The azido acid approach to beta-peptides: parallel synthesis of a tri-beta-peptide library by fluorous tagging

Liquid-Phase Peptide Synthesis (LPPS): A Third Wave for the Preparation of Peptides

Since the last century, peptides have gained wide acceptance as drugs, with almost 100 already in the market and a large number in the pipeline. In this context, peptide synthesis has grown massively as a stringent field for pharmaceuticals around the globe. Three methodologies, namely, classical solution peptide synthesis (CSPS), solid-phase peptide synthesis (SPPS), and liquid-phase peptide synthesis (LPPS), have made significant contributions to the field. This review provides a comprehensive and integrated vision of LPPS as the third wave for peptide synthesis. LPPS combines the advantages of CSPS and SPPS, where peptide elongation is carried out in solution and the growing peptide chain is supported on a soluble tag, which confers characteristic properties. LPPS protocols allow the large-scale production of peptides and reduce the use of excess reagents and solvents, thus meeting the principles of green chemistry. In this review, tags associated with LPPS are broadly discussed under the following headings: polydisperse polyethylene glycol (PEG), membrane-enhanced peptide synthesis (MEPS), fluorous technology, ionic liquids (ILs), PolyCarbon, hydrophobic polymers, and group-assisted purification (GAP). It also highlights the signature accomplishments of LPPS tags and the limitations of the same.

Rhodamine F: a novel class of fluorous ponytailed dyes for bioconjugation

Incorporation of fluorous ponytails such as polyfluorinated alkyl residues (CH2)m(CF2)nCF3 leads to a novel class of bright rhodamine-based fluorescence dyes. These dyes combine the excellent photophysical properties of the frequently used rhodamine dyes with the unique features of "light" fluorous molecules. One of those features is the possibility to separate substances utilizing fluorous solid-phase extraction (F-SPE), which is based on the specific intermolecular interaction between fluorous compounds. Thus, molecules, which are labeled with these new dyes, are not only accessible to fluorescence experiments, but can also be easily purified (via so-called FluoroFlash columns) prior to use. The dyes were bound to a cell penetrating peptoid (polycationic oligo(N-substituted) glycine) on solid supports. These conjugates were purified with F-SPE before their photophysical and biological properties were investigated.

Triple hybrids of steroids, spiroketals, and oligopeptides as new biomolecular chimeras

An oxidative enol ether rearrangement was the key methodology in the construction of steroid-spiroketal-RGD peptides. Biological studies demonstrated potent integrin CD11b/CD18 antagonistic effects.