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with active MnO2 (30 g) at rt for 5 h. The mixture was filtered through
Celite. Evaporation of the filtrate gave a residue, which was purified by CC
(acetone–hexane, 1 : 4) to provide the dienal 13b (1.20 g, 86%) as yellow
solids. 1H-NMR data were accordance with those reported7); UV lmax
CDCl3) d: 0.21, 0.27 (each 3H, s, SiMeꢃ2), 0.94 (9H, s, tert-Bu), 5.88 (1H,
s, 3-H), 6.23 (1H, s, 5-H), 6.37 (1H, d, Jꢂ3.5 Hz, 3ꢅ-H), 6.38 (1H, d,
Jꢂ15.5 Hz, 1ꢀ-H), 6.42 (1H, dd, Jꢂ2, 3.5 Hz, 4ꢅ-H), 6.43 (1H, dd, Jꢂ11,
14.5 Hz, 3ꢀ-H), 6.50 (1H, d, Jꢂ16 Hz, 6ꢀ-H), 6.54 (1H, dd, Jꢂ11, 14.5 Hz,
4ꢀ-H), 6.78 (1H, dd, Jꢂ11, 16 Hz, 5ꢀ-H), 6.88 (1H, dd, Jꢂ11, 15.5 Hz, 2ꢀ-
H), 7.41 (1H, d, Jꢂ2 Hz, 5ꢅ-H); MS m/z: 358.1599 [Calcd for C20H26O4Si
(Mꢄ) 358.1596].
1
(EtOH) nm: 350; IR (CHCl3) cmꢁ1: 1673 (conj. CꢂO), 1616 (CꢂC); H-
NMR (300 MHz, CDCl3) d: 6.21 (1H, dd, Jꢂ8, 15 Hz, 2-H), 6.77 (1H, dd,
Jꢂ11, 15 Hz, 4-H), 7.04 (1H, dd, Jꢂ3, 5 Hz, 4ꢀ-H), 7.12 (1H, d, Jꢂ15 Hz,
5-H), 7.18 (1H, d, Jꢂ3 Hz, 3ꢀ-H), 7.18 (1H, dd, Jꢂ11, 15 Hz, 3-H), 7.34
(1H, d, Jꢂ5 Hz, 5ꢀ-H), 9.58 (1H, d, Jꢂ8 Hz, CHO); MS m/z: 164.0279
[Calcd for C9H8OS (Mꢄ) 164.0296].
5-tert-Butyldimethylsilyloxy-4-[(1E,3E,5E)-6-(2-thienyl)hexa-1,3,5-
trienyl]-2(5H)-furanone 16b: Orange solid; UV lmax (EtOH) nm: 392; IR
(CHCl3) cmꢁ1: 1759 (CꢂO), 1624, 1581 (CꢂC); 1H-NMR (300 MHz,
CDCl3) d: 0.21, 0.27 (each 3H, s, SiMeꢃ2), 0.94 (9H, s, tert-Bu), 5.88 (1H,
s, 3-H), 6.23 (1H, s, 5-H), 6.37 (1H, d, Jꢂ16 Hz, 1ꢀ-H), 6.41 (1H, dd, Jꢂ11,
15 Hz, 3ꢀ-H), 6.55 (1H, dd, Jꢂ10, 15 Hz, 4ꢀ-H), 6.68 (1H, dd, Jꢂ10, 15 Hz,
5ꢀ-H), 6.86 (1H, d, Jꢂ15 Hz, 6ꢀ-H), 6.89 (1H, dd, Jꢂ11, 16 Hz, 2ꢀ-H), 6.70
(1H, dd, Jꢂ3.5, 5 Hz, 4ꢅ-H), 7.05 (1H, d, Jꢂ3.5 Hz, 3ꢅ-H), 7.24 (1H, d,
Jꢂ5 Hz, 5ꢅ-H); MS m/z: 374.1371 [Calcd for C20H26O3SSi (Mꢄ) 374.1370].
4-[(1E,3E,5E)-6-(2-Benzofuranyl)hexa-1,3,5-trienyl]-5-tert-butyl-
dimethylsilyloxy-2(5H)-furanone 16c: Orange solid; UV lmax (EtOH) nm:
401; IR (CHCl3) cmꢁ1: 1757 (CꢂO), 1625, 1578 (CꢂC); 1H-NMR
(300 MHz, CDCl3) d: 0.22, 0.28 (each 3H, s, SiMeꢃ2), 0.93 (9H, s, tert-
Bu), 5.91 (1H, s, 3-H), 6.25 (1H, s, 5-H), 6.43 (1H, d, Jꢂ15.5 Hz, 1ꢀ-H),
6.51 (1H, dd, Jꢂ10.5, 14.5 Hz, 3ꢀ-H), 6.61 (1H, dd, Jꢂ10, 14.5 Hz, 4ꢀ-H),
6.62 (1H, d, Jꢂ15.5 Hz, 6ꢀ-H), 6.69 (1H, s, 3ꢅ-H), 6.90 (1H, dd, Jꢂ10.5,
15.5 Hz, 2ꢀ-H), 7.05 (1H, dd, Jꢂ10, 15.5 Hz, 5ꢀ-H), 7.21 (1H, t-like,
Jꢂ7.5 Hz, 5ꢅ-H), 7.29 (1H, t-like, Jꢂ7.5 Hz, 6ꢅ-H), 7.44 (1H, d, Jꢂ7.5 Hz,
7ꢅ-H), 7.53 (1H, d, Jꢂ7.5 Hz, 4ꢅ-H); MS m/z: 408.1766 [Calcd for
C24H28O4Si (Mꢄ) 408.1755].
4-[(1E,3E,5E)-6-(2-Benzo[b]thienyl)hexa-1,3,5-trienyl]-5-tert-butyl-
dimethylsilyloxy-2(5H)-furanone 16d: Orange solid; UV lmax (EtOH) nm:
397; IR (CHCl3) cmꢁ1: 1757 (CꢂO), 1624, 1579 (CꢂC); 1H-NMR
(300 MHz, CDCl3) d: 0.22, 0.28 (each 3H, s, SiMeꢃ2), 0.94 (9H, s, tert-
Bu), 5.90 (1H, s, 3-H), 6.24 (1H, s, 5-H), 6.41 (1H, d, Jꢂ15.5 Hz, 1ꢀ-H),
6.48 (1H, dd, Jꢂ10.5, 14 Hz, 3ꢀ-H), 6.59 (1H, dd, Jꢂ10.5, 14 Hz, 4ꢀ-H),
6.74 (1H, dd, Jꢂ10.5, 15 Hz, 5ꢀ-H), 6.90 (1H, dd, Jꢂ10.5, 15.5 Hz, 2ꢀ-H),
6.95 (1H, d, Jꢂ15 Hz, 6ꢀ-H), 7.24 (1H, s, 3ꢅ-H), 7.32 (2H, m, Ar-H), 7.67—
7.78 (2H, m, Ar-H); MS m/z: 424.1541 [Calcd for C24H28O3SSi (Mꢄ)
424.1527].
Ethyl (2E,4E)-5-(2-Benzofuranyl)penta-2,4-dienoate 15c According
to the procedure for the preparation of the ester 15b, Emmons–Horner reac-
tion between the aldehyde 11c (930 mg, 6.58 mmol) and the phosphonate 14
followed by purification by CC (acetone–hexane, 1 : 4) provided the ester
15c (1.72 g, 82%) as pale yellow crystals; mp 47—48 °C (ether–hexane);
UV lmax (EtOH) nm: 345; IR (CHCl3) cmꢁ1: 1703 (conj. CꢂO), 1622, 1611
1
(CꢂC); H-NMR (300 MHz, CDCl3) d: 1.31 (3H, t, Jꢂ7.5 Hz, CH2CH3),
4.23 (2H, q, Jꢂ7.5 Hz, CH2CH3), 6.04 (1H, d, Jꢂ15.5 Hz, 2-H), 6.71 (1H, s,
3ꢀ-H), 6.72 (1H, d, Jꢂ15.5 Hz, 5-H), 7.00 (1H, dd, Jꢂ11.5, 15.5 Hz, 4-H),
7.19 (1H, t-like, Jꢂ7.5 Hz, 5ꢀ-H), 7.28 (1H, t-like, Jꢂ7.5 Hz, 6ꢀ-H), 7.40
(1H, dd, Jꢂ11.5, 15.5 Hz, 3-H), 7.43 (1H, d, Jꢂ7.5 Hz, 7ꢀ-H), 7.51 (1H, d,
Jꢂ7.5 Hz, 4ꢀ-H); MS m/z: 242.0934 [Calcd for C15H14O3 (Mꢄ) 242.0942].
Anal. Calcd for C15H14O3: C, 74.36; H, 5.82. Found: C, 74.46; H, 5.85.
(2E,4E)-5-(2-Benzofuranyl)penta-2,4-dienal 13c DIBAL-H (1.0 M in
hexane; 6.57 ml, 6.57 mmol) was added to a solution of the ester 15c (1.06 g,
4.38 mmol) in dry CH2Cl2 (20 ml) at 0 °C and the mixture was further stirred
for 5 min. The excess of DIBAL-H was destroyed by an addition of moist
silica gel (SiO2–H2O, 10 : 1), and the mixture was filtered through Celite.
The filtrate was dried and evaporated to give a crude alcohol, which without
purification was dissolved in THF and shaken with active MnO2 (15 g) at rt
for 5 h. The mixture was filtered through Celite. Evaporation of the filtrate
gave the crude product, which was recrystallized from AcOEt–ether–hexane
to afford the dienal 13c (643 mg, 74%) as pale yellow crystals; mp 87—
88 °C; UV lmax (EtOH) nm: 356; IR (CHCl3) cmꢁ1: 1671 (conj. CꢂO),
1620, 1607 (CꢂC); 1H-NMR (300 MHz, CDCl3) d: 6.32 (1H, dd, Jꢂ8,
14.5 Hz, 2-H), 6.84 (1H, s, 3ꢀ-H), 6.87 (1H, d, Jꢂ14 Hz, 5-H), 7.14 (1H, dd,
Jꢂ11, 14 Hz, 4-H), 7.23 (1H, td, Jꢂ1, 7.5 Hz, 5ꢀ-H), 7.23 (1H, dd, Jꢂ11,
14.5 Hz, 3-H), 7.34 (1H, td, Jꢂ1, 7.5 Hz, 6ꢀ-H), 7.50 (1H, dd, Jꢂ1, 7.5 Hz,
7ꢀ-H), 7.56 (1H, br d, Jꢂ7.5 Hz, 4ꢀ-H), 9.63 (1H, d, Jꢂ8 Hz, CHO); MS m/z:
198.0682 [Calcd for C13H10O2 (Mꢄ) 198.0681]. Anal. Calcd for C13H10O2:
C, 78.77; H, 5.09. Found: C, 78.79; H, 5.28.
Desilylation of Compounds 16a–d In the same manner as described
for the desilylation of compounds 10c and 10d, compounds 16a—d were
treated with TBAF to give compounds 17a (85%), 17b (64%), 17c (79%)
and 17d (79%), as orange solids, respectively.
Ethyl (2E,4E)-5-(2-Benzo[b]thieny)penta-2,4-dienoate 15d Accord-
ing to the procedure for the preparation of the ester 15b, the aldehyde 11d
(3.00 g, 18.5 mmol) was condensed with the phosphonate 14 to give solids,
which was recrystallized from MeOH to afford the ester 15d (4.28 g, 90%)
as orange crystals; mp 94—95 °C; UV lmax (EtOH) nm: 344; IR (CHCl3)
4-[(1E,3E,5E)-6-(2-Furanyl)hexa-1,3,5-trienyl]-5-hyxroxy-2(5H)-fura-
none 17a: UV lmax (EtOH) nm: 391; lmax (MeOH) nm (e): 350 (48400); IR
(KBr) cmꢁ1: 3343 (OH), 1752, 1736 (split) (CꢂO), 1616, 1576 (CꢂC); 1H-
NMR (500 MHz, DMSO-d6) d: 6.12 (1H, s, 3-H), 6.28 (1H, d, Jꢂ8.5 Hz, 5-
H), 6.51 (1H, d, Jꢂ15.5 Hz, 1ꢀ-H), 6.54 (1H, dd, Jꢂ1.5, 3.5 Hz, 4ꢅ-H), 6.58
(1H, dd, Jꢂ11.5, 14 Hz, 3ꢀ-H), 6.59 (1H, d, Jꢂ3.5 Hz, 3ꢅ-H), 6.67 (1H, d,
Jꢂ15 Hz, 6ꢀ-H), 6.73 (1H, dd, Jꢂ11, 14 Hz, 4ꢀ-H), 6.78 (1H, dd, Jꢂ11,
15 Hz, 5ꢀ-H), 6.97 (1H, dd, Jꢂ11.5, 15.5 Hz, 2ꢀ-H), 7.70 (1H, d, Jꢂ1.5 Hz,
5ꢅ-H), 7.84 (1H, d, Jꢂ8.5 Hz, 5-OH); 13C-NMR (125 MHz, DMSO-d6) d:
97.62 (C5), 110.78 (C3ꢅ), 112.41 (C4ꢅ), 115.19 (C3), 121.84 (C1ꢀ), 122.85
(C6ꢀ), 126.66 (C5ꢀ), 132.27 (C3ꢀ), 138.63 (C4ꢀ), 139.69 (C2ꢀ), 143.85 (C5ꢅ),
152.40 (C2ꢅ), 162.03 (C4), 170.85 (C2); MS m/z: 244.0757 [Calcd for
C14H12O4 (Mꢄ) 244.0735].
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cmꢁ1: 1703 (conj. CꢂO), 1621, 1590 (CꢂC); H-NMR (300 MHz, CDCl3)
d: 1.32 (3H, t, Jꢂ7 Hz, CH2CH3), 4.23 (2H, q, Jꢂ7 Hz, CH2CH3), 6.00 (1H,
d, Jꢂ15.5 Hz, 2-H), 6.71 (1H, dd, Jꢂ11, 15 Hz, 4-H), 7.09 (1H, dd, Jꢂ0.6,
15 Hz, 5-H), 7.29 (1H, s, 3ꢀ-H), 7.33 (2H, m, Ar-H), 7.41 (1H, ddd, Jꢂ0.6,
11, 15.5 Hz, 3-H), 7.68—7.79 (2H, m, Ar-H); MS m/z: 258.0714 [Calcd for
C15H14O2S (Mꢄ) 258.0714]. Anal. Calcd for C15H14O2S: C, 69.74; H, 5.46;
S, 12.39. Found: C, 69.76; H, 5.48; S, 12.44.
(2E,4E)-5-(2-Benzo[b]thieny)penta-2,4-dienal 13d In the same man-
ner as described for the preparation of the dienal 13c, reduction of the above
ester 15d (1.50 g, 5.81 mmol) with DIBAL-H followed by oxidation with
MnO2 gave solids, which was recrystallized from AcOEt–hexane to afford
the aldehyde 13d (913 mg, 73%) as orange crystals; mp 135—136 °C; UV
lmax (EtOH) nm: 357; IR (CHCl3) cmꢁ1: 1678 (conj. CꢂO), 1616, 1588
5-Hydroxy-4-[(1E,3E,5E)-6-(2-thienyl)hexa-1,3,5-trienyl]-2(5H)-fura-
none 17b: UV lmax (EtOH) nm: 387; UV lmax (MeOH) nm (e): 389
1
(60700); IR (KBr) cmꢁ1: 3271 (OH), 1744 (CꢂO), 1619, 1577 (CꢂC); H-
NMR (500 MHz, DMSO-d6) d: 6.11 (1H, s, 3-H), 6.27 (1H, br s, 5-H), 6.50
(1H, d, Jꢂ15.5 Hz, 1ꢀ-H), 6.57 (1H, dd, Jꢂ11, 14 Hz, 3ꢀ-H), 6.71 (1H, dd,
Jꢂ11, 14 Hz, 4ꢀ-H), 6.75 (1H, dd, Jꢂ11, 14.5 Hz, 5ꢀ-H), 6.97 (1H, dd,
Jꢂ11, 15.5 Hz, 2ꢀ-H), 6.99 (1H, d, Jꢂ14.5 Hz, 6ꢀ-H), 7.05 (1H, dd, Jꢂ3.5,
5.5 Hz, 4ꢅ-H), 7.19 (1H, d, Jꢂ3.5 Hz, 3ꢅ-H), 7.50 (1H, d, Jꢂ5.5 Hz, 5ꢅ-H),
7.84 (1H, br s, 5-OH); 13C-NMR (125 MHz, DMSO-d6) d: 97.69 (C5),
115.23 (C3), 121.84 (C1ꢀ), 126.59. (C5ꢅ), 127.70 (C3ꢅ), 128.03 (C5ꢀ),
128.27 (C4ꢅ), 128.52 (C6ꢀ), 132.07 (C3ꢀ), 138.61 (C4ꢀ), 139.72 (C2ꢀ),
141.86 (C2ꢅ), 162.01 (C4), 170.85 (C2); MS m/z: 260.0517 [Calcd for
C14H12O3S (Mꢄ) 260.0506].
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(CꢂC); H-NMR (300 MHz, CDCl3) d: 6.26 (1H, dd, Jꢂ8, 15.5 Hz, 2-H),
6.81 (1H, dd, Jꢂ11, 15.5 Hz, 4-H), 7.20 (1H, d, Jꢂ15.5 Hz, 5-H), 7.20 (1H,
dd, Jꢂ11, 15.5 Hz, 3-H), 7.31—7.38 (2H, m, Ar-H), 7.36 (1H, s, 3ꢀ-H),
7.70—7.81 (2H, m, Ar-H) 9.60 (1H, d, Jꢂ8 Hz CHO); MS m/z: 214.0448
[Calcd for C13H10OS (Mꢄ) 214.0452]. Anal. Calcd for C13H10OS: C, 72.87;
H, 4.70; S, 14.96. Found: C, 72.63; H, 4.86; S, 15.06.
Preparation of Compounds 16a—d In the same manner as described
for the preparation of compounds 8a—c via the aldol reaction between the
TESO-butenolide 3 and aldehydes 2a—c, compounds 16a (43% from
13a7)), 16b (35% from 13b), 16c (35% from 13c) and 16d (79% from 13d)
were similarly prepared by the reaction of the TBSO-butenolide 4 with alde-
hydes 13a—d and subsequent dehydration.
5-tert-Butyldimethylsilyloxy-4-[(1E,3E,5E)-6-(2-furanyl)hexa-1,3,5-
trienyl]-2(5H)-furanone 16a: Orange solid; UV lmax (EtOH) nm: 393; IR
(CHCl3) cmꢁ1: 1751 (CꢂO), 1618, 1581 (CꢂC); 1H-NMR (500 MHz,
4-[(1E,3E,5E)-6-(2-Benzofuranyl)hexa-1,3,5-trienyl]-5-hydroxy-2(5H)-
furanone 17c: UV lmax (EtOH) nm: 398; UV lmax (MeOH) nm (e): 398
(61700); IR (KBr) cmꢁ1: 3246 (OH), 1747, 1719 (split) (CꢂO), 1613, 1573
1
(CꢂC); H-NMR (500 MHz, DMSO-d6) d: 6.17 (1H, s, 3-H), 6.31 (1H, d,
Jꢂ8.5 Hz, 5-H), 6.58 (1H, d, Jꢂ16 Hz, 1ꢀ-H), 6.72 (1H, dd, Jꢂ11, 15 Hz,
3ꢀ-H), 6.82 (1H, dd, Jꢂ11, 15 Hz, 4ꢀ-H), 6.85 (1H, d, Jꢂ15 Hz, 6ꢀ-H), 7.01
(1H, s, 3ꢅ-H), 7.02 (1H, dd, Jꢂ11, 16 Hz, 2ꢀ-H), 7.07 (1H, dd, Jꢂ11, 15 Hz,