Ethyl Acetate → N-Succinimidyl 4-(2-pyridyldithio)butanoate

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Reaction Steps

Compound 11a (1.10 g, 4.8 mmol) and N-hydroxysuccinimide (0.64 g, 5.5 mmol) were dissolved in dichloromethane (50 mL). The solution was magnetically stirred as 1-[3-(dimethylamino)propyl]-3 ethylcarbodiimide (1.05 g, 5.5 mmol) was added. After 2 h, ethyl acetate (150 mL) was added and the solution was transferred to a separatory funnel and washed consecutively with 0.5 M HCl (30 mL) and saturated sodium chloride (20 mL). The organic layer was dried over anhydrous sodium sulfate, and then the solvent was removed under vacuum. The residue was taken up in a minimum volume of ethyl acetate and was purified by silica chromatography using a mobile phase of hexanes:ethyl acetate:acetic acid (2.5:1:0.02, v/v/v). Fractions containing pure product were combined and solvent was removed to give N-succinimidyl 4-(2-pyridyldithio)butanoate (SPDB, 3a) (1.2 g, 76% yield). 1H NMR (CDCl3): δ 2.12-2.19 (2H, m), 2.78-2.87 (6H, m), 2.91 (2H, t, J=7.0), 7.06-7.12 (1H, m), 7.62-7.71 (2H, m), 8.48 (1H, d, 4.4 Hz). MS (M+Na+) Found: 348.8 Calculated: 349.4.

Provenance & Evidence