8.51087 EMD Millipore


PyClock 6-Chloro-benzotriazole-1-yloxy-tris-pyrrolidinophosphonium hexafluorophosphate Novabiochem®. CAS 893413-42-8, molar mass 554.84 g/mol., 6-Chloro-benzotriazole-1-yloxy-tris-pyrrolidinophosphonium hexafluorophosphate Novabiochem®

Synonym: 6-Chloro-benzotriazole-1-yloxy-tris-pyrrolidinophosphonium hexafluorophosphate

  • CAS Number 893413-42-8

  • Linear Formula C₁₈H₂₇ClF₆N₆OP₂

  • Molecular Weight 554.84 g/mol



brand family   Novabiochem
packaging   100 g in Glass bottle (8510870100)
  25 g in Glass bottle (8510870025)
mp   165 - 175 °C
shipped in   ambient
storage temp.   Store at +2°C to +8°C.
specifications   Colour (visual): white to slight yellow to beige
  Appearance of substance (visual): powder
  Identity (IR): conforms
  Assay (HPLC, area%): ≥ 98.0 % (a/a)
  Solubility (5% in NMP (1-Methyl-2-pyrrolidone)): clear


Background information

PyClocK is the 6-chloro analog of PyBOP. Reaction of protected amino acids with PyClocK in the presence of base generates the corresponding 6-chloro-1-benzotriazolyl (Cl-OBt) ester. These active esters are considerably more reactive than those produced when using PyBOP or HBTU, owing to 6-chloro-1-hydroxybenzotriazole (Cl-HOBt) being more acidic than HOBt.

PyClocK is an excellent coupling reagent for situations where carboxyl activation may be sluggish, such as cyclizations and fragment condensations, as unlike imminium-based reagents such as HBTU and HATU excess PyClocK cannot cause end-capping of peptide chains.

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Safety & Documentation

Safety Information

HS Code 
2933 99 80
Hazard Statement(s) 
H315: Causes skin irritation.
H319: Causes serious eye irritation.
H335: May cause respiratory irritation.
Precautionary Statement(s) 
P302 + P352: IF ON SKIN: Wash with plenty of soap and water.
P305 + P351 + P338: IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
Storage class 
10 - 13 Other liquids and solids
WGK 3 highly water endangering
Hazard Pictogram(s) 
GHS07  GHS07
Hazard Symbols 
Irritant  Irritant
R Phrase 
R 36/37/38
Irritating to eyes, respiratory system and skin.
Protocols & Articles


Peptide Coupling Reagents Selection Guide

The Novabiochem® brand offers one of the most extensive ranges of high-quality coupling reagents for in situ activation on the market. However, with such a plethora of reagents available, the choice ...
Keywords: Condensations, Coupling reactions, Cyclizations, Racemizations, Solid phase peptide synthesis

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