Pregnenolone

Athanor · official

C₂₁H₃₂O₂ · 316.5 g/mol

IUPAC name: 1-[(3S,8S,9S,10R,13S,14S,17S)-3-hydroxy-10,13-dimethyl-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-17-yl]ethanone

Also called P5, steroid precursor, prohormone

Hormones Lipids

Open in Athanor

Drawn from its SMILES with RDKit

WarningHarmful if swallowed · Harmful in contact with skin · Harmful if inhaled · Suspected of causing cancer · Suspected of damaging fertility or the unborn child

Names and identifiers

IUPAC name: 1-[(3S,8S,9S,10R,13S,14S,17S)-3-hydroxy-10,13-dimethyl-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-17-yl]ethanone
Synonyms: P5, steroid precursor, prohormone
+ 38 more
3beta-Hydroxypregn-5-en-20-one, Arthenolone, Regnosone, Skinostelon, Enelone, Natolone, Bina-Skin, 5-Pregnen-3beta-ol-20-one, delta5-Pregnenolone, 5-Pregnen-3-beta-ol-20-one, Pregnenolona, Pregnenolonum, DTXSID1036541, 3-beta-Hydroxypregn-5-en-20-one, Pregn-5-en-20-one, 3-hydroxy-, (3beta)-, 73R90F7MQ8, 1-[(3S,8S,9S,10R,13S,14S,17S)-3-hydroxy-10,13-dimethyl-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-17-yl]ethanone, DTXCID9016541, CHEBI:16581, NSC1616, 5 Pregnen 3 beta ol 20 one, 1-((3S,8S,9S,10R,13S,14S,17S)-3-hydroxy-10,13-dimethyl-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta(a)phenanthren-17-yl)ethanone, RefChem:868471, 205-647-4, Prenolon, Pregnetan, Pregneton, Pregnolon, (3BETA)-3-HYDROXYPREGN-5-EN-20-ONE, 3beta-Hydroxy-5-pregnen-20-one, 5-Pregnenolone, NSC 1616, MFCD00003628, Prestwick_859, Pregnenolone (Standard), Prestwick3_000546, Pregnenolone (JAN/INN), Pregn-5-en-20-one, 3beta-hydroxy-
Molecular formula: C₂₁H₃₂O₂
Empirical formula: C₂₁H₃₂O₂
Molecular weight: 316.5 g/mol
Exact mass: 316.24023
CAS number: 145-13-1
PubChem CID: 8955
Canonical SMILES: CC(=O)C1CCC2C1(CCC3C2CC=C4C3(CCC(C4)O)C)C
Isomeric SMILES: CC(=O)[C@H]1CC[C@@H]2[C@@]1(CC[C@H]3[C@H]2CC=C4[C@@]3(CC[C@@H](C4)O)C)C
InChI: InChI=1S/C21H32O2/c1-13(22)17-6-7-18-16-5-4-14-12-15(23)8-10-20(14,2)19(16)9-11-21(17,18)3/h4,15-19,23H,5-12H2,1-3H3/t15-,16-,17+,18-,19-,20-,21+/m0/s1
InChIKey: ORNBQBCIOKFOEO-QGVNFLHTSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Calculated

Heavy atoms: 23
Rings: 4
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0.86
H-bond donors: 1
H-bond acceptors: 2
Rotatable bonds: 1
TPSA (Å²): 37.3
Formal charge: 0
XLogP3: 4.2 PubChem
Complexity: 550 PubChem
Stereocenters: 7 definedCIP: C4: S · C7: S · C8: S · C13: S · C17: R · C19: S · C22: S
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C79.70%
H10.19%
O10.11%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 4.52 Crippen (Wildman and Crippen 1999)
log S (water solubility): -4.58 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 4.08 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 316.49
log P ≤ 5 (Crippen): 4.52
H-bond donors ≤ 5: 1
H-bond acceptors ≤ 10: 2

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Warning

Most widely reported: 23 company reports to ECHA. Source [1].

Harmful or irritant
Health hazard

H302Harmful if swallowed (87% of reports)
H312Harmful in contact with skin (87% of reports)
H332Harmful if inhaled (87% of reports)
H351Suspected of causing cancer (87% of reports)
H361Suspected of damaging fertility or the unborn child (87% of reports)

Precautionary statements: P203, P261, P264, P270, P271, P280, P301+P317, P302+P352, P304+P340, P317, P318, P321, P330, P362+P364, P405, P501

View all classifications (2)

[1] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 13% (3 of 23) of reports.
[1] European Chemicals Agency (ECHA) · 23 reports · WarningH302, H312, H332, H351, H361

Safety data sheets on the supplier’s page: Aladdin Scientific, INTERBIOSCREEN, Alfa Chemistry.

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[2]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[3]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[4]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[5]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[6]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.