D. A. Devalankar et al. / Tetrahedron: Asymmetry 23 (2012) 240–244
243
with brine, dried over anhydrous Na2SO4 and concentrated under
reduced pressure to give a crude product, which was then purified
by column chromatography (packed with silica gel 60–120 mesh)
using dichloromethane and petroleum ether (7:3) as eluents to af-
ford products 6a and 7a in pure form.
4.2.1.6. (R)-5-(4-Methoxybenzyl)furan-2(5H)-one 6f. Yield: 70%;
White solid, mp 62 °C; ½a D25
¼ ꢀ159:0 (c 1, CHCl3); IR: (CHCl3)
ꢂ
1514, 1613, 1755, 2924; 1H NMR (200 MHz, CDCl3): d 2.84–2.95
(dd, J = 13.9, 7.0 Hz, 1H), 3.06–3.16 (dd, J = 13.8, 6.0 Hz, 1H), 3.79
(s, 3H), 5.17 (m, 1H), 6.06 (dd, J = 5.8, 2.0 Hz, 1H), 6.81 (d,
J = 8.7 Hz, 2H), 7.10 (d, J =8.7 Hz, 2H), 7.37 (dd, J = 5.6, 1.3 Hz,
1H); 13C NMR (50 MHz, CDCl3): d 38.7, 55.1, 83.5, 114.1, 122.1,
126.6, 130.4, 155.4, 158.8, 172.5; Anal. C12H12O3 required C,
70.57; H, 5.92. Found: C, 70.50; H, 5.80; enantiomeric purity:
98% ee determined by HPLC analysis ((R,R)-whelk column, Hex/i-
PrOH 90:10, 0.5 mL/min, 254 nm). Retention time: tmajor = 35.35
and tminor = 46.28 min.
4.2.1.1. (R)-5-Propylfuran-2(5H)-one 6a. Yield: 63%; colorless
oil; ½a 2D5
ꢂ
¼ ꢀ102:6 (c 1, CHCl3) {lit.17a
½
a 2D5
ꢂ
¼ þ110 for its antipode
(c 1.16, CHCl3)}; IR: (CHCl3) 1164, 1265, 1465, 1603, 1755, 2926; 1H
NMR (200 MHz, CDCl3): d 0.98 (t, J = 7.2 Hz, 3H), 1.40–1.81 (m, 4H),
5.04 (m, 1H), 6.10 (dd, J = 5.8, 2.0 Hz, 1H), 7.44 (dd, J = 5.8, 1.5 Hz,
1H); 13C NMR (50 MHz, CDCl3): d 13.8, 18.4, 35.2, 83.1, 121.5,
156.1, 172.9; Anal. C7H10O2 required C, 66.65; H, 7.99. Found: C,
66.50; H, 7.81; enantiomeric purity: 99% ee determined by HPLC
analysis (Chiral OJ-H column, Hex/i-PrOH 95:5, 0.5 mL/min,
210 nm). Retention time: tminor = 25.29 and tmajor = 26.83 min.
4.2.1.7. (R)-5-(3-((tert-Butyldiphenylsilyl)oxy)propyl)furan-2(5H)-
one 6g. Yield: 62%; colorless oil; ½a D25
¼ ꢀ38:9 (c 1, CHCl3); IR:
ꢂ
(CHCl3) 1110, 1427, 1755, 2856, 2930; 1H NMR (200 MHz, CDCl3):
d 1.06 (s, 9H), 1.68–1.80 (m, 3H), 1.90–1.96 (m, 1H), 3.71 (m, 2H),
5.05 (m, 1H), 6.11 (dd, J = 5.7, 1.8 Hz, 1H),7.39 (m, 7H), 7.64 (m,
4H); 13C NMR (50 MHz, CDCl3): 19.2, 26.9, 27.8, 29.9, 63.0, 83.0,
121.7, 127.7, 129.7, 133.6, 135.5, 156.0, 172.8; Anal. C23H28O3Si re-
quired C, 72.59; H, 7.42. Found: C, 72.63; H, 7.38; enantiomeric
purity: 99% ee determined by HPLC analysis (Chiral OJ-H column,
Hex/ i-PrOH 95:5, 0.5 mL/min, 210 nm). Retention time: tmi-
nor = 45.30 and tmajor = 46.86 min.
4.2.1.2. (R)-5-Butylfuran-2(5H)-one 6b. Yield: 66%; colorless oil;
½
a 2D5
ꢂ
¼ ꢀ101:2 (c 1, CHCl3) {lit.9
½
a 2D5
ꢂ
¼ þ103:5 for its antipode (c
0.7, CHCl3)}; IR: (CHCl3) 1162, 1463, 1495, 1603, 1755, 2861,
2929; 1H NMR (200 MHz, CDCl3): d 0.93 (t, J = 6.8 Hz, 3H), 1.29–
1.52 (m, 4H), 1.65–1.84 (m, 2H), 5.02 (m, 1H), 6.09 (dd, J = 5.6,
2.0 Hz, 1H), 7.43 (dd, J = 5.6, 1.3 Hz, 1H); 13C NMR (50 MHz, CDCl3):
d 13.8, 22.4, 27.0, 32.9, 83.1, 121.6, 155.9, 172.6; Anal. C8H12O2 re-
quired C, 68.54; H, 8.63. Found: C, 68.42; H, 8.70; enantiomeric
purity: 99% ee determined by HPLC analysis (Chiral OJ-H column,
Hex/i-PrOH 95:5, 0.5 mL/min, 210 nm). Retention time: tmi-
nor = 22.11 and tmajor = 22.92 min.
4.2.1.8. (R)-(E)-Ethyl 4-hydroxyhept-2-enoate 7a. Yield: 21%;
colorless liquid; ½a D25
¼ ꢀ21:0 (c 1, CHCl3); IR: (CHCl3) 1277,
ꢂ
1659, 1714, 2931, 3438; 1H NMR (200 MHz, CDCl3): d 0.95 (t,
J = 6.9 Hz, 3H), 1.30 (t, J = 7.3 Hz, 3H), 1.35–1.65 (m, 4H), 1.79 (br
s, 1H), 4.18 (q, J = 7.2 Hz, 2H), 4.31 (m, 1H), 6.01 (dd, J = 15.6,
1.6 Hz, 1H), 6.93 (dd, J = 15.8, 5.0 Hz, 1H); 13C NMR (50 MHz,
CDCl3): d 13.9, 14.2, 18.4, 38.7, 60.3, 70.8, 120.0, 150.3, 166.4; Anal.
C9H16O3 required C, 62.77; H, 9.36. Found: C, 62.79; H, 9.50; enan-
tiomeric purity: 99% ee determined by HPLC analysis ((R,R)-whelk
column, Hex/EtOH 95:5, 0.5 mL/min, 210 nm). Retention time: tmi-
nor = 10.56 and tmajor = 11.07 min.
4.2.1.3. (R)-5-Pentylfuran-2(5H)-one 6c. Yield: 68%; colorless
oil; ½a 2D5
ꢂ
¼ ꢀ96:8 (c 1, CHCl3) {lit.9
½
a 2D5
ꢂ
¼ þ97 for its antipode (c
0.6, CHCl3)}; IR: (CHCl3) 1162, 1602, 1752, 2861, 2929; 1H NMR
(200 MHz, CDCl3): d 0.90 (t, J = 6.5 Hz, 3H), 1.21–1.48 (m, 6H),
1.61–1.79 (m, 2H), 5.03 (m, 1H), 6.10 (dd, J = 5.6, 2.0 Hz, 1H),
7.42 (dd, J = 5.6, 1.3 Hz, 1H); 13C NMR (50 MHz, CDCl3): d 13.9,
22.4, 24.7, 31.5, 33.2, 83.2, 121.6, 155.9, 172.7; Anal. C9H14O2 re-
quired C, 70.10; H, 9.15. Found: C, 70.22; H, 9.17; enantiomeric
purity: 98% ee determined by HPLC analysis (Chiral OJ-H column,
Hex/i-PrOH 95:5, 0.5 mL/min, 210 nm). Retention time: tmi-
nor = 19.50 and tmajor = 20.35 min.
4.2.1.9. (R)-(E)-Ethyl 4-hydroxyoct-2-enoate 7b. Yield: 20%; col-
orless liquid; ½a D25
ꢂ
¼ ꢀ19:5 (c 1, CHCl3) {lit.17b
½
a 2D4
ꢂ
¼ ꢀ19:3 (c 0.36,
CHCl3)}; IR: (CHCl3) 1267, 1372, 1658, 1719, 2960, 3456; 1H NMR
(200 MHz, CDCl3): d 0.92 (t, J = 7.3 Hz, 3H), 1.30 (t, J = 7.2 Hz, 3H),
1.37 (m, 4H), 1.60 (m, 2H), 4.20 (q, J = 7.2 Hz, 2H), 4.31 (m, 1H),
6.01 (dd, J = 15.6, 1.6 Hz, 1H), 6.94 (dd, J = 15.6, 4.9 Hz, 1H); 13C
NMR (50 MHz, CDCl3): d 13.9, 14.2, 22.5, 27.3, 36.3, 60.3, 70.9,
120.0, 150.4, 166.5; Anal. C10H18O3 required C, 64.49; H, 9.74.
Found: C, 64.32; H, 9.88.
4.2.1.4. (R)-5-Hexylfuran-2(5H)-one 6d. Yield: 65%; colorless oil;
½
a 2D5
ꢂ
¼ ꢀ91:8 (c 1, CHCl3) {lit.17a
½
a 2D5
ꢂ
¼ þ89:4 for its antipode (c
1.01, CHCl3)}; IR: (CHCl3) 1163, 1464, 1603, 1756, 2854, 2925; 1H
NMR (200 MHz, CDCl3): d 0.89 (t, J = 6.9 Hz, 3H), 1.25–1.45 (m,
8H), 1.61–1.83 (m, 2H), 5.02 (m, 1H), 6.10 (dd, J = 5.6, 1.8 Hz,
1H), 7.43 (dd, J = 5.6, 1.3 Hz, 1H); 13C NMR (50 MHz, CDCl3): d
14.0, 22.5, 24.9, 29.0, 31.5, 33.2, 83.2, 121.6, 155.9, 172.7; Anal.
4.2.1.10. (R)-(E)-Ethyl 4-hydroxynon-2-enoate 7c. Yield: 19%;
colorless liquid; ½a D25
¼ ꢀ21:0 (c 1, CHCl3); IR: (CHCl3) 1248,
ꢂ
C10H16O2 required C, 71.39; H, 9.59. Found: C, 71.22; H, 9.68; enan-
1513, 1656, 1717, 2926, 3421; 1H NMR (200 MHz, CDCl3): d 0.90
(t, J = 6.5 Hz, 3H), 1.30 (t, J = 7.0 Hz, 3H), 1.35 (m, 6H), 1.60 (m,
2H), 4.20 (q, J = 7.2 Hz, 2H), 4.30 (m, 1H), 6.02 (dd, J = 15.6,
1.6 Hz, 1H), 6.93 (dd, J = 15.6, 4.9 Hz, 1H); 13C NMR (50 MHz,
CDCl3): d 14.0, 14.2, 22.5, 24.9, 31.7, 36.6, 60.3, 71.0, 120.0,
150.3, 166.4; Anal. C11H20O3 required C, 65.97; H, 10.07. Found:
C, 65.80; H, 10.12.
tiomeric purity: 98% ee determined by HPLC analysis (Chiral OJ-H
column, Hex/i-PrOH 95:5, 0.5 mL/min, 210 nm). Retention time:
tminor = 18.60 and tmajor = 19.44 min.
4.2.1.5. (R)-5-Benzylfuran-2(5H)-one 6e. Yield: 64%; yellow oil;
½
a 2D5
ꢂ
¼ ꢀ112:0 (c 1, CHCl3) {lit.17d
½
a 2D5
ꢂ
¼ þ117 for its antipode
(c 2.19, 1,4-dioxane)}; IR: (CHCl3) 1496, 1600, 1755, 2928; 1H
NMR (200 MHz, CDCl3): d 2.89–2.99 (dd, J = 13.7, 7.2 Hz, 1H),
3.12–3.22 (dd, J = 13.7, 6.3 Hz, 1H), 5.22 (m, 1H), 6.08 (dd,
J = 5.6, 1.9 Hz, 1H), 7.17–7.33 (m, 5H), 7.39 (dd, J = 5.68, 1.5 Hz,
1H); 13C NMR (50 MHz, CDCl3): d 39.7, 83.2, 122.1, 127.3, 128.7,
129.3, 134.7, 155.3, 172.4; Anal. C11H10O2 required C, 75.84; H,
5.79. Found C, 76.60; H, 5.88; enantiomeric purity: 99% ee deter-
mined by HPLC analysis ((R,R)-whelk column, Hex/EtOH 90:10,
4.2.1.11. (R)-(E)-Ethyl 4-hydroxydec-2-enoate 7d. Yield: 19%;
colorless liquid; ½a D25
ꢂ
¼ ꢀ21:9 (c 1, CHCl3) {lit.17c
½
a 2D0
ꢂ
¼ ꢀ22:4 (c
1.03, CHCl3)}; IR: (CHCl3) 1177, 1658, 1722, 2929, 3439; 1H NMR
(200 MHz, CDCl3): d 0.89 (t, J = 6.8 Hz, 3H), 1.21–1.41 (m, 11H),
1.56 (m, 2H), 1.99 (br s, 1H), 4.19 (q, J = 7.2 Hz, 2H), 4.30 (m, 1H),
6.01 (dd, J = 15.6, 1.5 Hz, 1H), 6.93 (dd, J = 15.6, 4.9 Hz, 1H); 13C
NMR (50 MHz, CDCl3): d 14.1, 14.2, 22.6, 25.2, 29.1, 31.7, 36.6,
60.3, 71.0, 120.0, 150.3, 166.4; Anal. C12H22O3 required C, 67.26;
H, 10.35. Found: C, 67.18; H, 10.46.
0.5 mL/min, 210 nm). Retention time: tmajor = 16.45 and tminor
=
17.40 min.