Sustainable Peptide Synthesis Enabled by a Transient Protecting Group

Abstract

The growing interest in synthetic peptides has prompted the development of viable methods for their sustainable production. Currently, large amounts of toxic solvents are required for peptide assembly from protected building blocks, and switching to water as a reaction medium remains a major hurdle in peptide chemistry. We report an aqueous solid‐phase peptide synthesis strategy that is based on a water‐compatible 2,7‐disulfo‐9‐fluorenylmethoxycarbonyl (Smoc) protecting group. This approach enables peptide assembly under aqueous conditions, real‐time monitoring of building block coupling, and efficient postsynthetic purification. The procedure for the synthesis of all natural and several non‐natural Smoc‐protected amino acids is described, as well as the assembly of 22 peptide sequences and the fundamental issues of SPPS, including the protecting group strategy, coupling and cleavage efficiency, stability under aqueous conditions, and crucial side reactions.

Novel amino‐Li resin for water‐based solid‐phase peptide synthesis

“…It is important to mention that N α -Smoc building blocks D, N, Q, R, Y possessed unprotected side chains. 20 High-performance liquid chromatography (HPLC) traces of crude peptides, shown at Figure 3, clearly demonstrate that all constructs were assembled in sufficient purity and good yield (see also Section 2). Electrospray ionization mass spectrometry (ESI-MS) analysis revealed that the observed mz signals corresponded to the calculated ones.…”

“…18,19 In our earlier paper, we have described a sulfonated version of an Fmoc protecting group, 2,7-disulfo-9-fluorenylmethoxycarbonyl (Smoc), that allowed SPPS under aqueous conditions as well as efficient postsynthetic purification of the peptides. 20 Thus, we have established a concept for efficient aqueous solid-phase peptide synthesis (ASPPS) and optimized it in view of coupling efficiency and N-terminal deprotection conditions. However, the majority of current solid supports and linker systems are not suitable for SPPS under aqueous conditions.…”

“…To date, from the set of available supports, [26][27][28][29][30][31] the PEG-based coreless ChemMatrix resin 32,33 was found to be the most suitable for aqueous SPPS. 20 However, this support shares the common drawbacks of its class, namely, low loading capacity, unpredictable swelling, and acid lability. Recently, as an alternative, a second generation of aminopolyacrylamide resin (amino-Li-resin, 33,34 Figure 1) was developed that has proven applicability for SPPS 33 in view of its excellent swelling in most polar organic solvents, including the green solvents most commonly used in SPPS, water, and even in aqueous buffers.…”

Chemical Protein Synthesis in Medicinal Chemistry

“…Hopefully, SPPS is already experiencing a smooth transition to greener chemistries, 64 which include the use of water as the solvent for the concatenation of amino acids. 65 Post Another trend, which is critical to the discovery of small protein therapeutics, is the development of fast methods for the production of synthetic protein libraries. The development of fast synthesis techniques will enable full benefit from the high throughput methods that are available for screening small molecules.…”

Self-Assembly and Cytocompatibility of Amino Acid Conjugates Containing a Novel Water-Soluble Aromatic Protecting Group

“…There is great interest in reducing the environmental impact of organic solvents used in synthetic reactions, in peptide synthesis, and other fields. Many approaches to cleaner peptide synthesis have been investigated. − Recently, the Fmoc group has been modified with sulfonic acid groups to confer water solubility, hence enabling sustainable green synthesis of peptides in aqueous media. , This follows on from Merrifield’s original development of monosulfated 2-sulfo-9-fluorenylmethyloxycarbonyl chloride amino acids for peptide purification . A range of amino acids linked to the 2,7-disulfo-9-fluorenylmethoxycarbonyl (Smoc) group (Scheme ) is now commercially available.…”