Diisopropylcarbodiimide → HCID 131729453, compound

Participants

Reaction Steps

All chemicals, unless otherwise indicated, were purchased from Sigma Chemical Co. (St. Louis, Mo.) or Fisher Scientific (Houston, Tex.) and used as received. t-boc-glycine (0.31 g, 1.71 mmol; Bachem, Bioscience Inc., King of Prussia, Pa.) was dissolved in 20 mL of anhydrous methylene chloride at room temperature. To this solution was added 1,3-diisopropylcarbodiimide (DIPC, 267.7 mL, 1.71 mmol), 4-dimethylamino-pyridine (DMAP, 0.14 g, 1.14 mmol) and camptothecin (CPT, 0.20149 g, 0.57 mmol) at 0° C. While CPT (Sigma Chemical Co., St. Louis, Mo.) was dissolved in dimethyl sulfoxide (DMSO) because of its low solubility, the concentration of DMSO in working solutions was less than 1.0%; a concentration which did not have a significant effect on cells. The reaction mixture was allowed to warm to room temperature and incubated overnight. The product was washed with 0.1 N HCl, dried and evaporated under reduced pressure to yield the sold product. The product was recrystallized from methanol to give CPT-glycinate. The t-boc protection group was removed by dissolving the CPT-glycinate in a mixture of methylene chloride and trifluoracetic acid (TFA) (50:50) and stirring at room temperature for 3 hours. Solvent was evaporated under reduced pressure and precipitated using ether to give CPT-glycinate-TFA salt. CPT-glycinate-TFA salt (34.0 mg or 50 mg) and PEG-NHS (100 mg; MW ˜3400; Shearwater Corporation, Huntsville, Ala.) were added to methylene chloride (5 ml) and DIEA (50 ml) was added to adjust the pH to basic. The reaction was stirred for 3 hours at room temperature. The product was recrystallized from cold ether and dried under vacuum overnight.

Provenance & Evidence