From a more general point of view, a practical treatment of stereochemistry within the information theory framework is still waited for. The grap hical treatment displays clearly the key step(s) in a given strategy. Such steps are often characterized by a large change in complexity and /or similarity. This semiquantitative representation converges with, o n one hand, the interest of some rearrangements in shorter synthesis a nd, on the other hand, the interest and the limits of the class of rea ctions variously christened as cascades, domino, tandem. The treatment shows also the indissociable counterpart of these reaction-centered a pproaches: the structural entities which make them possible. Such stru ctural entities (holosynthons) call attention to synthetic strategies where a global part (holos: whole) of the target is looked at, this vi ew complements the more classical bond by bond, disconnection approach .