(2,3,4,5,6-pentafluorophenyl) 6-(2,5-dioxopyrrol-1-yl)hexanoate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To 924 mg (3 mmol) of 6-maleimidocaproic acid pentafluorophenyl ester 1 (see Example 11) dissolved in dry methylene chloride (30 ml) was added 10 g (1 mmol) of alpha-amino-omega-carboxy-PEG (2) (MW 10,000, n=226) and 4-dimethylpyridine (402 mg, 3 mmol) dissolved in 50 ml of dry methylene chloride. The reaction mixture was stirred at room temperature for 2 h and the product precipitated in ether (100 ml). After cooling to 4° C. the crude amide of formula 3 was collected by filtration and precipitated twice from methylene chloride by addition of ether to give 9 g of compound 3 as a white solid. the product precipitated in ether (100 ml) After cooling to 4° C. the crude amide of formula 3 was collected by filtration precipitated twice from methylene chloride by addition of ether