tert-butyl N-[(2S)-1-amino-3-methyl-1-oxobutan-2-yl]carbamate

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

Procedure: Boc-valineamide (0.5 g) was stirred in dry THF at room temperature under argon. Lawesson's reagent (1.56 g, 0.6 eq) was added and the mixture was stirred overnight. The solvent was evaporated and the residue chromatographed (silica, 2.5% methanol/dichloromethane) to give the title compound as a white solid (0.373 g, 70%). NMR(CDCl3) δ 8.59 (1H, br s), 8.09 (1H, br s), 5.41 (1H, d (br)), 4.20 (1H, dd), 1.99 (1H, m), 1.39 (9H, s), 0.90 (6H, m). The solvent was evaporated the residue chromatographed (silica, 2.5% methanol/dichloromethane)

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

Procedure: Boc-valineamide (0.5 g) was stirred in dry THF at room temperature under argon. Lawesson's reagent (1.56 g, 0.6 eq) was added and the mixture was stirred overnight. The solvent was evaporated and the residue chromatographed (silica, 2.5% methanol/dichloromethane) to give the title compound as a white solid (0.373 g, 70%). NMR(CDCl3) δ 8.59 (1H, br s), 8.09 (1H, br s), 5.41 (1H, d (br)), 4.20 (1H, dd), 1.99 (1H, m), 1.39 (9H, s), 0.90 (6H, m). The solvent was evaporated the residue chromatographed (silica, 2.5% methanol/dichloromethane)

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

Procedure: In such a synthesis, the lysine side chain is protected by a MSOC protective group introduced onto Boc-Lys-OH so as to form Boc-Lys(MSOC)-OH. The diprotected N(α),N(ε) lysine is coupled with Boc-Pro-Val-NH2, HCl by the conventional DCC/HOBt method. The Boc-Pro-Val-NH2, HCl reactant is in turn obtained in two steps from Boc-Pro-OH and Boc-Val-NH2. The overall yield is 33% calculated based on Boc-Lys(MSOC)-OH. The global synthesis scheme is illustrated in the scheme (I) hereunder:

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

Procedure: In such a synthesis, the lysine side chain is protected by a MSOC protective group introduced onto Boc-Lys-OH so as to form Boc-Lys(MSOC)-OH. The diprotected N(α),N(ε) lysine is coupled with Boc-Pro-Val-NH2, HCl by the conventional DCC/HOBt method. The Boc-Pro-Val-NH2, HCl reactant is in turn obtained in two steps from Boc-Pro-OH and Boc-Val-NH2. The overall yield is 33% calculated based on Boc-Lys(MSOC)-OH. The global synthesis scheme is illustrated in the scheme (I) hereunder:

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

Procedure: Boc-valineamide (0.5 g) was stirred in dry THF at room temperature under argon. Lawesson's reagent (1.56 g, 0.6 eq) was added and the mixture was stirred overnight. The solvent was evaporated and the residue chromatographed (silica, 2.5% methanol/dichloromethane) to give the title compound as a white solid (0.373 g, 70%). NMR(CDCl3) δ 8.59 (1H, br s), 8.09 (1H, br s), 5.41 (1H, d (br)), 4.20 (1H, dd), 1.99 (1H, m), 1.39 (9H, s), 0.90 (6H, m). The solvent was evaporated the residue chromatographed (silica, 2.5% methanol/dichloromethane)