20 Oct 2026 · KUGAKI Technical Team
Building blocks for medicinal chemistry, click chemistry and bioconjugation
Modern medicinal chemistry is largely assembly: join reliable building blocks with reliable reactions. A small set of functional handles covers most of that work, from scaffold synthesis to attaching a drug to a protein.
Cross-coupling partners
The Suzuki–Miyaura reaction joins an aryl boronic acid to an aryl halide with a palladium catalyst. It tolerates many functional groups and is one of the most used C–C bond-forming reactions in drug discovery.
- Boronic acids: Phenylboronic acid, 4-Fluorophenylboronic acid. Fluorinated aryl groups are a common way to tune metabolic stability and lipophilicity.
- Halo-heterocycles: 3-Bromopyridine, 4-Bromopyrazole. Pyridines and pyrazoles appear widely in kinase inhibitors and other approved drugs.
- Scaffold acids: Indole-2-carboxylic acid for amide coupling into indole-based series.
Click chemistry
Azide–alkyne cycloaddition forms a stable triazole under mild conditions:
- Copper-catalysed (CuAAC): a terminal alkyne, for example from Boc-propargyl-Gly-OH, reacts with an azide in the presence of Cu(I).
- Strain-promoted (SPAAC): cyclooctynes such as DBCO-amine react with azides with no copper at all, which is why they suit live cells and sensitive proteins.
Bioconjugation handles
| Target group | Reagent | Notes |
|---|---|---|
| Amines (lysine, N-terminus) | N-Hydroxysuccinimide (NHS) with EDC (free base) | EDC activates a carboxylic acid; NHS turns it into a more stable active ester. Use amine-free buffers such as MES or phosphate. |
| Thiols (cysteine) | Maleimides, e.g. N-Phenylmaleimide | Selective at pH 6.5–7.5; above that, amines start to compete. |
| Spacing and solubility | PEG linkers, e.g. Fmoc-NH-PEG3-COOH | Add flexibility and water solubility between two partners. |
| Lipid anchoring | mPEG2000-DSPE | PEG-lipid used in liposome and lipid nanoparticle formulation research. |
Sourcing building blocks
For library work, consistency matters more than headline purity: check the CoA for identity (NMR or HPLC) and water content. Browse Organic Building Blocks, Heterocyclic Building Blocks, Click Chemistry & Linkers and Bioconjugation. Larger quantities and custom pack sizes can be quoted on request.
Products in this guide
Phenylboronic acidCAS 98-80-6
4-Fluorophenylboronic acidCAS 1765-93-1
3-BromopyridineCAS 626-55-1
4-BromopyrazoleCAS 2075-45-8
Indole-2-carboxylic acidCAS 1477-50-5
DBCO-amineCAS 1255942-06-3
Boc-propargyl-Gly-OHCAS 63039-48-5
N-Hydroxysuccinimide (NHS)CAS 6066-82-6
EDC (free base)CAS 1892-57-5
N-PhenylmaleimideCAS 941-69-5
Fmoc-NH-PEG3-COOHCAS 557756-85-1
mPEG2000-DSPECAS 147867-65-0
Related collections
Organic Building Blocks 1551 Heterocyclic Building Blocks 348 Click Chemistry & Linkers 17 Bioconjugation 17
Need larger quantities or a specific grade? Every lot ships with a certificate of analysis; SDS and TDS are available on request. Packs above 5 kg / 5 L are quoted individually.
Request a bulk quote Documents & CoA
All KUGAKI products are for research and further manufacturing use only. Not for human or veterinary use. Please read our End-Use Policy.