Renewable Feedstocks

Abstract

Because fossil feedstocks are becoming harder to extract, and the processes of mining, synthesis, and disposal are all polluting, green chemistry seeks to use renewable feedstocks, typically derived from plants. Renewable feedstocks should be commercially available, best from agricultural waste products. They can come in any physical form: solid, liquid or gas. Biofeedstocks typically have the advantage of oxidation state matching—the feedstock oxidation state is chosen to match that of the desired product to avoid unnecessary steps and toxic redox reagents. Biofeedstocks can also improve synthetic efficiency if the feedstock is chosen to match the structure and oxidation state of the product. Earth abundant elements such as Si, Al, and Fe can also be considered renewable. The most significant biofeedstocks in terms of quantity available are cellulose, sugars, lignins, proteins, and lipids. Genomatica produces 1,4-butanediol in E. coli from simple sugars as feedstocks. Nucleic acid bases have been used as a source of nitrogen-containing heterocycles for medicinal chemistry. The HIV drug, carbovir, has been synthesized from both pyrimidines and purines, and an enzymatic resolution led to an efficient single enantiomer synthesis. Tamiflu™ and Taxol™ are examples of medicines that can be produced very efficiently from complex natural product feedstocks.