1136
L.-X. Liu and P.-Q. Huang
(C55O), 136.53, 135.66 (2C), 135.52 (2C), 132.24, 131.93, 130.45, 130.30,
128.60 (2C), 128.38 (2C), 128.05 (3C), 127.51 (2C), 81.86 (C-5), 67.07 (C-
4), 43.61 (NCH2), 38.59 (C-3), 26.85 (3 ꢀ CH3), 19.11 (Si-C). MS (ESI)
(m/z): 446 (M þ Hþ, 100), 468 (M þ Naþ, 35). Anal. calcd. for
C27H31NO3Si: C, 72.77; H, 7.01; N, 3.14. Found: C, 72.48; H, 7.12; N, 3.08.
Trans-9 (minor isomer): [a]D20 270.9 (c 1.0, CHCl3). Mp 99–100 8C (Et2O).
1
IR (film) nmax: 3411, 2931, 1686, 1427, 1112 cm21. H NMR (500 MHz,
CDCl3): d 7.65 (m, 4H, Ar-H), 7.50–7.40 (m, 6H, Ar-H), 7.10 (m, 3H,
Ar-H), 6.60 (d, J ¼ 1.0 Hz, 2H, Ar-H), 5.10 (d, J ¼ 4.8 Hz, 1H, H-5), 4.69
(d, J ¼ 15.4 Hz, 1H, NCH2), 4.11 (ddd, J ¼ 7.5, 7.3, 4.8 Hz, 1H, H-4), 3.41
(d, J ¼ 15.4 Hz, 1H, NCH2), 2.68 (dd, J ¼ 16.6, 7.5 Hz, 1H, H-3), 2.62
(d, J ¼ 9.2 Hz, 1H, OH, D2O exchangeable), 2.60 (dd, J ¼ 16.6, 7.5 Hz,
1H, H-3), 1.10 (s, 9H, 3 ꢀ CH3). 13C NMR (125 MHz, CDCl3): d 172.64
(C55O), 136.43, 135.91 (2C), 135.66 (2C), 132.12, 131.42, 130.58,
130.43, 128.39 (2C), 128.32 (2C), 128.11 (2C), 127.49 (2C), 127.24, 83.55
(C-5), 67.41 (C-3), 43.59 (NCH2), 37.74 (C-4), 26.83 (3 ꢀ CH3), 19.58
(Si-C). MS (ESI) (m/z): 446 (M þ Hþ, 100), 468 (M þ Naþ, 25). Anal.
calcd. for C27H31NO3Si: C, 72.77; H, 7.01; N, 3.14. Found: C, 71.92; H,
7.12; N, 3.13.
Regioisomer 10 (more polar diastereomer): [a]2D0 þ 13.1 (c 1.0, CHCl3). IR
(film) nmax: 3327, 2931, 2858, 1674, 1428, 1112, 1084 cm21 1H NMR
.
(500 MHz, CDCl3): d 7.60–7.50 (m, 4H, Ar-H), 7.45–7.25 (m, 11H, Ar-H),
4.91 (d, J ¼ 15.2 Hz, 1H, NCH2), 4.76 (dd, J ¼ 6.0, 0.8 Hz, 1H, H-3), 4.13
(dd, J ¼ 5.5, 1.2 Hz, 1H, H-5), 4.09 (d, J ¼ 15.2 Hz, 1H, NCH2), 2.67
(m, 1H, H-4), 2.34 (m, 1H, H-4), 1.62 (s br, 1H, OH, superposed with the
peak of H2O in CDCl3, D2O exchangeable), 1.00 (s, 9H, 3 ꢀ CH3). 13C
NMR (125 MHz, CDCl3): d 173.63 (C55O), 136.07, 135.51 (4C), 132.87,
129.93, 129.86, 128.56 (2C), 127.77 (4C), 127.71 (3C), 127.38, 88.63 (C-
5), 72.85 (C-3), 42.85 (NCH2), 38.87 (C-4), 26.65 (3 ꢀ CH3), 18.87 (Si-C).
MS (ESI) (m/z): 446 (M þ Hþ, 100), 468 (M þ Naþ, 40).
(4S,5S)-1-Benzyl-4-[(RS)-(tert-butylphenylfluorosilyl)oxy]-5-
phenyl-2-pyrrolidinone (11)
.
BF3 OEt2 (0.42 mL, 3.40 mmol) was slowly added to a cooled (0 ꢀ 5 8C)
solution of cis-9 (302 mg, 0.67 mmol) in dry CH2Cl2 (4 mL) under N2 atmos-
phere. The mixture was stirred for 72 h at room temperature. Saturated
aqueous NaHCO3 (5 mL) was added at 0 8C, and the aqueous phase was
extracted with CH2Cl2 (3 ꢀ 5 mL). The combined organic phases were
washed with brine (5 mL), dried over anhydrous Na2SO4, filtered, and
concentrated under reduced pressure. Flash chromatographic purification
(eluent : EtOAc/PE ¼ 1 : 8) of the residue gave 11 (256 mg, yield: 85%) as
a diastereomeric mixture at the silicon. The diastereomeric ratio at the