Diisopropylethylamine → p-nitrobenzyl(1R,5S,6S)-2-{1-[4-((1S)-2-methyl-1-(p-nitrobenzyloxycarbonyl)-propylcarbamoyl)-1,3-thiazol-2-yl]azetidin-3-yl}thio-6-[(R)-1-t-butyldimethylsilyloxyethyl]-1-methylcarbapen-2-em-3-carboxylate

Participants

Reaction Steps

To a solution of p-nitrobenzyl (1R,5S,6S)-2-[1-(4-carboxy-1,3-thiazol-2-yl)azetidin-3-yl]thio-6-[(R)-1-t-butyldimethylsilyloxyethyl]-1-methylcarbapen-2-em-3-carboxylate (1.00 g, 1.48 mmol) (obtained as described in Reference Example 41(7)) and L-valine p-nitrobenzyl ester hydrochloride (514 mg, 1.78 mmol) (obtained as described in Reference Example 46(2)) in dimethylformamide (50 ml) were added diethylphosphoryl cyanide (275 μl, 1.78 mmol) and diisopropylethylamine (620 μl, 3.56 mmol) in an ice bath under an atmosphere of nitrogen. The mixture was stirred at room temperature for 2 hours. After checking the completion of the reaction, the reaction mixture was partitioned between ethyl acetate and 10% aqueous sodium chloride solution. The obtained organic layer was washed successively with saturated aqueous sodium hydrogencarbonate solution and saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by chromatography on a silica gel column using n-hexane:ethyl acetate (2:1→1:1) as the eluant to afford p-nitrobenzyl(1R,5S,6S)-2-{1-[4-((1S)-2-methyl-1-(p-nitrobenzyloxycarbonyl)-propylcarbamoyl)-1,3-thiazol-2-yl]azetidin-3-yl}thio-6-[(R)-1-t-butyldimethylsilyloxyethyl]-1-methylcarbapen-2-em-3-carboxylate (1.15 g, yield 86%).

Provenance & Evidence