Fragment Library

Rule of 3 compliant compounds for fragment-based drug discovery


  • More than 10,000 fragments from which researchers can custom select
  • A High Solubility Subset of fragments with high solubility in DMSO and PBS
  • Fluorinated fragments for NMR and brominated fragments for X-ray crystallography


The ChemBridge® Fragment Library collection offers more than 10,000 compounds that can be individually selected, allowing researchers to build fragment sets of size and composition best suited to their research objectives and methodologies. ChemBridge can also assist in the selection of diverse subsets including structurally diverse subsets. This collection of small molecule fragments provides compounds for use in fragment-based screening and drug discovery using high-throughput X-ray crystallography, NMR, SPR and high concentration bioassay methodologies. Compounds included in the Fragment Library collection were chosen based upon the commonly accepted Astex Rule of Three¹ criteria plus additional physiochemical property and substructure filters.

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High Solubility Subset

Fragments included in the High Solubility Subset (HSS) have a minimum DMSO solubility of 200mM and minimum solubility in phosphate buffered saline (PBS pH 7.4) of 200uM (with many fragments soluble at 1mM in PBS).

Fluorinated Subset

This subset of fragments offers an advantage for NMR-based fragment screens as 19F-NMR spectra have a wide range of chemical shifts which can be modified by the effects of neighboring atoms, particularly in the bound and unbound states of a fragment. Selection is based on the same criteria used for the overall Fragment Library collection.

Brominated Subset

A bromine-containing subset of fragments with potential use for X-ray crystallographic screening. The presence of the bromine atom in the X-ray analysis provides evdience for determing the location of the fragment bound to the target protein. Selection criteria is based on the same criteria used for the overall Fragment Library collection but with MW upper limit increased to 380 to allow for the contribution of the brmoine atom.


ChemBridge has applied Rule of Three considerations (MW ≤ 300, H-bond donors ≤ 3, H-bond acceptors ≤ 3, cLogP ≤ 3) along with a rotatable bond count limit (RB ≤ 3) and a TPSA limit (TPSA ≤ 120). For the Brominated Subset, the MW upper limit was adjusted to 380. For more details on the Fragment Library collection or subsets please contact


  • Download structures and custom select from more than 10,000 Fragment Library compounds.
  • Compounds are available in mg or umol amounts undissolved (mostly powders, some oils), as DMSO solutions in standard or deuterated DMSO, or as dry film.
  • Delivery in vials, minitube racks, or in 96-well or 384-well paltes.
  • All compounds have a minimum purity of 90% by NMR or by LC-MS/ELSD.
  • Follow-up stock is available for resupply, subject to availability.


¹Carr, R.A.E. et al., Drug Discovery Today, 2005, 10, 987-992.

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