Acetamidomethyl

NO2C6H4SCI, AcOH (results in disulfide formation), followed by NaBH4 or HS(CH2)20H or dithioerythritol, quant." 5-Triphenylmethyl, 5-4,4 -di-methoxydiphenylmethyl, and 5-acetamidomethyl groups are also removed by this method. 

Triphenylmethylcysteine is readily oxidized by iodine (MeOH, 25°) to cystine." The 5-triphenylmethylcysteine group can be selectively cleaved in the presence Of a —Cys(Acm)— group (Acm = acetamidomethyl). 5-Ben-zyl and 5-/-butyl thioethers are stable to the action of iodine. 

Benzamidomethyl-A -methylcysteine has been prepared as a crystalline derivative (H0CH2NHC0C6H 5, anhydr. CF3CO2H, 25°, 45 min, 88% yield as the tri-fluoroacetate salt) and cleaved (100% yield) by treatment with mercury(II) acetate (pH 4, 25°, 1 h) followed by hydrogen sulfide. Attempted preparation of S-acetamidomethyl-N-methylcysteine resulted in noncrystalline material, shown by TLC to be a mixture. ... 

The Npys group can be. cleaved reductively with BU3P, H2O or mercaptoethanol. It is stable to CF3COOH (24 h), 4 M HCl/dioxane (24 h), and HF (1 h). The related reagent, 2-pyridinesulfenyl chloride, has also been proposed as a useful reagent for the deprotection of the 5-trityl, 5-diphenylmethyl, 5-acetamidomethyl, 5-/-butyl, and S-r-butylsulfenyl groups, but this reagent is very susceptible to hydrolysis. ... 

S-Methoxymethyl, 471 S-lsobutoxymethyl, 471 S-Benzyloxymethyl, 472 S-2-Tetrahydropyranyl, 472 S-Benzylthiomethyl, 473 S-Phenylthiomethyl, 473 Thiazolidine, 473 S-Acetamidomethyl, 474... 

The details of the solid-phase technique have been improved substantially over the years, but the fundamental idea remains the same. The most commonly used resins at present are either the Wang resin or the PAM (phenyl-acetamidomethyl) resin, and the most commonly used N-protecting group is the fluorenylmethyloxycarbonyl, or Fmoc group, rather than Boc. 

C19H17IN2O7 94256-35-6) see Dextrothyroxine 4-(acetamidomethyl)henzenesulfonamide (C9H]2N20,S 2075-74-7) see Mafenide... 

S-ACETAMIDOMETHYL-L-CYSTEINE HYDR0C HL0RIDE,59, 190 N-( 2-Acetamido-3-phenylpropionyl)-pyrrolidine, 59, 52 Acetanilide, 59, 52... 

Thiol Protectton with the AcETAMiDOMErHYL Group S-Acetamidomethyl-l-... 

On several occasions the product isolated by the submitters was contaminated with L-cystine dihydrochloride, which was not easily removed by recrystallization. In this event the product was converted to the zwitterionic form and recrystallized in the following manner. The pH of a solution of the product in water was adjusted to 6 with aqueous 2.5N potassium hydroxide. The neutralized solution was evaporated to dryness under reduced pressure at ca. 40°. The residue was dissolved in a minimum amount of hot water, and two volumes of 95% ethanol were added to precipitate S-acetamidomethyl-L-cysteine monohydrate, dec. 187°, [a] 9 — 42.5° (c = 1, water). 

The present procedure provides a convenient method for preparing S-acetamidomethyl-L-cysteine hydrochloride." The zwitterionic form may be obtained readily from the hydrochloride by... 

S-Acetamidomethyl-L-cysteine hydrochloride Alanine, 3-[(acetamidomethyl)thio]-, monohydrochloride, i- (8) L-Cysteine, S-[(acetylamino)methyl]-, monohydrochloride (9) (28798-28-9) L-Cysteine hydrochloride, monohydrate (8, 9) (7048-04-6) Mercury(II) acetate Acetic acid, mercury (2) salt (8,9) (1600-27-7)... 

FIGURE 6.21 (A) Removal of trityl and acetamidomethyl from sulfhydryl by oxidative cleavage by iodine. (B) Cleavage of terf-butylsulfanyl by mercury(II) acetate,88 followed by displacement of the metal ion by hydrogen sulfide. 

DF Veber, JD Milkouski, RG Denkewalter, R Hirschmann. The synthesis of peptides in aqueous solution. IV. A novel protecting group for cysteine. (S-acetamidomethyl) Tetrahedron Lett 3057, 1968. 

D Sahal. Removal of iodine by solid phase adsorption to charcoal following iodine oxidation of acetamidomethyl-protected peptide precursors to their disulfide bonded products oxytocin and a Pre-S, peptide of hepatitis B illustrate the method. Int J Pept Res 53, 91, 1999. 

FIGURE 6.23 The synthesis of insulin, starting with a cystine-containing peptide. [Kamber et al., 1977]. Moc = methoxycarbonyl, Bpoc = biphenylisopropoxycarbonyl, Trt = trityl, Acm = acetamidomethyl. (a) HOBt-assisted carbodiimide-mediated coupling (b) removal of Trt by HC1 in CF3CH2OH-CH2Cl2 (9 1) at pH 3.5 (c) removal of Bpoc by CF3CH2OH-CH2 Cl2 (9 1) at 60°C (d) removal of Acm and oxidation by iodine. 

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