Chemical syntheses synthesis without protections

No application of CMR substances or other highly dangerous substances by cotmnercial users outside industrial installations, as experience demonstrates that the required protective measures are not observed in too many instances. Risk reduction by substitution is needed. In the case of closed industrial installations, especially for chemical synthesis, minimisation of technical emissions (without substitution) may be the better strategy. 

Although the chemical peptide synthesis have been successfully applied for products of biological and industrial interest, this synthetic methodology is still in need of innovations. The use of enzymes provide an alternative to chemical peptide synthesis, for which the most notable advantage lies on the stereo and regiospecifically peptide bond formation without the need of group protection and very mild operating conditions (2). 

In summary, the nucleoside phosphorylases provide a regio- and stereo-specific route for nucleoside synthesis which is applicable to nucleoside analogs which are modified in either the base or the sugar moiety. These processes provide good yields of products in most cases without the extensive protection and deprotection steps involved in traditional chemical synthesis of nucleosides. Application of this strategy to the synthesis of 2 -deoxy- and 2, 3 -dideoxynucleosides was reported with the use of N-deoxyribosyl transferase from Lactobacillus species1301, 312). 

In 1989, despite the hnge number of possible stereoisomers, a research group led by Professor Kishi managed to achieve the total chemical synthesis of a fully protected palytoxin carboxylic acid [7]. This was subsequently converted to palytoxin carboxylic acid and palytoxin amide without the use of protecting groups [60]. By comparison of biological activity, chromatographic behavior, and... 

Most enzymatic reactions are performed under mild conditions, such as in water, at room temperature, and at atmospheric pressure, leading to lower energy consumption and operational risks. In addition, it is widely known that enzymes are capable of catalyzing highly regio-, chemo-, and enantio-selective reactions without performing the lengthy chemical protection/ deprotection steps required in traditional chemical synthesis. 

This introduction would not be complete without mentioning a few key events in the history of peptide synthesis. In 1901 Emil Fischer reported the synthesis of a peptide, Leonidas Zervas developed the Z (Cbz) protecting group in 1932, and Vincent du Vigneaud was awarded the Nobel Prize in 1955 for the chemical synthesis of the cyclic peptide, oxytocin. In 1963 Robert Bruce Merrifield introduced the concept and the first implementation of solid-phase peptide synthesis for which he was awarded the 1984 Nobel Prize in chemistry [1,2]. Solid-phase peptide synthesis has for decades been the primary source of synthetic peptides on a laboratory scale. 

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