DIASTEREOSELECTIVE SYNTHESIS OF c-BUTENOLIDES
5g,6a]
1231
[
5
-(Hydroxy)(phenyl)methyl)furan-2(5H)-one (3f).
Compound 3f was
prepared according to the general procedure and purified by chromatography on sil-
ica gel (PE–EtOAc, 3:1) to afford 3f as a mixture of unseparable diastereoisomers,
1
yellow oil (80%). H NMR (400 MHz, CDCl ): d 7.41–7.30 (m, 6H), 6.12 [dd,
3
J ¼ 5.6, 2.0 Hz, 1H (anti)], 6.06 [dd, J ¼ 5.6, 2.0 Hz, 1H (syn)], 5.20–5.10 (m, 1H),
1
3
5
.05 [d, J ¼ 4.4 Hz, 1H (anti)], 4.71 [d, J ¼ 6.8 Hz, 1H (syn)], 3.56 (br s, 1H);
C
NMR (100 MHz, CDCl ): d 172.4, 152.2, 137.4, 127.7, 127.3, 125.1, 122.0, 85.8, 71.8.
3
[
5a]
5
pound 3g was prepared according to the general procedure and purified by chroma-
-(Hydroxy)(2-methoxyphenyl)methyl)furan-2(5H)-one (3g).
Com-
tography on silica gel (PE–EtOAc, 4:1) to afford 3g as the pure anti-diastereoisomer,
1
yellow oil (82%). H NMR (400 MHz, CDCl ): d ¼ 7.42 (dd, J ¼ 7.6, 1.6 Hz, 1H),
3
7
6
1
1
.36–7.24 (m, 2H), 7.00 (dt, J ¼ 7.2, 0.8 Hz, 1H), 6.90 (dd, J ¼ 8.4, 0.8 Hz, 1H),
.11 (dd, J ¼ 5.6, 1.2 Hz, 1H), 5.50–5.20 (m, 2H), 3.86 (s, 3H), 3.62 (d, J ¼ 3.6 Hz,
1
3
H); C NMR (100 MHz, CDCl ) d ¼ 172.6, 154.9, 152.6, 128.3, 126.3, 125.2,
3
21.7, 119.9, 109.3, 84.3, 67.7, 54.3.
[
5a]
5
pound 3h was prepared according to the general procedure and purified by chroma-
-(Hydroxy)(3-methoxyphenyl)methyl)furan-2(5H)-one (3h).
Com-
tography on silica gel (PE–EtOAc, 4:1) to afford 3h as a mixture of unseparable
1
diastereoisomers, yellow oil (83%). H NMR (400 MHz, CDCl ): d ¼ 7.34 [dd,
3
J ¼ 6.0, 1.6 Hz, 1H (anti)], 7.32–7.22 (m, 1H), 7.18 [dd, J ¼ 6.0, 2.0 Hz, 1H (syn)],
7
.0–6.8 (m, 3H), 6.11 [dd, J ¼ 5.6, 2.0 Hz, 1H (anti)], 6.06 [dd, J ¼ 5.6, 2.0 Hz, 1H
(
(
syn)], 5.20–5.10 (m, 1H), 5.03 [d, J ¼ 5.0 Hz, 1H (anti)], 4.67 [d, J ¼ 6.8 Hz, 1H
3
1
3
syn)], 3.79 (s, 3H), 3.70 (br s, 1H); C NMR (100 MHz, CDCl ) d ¼ 172.4, 158.7,
1
52.2, 139.1, 128.7, 121.9, 117.3, 112.7, 110.6, 85.8, 71.6, 54.2.
5-((2-Chlorophenyl)(hydroxyl)methyl)furan-2(5H)-one (3i). Compound 3i
was prepared according to the general procedure and purified by chromatography on
silica gel (PE–EtOAc, 3:1) to afford 3i as the pure anti-diastereoisomer, white solid
1
ꢁ
(
80%); R ¼ 0.14 (PE–EtOAc, 4:1); mp. 134.5–135.5 C; H NMR (400 MHz, CDCl )
f
3
d ¼ 7.61 (dd, J ¼ 7.6, 1.2 Hz, 1H), 7.20–7.45 (m, 4H), 6.20 (dd, J ¼ 5.6, 2.0 Hz, 1H),
1
3
5
(
6
6
.62 (t, J ¼ 4.0 Hz, 1H), 5.36–5.44 (m, 1H), 3.36 (d, J ¼ 4.4 Hz, 1H); C NMR
100 MHz, CDCl ) d ¼ 172.3, 151.2, 134.5, 130.8, 128.6, 126.9, 126.4, 122.5, 83.6,
3
8.4; IR (KBr) n 3390, 1726, 1465, 1437, 1342, 1188, 1108, 1025, 918, 819, 744,
ꢂ1
09 cm ; HRMS (ESI) calcd. for C H ClO Na: 247.0132; found: 247.0156.
1
1
9
3
[
6a]
5
-((2,4-Dichlorophenyl)(hydroxyl)methyl)furan-2(5H)-one (3j).
Com-
pound 3j was prepared according to the general procedure and purified by chroma-
tography on silica gel (PE–EtOAc, 4:1) to afford 3j as the pure anti-diastereoisomer,
1
white solid (79%). H NMR (400 MHz, CDCl ): d ¼ 7.56 (d, J ¼ 8.4 Hz, 1H), 7.42
3
(
6
d, J ¼ 2.0 Hz, 1H), 7.35 (dd, J ¼ 8.4, 2.0 Hz, 1H), 7.24 (dd, J ¼ 6.0, 1.6 Hz, 1H),
.21 (dd, J ¼ 5.6, 2.0 Hz, 1H), 5.56 (t, J ¼ 4.0 Hz, 1H), 5.44–5.34 (m, 1H), 3.65
3
1
3
(
1
d, J ¼ 4.4 Hz, 1H); C NMR (100 MHz, CDCl ) d ¼ 172.3, 151.0, 133.8, 133.1,
31.4, 128.3, 127.9, 126.7, 122.6, 83.4, 68.0.
[5g]
-(Furan-2-yl(hydroxyl)methyl)furan-2(5H)-one (3k).
5 Compound 3k was
prepared according to the general procedure and purified by chromatography on
silica gel (PE–EtOAc, 4:1) to afford 3k as a mixture of unseparable diastereoisomers,