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J. Halder et al. / Tetrahedron: Asymmetry 26 (2015) 1197–1208
1.29–1.15 (m, 6H). 13C NMR (CDCl3, 50 MHz) d = 175.7, 134.3,
1H NMR (CDCl3, 200 MHz): d = 5.72–5.64 (m, 2H), 4.18 (q,
J = 7.2 Hz, 2H), 3.79–3.73 (m, 1H), 2.63–2.59 (m, 1H), 2.63–1.81
(m, 8H), 1.27 (t, J = 7.2 Hz, 3H), 1.15 (d, J = 6.4 Hz, 3H).
133.9, 118.5, 118.2, 70.7, 60.9, 54.0, 37.7, 36.4, 18.2, 14.4. HRMS
(ESI) for
235.1318.
C
12H20O3Na [M+H]+ calculated: 235.1310, found:
13C NMR (CDCl3, 50 MHz) d = 176.7, 131.1, 131.0, 72.1, 60.8,
54.8, 31.5, 31.3, 24.8, 24.5, 19.1, 14.5. HRMS (ESI) for C12H20O3Na
[M+H]+ calculated: 235.1310, found: 235.1318.
4.3.9. (S)-Ethyl 2-(but-3-enyl)-2-(1-hydroxyethyl)hex-5-enoate
25
Rf = 0.4 (EtOAc/hexane, 1:10). [
a]
D
28 = +19.2 (c 0.6, CHCl3). 1H
4.3.16. (S)-Ethyl 1-(1-hydroxyethyl)cycloheptanecarboxylate 32
NMR (CDCl3, 200 MHz): d = 5.85–5.68 (m, 2H), 5.05–4.91 (m, 4H),
4.18 (q, J = 7.2 Hz, 2H), 4.00–3.93 (m, 1H), 3.06 (d, J = 6.4 Hz, 1H),
2.14–1.48 (m, 8H), 1.28 (t, J = 7.2 Hz, 3H), 1.16 (d, J = 6.4 Hz, 3H).
13C NMR (CDCl3, 50 MHz) d = 176.8, 138.7, 138.3, 114.9, 114.7,
70.2, 60.9, 53.2, 33.1, 31.3, 29.0, 28.8, 17.9, 14.4. HRMS (ESI) for
Rf = 0.4 (EtOAc/hexane, 1:10). [a]
28 = +29.2 (c 1.0, CHCl3). 1H
D
NMR (CDCl3, 200 MHz): d = 4.17 (q, J = 7.2 Hz, 2H), 3.74–3.64 (m,
1H), 2.58–2.54 (m, 1H), 2.17–2.06 (m, 1H), 1.92–1.88 (m, 2H),
1.53–1.42 (m, 9H), 1.27 (t, J = 7 Hz, 3H), 1.13 (d, J = 6.4 Hz, 3H).
13C NMR (CDCl3, 50 MHz) d = 177.4, 73.0, 60.7, 54.7, 32.7, 32.5,
30.4, 30.1, 24.3, 23.7, 18.9, 14.3. HRMS (ESI) for C12H22O3Na [M
+H]+ calculated: 237.2910, found: 237.2917.
C
14H24O3Na [M+H]+ calculated: 263.1623, found: 263.1629.
4.3.10. (S)-Ethyl 2,2-dibenzyl-3-hydroxybutanoate 26
Rf = 0.4 (EtOAc/hexane, 1:10). [
28 = +33.2 (c 0.5, CHCl3). 1H
a]
D
4.3.17. (S)-Ethyl 3-(tert-butyldimethylsilyloxy)-2,2-diethylbutanoate
33
NMR (CDCl3, 200 MHz): d = 7.26–7.15 (m, 10H), 4.11–3.98 (m,
3H), 3.32–2.86 (m, 4H), 1.31 (d, J = 6.4 Hz, 3H), 1.14 (t, J = 7.2 Hz,
3H). 13C NMR (CDCl3, 50 MHz) d = 176.4, 137.9, 137.6, 130.7,
130.2, 128.4, 128.2, 126.8, 126.7, 69.2, 61.0, 55.8, 39.7, 38.6, 18.1,
14.0. HRMS (ESI) for C20H24O3Na [M+H]+ calculated: 335.1623,
found: 335.1627.
To a solution of alcohol 18 (600 mg, 3.2 mmol) in 10 mL of
CH2Cl2, under argon at 0 °C, were successively added dry 2,6-
lutidine (0.63 mL, 5.44 mmol) and t-BuMe2SiOTf (1.1 mL, 4.8 mmol).
The reaction mixture was stirred at 0 °C to room temperature for 4 h
and then quenched by adding water. The aqueous phase was
reextracted with CH2Cl2. The combined organic layers were dried
(Na2SO4) and concentrated in vacuo. Flash chromatography
(EtOAc/hexane, 1:40) of the oily residue afforded 900 mg (93%) of
the silyloxy derivative 33 as a light yellow oil. Rf = 0.4 (EtOAc/hexane,
4.3.11. (S)-Ethyl 3-hydroxy-2,2-bis(4-methoxybenzyl)butanoate
27
Rf = 0.3 (EtOAc/hexane, 1:10). [a]
28 = +28.6 (c 1.0, CHCl3). 1H
D
NMR (CDCl3, 200 MHz): d = 7.15–7.06 (m, 4H), 6.84–6.78 (m, 4H),
4.17–3.95 (m, 3H), 3.81–3.13 (m, 6H), 3.21–2.73 (m, 4H), 1.31–
1.12 (m, 6H). 13C NMR (CDCl3, 50 MHz) d = 176.4, 158.4, 131.6,
131.2, 129.8, 129.4, 113.8, 113.6, 69.3, 60.9, 55.9, 55.4, 38.8, 37.7,
1:40). [a]D
28 = +30.2 (c 1.1, CHCl3). 1H NMR (CDCl3, 200 MHz):
d = 4.19–3.97 (m, 3H), 1.75–1.58 (m, 4H), 1.27–1.17 (m, 6H),
0.99–0.80 (m, 15H), 0.03 (s, 6H). 13C NMR (CDCl3, 50 MHz)
d = 175.6, 72.5, 60.0, 54.9, 25.9, 24.4, 24.3, 19.4, 18.1, 14.4, 9.5, 9.1,
18.2, 14.1. HRMS (ESI) for
395.1834, found: 395.1839.
C
22H28O5Na [M+H]+ calculated:
À3.8, À5.0. HRMS (ESI) for
C
16H34O3SiNa [M+H]+ calculated:
325.2175, found: 325.2179.
4.3.12. (S)-Ethyl 2-(1-hydroxyethyl)-2-(prop-2-ynyl)pent-4-ynoate
4.3.18. (S)-Ethyl 2-allyl-2-(1-(tert-butyldimethylsilyloxy)ethyl)
pent-4-enoate 34
28
Rf = 0.4 (EtOAc/hexane, 1:10). [
a]
D
28 = +15.6 (c 0.4, CHCl3). 1H
Prepared in 87% yield as light yellow oil analogous to the route
described for 33 from the enantiopure alcohol 24. Rf = 0.4 (EtOAc/
NMR (CDCl3, 200 MHz): d = 4.21 (q, J = 7 Hz, 2H), 4.03 (q,
J = 6.2 Hz, 1H), 2.92–2.55 (m, 5H), 2.02–2.02 (m, 2H), 1.30–1.18
(m, 6H). 13C NMR (CDCl3, 50 MHz) d = 173.2, 80.3, 79.8, 71.6,
71.5, 70.5, 61.6, 53.2, 22.4, 22.1, 19.0, 14.3. HRMS (ESI) for
hexane, 1:40).
[a]
28 = +18.9 (c 0.6, CHCl3). 1H NMR (CDCl3,
D
200 MHz): d = 5.96–5.67 (m, 2H), 5.07–4.98 (m, 4H), 4.14–4.01
(m, 3H), 2.41–2.38 (m, 4H), 1.28–1.10 (m, 6H), 0.86 (s, 9H), 0.03
(s, 6H). 13C NMR (CDCl3, 50 MHz) d = 174.7, 135.2, 117.5, 72.6,
60.5, 54.9, 37.2, 36.6, 26.0, 19.5, 18.2, 14.5, À3.7, À4.8. HRMS
C
12H16O3Na [M+H]+ calculated: 231.0997, found: 231.0992.
4.3.13. (S)-Ethyl 1-(1-hydroxyethyl)cyclopent-3-enecarboxylate
(ESI) for
349.2171.
C
18H34O3SiNa [M+H]+ calculated: 349.2175, found:
29
Rf = 0.4 (EtOAc/hexane, 1:10). [a]
28 = +38.2 (c 0.5, CHCl3). 1H
D
NMR (CDCl3, 200 MHz): d = 5.64–5.52 (m, 2H), 4.17 (q, J = 7 Hz,
2H), 3.92 (q, J = 6.4 Hz, 1H), 2.86–2.66 (m, 4H), 2.56–2.40 (m,
1H), 1.25 (t, J = 7.2 Hz, 3H), 1.08 (d, J = 6.4 Hz, 3H). 13C NMR (CDCl3,
50 MHz) d = 177.5, 129.3, 128.2, 71.6, 61.1, 57.1, 40.5, 38.5, 18.2,
14.3. HRMS (ESI) for C10H16O3Na [M+H]+ calculated: 207.0997,
found: 207.0991.
4.3.19. (S)-Ethyl 3-(tert-butyldimethylsilyloxy)-2,2-bis(4-methoxy-
benzyl)butanoate 35
Prepared in 80% yield as light yellow oil analogous to the route
described for 33 from the enantiopure alcohol 27. Rf = 0.6 (EtOAc/
hexane, 1:20).
[a]
28 = +44.2 (c 1.0, CHCl3). 1H NMR (CDCl3,
D
200 MHz): d = 7.26–7.01 (m, 4H), 6.78–6.73 (m, 4H), 4.23–4.03
(m, 3H), 3.77 (s, 6H), 3.04–2.84 (m, 4H), 1.19 (t, J = 7.2 Hz, 3H),
1.03–0.91 (m, 12H), 0.09 (s, 6H). 13C NMR (CDCl3, 50 MHz)
d = 174.8, 158.2, 158.1, 132.1, 131.4, 130.9, 130.2, 113.4, 113.2,
72.3, 60.3, 57.2, 55.2, 40.2, 36.8, 26.1, 20.0, 18.3, 14.1, À3.3, À4.8.
HRMS (ESI) for C28H42O5SiNa [M+H]+ calculated: 509.2699, found:
509.2692.
4.3.14. (S)-Ethyl 1-(1-hydroxyethyl)cyclopentanecarboxylate 30
Rf = 0.4 (EtOAc/hexane, 1:10). [a]
28 = +32.6 (c 1.0, CHCl3). 1H
D
NMR (CDCl3, 400 MHz): d = 4.16 (q, J = 7.2 Hz, 2H), 3.73–3.70 (m,
1H), 2.89–2.87 (m, 1H), 2.16–2.07 (m, 1H), 2.05–1.94 (m, 1H),
1.87–1.80 (m, 1H), 1.71–1.57 (m, 4H), 1.49–1.42 (m, 1H), 1.25 (t,
J = 7.2 Hz, 3H), 1.14 (d, J = 6.4 Hz, 3H). 13C NMR (CDCl3, 100 MHz)
d = 177.7, 72.8, 60.9, 59.1, 34.4, 33.0, 26.2, 25.8, 19.7, 14.4. HRMS
4.3.20. (S)-Ethyl 1-(1-(tert-butyldimethylsilyloxy)ethyl)cyclopent-
3-enecarboxylate 36
(ESI) for
209.1158.
C
10H18O3Na [M+H]+ calculated: 209.1154, found:
Prepared in 86% yield as light yellow oil analogous to the route
described for 33 from the enantiopure alcohol 29. Rf = 0.6 (EtOAc/
4.3.15. (S,Z)-Ethyl 1-(1-hydroxyethyl)cyclohept-4-enecarboxylate
hexane, 1:20). [a]
28 = +23.4 (c 0.8, CHCl3). 1H NMR (CDCl3,
D
31
200 MHz): d = 5.63–5.50 (m, 2H), 4.21–4.08 (m, 3H), 2.87–2.35
(m, 4H), 1.25 (t, J = 7.2 Hz, 3H), 1.02 (d, J = 6.2 Hz, 3H), 0.83
Rf = 0.4 (EtOAc/hexane, 1:10). [a]
28 = +22.7 (c 0.8, CHCl3).
D