Dicyclohexylcarbodiimide → HCID 53837275, compound

Participants

Reaction Conditions

Reaction Steps

3.37 g of triethylamine and 0.37 g of dimethylaminopyridine were added to a stirred mixture of 7.18 g of N-carbobenzyloxy-L-serine and 5.00 g of 1B in 150 ml of dry tetrahydrofuran at 0° C. under nitrogen. The stirred mixture was allowed to warm to about 5° C. (10 minutes), 6.19 g of N,N'-dicyclohexylcarbodiimide was added, heat being evolved, and the mixture was allowed to warm to 28° C. and held there (25 minutes). The mixture was stirred at room temperature over a weekend, when 3 ml of glacial acetic acid and 15 ml of methanol were added and the mixture was stirred at room temperature for 2.5 hours. Then sufficient triethylamine was added to make the mixture pH=7, the mixture was filtered and the solvents were evaporated from the filtrate under reduced pressure. The residue was mixed with 50 ml of methanol and 100 ml of ethyl acetate and filtered, and the solvents were evaporated from the filtrate under reduced pressure. The residue was flash-chromatographed, first with ethyl acetate as eluent to remove high Rf minor impurities, then a 9:1 v:v mixture of ethyl acetate and methanol. The solvents were evaporated, the residue was recrystallized from methylene chloride and hexane, and the product was held under very low pressure (<1 Torr.) overnight to give the N-(N-carbobenzyloxy-L-seryl)-3-azetidinecarboxylic acid methyl ester (1C), as a very hygroscopic, colorless solid, m.p.: 90°-95° C.

Provenance & Evidence