1,1,3,3-Tetramethylguanidine (0.046 g, 0.40 mmol) was added to a solution of rac.-N-[2-chloro-4-[[(3-methoxymethoxybenzyl)amino]carbonyl]benzoyl]-2-(dimethoxyphosphinyl)glycine methyl ester (Example 142; 0.047 g, 0.10 mmol) and 4-15 formylbenzenesulfonamide (lit.: Van Es, T.; Staskun, B. Organic Syntheses 1971, 51, 20-23; 0.019 g, 0.10 mmol) in DME (4 mL). The solution was stirred at room temperature for 20 h and then was poured into water (25 mL). The aqueous layer was extracted with ethyl acetate and the organic layers were dried (Na2SO4), filtered and evaporated to give crude (Z)-3-(4-aminosulfonylphenyl)-2-[[2-chloro-4-[[(3-methoxymethoxybenzyl)amino]carbonyl]benzoyl]amino]propenoic acid methyl ester. A solution of tetrahydrofuran/methanol/water (3:1:1; 4 mL) was added, followed by lithium hydroxide monohydrate (7 mg, 0.17 mmol). The mixture was stirred at room temperature for 24 h, neutralized with 1N hydrochloric acid solution and extracted with ethyl acetate.
