Molecular structure of E-64 (CAS 66701-25-5)

E-64

Also known as: N-(trans-Epoxysuccinyl)-L-leucine 4-guanidinobutylamide, trans-Epoxysuccinyl-L-leucylamido(4-guanidino)butane, L-trans-3-Carboxyoxiran-2-carbonyl-L-leucylagmatine, L-trans-Epoxysuccinyl-leu-4-guanidinobutylamide, (2S,3S)-3-{[(2S)-1-({4-[(diaminomethylidene)amino]butyl}amino)-4-methyl-1-oxopentan-2-yl]carbamoyl}oxirane-2-carboxylic acid, E-64 protease inhibitor, E64, trans-Epoxysuccinyl-L-leucylamido-(4-guanidino)butane, Epoxysuccinyl-L-leucylamido-(4-guanidino)butane, E-64 hemihydrate

E-64 (CAS 66701-25-5) is a compound in the Organic Acids category listed in the Jingsj chemical database. It has the molecular formula C15H27N5O5 and a molecular weight of 357.405 g/mol. Key properties include a melting point of 182ºC and a density of 1.4±0.1 g/cm3. It is classified under GHS with signal word Warning and hazard statements H371 — May cause damage to organs. No supplier offers are currently listed; request a quote. Record last updated Aug 21, 2026.

CAS No.: 66701-25-5
Jingsj CID: J-25438-2
Molecular Formula: C₁₅H₂₇N₅O₅
Molecular Weight: 357.405 g/mol
Category: Organic Acids
Last updated: 8/21/2026

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Physicochemical Properties

Melting Point	182ºC
Density	1.4±0.1 g/cm3
Exact Mass	357.201233
PSA	169.93000
LogP	-1.46
Refractive Index	1.618
Additional Property	H2O: 20 mg/mL, clear, colorless

GHS Safety & Compliance

Health HazardSignal word: Warning

H371 — May cause damage to organs

Activity & Biological Data

Target	IC50: 9 nM (Papain)[1]
Additional Information	[1]. Matsumoto K, et al. Structural basis of inhibition of cysteine proteases by E-64 and its derivatives. Biopolymers. 1999;51(1):99-107. [2]. Wadhawan M, et al. Inhibition of cathepsin B by E-64 induces oxidative stress and apoptosis in filarial parasite. PLoS One. 2014 Mar 25;9(3):e93161. [3]. Baldzizhar R, et al. Anti-serpin antibody-mediated regulation of proteases in autoimmune diabetes. J Biol Chem. 2013 Jan 18;288(3):1612-9. [4]. Blass G, et al. Chronic cathepsin inhibition by E-64 in Dahl salt-sensitive rats. Physiol Rep. 2016 Sep;4(17). pii: e12950.

Target

IC50: 9 nM (Papain)[1]

Additional Information

[1]. Matsumoto K, et al. Structural basis of inhibition of cysteine proteases by E-64 and its derivatives. Biopolymers. 1999;51(1):99-107. [2]. Wadhawan M, et al. Inhibition of cathepsin B by E-64 induces oxidative stress and apoptosis in filarial parasite. PLoS One. 2014 Mar 25;9(3):e93161. [3]. Baldzizhar R, et al. Anti-serpin antibody-mediated regulation of proteases in autoimmune diabetes. J Biol Chem. 2013 Jan 18;288(3):1612-9. [4]. Blass G, et al. Chronic cathepsin inhibition by E-64 in Dahl salt-sensitive rats. Physiol Rep. 2016 Sep;4(17). pii: e12950.

Frequently Asked Questions

What is the CAS number of E-64?

The CAS number of E-64 is 66701-25-5.

What are the molecular formula and molecular weight of E-64?

E-64 has molecular formula C15H27N5O5 and molecular weight 357.405 g/mol.

Is E-64 hazardous?

E-64 has GHS signal word Warning and hazard statements H371 — May cause damage to organs.

Data compiled from public chemical databases such as PubChem and supplier catalogs; supplier offers are provided by suppliers.

Last updated: 8/21/2026

How to cite: Jingsj. "E-64 (CAS 66701-25-5)". Jingsj Chemical Database. https://www.jingsj.com/compound/J-25438-2 (accessed 2026-11-07).

Data for reference only; verify product details with suppliers before purchase.