ith methyl N-(tert-butoxycarbonyl)-3-[(3S)-2-oxopyrrolidin-3-yl]-l-alaninate (10 g, 35 mmol), THF (200 mL), and chloroiodomethane (10.2 mL, 140 mmol), and the solution was cooled to −77 °C. LDA (140 mL, 210 mmol, 1.5 M mono-THF complex in cyclohexane) was added via a pressure-equalizing dropping funnel at such a