3-Maleimidopropionic acid N-hydroxysuccinimide ester (18) (4.0 g, 15.03 mmol, 1.0 equiv.) was dissolved in N,N-dimethylformamide (75 mL) and 3-aminopropyltriethoxysilane (17) (5.06 mL, 15.03 mmol, 1 equiv.) was added and the reaction mixture was allowed to stir for 22 hours. An aliquot (0.15 mL) was removed by syringe, concentrated in vacuo, and the resulting oil was analyzed by 1H NMR spectroscopy. The oil was consistent with desired product. The reaction mixture was then concentrated in vacuo at 50-55° C. and the residue obtained was dissolved in CH2Cl2 (75 mL), washed with water (3×50 mL) and brine (50 mL), filtered through granular Na2SO4, and concentrated under reduced pressure in vacuo to provide 6.65 g (>100% due to residual N,N-dimethylformamide) of the crude maleimide-silane (19) as a light yellow oil. Crude (19) was used without purification. 1H NMR (300 MHz, CDCl3) δ 6.65 (s, 2H), 6.00 (s, 1H), 3.77 (q, J=7 Hz, 6H), 3.70 (m, 2H), 3.17 (m, 2H), 2.46 (m, 2H), 1.56 (m, 2H), 1.18 (t, J=7 Hz, 9H), 0.57 (m, 2H). 13C NMR (75 MHz, CDCl3) δ 170.36, 169.28, 134.09, 58.35, 41.77, 34.56, 34.21, 23.20, 18.20, 7.65. FB-MS (pos): [M+H]+ 373 (373.2 calcd).
