The Invention of Solid-Phase Peptide Synthesis
| Category | Research |
|---|---|
| Also known as | SPPS invention, Merrifield 1963, solid phase synthesis history |
| Last updated | 2026-04-14 |
| Reading time | 3 min read |
| Tags | historysolid-phase-synthesissppcpeptide-chemistrymerrifield |
Overview
Solid-phase peptide synthesis (SPPS) is the technique in which a growing peptide is assembled while covalently attached to an insoluble polymer support. It was introduced in 1963 by Robert Bruce Merrifield at the Rockefeller Institute and has been the dominant method for synthesizing peptides ever since.
Before SPPS, peptide synthesis was performed in solution. Each coupling step required purification of the intermediate product before the next amino acid could be added. For peptides longer than a few residues, this became impractical: yields fell geometrically with length, and intermediates often proved difficult to purify. Merrifield's innovation was to attach the first amino acid to a solid polystyrene resin through its carboxyl group, leaving its amino group protected. Subsequent amino acids, properly protected themselves, were coupled one at a time, with the reagents and byproducts washed away between steps.
The original method used tert-butoxycarbonyl (Boc) protection for the alpha-amino group and acid-labile side-chain protecting groups. It was later supplanted — but not replaced — by the fluorenylmethoxycarbonyl (Fmoc) strategy introduced in the 1970s, which uses base-labile alpha protection and acid-labile side-chain groups. Both approaches remain in use today.
Key People
- Robert Bruce Merrifield (1921–2006): Invented SPPS and won the 1984 Nobel Prize.
- John M. Stewart: Long-time Merrifield collaborator who helped automate the method.
- Louis A. Carpino: Developed Fmoc protection strategy.
- Stephen B.H. Kent: Extended SPPS with native chemical ligation and related methods.
Timeline
- 1963: Merrifield publishes "Solid-phase peptide synthesis. I. The synthesis of a tetrapeptide" in J. Am. Chem. Soc.
- 1965: Merrifield and Stewart automate peptide synthesis.
- 1969: Merrifield reports the total synthesis of ribonuclease A.
- 1970s: Commercial peptide synthesizers (e.g., Applied Biosystems) make SPPS widely available.
- 1970s: Carpino introduces Fmoc-based SPPS.
- 1984: Merrifield awarded the Nobel Prize in Chemistry.
- 1990s: Native chemical ligation extends SPPS to large proteins.
Background
SPPS's success depends on several integrated innovations: orthogonal protecting groups, efficient coupling reagents (carbodiimides, uronium and aminium salts, phosphonium reagents), suitable resins (Merrifield resin, Wang resin, Rink amide resin), and reliable deprotection chemistries. Each of these has been refined over decades, yielding modern methods that can routinely produce peptides of 30-50 residues with high purity.
The broader significance of SPPS is that it reduced peptide chemistry to a reliable, reproducible, and automatable discipline. Individual laboratories could, for the first time, produce custom peptides in days rather than years. This opened immense new possibilities: peptide libraries for drug discovery, synthetic vaccines, mechanistic studies in receptor pharmacology, and of course, the entire modern peptide-drug industry.
Modern Relevance
Every approved peptide drug today is produced either by SPPS, by recombinant expression, or by a hybrid strategy. Commercially important agents including liraglutide, semaglutide, octreotide, leuprolide, and many others are made at industrial scale using optimized SPPS protocols.
SPPS continues to evolve. Flow-chemistry approaches and advanced solvents aim to reduce time, waste, and reagent cost. Hybrid solution-SPPS strategies are used for very long peptides. Native chemical ligation and sortase-mediated ligation extend chemical synthesis to full proteins. The original Merrifield insight — anchoring to a solid phase — continues to be the central organizing principle. See robert-bruce-merrifield for the inventor and nobel-prize-peptide-chemistry for broader context.
Related Compounds
Related entries
- The First Peptide Drug— The first peptide drug is generally considered to be animal-derived insulin, introduced in 1923, followed by synthetic peptide hormones in the 1950s and 1960s.
- Nobel Prizes for Peptide Chemistry— A survey of Nobel Prizes awarded for foundational advances in peptide chemistry, from Fischer in 1902 to Merrifield in 1984.
- Robert Bruce Merrifield— Robert Bruce Merrifield invented solid-phase peptide synthesis in 1963, a method that revolutionized the construction of peptides and won the 1984 Nobel Prize in Chemistry.