R. Cella et al. / Tetrahedron Letters 49 (2008) 16–19
19
27. Hanson, G. J.; Baran, J. S.; Lindberg, T. Tetrahedron Lett.
1986, 27, 3577.
28. Hamada, Y.; Shiori, T. Chem. Pharm. Bull. 1982, 30,
1921.
with NH4Clsat (2 · 15 mL), dried with MgSO4 and
concentrated under reduced pressure. The crude mixture
was purified by silica flash chromatography.
tert-Butyl
(3R,4S,5R)-5-methoxy-3-methyloct-7-en-4-yl-
29. Niel, G.; Roux, F.; Maisonnasse, Y.; Maugras, I.; Poncet,
J.; Jouin, P. J. Chem. Soc., Perkin Trans. 1 1994, 1275.
30. Brunel, F. M.; Taylor, K. G.; Spatola, A. F. Tetrahedron
Lett. 2003, 44, 1287.
(methyl)carbamate 13a: Product 13a was obtained in
20
1
80% of yield. ½aꢁD ꢀ18 (c 1, MeOH); H NMR (CDCl3)
(two conformers, 50:50) 0.88–0.93 (m, 6H), 0.96–1.09 (m,
1H), 1.31–1.43 (m, 1H), 1.44 (s, 4.5H), 1.45 (s, 4.5H), 1.89–
1.97 (m, 1H), 2.12–2.21 (m, 1H), 2.28–241 (m, 1H), 2.76 (s,
1.5H), 2.79 (s, 1.5H), 3.35 (s, 1.5H), 3.36 (s, 1.5H), 3.38–
3.41 (m, 1H), 3.64–3.69 (m, 0.5H), 3.83–3.87 (m, 0.5H),
5.01–5.12 (m, 2H), 5.78–5.95 (m, 1H). ESI-MS m/z (%):
309 (5, M+Na), 286 (19, M+1), 230 (100), 186 (85).
31. Typical procedure for the cyclisation of compounds 5 and
11a–b: To a solution of compound 5 (0.128 g, 0.5 mmol) in
THF (2 mL) at ꢀ5 ꢁC was added sodium hydride (60%
dispersion in mineral oil, 40 mg, 1 mmol). The mixture
was stirred overnight at room temperature and then was
hydrolysed with aq 5% KHSO4. After dilution with ethyl
acetate (80 mL), the organic layer was washed with brine,
dried with MgSO4, filtered and concentrated under
reduced pressure. The cyclised product was purified by
column chromatography on silica flash. 4-(1-Methyl-2-
propenyl)-3,1-oxazabicyclo[3.3.0]octan-2-one 6: Compound
tert-Butyl
(3S,4R)-4-methoxy-2-methylhept-6-en-3-yl-
(methyl)carbamate 13b: Product 13b was obtained in
20
1
80% of yield. ½aꢁD ꢀ18 (c 1, MeOH); H NMR (CDCl3)
(two conformers, 50:50) 0.85–0.88 (m, 3H), 0.96–1.00 (m,
3H), 1.47 (s, 9H), 2.12–2.21 (m, 2H), 2.32–2.39 (m, 1H),
2.79 (s, 1.5H), 2.82 (s, 1.5H), 3.36 (s, 1.5H), 3.38 (s, 1.5H),
3.37–3.44 (m, 1H), 3.58–3.62 (m, 0.5H), 3.78–3.82 (m,
0.5H), 5.04–5.14 (m, 2H), 5.84–5.93 (m, 1H). ESI-MS m/z
(%): 294 (3, M+Na), 272 (13, M+1), 216 (91), 172 (100).
37. Typical procedure to oxidative cleveage with RuO2: To a
solution of alkenes 7 or 13a–b (2.8 mmol) in a system
CH3CN/H2O/CCl4 (5:7.5:5 mL) were added NaIO4 (2.5 g,
11.6 mmol) and RuO2 (15.6 mg, 2.5 mol %) at room
temperature and the mixture was stirred for 72 h at same
temperature. Then it was diluted with ethyl acetate
(100 mL) and successively washed with Na2S2O3 (10%)
and brine. The organic layer was dried with MgSO4,
filtered and concentrated under reduced pressure. The
crude mixture was purified by silica flash chromatography
using AcOEt/hexane/MeOH (4:4:2) as eluant.
20
6 was prepared from compound 5 in 90% of yield. ½aꢁD
1
+38 (c 1, MeOH); H NMR (CDCl3) 1.21 (d, J = 6.5 Hz,
3H), 1.44–1.53 (m, 1H), 1.76–1.91 (m, 2H), 2.45–2.57 (m,
1H), 3.11–3.19 (m, 1H), 3.66–3.74 (m, 2H), 4.36 (dd,
J1 = 10.6 Hz J2 = 6.9 Hz, 1H), 5.11–5.19 (m, 2H), 5.62–
5.74 (m, 1H). GC–MS m/z (%): 181 (11, M+), 126 (94), 82
(100), 55 (43).
(4S,5R)-5-allyl-4-((R)-sec-butyl)oxazolidin-2-one
12a:
Compound 12a was prepared from compound 11a in
20
87% of yield. ½aꢁD ꢀ5 (c 1, MeOH); 1H NMR (CDCl3)
0.85–0.91 (m, 6H), 1.02–1.15 (m, 1H), 1.38–1.63 (m, 2H),
2.39–2.47 (m, 2H), 3.30–3.33 (m, 1H), 4.31 (dd,
J1 = 10.4 Hz J2 = 5.9 Hz, 1H), 5.10–5.19 (m, 2H), 5.70–
5.82 (m, 1H). GC–MS m/z (%): 183 (2, M+), 142 (68), 126
(100), 86 (40), 57 (61), 43 (68).
(2R,3R)-3-((S)-1-(tert-butoxycarbonyl)pyrrolidin-2-yl)-3-
methoxy-2-methylpropanoic acid; N-Boc-Dap 8: The N-
Boc-Dap 8 was prepared from compound 7 in 75% of
(4S,5R)-5-allyl-4-isopropyloxazolidin-2-one 12b: Com-
pound 12b was prepared from compound 11b in 84% of
20
20
yield. ½aꢁD +60 (c 1, MeOH); 1H NMR (CDCl3) 0.90–0.95
yield. ½aꢁD ꢀ50 (c 1, MeOH); H NMR (CDCl3) 1.19 (d,
J = 6.9 Hz, 3H), 1.40 (s, 9H), 1.65–1.72 (m, 1H), 1.79–1.89
(m, 3H), 2.40–2.44 (m, 1H), 3.12–3.20 (m, 1H), 3.37 (s,
3H), 3.32–3.49 (m, 1H), 3.70–3.85 (m, 2H), 9.29 (s, 1H).
ESI-MS m/z (%): 324 (32, M+K), 224 (5), 202 (100), 187
(15).
1
(m, 6H), 1.65–1.76 (m, 1H), 2.43–2.47 (m, 2H), 3.24–3.28
(m, 1H), 4.32 (dd, J1 = 10.6 Hz J2 = 5.9 Hz, 1H), 5.16–
5.22 (m, 2H), 5.73–5.87 (m, 1H). GC–MS m/z (%): 169 (1,
M+), 128 (77), 126 (92), 86 (20), 43 (75), 41 (100).
32. Dias, L. C.; Diaz, G.; Ferreira, A. A.; Meira, P. R. R.;
Ferreira, E. Synthesis 2003, 603.
(3R,4S,5R)-4-(tert-butoxycarbonyl(methyl)amino)-3-methoxy-
5-methylheptanoic acid 14a: The N-Boc-Dil 14a was
33. Batey, R. A.; Thadani, A. N.; Smil, D. V. Tetrahedron
Lett. 1999, 40, 4289.
34. Batey, R. A.; Thadani, A. N.; Smil, D. V.; Lough, A. J.
Synthesis 2000, 990.
35. Prashad, M.; Har, D.; Hu, B.; Kim, H.-Y.; Repic, O.;
Blacklock, T. J. Org. Lett. 2003, 5, 125.
36. Typical procedure to N,O-dimethylation reactions: To a
cooled (0 ꢁC) suspension of sodium hydride (60% disper-
sion in mineral oil, 96 mg, 2.44 mmol) in THF (3 mL) was
added a solution of substrates 11a–b (1.22 mmol) and
water (0.025 mL, 0.25 mmol) in THF (2.5 mL) dropwise
over a period of 10 min keeping the internal temperature
between 5 and 10ꢁC. The mixture was stirred at the same
temperature for 20 min, and dimethyl sulfate (0.23 mL,
2.5 mmol) was added over a period of 10 min. The stirring
was continued at room temperature for 5 h. The reaction
was quenched with 30% NH4OH and the stirring was
continued for an additional 1 h. The mixture was diluted
with ethyl acetate (30 mL). The organic layer was washed
20
prepared from compound 13a in 80% of yield. ½aꢁD ꢀ3
1
(c 1, MeOH); H NMR (CDCl3) (two conformers, 50:50)
0.77–0.88 (m, 3.5H), 0.94–1.03 (m, 3.5H), 1.22–1.33 (m,
1H), 1.40 (s, 4.5H), 1.43 (s, 4.5H), 1.88–1.98 (m, 1H), 2.43–
2.64 (m, 2H), 2.76 (s, 1.5H), 2.77 (s, 1.5H), 3.33 (s, 1.5H),
3.37 (s, 1.5H), 3.72–3.76 (m, 0.5H), 3.80–3.86 (m, 0.5H),
3.95–3.98 (m, 1H), 7.70 (s, 1H). ESI-MS m/z (%): 326 (18,
M+Na), 304 (9, M+1), 248 (100), 304 (67).
(3R,4S)-4-(tert-butoxycarbonyl(methyl)amino)-3-methoxy-
5-methylhexanoic acid 14b: The N-Boc-MMMAH 14b was
20
prepared from compound 14b in 83% of yield. ½aꢁD ꢀ17 (c
1, MeOH); 1H NMR (CDCl3) (two conformers, 50:50)
0.83–0.85 (m, 3H), 0.99–1.04 (m, 3H), 1.42 (s, 4.5H), 1.45
(s, 4.5H), 2.11–2.17 (m, 1H), 2.40–2.72 (m, 2H), 2.78 (s,
1.5H), 2.80 (s, 1.5H), 3.35 (s, 1.5H), 3.37 (s, 1.5H), 3.95–
3.98 (m, 0.5H), 3.76–3.80 (m, 0.5H), 3.95–4.08 (m, 1H),
9.63 (s, 1H). ESI-MS m/z (%): 312 (13, M+Na), 290 (6,
M+1), 234 (100), 190 (72).