UF Resine II Synthesized at pH 1.0, F/U 1.0, 50°C
Resins for Solid Phase Synthesis - Glycopep
This method was introduced by R.C. Sheppard in 1971. Fmoc stands for 9-Fluorenylmethoxycarbonyl which describes the Fmoc protecting group. To remove an Fmoc from a growing peptide chain, basic conditions (usually 20% piperidine in DMF) are used. Removal of side-chain protecting groups and peptide from the resin is achieved by incubating in trifluoroacetic acid (TFA). Fmoc deprotection is usually slow because the anionic nitrogen produced at the end is not a particularly favorable product, although the whole process is thermodynamically driven by the evolution of carbon dioxide. The main advantage of Fmoc chemistry is that no hydrofluoric acid is needed. It is therefore used for most routine synthesis.
Trityl resins are the most versatile resins for solid phase synthesis
When R. B. Merrifield invented SPPS in 1963, it was according to the tBoc method. t-Boc (or Boc) stands for tert-Butyloxycarbonyl. To remove Boc from a growing peptide chain, acidic conditions are used (usually neat TFA). Removal of side-chain protecting groups and the peptide from the resin at the end of the synthesis is achieved by incubating in hydrofluoric acid (which can be dangerous); for this reason Boc chemistry is generally disfavored. However for complex syntheses Boc is favourable. When synthesizing nonnatural peptide analogs which are base-sensitive (such as depsi-peptides), Boc is necessary.
CDNA Synthesis Kits | Life Science Research | Bio-Rad
Currently, two protective groups (Fmoc, Boc) are commonly used in solid-phase peptide synthesis. Their lability is caused by the carbamate group which readily releases CO2 for an irreversible decoupling step.
Pyridine synthesis - Organic chemistry
Before the Fmoc group became popular, the Boc group was commonly used for protecting the terminal amine of the peptide, requiring the use of more acid stable groups for side chain protection in orthogonal strategies. It retains usefulness in reducing aggregation of peptides during synthesis. Boc groups can be added to amino acids with boc anhydride and a suitable base.