A. Ritzén et al. / Tetrahedron: Asymmetry 9 (1998) 503–512
507
4.4. (Z0,Z00)-1-[20-(Benzyloxycarbonyl)-20 -[(tert-butyloxycarbonyl)amino]ethenyl]-3-[200 -
(methoxycarbonyl)-200 -[[2000-(trimethylsilyl)ethyloxycarbonyl]amino]ethenyl]benzene 10
Following the general procedure of coupling using the bromide 719 (0.86 g, 1.99 mmol) and olefin
219 (0.77 g, 3.14 mmol) the product was isolated as a viscous, pale yellow oil, 0.92 g (77%), after flash
chromatography using heptane:ethyl acetate (2:1) as eluent (TLC Rf=0.24). NOE experiments confirmed
the assigned (Z) stereochemistry.4 1H NMR (CDCl3, 400 MHz) δ 0.02 (s, 9H), 0.87–1.02 (m, 2H), 1.38
(s, 9H), 3.86 (s, 3H), 4.13–4.19 (m, 2H), 5.29 (s, 2H), 6.32 (br s, 2H), 7.26 (s, 2H), 7.34–7.44 (m,
6H) 7.51 (d, 2H, J=7.9 Hz), 7.64 (s, 1H); 13C NMR δ −1.33, 17.77, 28.24, 52.93, 64.47, 67.73, 81.35,
125.22, 128.58, 128.64, 128.81, 128.92, 129.48, 130.04, 130.43, 131.41, 134.26, 134.78, 135.62, 152.73
(br), 154.25 (br), 165.51, 165.90; HRMS (FAB+) m/z calcd for C31H40N2O8Si: 597.2632 [M+H]. Found:
597.2638.
4.5. (Z00,Z000)-4-[200-(Benzyloxycarbonyl)-200 -[(tert-butyloxycarbonyl)amino]ethenyl]-40 -[2000-
(methoxycarbonyl)-20 00-[[20000-(trimethylsilyl)ethyloxycarbonyl]amino]ethenyl]biphenyl 11
The coupling reaction was performed following the general procedure using 8 (0.50 g, 0.90 mmol) and
2 (0.29 g, 1.17 mmol). Purification of the crude product by chromatography (hexane:EtOAc=2:1, TLC
Rf=0.25) gave 11 in 74% yield. Recrystallisation from ethyl acetate:hexane afforded the analytically
pure compound (0.40 g, 66%, mp 161–162°C). 1H NMR (CDCl3, 400 MHz) δ 0.03 (s, 9H), 0.92–1.01
(m, 2H), 1.41 (s, 9H), 3.88 (s, 3H), 4.16–4.22 (m, 2H), 5.30 (s, 2H), 6.31 (br s, 2H), 7.34–7.46 (m,
7H), 7.61–7.63 (m, 8H); 13C NMR δ −1.28, 17.79, 28.33, 52.96, 64.53, 67.72, 81.32, 124.55, 127.18,
127.30, 128.64, 128.65, 128.84, 129.94, 130.53, 130.56, 130.82, 133.47, 133.85, 135.74, 140.97, 141.26,
152.84 (br), 154.27 (br), 165.69, 166.07; HRMS (FAB+) m/z calcd for C37H44N2O8Si: 672.2867. Found:
672.2861.
4.6. (20S,200S)-1-[20-(Benzyloxycarbonyl)-20 -[(tert-butyloxycarbonyl)amino]ethyl]-4-[200 -
(methoxycarbonyl)-200 -[[2000-(trimethylsilyl)ethyloxycarbonyl]amino]ethyl]benzene (S,S)-12
(a) Hydrogenation of bis-olefin 9: Bis-olefin 919 (400 mg, 0.670 mmol) was dissolved in methanol (20
mL) and hydrogenated at 2.8 atm at 40°C in the presence of [Rh(COD)((R,R)-DIPAMP)]+BF4− (10 mg)
as catalyst for 4 days. The solvent was then removed in vacuo and the crude mass was passed through a
short pad of silica to give the title compound (370 mg, 92%) as a highly viscous liquid using heptane:ethyl
acetate (2:1) as an eluent (TLC Rf=0.3); [α]D22 +30 (c 3.7, CHCl3). HPLC analysis (see Stereochemical
analysis) on an (R,R)-Whelk-O1 column (hexane:2-propanol=90:10+0.5% HOAc; 1.0 mL/min) gave a
single peak (Rt=16.8 min); d.r.≥90:10; e.e.≥98%. 1H NMR (CDCl3, 400 MHz) δ 0.03 (s, 9H), 0.95–0.99
(m, 2H), 1.42 (s, 9H), 3.00–3.11 (m, 4H), 3.70 (s, 3H), 4.12–4.17 (m, 2H), 4.58–4.63 (m, 2H), 4.98 (br
d, 1H, J=8.4 Hz), 5.06 (br d, 1H, J=8.4 Hz), 5.10 (d, 1H, J=12 Hz), 5.17 (d, 1H, J=12 Hz), 6.95–7.00
(m, 4H), 7.30–7.40 (m, 5H); 13C NMR δ −1.30, 17.86, 28.49, 38.02, 38.10, 52.46, 54.56, 54.80, 63.67,
67.30, 80.15, 128.69, 128.79, 129.58, 129.78, 134.70, 134.90, 135.37, 155.25, 156.19, 171.87, 172.35;
HRMS (CI-CH4) m/z calcd for C31H44N2O8Si: 601.2945 [M+H]. Found: 601.2929.
(b) Hydrogenation of mono-olefin (S,Z)-16: Olefin (S,Z)-16 (198 mg, 0.331 mmol) dissolved in
methanol (10 mL) was hydrogenated at 3 atm and at room temperature for 3 days using [Rh(COD)((R,R)-
DIPAMP)]+BF4− (6 mg) as a catalyst. The solvent was removed in vacuo and the crude viscous mass was
passed through a short pad of silica using hexane:ethyl acetate (2:1) as eluent to give the title compound