A solution of 0.431 g of methyl(E)-2-[[2-[2(R)-[1(S)-(tert-butoxycarbonyl)-4-phenyl-3-butenyl]-4-methylvaleryl]hydrazino]sulphonamido]acetate in 10 ml of tetrahydrofuran and 5 ml of methanol was treated with 0.040 g of lithium hydroxide monohydrate and the mixture was left to stir overnight. A further 0.020 g of lithium hydroxide monohydrate was added and stirring continued for 4 hours. The mixture was then diluted with water, acidified using 2M aqueous hydrogen chloride, and extracted with ethyl acetate. The ethyl acetate fraction was dried over anhydrous magnesium sulphate and evaporated to give 0.462 g of methyl(E)-2-[[2-[2(R)-[1(S)-(tert-butoxycarbonyl)-4-phenyl-3-butenyl]-4-methylvaleryl]hydrazino]sulphonamido]acetic acid as an oil.
