Lithium Hydroxide → (S)-1-{(S)-2-[(S)-2-(tert-butoxycarbonyl-methyl-amino)-propionylamino]-3-methyl-butyryl}-2,3-dihydro-1H-indole-2-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of (S)-1-{(S)-2-[(S)-2-(tert-butoxycarbonyl-methyl-amino)-propionylamino]-3-methyl-butyryl}-2,3-dihydro-1H-indole-2-carboxylic acid ethyl ester (2.93 g, 6.16 mmol) in THF/water/methanol (3:1:1; 60 mL) was added 1 M aqueous lithium hydroxide (18.5 mL, 18.5 mmol). The reaction mixture was stirred at 23° C. for 2.5 h and then concentrated in vacuo. The residue was diluted with water and acidified with 6 M and then 1 M aqueous HCl to pH˜2. The mixture was extracted with EtOAc, the organic layer was dried over Na2SO4 and concentrated in vacuo to give (S)-1-{(S)-2-[(S)-2-(tert-butoxycarbonyl-methyl-amino)-propionylamino]-3-methyl-butyryl}-2,3-dihydro-1H-indole-2-carboxylic acid (2.70 g) as an off-white foam, m/z=470 (M+Na).

Provenance & Evidence