Chemical Structure and Physical Properties of SLU-PP-332

SLU-PP-332 is a synthetic small-molecule pan-estrogen-related receptor (ERR) agonist, rather than a peptide or steroid. It is primarily used as an experimental chemical tool for studying ERRα/β/γ signaling, mitochondrial metabolism, and exercise-mimetic effects.

1. Chemical identity

These identity and physical-form data are reported by PubChem and commercial research-reagent suppliers.

2. Molecular structure

SLU-PP-332 contains three particularly important structural components:

A. 4-hydroxybenzamide portion

• A benzene ring bearing a para-hydroxyl (-OH) group.

• The ring is attached to an amide/hydrazide functional group.

B. Hydrazone linkage

• The molecule contains a characteristic –C(=O)–NH–N=CH– linkage.

• The C=N double bond has defined E stereochemistry, which is reflected in its systematic name.

C. Naphthalene group

• The other end contains a fused naphthalene aromatic system (C₁₀H₇).

• This relatively hydrophobic aromatic region contributes substantially to the molecule’s lipophilic character.

PubChem gives the SMILES representation as:

C1=CC=C2C=C(C=CC2=C1)/C=N/NC(=O)C3=CC=C(C=C3)O

and reports one defined bond stereocenter associated with the E-configured C=N bond.

3. Important calculated physicochemical properties

The calculated physicochemical descriptors are from PubChem.

4. Physical characteristics

SLU-PP-332 is generally supplied as a white to beige powder or crystalline solid. Commercial specifications commonly recommend cold storage, although exact conditions vary by supplier. Sigma-Aldrich lists 2–8°C, while Tocris lists −20°C for its research material.

Its water solubility is relatively limited, consistent with its aromatic and moderately lipophilic structure. DMSO is commonly used as the solvent. Sigma reports approximately 2 mg/mL in DMSO, producing a clear solution when warmed; Tocris reports preparation in DMSO up to 100 mM.

5. Structure–property relationship

The structure helps explain its physicochemical behavior:

Naphthalene ring → increased lipophilicity

The fused aromatic naphthalene system provides a substantial hydrophobic surface, contributing to the XlogP of approximately 3.7.

Phenolic OH + hydrazide → hydrogen bonding

The hydroxyl and hydrazide groups provide hydrogen-bonding capacity and increase polarity relative to a purely hydrocarbon aromatic compound.

Hydrazone C=N → defined geometry

The E configuration gives SLU-PP-332 a relatively organized, planar molecular arrangement that is important for receptor interaction.

Two aromatic systems → relatively rigid molecule

The benzene and naphthalene rings substantially restrict conformational flexibility. This contrasts with highly flexible aliphatic compounds.

6. Key chemical-property summary

In simple terms, SLU-PP-332 can be characterized as:

A neutral, moderately lipophilic, aromatic hydrazide/hydrazone small molecule with two fused/linked aromatic systems, moderate hydrogen-bonding capacity, and relatively high structural rigidity.

Its molecular formula is C₁₈H₁₄N₂O₂, molecular weight 290.32 g/mol, XlogP approximately 3.7, and TPSA 61.7 Ų.

One important distinction: these physicochemical properties should not be interpreted as evidence that SLU-PP-332 is suitable for human supplementation or therapeutic use. Current research primarily concerns experimental ERR agonism in cellular and animal models.