122
U. Ramulu et al. / Tetrahedron: Asymmetry 23 (2012) 117–123
138.3, 134.8, 130.1, 129.3, 128.2, 127.5, 122.1, 119.5, 113.7, 81.7,
77.8, 72.0, 70.5, 70.4, 68.4, 55.1, 35.0, 31.0, 25.8, 23.8, 15.2, -4.4, -
4.7; ESI/MS (m/z): 605 (M+Na+).
(123 mg, 82%) as a colorless gummy liquid: ½a D25
¼ ꢀ10:8 (c 0.65,
ꢃ
CHCl3); IR (neat, cmꢀ1): mmax 3450, 2922, 2852, 1712, 1639, 1276,
1202, 1050, 985, 761; 1H NMR (300 MHz, CDCl3): d 6.95 (dd,
J = 15.8, 4.5 Hz, 1H), 6.40 (dd, J = 17.3, 1.5 Hz, 1H), 6.16–6.03 (m,
2H), 5.92–5.79 (m, 2H), 5.42–5.23 (m, 2H), 5.09–4.97 (m, 2H),
4.40–4.23 (m, 2H), 1.80–1.51 (m, 4H), 1.28 (d, J = 6.0 Hz, 3H),
1.24 (d, J = 6.0 Hz, 1H); 13C NMR (75 MHz, CDCl3): d 166.1, 166.0,
150.3, 135.6, 130.7, 128.7, 120.3, 117.4, 74.7, 73.5, 70.9, 70.6,
32.2, 31.6, 20.0, 14.4; ESI/MS (m/z): 335 (M+Na+).
4.12. (4R,7R,E)-((2R,3S)-3-(Benzyloxy)pent-4-en-2-yl)7-hydroxy-
4-(4-methoxybenzyloxy)oct-2-enoate 18
To a cooled (0 °C) solution of 17 (500 mg, 0.857 mmol) in MeOH
(10 mL) was added PTSA (147 mg, 0.857 mmol) and stirred at the
same temperature for 0.5 h. After completion of the reaction, the
mixture was quenched with solid sodium bicarbonate, filtered,
and MeOH was evaporated under reduced pressure to afford a
crude product, which was purified by column chromatography on
silica gel (hexane/ethylacetate, 70:30) to give alcohol 18 (352 mg,
4.14.1. Clonostachydiol 1
A solution of compound 20 (30 mg, 0.096 mmol) in dry toluene
(110 mL) was bubbled with a nitrogen flow, after which Hoveyda
Grubbs II generation catalyst (6 mg, 0.009 mmol) was added at
once and the resulting mixture was heated under nitrogen at
80 °C for 0.5 h. After completion of the reaction, the mixture was
cooled to room temperature and the solvent was evaporated in va-
cuo. The crude residue was purified by column chromatography on
88%) as a colorless liquid: ½a D25
¼ þ6:2 (c 0.4, CHCl3); IR (neat,
ꢃ
cmꢀ1): mmax 3448, 2925, 2860, 1716, 1613, 1512, 1445, 1250,
1172, 1068; 1H NMR (30 0 MHz, CDCl3): d 7.33–7.17 (m, 7H),
6.86–6.75 (m, 3H), 5.96 (d, J = 16.6 Hz, 1H), 5.85–5.71 (m, 1H),
5.38–5.26 (m, 2H), 5.08–4.99 (m, 1H), 4.64 (d, J = 12.0 Hz, 1H),
4.51 (d, J = 11.3 Hz, 1H), 4.41 (d, J = 12.0 Hz, 1H), 4.28 (d, J = 11.3
Hz, 1H), 3.86–3.64 (m, 5H), 3.99–3.90 (m, 1H), 1.79–1.37 (m, 4H),
1.29 (d, J = 6.8 Hz, 3H), 1.16 (d, J = 6.0 Hz, 3H); 13C NMR (75 MHz,
CDCl3): d 165.4, 159.1, 148.1, 138.2, 134.6, 129.7, 129.3, 128.2,
127.5, 122.2, 119.5, 113.7, 81.7, 77.6, 72.0, 70.6, 70.3, 67.6, 55.1,
34.6, 31.0, 23.4, 15.2; ESI/MS (m/z): 491 (M+Na+).
silica gel (hexane/ethylacetate, 50:50) to give compound
1
(21.8 mg, 80%) as a white solid, mp 165 °C, (Lit.5 mp 164 °C);
½
a 2D5
ꢃ
¼ þ101:6 (c 0.5, MeOH), [Lit.5 = +103 (c 1.0, MeOH)]. IR (neat,
cmꢀ1):
mmax 3407, 2979, 2920, 2851, 1711, 1639, 1461, 1370, 1225,
1179, 1049, 978; 1H NMR (300 MHz, DMSO-d6): d 6.68 (dd, J = 15.8,
4 Hz, 1H), 6.48 (dd, J = 15.8, 7.9 Hz, 1H), 5.91 (d, J = 15.8 Hz, 1H),
5.78 (dd, J = 15.8, 2 Hz, 1H), 5.68 (d, J = 5 Hz, 1H), 5.07–4.99 (m,
2H), 4.77–4.66 (m, 1H), 4.49–4.42 (m, 1H), 3.92–4.0 (m, 1H),
1.87–1.77 (m, 1H), 1.61–1.53 (m, 1H), 1.51–140 (m, 2H), 1.34 (d,
J = 6.5 Hz, 3H), 1.13 (d, J = 6.5); 13C NMR (75 MHz, CDCl3): d
165.0, 164.1, 150.8, 145.4, 123.8, 120.3, 77.2, 73.7, 70.4, 70.1,
30.6, 27.4, 18.6, 18.0;ESI/MS (m/z): 307 (M+Na)+; HRMS Calcd for
4.13. (4R,7R,E)-((2R,3S)-3-(Benzyloxy)pent-4-en-2-yl)7-(acry-
loyloxy)-4-(4-methoxybenzyl- oxy)oct-2-enoate 19
To a cooled (0 °C) solution of alcohol 18 (300 mg, 0.640 mmol)
in dry DCM (10 mL) were added triethylamine (0.22 mL, 1.6 mmol)
and acryloyl chloride (0.1 mL, 1.28 mmol) and stirred at the same
temperature for 0.5 h. After completion of the reaction, the reac-
tion mixture was quenched with saturated sodium bicarbonate
(10 mL) and extracted into DCM (3 ꢂ 30 mL). The combined organ-
ic phase was washed with brine and dried over anhydrous Na2SO4.
The solvent was removed under reduced pressure, and the crude
residue was purified by column chromatography on silica gel (hex-
ane/ethyl acetate, 90:10) to acryl ester 19 (291 mg, 87%) as a color-
C
14H20O6Na (M+Na+) 307.1152. Found: 307.1157.
Acknowledgments
The authors D.R., S.R., S.P.R. and K.V. are thankful to MOES and
the CSIR-UGC, New Delhi, India, respectively, for the financial sup-
port and Dr. J. S. Yadav Director, the Indian Institute of Chemical
Technology (IICT) for his encouragement.
less liquid: ½a 2D5
ꢃ
¼ þ2:5 (c 0.2, CHCl3); IR (neat, cmꢀ1): mmax 2925,
2855, 1719, 1613, 1513, 1272, 1248, 1200, 1065, 985, 756; 1H
NMR (300 MHz, CDCl3): d 7.31–7.15 (m,7H), 6.82 (d, J = 8.9 Hz,
2H), 6.76 (dd, J = 15.8, 5.9 Hz, 1H), 6.35 (d, J = 17.8 Hz, 1H), 6.06
(dd, J = 17.8, 10.8 Hz, 1H), 5.94 (d, J = 15.8 Hz, 1H), 5.82–5.72 (m,
2H), 5.35–5.25 (m, 2H), 5.06–4.99 (m, 1H), 4.97–4.89 (m, 1H),
4.63 (d, J = 11.8, 1H), 4.48 (d, J = 11.8, 1H), 4.41 (d, J = 11.8, 1H),
4.26 (d, J = 11.8, 1H), 3.94–3.81 (m, 2H), 3.79 (s, 3H), 1.72–154
(m, 4H), 1.28 (d, J = 5.9 Hz, 3H), 1.24 (d, J = 5.9 Hz, 3H); 13C NMR
(75 MHz, CDCl3): d 165.6, 165.3, 159.2, 147.9, 138.2, 134.7, 130.3,
129.9, 129.3, 128.7, 128.2, 127.5, 122.4, 119.5, 113.7, 81.6, 77.3,
72.0, 70.8, 70.6, 70.3, 55.1, 31.4, 30.7, 19.9, 15.2; ESI/MS (m/z):
545 (M+Na+).
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4.14. (4R,7R,E)-((2R,3S)-3-Hydroxypent-4-en-2-yl)7-(acry-
loyloxy)-4-hydroxyoct-2-enoate 20
To a cooled (0 °C) solution of 19 (250 mg, 0.478 mmol) in dry
DCM (7 mL) was added a solution of TiCl4 (0.21 mL, 1.915 mmol)
in dry DCM (2 mL) under N2 and the mixture was stirred at the
same temperature for 1 h. After completion of the reaction, the
reaction mixture was quenched with saturated sodium bicarbon-
ate (10 mL), and extracted into DCM (3 ꢂ 20 mL). The combined or-
ganic phase was washed with brine, and dried over anhydrous
Na2SO4. The solvent was removed under reduced pressure, and
the crude residue was purified by column chromatography on sil-
ica gel (hexane/ethyl acetate, 55:45) to give pure compound 20