Functional Group Interconversions as Strategic Tools in a Total Synthesis

9 FUNCTIONAL GROUP INTERCONVERSIONS AS STRATEGIC TOOLS IN A TOTAL SYNTHESIS 

As illustrated, the major steps in the conversion of 140 to 139 correspond to non-isohypsic transformations of functional groups the reduction of an aldehyde to a primary alcohol, the oxidation of a secondary alcohol to a ketone, and the oxidation of a primary alcohol to a carboxylic acid. The introduction and removal of the isopropylidene protecting groups and the use of the bacterium Aeetobacter suboxydans (a non-typical oxidizing agent) ensures selectivity in the reactions of the polyfunctional intermediate compounds. 

The synthesis of two other important biopolymers, proteins and nucleic acids, also involves a sequence of functional group transformations. Simple (amidic or phosphodiester) bonds are formed between readily available monomeric units (amino acids or nucleotides). Almost all synthetic efforts in this area are centered around the elaboration of an optimal method to achieve an efficient formation of this bond. Given the complexity of the final structure, this task is never too simple. 

It should now be clear that functional group transformations play more than an auxiliary role in synthesis. The importance of these reactions, especially with respect to the chemistry of natural compounds, makes it imperative to have a multitude of diverse and, at times, rather sophisticated methods to effect these often apparently trivial transformations. 

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