Dicyclohexylcarbodiimide → 2-[[[1-(2-Amino-4-thiazolyl)-2-[[1-[[[[3-[(3,4-dihydroxybenzoyl)amino]-2-oxo-1-imidazolidinyl]sulfonyl]amino]carbonyl]-2-oxo-3-azetidinyl]amino]-2-oxoethylidene]amino]oxy]-2-methylpropanoic acid, diphenylmethyl ester

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Reaction Steps

(Z)-2-Amino-α-[[1-(diphenylmethoxycarbonyl)-1-methylethoxy]imino]-4-thiazoleacetic acid (0.88 g, 0.002 mol) was dissolved in 20 ml of dimethylformamide followed by 0.3 g of N-hydroxybenzotriazole (containing 13% water), followed by 0.5 g of dicyclohexylcarbodiimide and 0.28 ml of triethylamine. The mixture was stirred at room temperature for 1 hour, then 1.08 g (0.002 mol) of (S)-3-amino-N-[[3-[(3,4-dihydroxybenzoyl)amino]-2-oxo-1-imidazolidinyl]sulfonyl]-2-oxo-1-azetidinecarboxamide, trifluoroacetate salt (see Example 1D) was added. The mixture was stirred at room temperature overnight. The precipitate (dicyclohexylurea) was filtered off and the filtrate evaporated in vacuo. Trituration of the remaining syrup with ether yielded 1.8 g of the title compound in crude form.

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