Protecting groups enzymes

Enzymic Protecting Group Techniques. Waldmann, H. Sebastian, D. Chem. Rev. 1994, 94, 91L... 

APA may be either obtained directly from special Penicillium strains or by hydrolysis of penicillin Q with the aid of amidase enzymes. A major problem in the synthesis of different amides from 6-APA is the acid- and base-sensitivity of its -lactam ring which is usually very unstable outside of the pH range from 3 to 6. One synthesis of ampidllin applies the condensation of 6-APA with a mixed anhydride of N-protected phenylglydne. Catalytic hydrogenation removes the N-protecting group. Yields are low (2 30%) (without scheme). 

An enzyme-catalyzed appHcation has been used to prepare the enantiomers of hydroxy-substituted tetrahydroisoquinolines (160). The synthesis of ( V)-reticuline [485-19-8] (30) has been reported using similar methodology (161). The substitution of formic acid and paraformaldehyde in this method leads to lower reaction temperatures, freedom from hydrolysis of protective groups, and improved yields (162). 

Several dozens of aldolases have been identified so far in nature [23,24], and many of these enzymes are commercially available at a scale sufficient for preparative applications. Enzyme catalysis is more attractive for the synthesis and modification of biologically relevant classes of organic compounds that are typically complex, multifunctional, and water soluble. Typical examples are those structurally related to amino acids [5-10] or carbohydrates [25-28], which are difficult to prepare and to handle by conventional methods of chemical synthesis and mandate the laborious manipulation of protective groups. 

Scheme 8.5. Enzyme-triggered fragmentation of protective groups for amines, alcohols and carboxylic acids.

Enzyme Labile Carboxyl Protecting Groups Choline Ester (OCho)... 

The suitability of the Aloe group for the construction of lipidated peptides is emphasized by the synthesis of the maleimidocaproyl-modified, S-palmi-toylated and farnesylated heptapeptide 16 which corresponds to the N-Ras C-terminus (Scheme 10).1211 In contrast to classical urethane-type protecting groups, the Aloe group can be removed in the presence of additional functional groups and under neutral conditions. It is therefore a very convenient protecting group for the synthesis of very hydro-phobic lipid-modified peptides, which are not soluble in the aqueous media required for enzyme catalyzed transformations. 

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