ethyl carbamimidothioate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: H2O (n=1) was prepared from glycyl-L-histidine and S-ethylisothiourea.H2SO4. Solutions of 1.50 g. of S-ethylisothiourea.H2SO4 in 5 ml of H2O and 1.74 g. of Gly-His.HCl in 3 ml of H2O were adjusted to pH 8-9 with 4 N NaOH. They were then mixed and kept at room temperature for a week. The cloudy suspension was filtered and the filtrate concentrated to dryness in vacuo. The residue, after addition of a small amount of EtOH, was dried in vacuo. A small amount of H2O was added to dissolve the dry residue and resulting solution was poured onto the column (2.5 cm i.d. × 30 cm Amberlite CG-120, 200-400 mesh, pyridine form). H2O, 1.0 M pyridine, 2.0 M pyridine, and 1.0 M pyridine--0.5 M NH4OH were used as the effluent solutions. Each fraction was tested for ninhydrin, Pauli, and Sakaguchi reactions. The fractions containing guanidinoacetyl-L-histidine were pooled and concentrated to dryness in vacuo. Cryst from H2O--EtOH; yield, 69.2%; mp, 108-111° C., decomp. Hydrolysis (6 N HCl, 110° , 24 hours.) gave guanidinoacetic acid and histidine, as confirmed be tlc. (thin layer chromatography). They were then mixed kept at room temperature for a week The cloudy suspension was filtered the filtrate concentrated to dryness in vacuo The residue, after addition of a small amount of EtOH was dried in vacuo A small amount of H2O was added to dissolve the dry residue resulting solution concentrated to dryness in vacuo yield

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of ethyl propionate (1.2 mL, 10 mmol) in DMF (1 mL) was added sodium methoxide (740 mg, 13 mmol), and to this was added ethyl formate (560 μL, 6.7 mmol) very slowly over 1 h period. The reaction mixture was stirred for 30 min then 2-ethyl-2-thiopseudourea (1.3 g, 6.7 mmol) in methanol (2.5 mL) was added at once. The mixture was heated and maintained at reflux for 2 h, cooled to room temperature and acidified to pH 6 with concentrated HCl. The resulting slurry was kept in ice bath for 30 minutes. The solid was collected and was rinsed with methanol. The solid was dried under vacuum to give 154 mg of the title compound. Mass spectrum 171.1 (CI, M+1). The mixture was heated maintained at reflux for 2 h for 30 minutes The solid was collected was rinsed with methanol The solid was dried under vacuum

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of potassium hydroxide (640 mg, 10 mmol) in methanol (6 mL) at 0° C. was added 2-ethyl-2-thiopseudourea (1.85 g, 10 mmol). The mixture was warmed to room temperature, stirred for 5 min, then filtered off potassium bromide under N2. The filtrate was cooled down to 0° C. then ethyl (ethoxymethylene)cyanoacetate (420 mg, 2.5 mmol) was added. The mixture was gradually warmed to room temperature and stirred for 20 h. The solvent was removed under reduced pressure, and the crude material was purified by flash chromatography using 4% 2M NH3 in MeOH/CH2Cl2 system to obtain 288 mg of the title compound. Mass spectrum 181 (EI, M+). filtered off potassium bromide under N2 The filtrate was cooled down to 0° C. The mixture was gradually warmed to room temperature stirred for 20 h The solvent was removed under reduced pressure the crude material was purified by flash chromatography

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: ε-Guanidinohexanoyl-L-histidine (n=5) -- S-Ethylisothiourea. H2SO4 (1.4 g.) and εAhx-His (1.7 g.) were treated in the same way as Example 2; yield, 56.1%; mp, 102°-103° C., decomp. Hydrolysis as above gave ε-guanidinohexanoic acid and histidine (tlc). yield Hydrolysis as

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To prepare beta-guanidinopropionyl-L-histidine.H2O, (n=2) S-ethylisothiourea.H2SO4 (5.0 g) and βAla-His (5.3 g) were reacted by the procedure described in Example 1: yield, 38.8%; mp, 121°-124° C., decomp. Hydrolysis as described in Example 1 gave beta-guanidinopropionic acid and histidine tlc. yield Hydrolysis