Benzotriazole-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate
[CAS 128625-52-5]

Identification

• Classification: Biochemical >> Amino acids and their derivatives >> Other protected amino acids
• Name: Benzotriazole-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate
• Synonyms: PyBOP
• Molecular Formula: C₁₈H₂₈N₆OP.PF₆
• Molecular Weight: 520.40
• CAS Registry Number: 128625-52-5
• EC Number: 603-290-2
• SMILES: C1CCN(C1)[P+](N2CCCC2)(N3CCCC3)ON4C5=CC=CC=C5N=N4.F[P-](F)(F)(F)(F)F

Properties

• Melting point: 150 °C (Expl.)
• Solubility: 1 mm in 2 mL DMF (Expl.)

Safety Data

• Hazard Symbols: GHS07;GHS09 Warning
• Risk Statements: H302-H315-H317-H319-H335-H410
• Safety Statements: P261-P264-P264+P265-P270-P271-P272-P273-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P333+P317-P337+P317-P362+P364-P391-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H302
Skin sensitization	Skin Sens.	1	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400

chemBlink Chemical Story

PyBOP was introduced in 1990 as a peptide-coupling reagent designed not only for reactivity but also for safer byproduct chemistry. Peptide synthesis repeatedly requires activation of a carboxylic acid so that it will form an amide bond efficiently with an amino group.

PyBOP is a phosphonium reagent containing a benzotriazol-1-yloxy group and three pyrrolidino substituents. It was developed as an analogue of BOP. BOP was effective, but its reaction chemistry could generate hexamethylphosphoramide, HMPA, a toxic byproduct.

Replacing the dimethylamino groups with pyrrolidino groups preserved useful coupling performance while avoiding that particular byproduct. PyBOP therefore marks an important evolution in reagent design: chemists began asking not only whether a bond could be made, but also what unwanted chemistry accompanied it.

References:
Coste J., Le-Nguyen D., Castro B. PyBOP: A new peptide coupling reagent devoid of toxic by-product. Tetrahedron Letters, 1990, 31, 205-208.

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