J2ЈB,2ЈA14.1, J2ЈB,1ЈЈ6.5, C(2Ј)HB), 3.24 (1H, d, J 8.6, C(4)HA), 3.50
(1H, d, J 8.6, C(4)HB), 4.24 (1H, d, J 3.7, OH ), 5.44–5.48 (1H,
m, C(1Ј)H ); δC (100 MHz, CDCl3) 27.2, 27.3 (C(5)(CH3)2), 29.6
(C(3Ј)), 29.8 (C(3Ј)(CH3)3), 46.6 (C(2Ј)H2), 50.8 (C(4)H2), 75.3
(C(1Ј)H), 78.5 (C(5)Me2), 157.6 (OCON); νmax (KBr) 3352
Preparation of (E )- and (Z )-ethyl 5,5-dimethylhex-2-enoate 33
and 34 from 24
Following Representative Procedure 3, DIBAL (1.0 M in THF,
1.69 mL, 1.69 mmol), 24 (300 mg, 1.41 mmol), triethyl
phosphonoacetate (0.71 mL, 3.53 mmol) and n-BuLi (2.5 M,
1.41 mL, 3.53 mmol) in anhydrous THF (20 mL) gave, after
purification by flash column chromatography on silica (30 : 1
hexane–Et2O), (Z)-3428 (11 mg, 7%); δH (500 MHz, CDCl3)
0.95 (9H, s, C(CH3)3), 1.25 (3H, t, J 7.2, CO2CH2CH3), 2.59
(2H, dd, J4,37.8, J4,21.2, C(4)H2), 4.16 (2H, q, J 7.2, CO2-
CH2Me), 5.84 (1H, dt, J2,3 11.6, J2,4 1.7, C(2)H ), 6.29 (1H, dt,
J3,2 11.6, J3,4 7.8, C(3)H ). Further elution gave polar fraction
(E)-3328 (90 mg, 36%); δH (500 MHz, CDCl3) 0.93 (9H, s,
C(CH3)3), 1.29 (3H, t, J 7.2, CO2CH2CH3), 2.08 (2H, dd, J4,3
6.6, J4,2 1.2, C(4)H2), 4.18 (2H, q, J 7.2, CO2CH2Me), 5.80 (1H,
dt, J2,3 15.5, J2,4 1.2, C(2)H ), 6.98 (1H, dt, J3,2 15.5, J3,4 7.8,
C(3)H ).
(O–H), 1732 (C᎐O); m/z (APCIϩ) 170.0 (MHϩ, 5%).
᎐
Preparation of (E )- and (Z )-ethyl hex-2-enoate 27 and 28 from
22
Following Representative Procedure 3, DIBAL (1.0 M in THF,
1.95 mL, 1.95 mmol), 22 (300 mg, 1.62 mmol), triethyl
phosphonoacetate (0.81 mL, 4.05 mmol) and n-BuLi (2.5 M,
1.62 mL, 4.05 mmol) in anhydrous THF (20 mL) gave, after
purification by flash column chromatography on silica (30 : 1
hexane–Et2O), (Z)-2827 (10 mg, 4%); δH (400 MHz, CDCl3)
0.95 (3H, t, J 7.3, C(6)H3), 1.30 (3H, t, J 7.1, CO2CH2CH3),
1.43–1.54 (2H, m, C(5)H2), 2.61–2.67 (2H, m, C(4)H2), 4.17
(2H, q, J 7.1, CO2CH2CH3), 5.78 (1H, dt, J2,310.0, J2,41.7,
C(2)H ), 6.23 (1H, dt, J2,111.5, J2,37.5, C(3)H ). Further elution
gave (E)-2727 (92 mg, 40%); δH (400 MHz, CDCl3) 0.94 (3H, t,
J 7.4, C(6)H3), 1.29 (3H, t, J 7.1, CO2CH2CH3), 1.45–1.54 (2H,
m, C(5)H2), 2.15–2.21 (2H, m, C(4)H2), 4.19 (2H, q, J 7.1,
CO2CH2Me), 5.82 (1H, dt, J2,3 15.6, J2,4 1.5, C(2)H ), 6.97 (1H,
dt, J3,2 15.6, J3,4 7.0, C(3)H ). Further elution gave 5,5-dimethyl-
oxazolidin-2-one 9 (55 mg, 0.48 mmol, 56%).
Preparation of (E )- and (Z )-tert-butyl hex-2-enoate 35 and 36
from 21
Following Representative Procedure 3, DIBAL (1.0 M in THF,
1.95 mL, 1.95 mmol), 21 (300 mg, 1.15 mmol), tert-butyl di-
methoxyphosphonoacetate (910 mg, 4.05 mmol) and n-BuLi
(1.6 M, 2.6 mL, 4.05 mmol) in anhydrous THF (20 mL) gave,
after purification by flash column chromatography on silica
(150 : 1 hexane–Et2O) (Z)-3629 (56 mg, 20%); δH (400 MHz,
CDCl3) 0.95 (3H, t, J 7.4, CH2CH2CH3), 1.49 (9H, s, C(CH3)3),
Preparation of (E )- and (Z )-ethyl hepta-2,6-dienoate 29 and 30
from 22
1.40–1.57 (2H, obscured m, CH2CH2Me), 2.56–2.62 (2H, m,
t
CH2CH2Me), 5.69 (1H, d, J2,31.6, CH᎐CHCO Bu), 6.12 (1H,
᎐
2
Following Representative Procedure 3, DIBAL (1.0 M in THF,
1 mL, 1.5 mmol), 22 (200 mg, 1.02 mmol), triethyl phosphono-
acetate (0.51 mL, 2.54 mmol) and n-BuLi (1.66 M, 1.6 mL, 2.54
mmol) in anhydrous THF (15 mL) gave, after purification by
flash column chromatography on silica (30 : 1 hexane–Et2O),
(Z)-30 (12 mg, 8%); δH (400 MHz, CDCl3) 1.30 (3H, t, J 7.2,
t
dt, J3,2 11.6, J3,4 7.5, CH᎐CHCO Bu). Further elution gave
᎐
2
(E)-35 (210 mg, 76%); δH (400 MHz, CDCl3) 0.94 (3H, t, J 7.4,
CH2CH2CH3), 1.20–1.40 (2H, m, CH2CH2Me), 1.49 (9H, s,
C(CH3)3), 2.13–2.18 (2H, m, CH2CH2Me), 5.74 (1H, dt, J2,3
t
12.6, J2,41.5, CH᎐CHCO Bu), 6.86 (1H, dt, J3,215.6, J3,47.0,
᎐
2
t
CH᎐CHCO Bu).
᎐
2
CO CH CH ), 2.21–2.43 (4H, m, CH CH CH᎐CH ), 3.49 (2H,
᎐
2
2
3
2
2
2
q, J 7.0, CO CH Me), 4.95–5.08 (2H, m, CH᎐CH ), 5.77–5.86
᎐
2
2
2
Preparation of 3-(2Ј-benzylpropionyl)-5,5-dimethyloxazolidin-2-
one 37
(2H, m, CH᎐CH and CH᎐CHCO Et), 6.22 (1H, dt, J 11.5,
᎐
᎐
2
2
3,2
J3,4 7.4, CH᎐CHCO Et). Further elution gave (E)-29 (96 mg,
᎐
2
62%); δH (400 MHz, CDCl3) 1.33 (3H, t, J 7.1, CO2CH2CH3),
Following Representative Procedure 4, LHMDS (1 M, 1.21
mL, 1.21 mmol), 12 (200 mg, 0.81 mmol) and MeI (0.15 mL,
2.43 mmol) in anhydrous THF (10 mL) gave, after purification
by flash column chromatography on silica (2 : 1 40–60 petrol–
EtOAc), 37 (190 mg, 90%) as a colourless oil; νmax (film) 1783
2.24–2.38 (4H, m, CH ᎐CHCH CH ), 4.23 (2H, q, J 7.1,
᎐
2
2
2
CO CH Me), 5.04–5.13 (2H, m, CH ᎐CH), 5.80–5.90 (2H, m,
᎐
2
2
2
CH =CH and CH᎐CHCO Et), 7.00 (1H, dt, J3,215.6; J3,4 6.7,
᎐
2
2
CH᎐CHCO Et); δ (100 MHz, CDCl3) 22.6 (CO2CH2CH3),
᎐
2
C
31.4, 32.0 (CH CH CH᎐CH ), 60.2 (CO CH Me), 115.5
᎐
2
2
2
2
2
(C᎐O endocyclic), 1703 (C᎐O exocyclic); δH (200 MHz, CDCl3)
᎐ ᎐
(CH᎐CH ), 121.7 (CH᎐CH ), 137.1 (CH᎐CHCO Et), 148.2
᎐
᎐
᎐
2
2
2
1.19 (3H, d, J 6.8, C(3Ј)H3), 1.34, 1.43 (2 × 3H, s, C(CH3)2),
2.67 (1H, dd, JA,B13.2, JA,2Ј7.7, CHAHBPh), 3.04 (1H, dd,
JB,A13.2, JB,2Ј7.3, CHAHBPh), 3.58–3.72 (2H, m, C(4)H2), 4.09–
4.20 (1H, m, C(2Ј)H ), 7.16–7.32 (5H, m, Ph); δC (50 MHz,
CDCl3) 16.7 (C(3Ј)H3), 26.9, 27.0 (C(CH3)2), 39.3 (C(2Ј)H),
40.0 (C(2Ј)CH2Ph), 54.4 (C(4)H2), 78.3 (C(5)), 126.3, 128.1,
128.3 (Phortho-,meta-,para-), 139.2 (Phipso), 152.3 (CO), 176.8
(OCON); HRMS (APCIϩ), C15H20NO3 requires 262.1443,
found 262.1448.
(CH᎐CHCO Et), 166.6 (CO Et); ν
(film) 1716 (C᎐O), 1656
᎐
᎐
2
2
max
(C ᎐C ); HRMS C H O (MHϩ) requires 155.1072, found
᎐
2
3
9
15
2
155.1073; m/z (APCIϩ) 155.1 (MHϩ, 100%).
Preparation of (E )- and (Z )-ethyl 6-methylhept-2-enoate 31 and
32 from 23
Following Representative Procedure 3, DIBAL (1.0 M in THF,
1.41 mL, 1.41 mmol), 23 (200 mg, 0.94 mmol), triethyl
phosphonoacetate (0.47 mL, 2.35 mmol) and n-BuLi (1.6 M,
1.47 mL, 2.35 mmol) in anhydrous THF (15 mL) gave, after
purification by flash column chromatography on silica (30 : 1
hexane–Et2O), (Z)-32 (10 mg, 6%); δH (400 MHz, CDCl3)
0.91 (6H, d, J 6.6, C(6)H(CH3)2), 1.20–1.66 (6H, obscured m,
CO2CH2CH3, C(5)H2CHMe2 and CH2C(6)HMe2), 2.64–2.69
(2H, m, C(4)H2CH2CHMe2), 4.18 (2H, q, J 7.1, CO2CH2Me),
Preparation of 3-(2Ј-benzylpent-4Ј-enoyl)-5,5-dimethyloxazol-
idin-2-one 38
Following Representative Procedure 4, LHMDS (1.0 M,
3.0 mL, 3.0 mmol), 12 (0.50 g, 2.02 mmol) and allyl bromide
(0.53 mL, 6.07 mmol) in anhydrous THF (25 mL) gave 38 as a
yellow solid (0.47 g, 1.65 mmol, 82%) after purification by flash
column chromatography on silica (3 : 1 hexane–Et2O; Rf 0.33);
mp 53–55 ЊC; δH (400 MHz, CDCl3) 1.25 (3H, s, C(CH3)2), 1.43
5.75 (1H, dt, J2,311.5, J2,41.7, CH᎐C(2)HCO Et), 6.22 (1H, dt,
᎐
2
J3,211.5, J3,47.6, C(3)H᎐CHCO Et). Further elution gave (E)-31
᎐
2
(71 mg, 45%); δH (400 MHz, CDCl3) 0.90 (6H, d, J 6.6,
C(6)H(CH3)2), 1.29 (3H, t, J 7.1, CO2CH2CH3), 1.31–1.37 (2H,
obscured m, C(5)H2CHMe2), 1.54–1.61 (1H, m, C(6)HMe2),
2.17–2.23 (2H, m, C(4)H2CH2CHMe2), 4.18 (2H, q, J 7.1,
(3H, s, C(CH ) ), 2.28–2.34 (1H, m, CH H CH᎐CH ), 2.44–
᎐
3 2 A B 2
2.51 (1H, m, CH H CH᎐CH ), 2.8 (1H, dd, JA,B13.4, JA,26.6,
᎐
A
B
2
CHAHBPh), 2.96 (1H, dd, JB,A13.4, JB,2 8.7, CHAHBPh), 3.58
(2H, ABq, J 11.0, CH2CMe2), 4.34–4.12 (1H, m, CHCH2-
CO2CH2Me), 5.82 (1H, dt, J2,314.1, J2,41.5, CH᎐C(2)HCO Et),
CH᎐CH ), 5.01–5.10 (2H, m, CH᎐CH ), 5.76–5.86 (1H, m,
᎐ ᎐
2 2
᎐
2
6.97 (1H, dt, J3,2 15.6, J3,47.0, C(3)H᎐CHCO Et).
CH᎐CH ), 7.16–7.28 (5H, m, Ph); δ (100 MHz, CDCl3)
᎐
2 C
᎐
2
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 2 0 0 1 – 2 0 1 0
2008