(2S)-1-((tert-butoxy)carbonyl)-4-methylidenepyrrolidine-2-carboxylic acid → (4S)-1-(tert-Butoxycarbonyl)-4-methyl-L-proline

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Reaction Steps

A solution of (S)-1-(tert-butoxycarbonyl)-4-methylenepyrrolidine-2-carboxylic acid Example M.4b (4 g, 17.60 mmol) in 2-propanol (10 mL) was added to a nitrogen purged suspension of 10% palladium on carbon (936 mg) in 2-propanol (240 mL) and the flask was charged with hydrogen gas (1 atm). After being stirred 18, the catalyst was removed by filtration over celite and the filtrate concentrated. LC analysis showed the sample contained ˜14% of the trans isomer, and recrystallization from toluene enriched the cis isomer, Example M.4c, to 96% purity (16:1). 1H NMR (500 MHz, MeOD) δ ppm 4.21-4.17 (m, 1H), 3.76-3.67 (m, 1H), 2.96-2.92 (m, 1H), 2.49-2.46 (m, 1H), 2.30-2.29 (m, 1H), 1.59-1.51 (m, 1H), 1.47/1.43 (m, 9H), 1.10-1.06 (m, 3H).

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