A solution of the generation two amine-terminated triazine dendrimer was prepared by dissolving 50.0 mg (0.0169 mmol) of the solids into 2.0 mL of the appropriate solvent (methanol or tetrahydrofuran). To this, methyl bromoacetate (37.2 mg, 22.4 µL, 0.244 mmol) corresponding to 1.2 mole equivalents per NH2, was added. The reaction mixture was allowed to stir at room temperature for 2 hours. Formation of white precipitate was observed (presumably the hydrobromide salt of the partially substituted dendrimer). Then, 68.7 µL of a separately-prepared methanolic solution of potassium hydroxide (prepared by dissolving 206 mg of solid potassium hydroxide in 1.0 methanol under rigorous stirring) was added to the dendrimer-containing reaction mixture. The mixture was stirred at room temperature and sample was taken for analysis by MALDI-TOF-MS after 14 hours of reaction time. Further additions of 1.2 mole equivalents of methyl bromoacetate per NH2 were required, each one accompanied by the addition of 68.7 µL of the methanolic potassium hydroxide solution. Progress of the reaction was monitored using MALDI-TOF-MS. A total of 8.4 mole equivalents of methyl bromoacetate per NH2 had been added when signals corresponding to 25- and 26-ester-bearing dendrimers were observed along with the desired 24-ester-bearing species, along with signals corresponding to incompletely substituted dendrimers.
An aliquot of the reaction mixture corresponding to 10.0 mg of dendrimer was taken, and the solvent was removed under reduced pressure. The glassy material that remained was dissolved in 400 µL of 4M HCl and allowed to react at room temperature. Progress of the hydrolysis reaction was monitored using MALDI-TOF-MS. A 200 µL aliquot of the solution was then transferred into a preconditioned Centricon centrifugal filter device (Amicon Bioseparations) having a regenerated cellulose membrane with a 3,000 molecular weight cut-off. The retained solution was collected and used as is for further analysis.
An aliquot of the reaction mixture corresponding to 10.0 mg of dendrimer was taken, and the solvent was removed under reduced pressure. The glassy material that remained was dissolved in 400 µL of 4M HCl and allowed to react at room temperature. Progress of the hydrolysis reaction was monitored using MALDI-TOF-MS. A 200 µL aliquot of the solution was then transferred into a preconditioned Centricon centrifugal filter device (Amicon Bioseparations) having a regenerated cellulose membrane with a 3,000 molecular weight cut-off. The retained solution was collected and used as is for further analysis.
