A stirred mixture of 5-methylsulfanyl-pyridine-2-carboxylic acid (0.34 g, 2.00 mmol) and CDI (0.34 g, 2.10 mmol) in N,N-dimethylformamide (20 mL) was heated to 40° C. under nitrogen. After 2 h, 5-aminomethyl-2-(3-methyl-2,6-dioxo-piperidin-3-yl)-isoindole-1,3-dione hydrochloride (0.68 g, 2.00 mmol) was added and the mixture was heated at 40° C. for 2 h. The mixture was cooled to rt and EtOAc (75 mL) was added. The organic layer was washed with sat. aq. NaHCO3 (3×100 mL) then concentrated in vacuo. The crude residue was purified by column chromatography (0-5% gradient, MeOH/CH2Cl2, 0-5% gradient, product eluted after 4.7 min). The product fractions were combined, concentrated and the residue was triturated in MeCN (50 mL) for 1.5 h. The product was isolated by filtration and dried in vacuo to give 5-methylsulfanyl-pyridine-2-carboxylic acid [2-(3-methyl-2,6-dioxo-piperidin-3-yl)-1,3-dioxo-2,3-dihydro-1H-isoindol-5-ylmethyl]-amide as a white solid (0.52 g, 57% yield): HPLC: Waters Symmetry C18, 5 μm, 3.9×150 mm, 1 mL/min, 240 nm, 40/60 CH3CN/0.1% H3PO4, 4.89 min (98.54%); mp: 210-212° C.; 1H NMR (DMSO-d6) δ 1.88 (s, 3H), 1.97-2.12 (m, 1H), 2.53-2.78 (m, 6H), 4.62 (d, J=6.2 Hz, 2H), 7.68-7.90 (m, 4H), 7.91-8.04 (m, 1H), 8.52 (d, J=1.7 Hz, 1H), 9.51 (t, J=6.3 Hz, 1H), 11.01 (s, 1H); 13C NMR (DMSO-d6) δ 13.93, 21.02, 28.57, 29.09, 42.35, 58.73, 121.75, 122.05, 123.15, 129.59, 131.34, 133.53, 133.82, 139.65, 145.00, 145.90, 147.39, 164.07, 167.73, 167.88, 172.15; LCMS: MH=453; Anal Calcd for C22H20N4O5S: C, 58.40; H, 4.46; N, 12.38. Found: C, 58.24; H, 4.33; N, 12.16.
