Acetone → benzyl (S)-1-[(1S,2R,4R)-4-(isopropyl(methyl)amino)-2-propylcyclohexyl]-2-oxopyrrolidin-3-ylcarbamate

Participants

Reaction Steps

The entirety of benzyl (S)-1-[(1S,2R,4R)-4-amino-2-propylcyclohexyl]-2-oxopyrrolidin-3-ylcarbamate prepared in Step 1 (assumed 8.2 mmol) was dissolved in methanol (40 mL). The resultant solution was charged with acetone (6 mL, 82 mmol) and stirred at RT for 10 min before sodium cyanoborohydride (2.6 g, 41 mmol) was added in one portion. The reaction was stirred at RT for 10 h and then charged successively with formaldehyde (3.0 mL of 37 wt % aq soln, 41 mmol) and sodium cyanoborohydride (0.52 g, 8.2 mmol). The reaction was stirred for another 9 h at RT and then quenched with sat. NaHCO3 (150 mL). The aqueous mixture was extracted with EtOAc (200 mL, then 2×75 mL). The organic extracts were combined, washed with brine (30 mL), dried (MgSO4), filtered, and concentrated in vacuo. After the resulting oil stood, some paraformaldehyde-related products solidified; these were removed by dissolving the mixture in a minimal volume of EtOAc and filtering. Subsequent concentration provided benzyl (S)-1-[(1S,2R,4R)-4-(isopropyl(methyl)amino)-2-propylcyclohexyl]-2-oxopyrrolidin-3-ylcarbamate. MS found: (M+H)+=430.5.

Provenance & Evidence