Fragment Library

Rule of 3 compliant compounds for fragment-based drug discovery


  • More than 13,500 fragments to select from
  • A subset that meets High Solubility criteria (200mM in DMSO and 200uM or higher in PBS)
  • Fluorinated fragments for NMR and brominated fragments for X-ray crystallography


The ChemBridge® Fragment Library offers more than 13,500 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 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.

View Product Sheet

High Solubility Subset

Fragments that meet the High Solubility criteria must have a minimum DMSO solubility of 200mM and minimum solubility in phosphate buffered saline (PBS pH 7.4) of 200uM (many fragments in the High Solubility subset are also 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 evidence for determining 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 bromine 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


  • To view all fragments, download the Fragment Library Part 1 file and the Fragment Library Part 2 file.
  • For a file of High Solubility fragments only, please email
  • Brominated and fluorinated fragments are available as separate files on the download page and also included in the Fragment Library Part 1 file.
  • Custom select fragments meeting your research objectives and methodologies
  • Fragments are available in mg or micromole (umol) amounts in dry format or as DMSO solutions (in standard or deuterated DMSO).
  • Delivery in vials, 96-well format minitube racks, or in 96-well or 384-well plates available.
  • 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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