Selected Total and Partial Syntheses

Camptothecin.— The alkaloid camptothecin (3), which exhibits antileukemic and cytostatic activity, has been a vogue target for a number of years, and several syntheses are known. Biichi has now devised a short synthesis of the racemic compound (3) in which the fragment (5) was coupled with the amine (4) to give an intermediate (6). This substance (6) was then cyclized as indicated, and two further steps gave the target, (3). Crouse, under Corey s direction, has described the first 

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As a testament to the utility of the carbenoid C-H insertion methodology, it has already been utilized as a key component of many partial and total syntheses of natural products and pharmaceuticals. Several were highlighted in this chapter, and many more instances will likely emerge on the scene in the coming years as the chemistry continues to improve. In the future, research will continue to focus on development of new and more selective chiral catalysts, as well as expanding the scope of the acceptable donor and acceptor groups compatible with the carbenoids themselves. With continued advancements, this area of C-H activation will remain a synthetically important part of organic chemistry for decades to come. 

There are several examples of investigations of oxidation processes, involving radiotracers. Many substances can be partially oxidized by O2, if selective catalysts are used to control kinetically the oxidation process, otherwise the partial oxidation products will react further resulting in total combustion to CO2 and H2O. It is possible to introduce O2 into hydrocarbons such as olefins and aromatics to synthesize aldehydes (for example, acrolein and benzaldehyde) and acids (for example, acrylic acid, phthalic acid anhydride). In some reactions a selective oxidation can also result in dehydrogenation (butene butadiene) or dealkylation (toluene benzene) processes. 

In spite of a multitude of total syntheses of statins, those which occur naturally are obtained on an industrial scale by fermentation, and in the case of simvastatin, by partial synthesis. Only those statins containing a nitrogen heterocycle are obtained by total syntheses. [391] Hereafter, selected representative examples are presented. 

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