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4.3.10. 2-Cyclopentylidene-4-methoxy-4-oxobutanoic
acid, 9j. Yield 84%; white solid, mp 1038C; IR (cm21
4.4.6. (E)-9-Hydroxy-3-(methoxycarbonyl)nonanoic
acid, 10f. Yield 97%; yellow oil; IR (cm21, neat) 1735,
3400; 1H NMR d (ppm) 1.20–1.40 (m, 6H), 1.41–1.69 (m,
4H), 2.40 (dd, 1H, J¼15.4, 4.4 Hz), 2.63–2.85 (m, 2H),
3.54 (t, 2H, J¼6.6 Hz), 3.64 (s, 3H), 6.21 (bs, 2H). 13C
NMR d (ppm) 25.5, 26.9, 29.2, 31.7, 32.5, 36.2, 41.1, 51.9,
62.6, 175.2, 175.8. Anal. calcd for C11H20O5 (232.27) C,
56.88; H, 8.68. Found C, 56.83; H, 8.70.
,
KBr) 1690, 1711, 1738, 3250; 1H NMR d (ppm) 1.62–1.83
(m, 4H), 2.42 (t, 2H, J¼6.2 Hz), 2.85 (t, 2H, J¼6.2 Hz),
3.34 (s, 2H), 3.68 (s, 3H), 11.81 (s, 1H). 13C NMR d (ppm)
25.6, 27.1, 34.9, 35.1, 35.8, 52.1, 116.6, 168.9, 172.1, 173.0.
Anal. calcd for C10H14O4 (198.21) C, 60.59; H, 7.12. Found
C, 60.55; H, 7.10.
4.4. General procedure for catalytic hydrogenation of
monoesters 7,9
4.4.7. (E)-3-(Methoxycarbonyl)-7-oxooctanoic acid, 10g.
Yield 93%; clear oil; IR (cm21, neat) 1710, 1735, 3320; 1H
NMR d (ppm) 1.42–1.78 (m, 4H), 2.12 (s, 3H), 2.41–2.54
(m, 3H), 2.73–2.84 (m, 2H), 3.68 (s, 3H), 9.25 (bs, 1H). 13C
NMR d (ppm) 21.1, 30.1, 31.2, 35.8, 40.8, 43.2, 52.2, 175.2,
177.6, 208.8. Anal. calcd for C10H16O5 (216.23) C, 55.55;
H, 7.46. Found C, 55.50; H, 7.49.
Monoester 7,9 (2 mmol) was dissolved in EtOAc (20 mL)
and 10% Pd/C (0.1 g) was added. The suspension was
hydrogenated (3 atm) at room temperature for 16 h. The
catalyst was removed by filtration through celite pad and
washed with EtOAc (3£5 mL). After evaporation of the
solvent the crude product 10,11 was purified by flash
chromatography (5:95 methanol–chloroform).
4.4.8. (E)-3-(Methoxycarbonyl)-5-methylhexanoic acid,
10h. Yield 98%; clear oil; IR (cm21, neat) 1712, 1740,
3280; 1H NMR d (ppm) 0.86–0.94 (m, 6H), 1.22–1.37 (m,
1H), 1.48–1.67 (m, 2H), 2.43 (dd, 1H, J¼16.8, 4.9 Hz),
2.62–2.79 (m, 1H), 2.82–2.98 (m, 1H), 3.67 (s, 3H), 11.17
(br s, 1H). 13C NMR d (ppm) 22.4, 22.7, 25.9, 36.2, 39.4,
41.3, 52.1, 176.0, 178.2. Anal. calcd for C9H16O4 (188.22)
C, 57.43; H, 8.57. Found C, 57.38; H, 8.61.
4.4.1. (E)-3-(Methoxycarbonyl)octanoic acid, 10a. Yield
1
95%; yellow oil; IR (cm21, neat) 1709, 1733, 3300; H
NMR d (ppm) 0.87 (t, 3H, J¼7.0 Hz), 1.21–1.38 (m, 6H),
1.40–1.63 (m, 2H), 2.43–2.50 (m, 1H), 2.69–2.85 (m, 2H),
3.69 (s, 3H), 11.21 (bs, 1H). 13C NMR d (ppm) 14.1, 22.6,
26.7, 31.7, 32.0, 35.9, 41.0, 52.1, 175.6, 178.4. Anal. calcd
for C10H18O4 (202.25) C, 59.39; H, 8.97. Found C, 59.34; H,
9.01.
4.4.9. (E)-3-(Methoxycarbonyl)-6-methylheptanoic acid,
10i. Yield 91%; clear oil; IR (cm21, neat) 1712, 1739, 3308;
1H NMR d (ppm) 0.84 (d, 6H, J¼6.6 Hz), 1.08–1.34 (m,
2H), 1.40–1.78 (m, 3H), 2.38–2.58 (m, 1H), 2.62–2.91 (m,
2H), 3.68 (s, 3H), 11.03 (bs, 1H). 13C NMR d (ppm) 22.6,
28.1, 29.9, 35.9, 36.1, 41.2, 52.1, 175.7, 178.3. Anal. calcd
for C10H18O4 (202.25) C, 59.39; H, 8.97. Found C, 59.37; H,
9.00.
4.4.2. 3-Cyclohexyl-4-methoxy-4-oxobutanoic acid, 10b.
Yield 93%; clear oil; IR (cm21, neat) 1761, 1790, 3300; 1H
NMR d (ppm) 0.98–1.36 (m, 5H), 1.54–1.82 (m, 6H),
2.38–2.60 (m, 1H), 2.63–2.83 (m, 2H), 3.71 (s, 3H). 13C
NMR d (ppm) 25.8, 26.1, 29.9, 30.3, 32.8, 39.6, 46.5, 51.4,
174.7, 177.2. Anal. calcd for C11H18O4 (214.26) C, 61.66;
H, 8.47. Found C, 61.61; H, 8.51.
4.4.10. 3-Cyclopentyl-4-methoxy-4-oxobutanoic acid,
10j. Yield 95%; yellow oil; IR (cm21, neat) 1711, 1734,
3270; 1H NMR d (ppm) 1.10–1.30 (m, 2H), 1.41–1.85 (m,
6H), 1.88–2.05 (m, 1H), 2.38–2.60 (m, 1H), 2.61–2.83 (m,
2H), 3.71 (s, 3H), 10.1 (bs, 1H). 13C NMR d (ppm) 25.0,
25.1, 30.6, 30.7, 35.6, 42.5, 46.1, 51.9, 175.6, 178.2. Anal.
calcd for C10H16O4 (200.23) C, 59.99; H, 7.58. Found C,
59.94; H, 7.60.
4.4.3. (E)-3-(Methoxycarbonyl)hexanoic acid, 10c. Yield
1
96%; yellow oil; IR (cm21, neat) 1707, 1742, 3290; H
NMR d (ppm) 0.89 (t, 3H, J¼7.0 Hz), 1.24–1.42 (m, 2H),
1.44–1.67 (m, 2H), 2.44 (dd, 1H, J¼16.1, 4.3 Hz), 2.68–
2.86 (m, 2H), 3.68 (s, 3H), 10.57 (bs, 1H). 13C NMR d
(ppm) 14.0, 20.3, 34.2, 35.9, 40.9, 52.1, 175.7, 178.2. Anal.
calcd for C8H14O4 (174.19) C, 55.16; H, 8.10. Found C,
55.18; H, 8.07.
4.4.11. (E)-2-(2-Methoxy-2-oxoethyl)heptanoic acid, 11a.
Yield 89%; yellow oil; IR (cm21, neat) 1701, 1742, 3300;
1H NMR d (ppm) 0.89 (t, 3H, J¼7.1 Hz), 1.20–1.67 (m,
8H), 2.44 (dd, 1H, J¼16.6, 5.1 Hz), 2.66–2.85 (m, 2H),
3.67 (s, 3H), 10.62 (bs, 1H). 13C NMR d (ppm) 14.2, 22.6,
26.7, 30.6, 31.7, 35.6, 41.3, 52.1, 172.6, 181.4. Anal. calcd
for C10H18O4 (202.25) C, 59.39; H, 8.97. Found C, 59.44; H,
8.93.
4.4.4. (E)-3-(Methoxycarbonyl)nonanoic acid, 10d. Yield
97%; clear oil; IR (cm21, neat) 1712, 1741, 3300; 1H NMR
d (ppm) 0.89 (t, 3H, J¼6.6 Hz), 1.24–1.38 (m, 8H), 1.48–
1.72 (m, 2H), 2.49 (dd, 1H, J¼15.4, 1.8 Hz), 2.78–2.92 (m,
2H), 3.72 (s, 3H). 13C NMR d (ppm) 14.0, 22.5, 26.8, 29.0,
31.6, 31.9, 35.5, 40.9, 51.9, 175.4, 176.7. Anal. calcd for
C11H20O4 (216.27) C, 61.09; H, 9.32. Found C, 61.015; H,
9.28.
4.4.12. 2-Cyclohexyl-4-methoxy-4-oxobutanoic acid,
11b. Yield 98%; yellow oil; IR (cm21, neat) 1705, 1756,
3270; 1H NMR d (ppm) 1.01–1.35 (m, 5H), 1.60–1.84 (m,
6H), 2.42–2.58 (m, 1H), 2.70–2.83 (m, 2H), 3.69 (s, 3H).
13C NMR d (ppm) 26.3, 26.5, 30.0, 30.8, 33.0, 39.9, 46.9,
52.0, 173.2, 178.9.0. Anal. calcd for C11H18O4 (214.26) C,
61.66; H, 8.47. Found C, 61.72; H, 8.50.
4.4.5. (E)-3-(Methoxycarbonyl)-4-methylpentanoic acid,
10e. Yield 94%; yellow oil; IR (cm21, neat) 1710, 1736,
3300; 1H NMR d (ppm) 0.94 (d, 3H, J¼6.7 Hz), 0.97 (d, 3H,
J¼6.7 Hz), 1.92–2.10 (m, 1H), 2.50 (dd, 1H, J¼15.7,
2.9 Hz), 2.64–2.81 (m, 2H), 3.65 (s, 3H), 10.61 (bs, 1H).
13C NMR d (ppm) 19.7, 20.2, 30.3, 32.9, 47.4, 51.9, 175.0,
178.0. Anal. calcd for C8H14O4 (174.19) C, 55.16; H, 8.10.
Found C, 55.22; H, 8.13.
4.4.13. (E)-2-(2-Methoxy-2-oxoethyl)-3-methylbutanoic
acid, 11c. Yield 97%; yellow oil; IR (cm21, neat) 1705,