Cl.[CH2:2]([N:4]([CH2:9][C:10]1[C:15]([N+:16]([O-])=O)=[CH:14][CH:13]=[C:12]([Cl:19])[C:11]=1[Cl:20])[CH2:5][C:6]([OH:8])=[O:7])[CH3:3].O.O.[Sn](Cl)(Cl)(Cl)Cl.NCC(O)=O.[Sn]>Cl>[CH2:2]([N:4]([CH2:9][C:10]1[C:15]([NH2:16])=[CH:14][CH:13]=[C:12]([Cl:19])[C:11]=1[Cl:20])[CH2:5][C:6]([OH:8])=[O:7])[CH3:3]A suspension of 30 g of ethyl N-(2,3-dichloro-6-nitrobenzyl)glycine hydrochloride (compound VI) in 120 mL of concentrated hydrochloric acid was prepared. Separately, a mixture of tin chloride dihydrate (88.6 g) in 60 mL of hydrochloric acid is prepared. The glycine solution is slowly added to the tin solution and the resulting reaction mixture heated for 2 hours at 40-50° C. The solids are filtered, and the filter cake dissolved in water and methylene chloride. The pH of this solution is adjusted to 12.5 with 50% NaOH. The organic phase is separated and the aqueous phase extracted with methylene chloride. The combined organic phases are washed with water, and dried azeotropically. The solution is concentrated, isopropanol and heptane are added, and the solution cooled to −20 to −30° C. The precipated solids are collected by filtration. The crude product is recrystallized from heptane to give compound I in 58 to 67% yield.
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