The chemicals are presented in alphabetical order (with numbers, Greek letters, and other notations such as n- or tert-
ignored to allow easier alphabetical location), but can also be located using Chemical Abstracts Service registry numbers.
Yellow oil; yield 82.2%;1H NMR (500 MHz, CDCl3): and 0.96 (s, 9H, tert-
Leu-C(CH3)3), 1.48 (s, 9H, C(CH3)3), 1.80-1.88 (m,2H, Pro-CH2), 2.16-2.20 (m, 1H, Pro-CH2), 2.36-2.42 (m, 1H, Pro-CH2), 3.31-3.49 (m, 2H, Pro-CH2), 3.71 (s, 3H, OCH3), 4.25-4.46 (m, 2H, Pro-CH, tert-Leu- CH), 7.65 (bs, 1H, tert-Leu-NH) ppm; FTIR (atr): 3333, 2968, 2876, 1740, 1686 cm-1.(2S,4R)-tert-Butyl 4-hydroxy-2-((S)-1-methoxy-3,3- dimethyl-1-oxobutan-2-ylcarbamoyl) pyrrolidine-2- carboxylate (4)