Benzamidine residues

A solution of ethyl benzimidate hydrochloride (496.9 mmol) in 300.0 ml methyl alcohol was cooled to 0°C, then treated with a solution of aminoacetaldehyde dimethyl acetal (670.9 mmol) in 75 ml methyl alcohol at such a rate that the temperature was kept below 5°C. The solution was stirred 3 days at or below 5°C, then concentrated, and an yellow oil isolated. The residue was dissolved in 750 ml 1M NaOH, then extracted four times with 250 ml CH2C12, dried with MgS04, concentrated, and 108.13 g of crude /V-(2,2-dimethoxyethyl)benzamidine was isolated as an yellow oil. It was used without further purification. 

The isolation of the benzamidines as done originally by Searle s Discovery group was carried out by removal of the glacial acetic acid by vacuum distillation followed by the crystallization from a mixture of MeOH, EtOH and CH3CN. An intermediate process that was developed for this isolation involved the removal of the majority of the glacial acetic acid by vacuum distillation and recystallization of the residue from a mixture of glacial acetic acid and IPA in the ratio of 1 g of crude residue to 2 mL of glacial acetic acid to 12 mL of IPA. While this process was doable it was less than ideal. 

To a 75 mL solution of NaOEt in absolute ethanol prepared by addition of 4.5 g sodium in absolute ethanol were added 9.0 g benzamidine hydrochloride and 10 g carefully purified methyl a,a-diethylmalonate. The mixture was heated for 5 h at 70°C. The alcohol was partially removed by a current of dry air, and the residue was acidified with a slight excess of cone. HCl. After removal of the precipitated NaCl, the solution was further concentrated on the steam bath. The addition of water caused 5,5-diethyl-2-phenyl-4,6-diketo-tetrahydro-pyrimidine to separate in white needles, in an amount of 3.0 g. The product was further purified by recrystallization from dilute acetic acid. 

Low-molecular-weight ligands for affinity chromatc raphy include those shown in Fig. 6 benzamidine with selectivity toward serin proteases [60], boronic acid for carbohydrates and glycoproteins [61], and iminodiacetic acid, which offers chelation with transition m l ions (Cu, Zn, Ni) and exhibits selectivity for proteins and peptides containing histidine residues [62]. 

A. Synthesis of m-[2-[o- m-Fluorosulfonylbenzamido)phenoxy]-ethoxyjbenzamidine (I). To a solution of 10 mmoles of m-(o-amino-phenoxyethoxy)benzamidine (Iff) in 2 ml of dry i T,iV-dimethylformamide (DMF) are added 2.0 mmoles of pyridine. After stirring at ambient temperature for 1 hr, a solution of m-fluorosulfonylbenzoylchloride (17) in 2 ml of dry DMF is added. The mixture is stirred 1 hr at ambient temperature and poured into 75 ml of diethyl ether. The resulting mixture is chilled, and the ether is decanted. The residue is dissolved in hot 95% aqueous ethanol, and excess p-toluenesulfonic acid is added upon cooling, a crystalline product is obtained. Recrystallization from 95% ethanol gives compound 1. 

Eastman) in 5 ml of DMF is added dropwise to this 0° mixture. After 3 hr at ambient temperature, the mixture is diluted with 50 ml of ether, and the solution is decanted from the precipitated oil. The residual oil is recrystallized from aqueous toluenesulfonic acid solution to give m- (3-phenylpropionamidobenzene) benzamidine p-toluenesulfonate (i9), m.p. 192°-m°. 

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