S. P. Chavan, C. Praveen / Tetrahedron Letters 46 (2005) 1939–1941
1941
OH
O
O
O
OH
O
c
a
b
3 + 4
n-C6H13
n-C6H13
n-C6H13
O
O
O
O
O
O
OMOM
OH
OMOM
1
18
2
Scheme 4. Reagents and conditions: (a) DCC, DMAP, CH2Cl2, rt, 18 h, 76%; (b) (PCy3)2Ru(Cl)2CH@Ph (20 mol%), CH2Cl2, reflux, 28 h, 67%;
(c) BF3:Et2O, (CH2SH)2, CH2Cl2, 0 °C, 1 h, 76%.
7. Hanack, M.; Kunzmann, E.; Schumacher, W. Synthesis
1978, 26.
lyst under highly diluted, degassed conditions gave the
10-membered lactone as E and Z isomers in 67:33 ratio.
The desired E isomer could be separated by column
chromatography from the Z isomer. Global deprotec-
tion of E 18 gave microcarpalide 1 (Scheme 4). The spec-
troscopic and analytical data of compound 1 and other
compounds were in good agreement with the literature
data.1,3,9
8. (a) Iida, H.; Imazaki, N.; Kibayashi, C. J. Org. Chem. 1987,
52, 3337–3342; (b) Clough, S.; Raggatt, M. E.; Simpson, T.
J.; Willis, C. L.; Whiting, A.; Wrigley, S. K. J. Chem. Soc.,
Perkin Trans. 1 2000, 2475–2481; (c) Schnurrenberger, P.;
Hungerbubler, E.; Seebach, D. Liebigs Ann. Chem. 1987,
733–744.
9. Spectral data for compound 3: 1H NMR (200 MHz, CDCl3)
d, ppm: 1.38 (6H, s), 1.72–2.04 (2H, m), 2.38–2.57 (2H, m),
3.69 (1H, dt, J = 8.2, 3.9 Hz), 3.97 (1H, dd, J = 8.2, 7.2 Hz),
5.28 (1H, ddd, J = 10.2, 1.5, 0.8 Hz), 5.39 (1H, ddd,
J = 17.2, 1.5, 0.8 Hz), 5.79 (1H, ddd, J = 17.2, 10.2,
7.3 Hz) 13C NMR (50 MHz) d: 26.5, 26.9, 27.1, 30.4, 79.5,
82.4, 108.8, 119.2, 135.1, 178.6 ppm. Anal. Calcd for
C10H16O4: C, 60.0; H, 8.0. Found: C, 59.8; H, 7.9.
Compound 4: 1H NMR (200 MHz, CDCl3) d, ppm: 0.89
(3H, t, J = 6.8 Hz), 1.22–1.38 (8H, m), 1.46–1.62 (2H, m),
2.12–2.39 (2H, m), 2.71 (1H, d, J = 4.0 Hz, –OH), 3.32–3.39
(1H, m), 3.40 (3H, s), 3.56 (1H, m), 4.67 (2H, s), 5.06 (1H,
m) 5.12 (1H, m), 5.86 (1H, m) 13C NMR (50 MHz) d: 14.0,
22.5, 25.1, 29.3, 30.8, 31.7, 37.8, 55.7, 72.0, 82.4, 97.0, 117.2,
134.9 ppm. Anal. Calcd for C13H26O3: C, 67.77; H, 11.38.
Found: C, 67.72; H, 11.14. Compound 2: 1H NMR
(200 MHz, CDCl3) d, ppm: 0.89 (3H, t, J = 6.9 Hz), 1.28–
1.34 (8H, m), 1.40 (6H, s), 1.50 (2H, m), 1.82 (1H, m), 1.95
(1H, m), 2.34–2.52 (4H, m), 3.39 (3H, s), 3.59 (1H, m), 3.70
(1H, td, J = 8.3, 3.4 Hz), 3.99 (1H, t, J = 7.9 Hz), 4.69 (2H,
ABq, J = 3.4 Hz), 5.07 (2H, m), 5.09 (1H, dd, J = 17.6,
1.6 Hz), 5.26 (1H, d, J = 10.4 Hz), 5.37 (1H, d,
J = 17.6 Hz), 5.77 (2H, m) 13C NMR (75 MHz) d: 14.0,
22.5, 25.3, 26.8, 26.9, 27.2, 29.3, 30.5, 30.7, 31.7, 34.6, 55.8,
73.7, 78.1, 79.5, 82.4, 96.7, 108.8, 117.6, 118.9, 133.9, 135.2,
172.5 ppm. Anal. Calcd for C23H40O6: C, 66.95; H, 9.78.
Found: C, 66.62; H, 10.04. Compound 18: 1H NMR
(300 MHz, CDCl3) d, ppm: 0.89 (3H, t, J = 7.0 Hz), 1.24–
1.36 (8H, m), 1.41 (6H, s), 1.60 (2H, m), 1.96–2.06 (2H, m),
2.28–2.64 (4H, m), 3.42 (3H, s), 3.62 (2H, m), 3.93 (1H, t,
J = 8.8 Hz), 4.69 (2H, m), 4.95 (1H, ddd, J = 8.8, 3.8,
2.5 Hz), 5.35 (1H, dd, J = 15.8, 9.4 Hz), 5.78 (1H, ddd,
J = 15.8, 11.4, 4.7 Hz), 13C NMR (75 MHz) d: 14.0, 22.6,
25.3, 25.4, 26.9, 27.1, 29.4, 30.5, 30.8, 31.7, 34.2, 56.0, 73.6,
79.3, 79.8, 84.4, 96.5, 108.8, 129.4, 130.1, 171.7 ppm. Anal.
Calcd for C21H36O6: C, 65.59; H, 9.43. Found: C, 65.3; H,
9.32. Compound 1: colorless oil. ½aꢁD ꢀ22.3 (c 0.4; MeOH),
lit.1,3 ½aꢁD ꢀ22 (c 0.67; MeOH); Anal. Calcd for C16H28O5
C, 63.97; H, 9.40. Found: C, 64.12; H, 9.28.
In conclusion we have described a highly convergent
and efficient synthesis of (ꢀ)-microcarpalide. Further
work in this direction is underway in our laboratory.
Acknowledgements
C.P. thank CSIR (New Delhi) for a research fellowship.
Funding from DST (SP/S1/G-28/2000, New Delhi) to
S.P.C. is gratefully acknowledged.
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