L-Cysteine, methyl ester, hydrochloride

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  • Identifiers

    CAS number
    18598-63-5

    Molecular formula
    C4H10ClNO2S

    SMILES
    COC(=O)[C@H](CS)N.Cl

    Safety labels

    Irritant
    Irritant

  • Odor profile

    Fragrance
    Sulfurous 56.92%
    Meaty 43.74%
    Savory 34.61%
    Roasted 32.22%
    Odorless 31.73%
    Fruity 29.33%
    Cheesy 28.11%
    Tropical 27.94%
    Cooked 27.74%
    Onion 26.44%

     

    Flavor
    Odorless 40.3%
    Sulfury 32.03%
    Cooked 27.95%
    Sulfurous 27.93%
    Roasted 27.81%
    Mild 27.2%
    Bland 22.85%
    Fruity 22.05%
    Yeast 21.26%
    Sweet-like 21.23%

     

    Odor impact est.
    High

  • Properties

    pKa est.
    6.59 (neutral)

    Molecular weight
    171.65 g/mol

    Vapor pressure est.

    • hPa @ 20°C
    • hPa @ 25°C

    Evaporation rate
    Moderately slow

    Boiling point est.
    220°C

    Flash point

    • 80.39 ˚C est.

    Solubility expt.

    • Soluble
    • Soluble (in ethanol)
    • >25.7 [ug/mL] (The mean of the results at pH 7.4)

  • Synonyms

    • 18598-63-5
    • L-CYSTEINE METHYL ESTER HYDROCHLORIDE
    • Mecysteine hydrochloride
    • Acdrile
    • Actiol
    • L-Cysteine, methyl ester, hydrochloride
    • Methyl L-cysteine hydrochloride
    • NSC-161611
    • 33RG619160
    • METHYL (R)-2-AMINO-3-MERCAPTOPROPANOATE HYDROCHLORIDE
    • RefChem:810830
    • mecysteine hydrochloride, (L)-
    • 242-435-0
    • L-Methylcysteine hydrochloride
    • H-Cys-OMe.HCl
    • H-Cys-OMe HCl
    • MFCD00038985
    • Methyl L-cysteinate hydrochloride
    • (R)-Methyl 2-amino-3-mercaptopropanoate hydrochloride
    • L-Cystein methyl ester hydrochloride
    • Cysteine Methyl Ester Hydrochloride(1:1)
    • (R)-Cysteine methyl ester hydrochloride
    • L-Cysteine methyl ester (hydrochloride)
    • MLS000028400
    • DTXSID9046520
    • cysteine methyl ester hydrochloride
    • methyl (2R)-2-amino-3-sulfanylpropanoate;hydrochloride
    • SMR000058406
    • methyl (2R)-2-amino-3-sulfanylpropanoate hydrochloride
    • 871018-11-0
    • Methyl L-cysteine hydrochloride (JAN)
    • L-Cys-OMe.HCl
    • METHYL L-CYSTEINE HYDROCHLORIDE [JAN]
    • NCGC00166005-01
    • methyl cysteinate hydrochloride
    • SR-01000695426
    • Visclair (TN)
    • L-Cys-OMe hydrochloride
    • Opera_ID_1638
    • Mecysteine (hydrochloride)
    • SCHEMBL21033
    • MLS002207278
    • (R)-METHYL 2-AMINO-3-MERCAPTOPROPANOATE HCL
    • orb1308231
    • CHEMBL1426508
    • DTXCID7026520
    • CHEBI:31806
    • HY-B1038
    • L-cysteine methylester hydrochloride
    • Tox21_112287
    • EBC-50096
    • MECYSTEINE HYDROCHLORIDE [MI]
    • AKOS015846052
    • AKOS015892736
    • AC-8650
    • CS-4557
    • FD21234
    • FM25033
    • cysteine methyl ester hydrochloride salt
    • MECYSTEINE HYDROCHLORIDE [MART.]
    • MECYSTEINE HYDROCHLORIDE [WHO-DD]
    • AS-12760
    • BP-10751
    • L-Cysteine, methyl ester, dihydrochloride
    • SY021999
    • CAS-18598-63-5
    • L-Cysteine methyl ester hydrochloride, 98%
    • NS00026088
    • ST51037568
    • D01574
    • EN300-198450
    • Methyl L-cysteinate--hydrogen chloride (1/1)
    • L-Cysteine, methyl ester, hydrochloride (1:1)
    • 598C635
    • F045338
    • methyl (2R)-2-amino-3-sulfanylpropanoate, chloride
    • SR-01000695426-2
    • Q27256295
    • Z1741970632
    • [(1R)-2-methoxy-2-oxo-1-(sulfanylmethyl)ethyl]ammonium;chloride
    • 18598-63-5

  • Applications

    L-Cysteine, methyl ester, hydrochloride (CAS 18598-63-5) is primarily used as a protected cysteine building block in chemical and pharmaceutical synthesis. In pharmaceutical manufacturing and medicinal chemistry, it serves as an intermediate for the preparation of cysteine-containing peptides and small-molecule drug candidates, with the methyl ester and HCl salt improving solubility and enabling controlled coupling. It is commonly used in organic synthesis workflows as a starting material or intermediate to introduce cysteine motifs, and in research and development settings for peptide library generation and structure–activity studies. The salt form can enhance stability, handling, and storage of the reactive amino acid derivative, while remaining suitable for subsequent deprotection and peptide elongation. It may also find applications in cosmetics-related formulation research, subject to local regulations.

    gpt-5-nano

  • Solubility @25˚C

    Solvent Solubility (g/L)
    ethanol 58.43
    methanol 222.71
    isopropanol 17.6
    water 275.42
    ethyl acetate 3.0
    n-propanol 24.12
    acetone 21.58
    n-butanol 14.24
    acetonitrile 7.75
    DMF 100.89
    toluene 0.81
    isobutanol 11.89
    1,4-dioxane 14.1
    methyl acetate 6.12
    THF 20.02
    2-butanone 9.6
    n-pentanol 11.39
    sec-butanol 10.7
    n-hexane 0.28
    ethylene glycol 109.76
    NMP 97.77
    cyclohexane 0.4
    DMSO 221.5
    n-butyl acetate 3.15
    n-octanol 6.19
    chloroform 3.34
    n-propyl acetate 3.64
    acetic acid 111.73
    dichloromethane 3.5
    cyclohexanone 17.54
    propylene glycol 44.33
    isopropyl acetate 2.41
    DMAc 69.52
    2-ethoxyethanol 57.8
    isopentanol 10.14
    n-heptane 0.5
    ethyl formate 13.0
    1,2-dichloroethane 3.16
    n-hexanol 7.17
    2-methoxyethanol 104.09
    isobutyl acetate 2.47
    tetrachloromethane 1.78
    n-pentyl acetate 5.67
    transcutol 63.77
    n-heptanol 7.95
    ethylbenzene 0.91
    MIBK 5.16
    2-propoxyethanol 28.57
    tert-butanol 15.97
    MTBE 3.99
    2-butoxyethanol 25.33
    propionic acid 24.75
    o-xylene 1.66
    formic acid 322.87
    diethyl ether 2.41
    m-xylene 1.21
    p-xylene 1.56
    chlorobenzene 1.78
    dimethyl carbonate 3.72
    n-octane 0.37
    formamide 218.47
    cyclopentanone 26.61
    2-pentanone 6.18
    anisole 4.12
    cyclopentyl methyl ether 5.03
    gamma-butyrolactone 34.42
    1-methoxy-2-propanol 39.14
    pyridine 8.99
    3-pentanone 4.37
    furfural 58.21
    n-dodecane 0.32
    diethylene glycol 61.77
    diisopropyl ether 1.02
    tert-amyl alcohol 12.49
    acetylacetone 11.09
    n-hexadecane 0.34
    acetophenone 8.69
    methyl propionate 4.29
    isopentyl acetate 3.73
    trichloroethylene 7.26
    n-nonanol 5.68
    cyclohexanol 8.78
    benzyl alcohol 11.37
    2-ethylhexanol 4.28
    isooctanol 6.54
    dipropyl ether 2.04
    1,2-dichlorobenzene 3.0
    ethyl lactate 9.11
    propylene carbonate 13.32
    n-methylformamide 70.58
    2-pentanol 5.61
    n-pentane 0.35
    1-propoxy-2-propanol 15.27
    1-methoxy-2-propyl acetate 6.95
    2-(2-methoxypropoxy) propanol 23.17
    mesitylene 1.32
    ε-caprolactone 15.67
    p-cymene 1.77
    epichlorohydrin 18.82
    1,1,1-trichloroethane 2.08
    2-aminoethanol 91.37
    morpholine-4-carbaldehyde 74.27
    sulfolane 88.42
    2,2,4-trimethylpentane 0.39
    2-methyltetrahydrofuran 9.41
    n-hexyl acetate 6.9
    isooctane 0.27
    2-(2-butoxyethoxy)ethanol 29.74
    sec-butyl acetate 2.06
    tert-butyl acetate 4.01
    decalin 0.38
    glycerin 106.13
    diglyme 48.97
    acrylic acid 40.19
    isopropyl myristate 2.95
    n-butyric acid 18.09
    acetyl acetate 3.89
    di(2-ethylhexyl) phthalate 8.56
    ethyl propionate 2.65
    nitromethane 88.92
    1,2-diethoxyethane 6.06
    benzonitrile 6.73
    trioctyl phosphate 6.02
    1-bromopropane 1.07
    gamma-valerolactone 53.5
    n-decanol 4.25
    triethyl phosphate 3.64
    4-methyl-2-pentanol 4.04
    propionitrile 4.22
    vinylene carbonate 14.65
    1,1,2-trichlorotrifluoroethane 50.16
    DMS 5.87
    cumene 1.33
    2-octanol 4.52
    2-hexanone 5.61
    octyl acetate 4.59
    limonene 2.45
    1,2-dimethoxyethane 37.23
    ethyl orthosilicate 3.38
    tributyl phosphate 5.47
    diacetone alcohol 16.27
    N,N-dimethylaniline 6.15
    acrylonitrile 9.69
    aniline 4.81
    1,3-propanediol 73.28
    bromobenzene 1.03
    dibromomethane 2.02
    1,1,2,2-tetrachloroethane 6.76
    2-methyl-cyclohexyl acetate 5.72
    tetrabutyl urea 9.21
    diisobutyl methanol 3.05
    2-phenylethanol 8.76
    styrene 0.98
    dioctyl adipate 6.56
    dimethyl sulfate 16.85
    ethyl butyrate 3.08
    methyl lactate 15.44
    butyl lactate 11.38
    diethyl carbonate 2.41
    propanediol butyl ether 29.9
    triethyl orthoformate 3.26
    p-tert-butyltoluene 1.8
    methyl 4-tert-butylbenzoate 16.57
    morpholine 20.71
    tert-butylamine 6.48
    n-dodecanol 3.21
    dimethoxymethane 20.89
    ethylene carbonate 8.96
    cyrene 37.95
    2-ethoxyethyl acetate 10.26
    2-ethylhexyl acetate 2.76
    1,2,4-trichlorobenzene 4.51
    4-methylpyridine 6.61
    dibutyl ether 2.27
    2,6-dimethyl-4-heptanol 3.05
    DEF 13.43
    dimethyl isosorbide 31.33
    tetrachloroethylene 8.05
    eugenol 22.49
    triacetin 12.77
    span 80 20.99
    1,4-butanediol 42.26
    1,1-dichloroethane 1.52
    2-methyl-1-pentanol 8.65
    methyl formate 48.64
    2-methyl-1-butanol 9.86
    n-decane 0.47
    butyronitrile 4.77
    3,7-dimethyl-1-octanol 5.44
    1-chlorooctane 1.63
    1-chlorotetradecane 0.81
    n-nonane 0.43
    undecane 0.38
    tert-butylcyclohexane 0.42
    cyclooctane 0.24
    cyclopentanol 13.68
    tetrahydropyran 4.94
    tert-amyl methyl ether 3.92
    2,5,8-trioxanonane 38.81
    1-hexene 0.84
    2-isopropoxyethanol 24.21
    2,2,2-trifluoroethanol 55.33
    methyl butyrate 5.66

    Scent© AI

1 4

IFRA standard 51

Recommendation
No restriction
Maximum acceptable concentrations in the finished product (%)
Category 1
Products applied to the lips
 No restriction Category 7A
Rinse-off products applied to the hair with some hand contact
 No restriction
Category 2
Products applied to the axillae
 No restriction Category 7B
Leave-on products applied to the hair with some hand contact
 No restriction
Category 3
Products applied to the face/body using fingertips
 No restriction Category 8
Products with significant anogenital exposure
 No restriction
Category 4
Products related to fine fragrance
 No restriction Category 9
Products with body and hand exposure, primarily rinse off
 No restriction
Category 5A
Body lotion products applied to the body using the hands (palms), primarily leave on
 No restriction Category 10A
Household care products with mostly hand contact
 No restriction
Category 5B
Face moisturizer products applied to the face using the hands (palms), primarily leave on
 No restriction Category 10B
Household care products with mostly hand contact, including aerosol/spray products (with potential leave-on skin contact)
 No restriction
Category 5C
Hand cream products applied to the hands using the hands (palms), primarily leave on
 No restriction Category 11A
Products with intended skin contact but minimal transfer of fragrance to skin from inert substrate without UV exposure
 No restriction
Category 5D
Baby Creams, baby Oils and baby talc
 No restriction Category 11B
Products with intended skin contact but minimal transfer of fragrance to skin from inert substrate with potential UV exposure
 No restriction
Category 6
Products with oral and lip exposure
 No restriction Category 12
Products not intended for direct skin contact, minimal or insignificant transfer to skin
 No restriction