Proteeting-Group-Free Total Syntheses: A Challenging Approach

摘要

Multistep synthesis, and in particular, total synthesis of natural product is a refined scientific activity. After two centuries of breakthroughs, organic chemistry has become a "predictive science" just as, for example, nuclear physic. However, total synthesis remains an activity so difficult that designing a totally reliable relrosynthctic plan remains almost impossible. Over many decades, the objectives of total synthesis were solely to get higher yields, higher chemo- and stereoselectivity, and higher convergence. Nevertheless, this led to much innovative success. In the mid 90s, a new philosophy arose for multistep synthesis that took new constrains into account: step economy, atom economy, and redox economy. This put stimulating pressure on chemists' inventiveness and led to even more aesthetic and straightforward syntheses. Pushed forward by the demands of our society, chemical science must now go one more step toward maturity by taking into account ecologic considerations. This means that chemists must now design retrosynthetic plans incorporating protective-group-free strategies, thus adding a further refinement to the already complicated art of total synthesis. Thanks to tremendous advances recently accomplished in organic chemistry, and particularly in catalyzed processes, this refinement is now a reachable aim. Thus, many new kinds of catalyst are now described, and they are endowed with always higher selectivity, functional group tolerance, thus allowing milder conditions and accomplishing ewactions hitherto unprecedented. Chemistry catalogues list many of them, and these catalysts involve almost all the elements of the periodic table.