X. Feng, E. D. Edstrom / Tetrahedron: Asymmetry 10 (1999) 99–105
105
25
silica gel using 20% EtOAc:hexanes to provide 18b (0.15 g, 41%) as a white foam. [α]D −17 (c 0.98,
EtOAc); IR (film) 3060, 2980, 2850, 1690, 1595, 1500, 1460, 1385, 1250, 1170, 1060 cm−1; 1H NMR
(400 MHz, CDCl3, chemical shifts sensitive to the ratio of rotamers) δ 6.61–7.39 (series of m, 13H), 5.51
(br s, 1H), 5.02–5.19 (two A2B2 q, 2H, Cbz benzylic), 4.03 and 3.95 (two sets of m, 1H, αH), 3.70–3.80
(m, 2H), 2.90 and 3.10 (two sets of dd, 1H, dopa benzylic), 2.55 (t, 1H, dopa benzylic), 1.42, 1.48, 1.50
and 1.58 (series of s, 6H, oxazolidine Me); 13C NMR (100.59 MHz, CDCl3) δ major isomer 156.70,
152.20, 146.20, 143.15, 136.25, 130.68, 129.92, 128.53, 128.13, 127.98, 125.49, 123.61, 119.72, 117.76,
116.21, 94.80, 66.74, 66.23, 59.00, 38.85, 26.62, 23.14; minor isomer 152.60, 127.10, 125.85, 120.00,
116.10, 67.08, 65.77, 59.58, 37.55, 27.50, 24.56; HRMS m/e 433.1883 (C26H27NO5 requires 433.1889).
Acknowledgements
This research was supported by funds provided from the Montana NSF EPSCoR Program (MONTS)
and the Research Office, University of Montana.
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