Yield:-

Reaction Conditions:

with sulfuric acid in 1,4-dioxane at -78 - 20; for 72 h;

Steps:

VII (S)-2-[(1-1H-Benzimidazol-5-yl-methanoyl)-amino]-4-phenyl-butyric acid hydrochloride

The solution of starting material is then cooled to -78° C. and the cold liquid isobutylene is added. The mixture is stirred at room temp in a pressure bottle for 3 days. The bottle is then cooled to -78° C. and opened. It is then stirred while open and allowed to warm up in an ice bath. After 20 minutes of stirring, 55 ml of 2N NaOH are added slowly at 0° C. The product is extracted with ether and washed with dilute sodium bicarbonate. The solution is dried over sodium sulfate and the solvent is removed to give 4.9 g of the t-butyl ester as a yellow oil.

References:

US2004/6104,2004,A1 Location in patent:Page/Page column 11