12
E. Jubeli et al. / Bioorg. Med. Chem. xxx (2015) xxx–xxx
All of the compounds prepared in this paper are racemic.
(2H, ddt, J 17.0, 10.1 and 6.7, 2 ꢃ H2C@CH), 5.26 (1H, tt, J 4.3 and
5.9, COOCH), 5.02–4.94 (4H, m, 2 ꢃ H2C@CH), 4.32 (1H, dd, J 4.3
and 11.8, COOCHH), 4.30 (1H, dd, J 4.3 and 11.8, COOCHH), 4.14
(2H, dd, J 5.9 and 11.8, CH2OOC), 3.40 (2H, t, J 6.5, CH2Br),
2.37–2.30 (6H, m, 2 ꢃ CH2COO and OOCCH2), 2.08–2.03 (4H, m,
2 ꢃ H2C@CHCH2), 1.93–1.84 (2H, m, CH2CH2CH2Br), 1.82–1.73
(2H, m, CH2CH2Br), 1.67–1.59 (4H, m, 2 ꢃ CH2), 1.46–1.37 (4H, m,
2 ꢃ CH2); dC (100 MHz, CDCl3) 173.1, 172.7, 172.5, 138.3, 114.8,
68.9, 62.3, 62.0, 34.0, 33.8, 33.3, 32.9, 32.8, 31.8, 28.2, 28.2, 24.3,
24.2, 23.3; m/z (ES) 492.1966 (M++NH4, 96%, C22H39BrO6N requires
492.1955).
5.2. Synthesis of selected triester cationic lipids
A representative set of experimental procedures and data for
the construction of the cationic lipids 4 (SC7 DMA) and 8 (SC7
TMA), together with all synthetic intermediates leading to these
compounds, appears below. The experimental for all remaining
synthetic intermediates and cationic lipids reported herein appears
in full in the Supplementary data.
5.2.1. 2,3-Dihydroxypropyl 5-bromopentanoate (24)
DCC (5.14 g, 24.9 mmol, 1.5 equiv) and DMAP (600 mg,
4.9 mmol, 0.3 equiv) were sequentially added to a solution of
5-bromovaleric acid (3.31 g, 18.3 mmol, 1.1 equiv) in CH2Cl2
(110 mL, 0.15 M) at 0 °C and stirred for 30 min. A solution of
DL-1,2-isopropylideneglycerol (17) (2.1 mL, 17 mmol, 1 equiv) in
CH2Cl2 (220 mL, 0.075 M) was added to the reaction mixture,
which was then stirred at rt for 18 h. The reaction mixture was
filtered through celite, washed with CH2Cl2 (50 mL), and then con-
centrated in vacuo. The crude residue was purified by flash column
chromatography on silica using 30% ethyl acetate in petroleum
ether as eluent to give the ester (3.78 g, 75%) as a pale yellow
oil; mmax (CDCl3/cmꢀ1) 2987, 2939, 2886, 1739, 1213, 1256, 1085
and 648; dH (300 MHz, CDCl3) 4.36–4.28 (1H, ddt, J 4.6, 5.9 and
6.1, OCH), 4.18 (1H, dd, J 4.6 and 11.6, CHHCOO), 4.12–4.06 (2H,
m, OCHHCHCHHOOC), 3.74 (1H, dd, J 6.1 and 8.4, OCHHCH), 3.42
(2H, t, J 6.4, CH2Br), 2.40 (2H, t, J 7.1, OOCCH2), 1.95–1.73 (4H, m,
CH2CH2CH2Br), 1.43 (3H, s, CH3), 1.37 (3H, s, CH3); dC (75 MHz,
CDCl3) 173.0, 110.0, 73.7, 66.4, 64.9, 33.2, 33.0, 32.0, 26.8, 25.5,
23.5; m/z (ES) 295.0546 (M++H, 82%, C11H20O4Br requires
295.0539).
5.2.3. (E)- and (Z)-(5,16-Dioxo-1,4-dioxacyclohexadec-10-en-2-
yl)methyl 5-bromopentanoate (28)
Using a two-neck round bottom flask the diene 25 (424.0 mg,
0.895 mmol, 1 equiv) was dissolved in CH2Cl2 (895 mL, 0.001 M)
and then sparged with argon for 20 min. Grubbs’ 1st generation
pre-catalyst (73 mg, 0.10 mmol, 0.1 equiv) was added in one por-
tion to the solution, which was then sparged for 10 min. The reac-
tion mixture was stirred at 45 °C for 12 h, and then cooled to rt,
exposed to air for 90 min, and then concentrated in vacuo. The
crude residue was adsorbed onto silica, and then purified by flash
column chromatography on silica using 10% ethyl acetate in petro-
leum ether as eluent to give an inseparable 3.4:1 mixture of the
(E)- and (Z)-macrocycles 28 (270 mg, 68%) as a colourless oil; mmax
(CDCl3/cmꢀ1) 3016, 2932, 2857, 1744, 1640, 1256, 1222, 1169 and
650; NMR data reported for the major (E)-isomer: dH (400 MHz,
CDCl3) 5.38–5.18 (3H, m, HC@CH and COOCH), 4.31 (1H, dd, J 4.8
and 12.0, COOCHH), 4.28 (1H, dd, J 2.5 and 12.0, COOCHH), 4.16
(1H, dd, J 7.4 and 12.1, CHHOOC), 4.15 (1H, dd, J 5.4 and 12.1,
CHHOOC), 3.41 (2H, t, J 6.6, CH2Br), 2.37 (2H, t, J 7.3, OOCCH2),
2.35–2.24 (4H, m, 2 ꢃ CH2COO), 2.14–1.99 (4H, m, 2 ꢃ CH2CH = ),
1.93–1.87 (2H, m, CH2CH2CH2Br), 1.82–1.76 (2H, m, CH2CH2Br),
1.71–1.53 (4H, m, 2 ꢃ CH2), 1.51–1.37 (4H, m, 2 ꢃ CH2); dC
(100 MHz, CDCl3) 173.4, 173.1, 173.7, 131.2, 131.1, 69.0, 62.7,
62.4, 35.04, 35.01, 33.1, 33.0, 32.17, 32.13, 32.0, 28.21, 28.19,
24.9, 24.8, 23.5; m/z (ES) 464.1629 (M++NH4, 100%, C20H35NO6Br
requires 464.1642).
Copper(II) chloride dihydrate (900 mg, 5.28 mmol, 1.5 equiv)
was added to a solution of the dioxolane (1.05 g, 3.56 mmol,
1 equiv) in acetonitrile (71 mL, 0.05 M) and stirred at rt for 18 h.
The reaction mixture was concentrated in vacuo, diluted with
diethyl ether (100 mL), and then successively washed with a
saturated aqueous solution of sodium hydrogen carbonate
(50 mL) and brine (40 mL). The organic layer was dried over
sodium sulfate, filtered and then concentrated in vacuo. The crude
residue was purified by flash column chromatography on silica
using 30% ethyl acetate in petroleum ether as eluent to give the
5.2.4. (5,16-Dioxo-1,4-dioxacyclohexadecan-2-yl)methyl 5-
bromopentanoate (30)
diol 24 (616 mg, 68%) as a colourless oil; mmax (CDCl3/cmꢀ1
)
Palladium on carbon (10% w/w) (38 mg, 0.36 mmol, 0.3 equiv)
was added to a 3.4:1 mixture of the (E)- and (Z)-alkenes 28
(54 mg, 0.12 mmol, 1 equiv) in glacial acetic acid (0.400 mL,
0.003 M) and ethanol (3.60 mL, 0.030 M). The reaction mixture
was stirred under an atmosphere of hydrogen gas, using a balloon,
at rt for 50 min. The reaction mixture was diluted with CH2Cl2
(10 mL) filtered through celite, which was then washed with
CH2Cl2 (20 mL). The filtrate was washed twice with a saturated
aqueous sodium hydrogen carbonate solution (50 mL) and then
dried over sodium sulfate, filtered and concentrated in vacuo.
The crude residue was purified by flash column chromatography
on silica using 10% ethyl acetate in petroleum ether as eluent to
give the saturated lipid 30 (49 mg, 92%) as a colourless oil; mmax
(CDCl3/cmꢀ1) 2933, 2861, 1736, 1166 and 645; dH (400 MHz, CDCl3)
5.32–5.27 (1H, m, COOCH), 4.38 (1H, dd, J 2.2 and 12.4, COOCHH),
4.30 (1H, dd, J 5.0 and 11.8, CHHOOC), 4.18 (1H, dd, J 6.3 and 11.8,
CHHOOC), 4.16 (1H, dd, J 6.0 and 12.4, COOCHH), 3.40 (2H, t, J 6.1,
CH2Br), 2.36 (2H, t, J 7.3, CH2COO), 2.37–2.32 (4H, m, 2 ꢃ CH2COO),
1.95–1.86 (2H, m, CH2CH2CH2Br), 1.82–1.74 (2H, m, CH2CH2Br),
1.73–1.59 (4H, m, 2 ꢃ CH2), 1.36–1.32 (12H, m, 6 ꢃ CH2); dC
(100 MHz, CDCl3) 173.6, 173.2, 172.6, 69.1, 62.8, 62.4, 33.88,
33.85, 33.1, 33.0, 32.0, 27.1, 26.9, 26.2, 26.18, 26.12, 26.0, 24.39,
24.32, 23.4; m/z (ES) 449.1530 (M++H, 100%, C20H34O6Br requires
449.1533).
3449, 2985, 2942, 2907, 2874, 1732, 1114, 1097, 1040 and 645;
dH (300 MHz, CDCl3) 4.20 (1H, dd, J 4.8 and 11.5, CHHOOC), 4.14
(1H, dd, J 5.9 and 11.5, CHHOOC), 3.97–3.90 (1H, m, HOCH), 3.70
(1H, dd, J 3.8 and 11.5, HOCHH), 3.59 (1H, dd, J 5.9 and 11.5,
HOCHH), 3.41 (2H, t, J 6.4, CH2Br), 2.56 (2H, br. s, 2 ꢃ OH), 2.40
(2H, t, J 7.1, OOCCH2), 1.95–1.74 (4H, m, CH2CH2CH2Br); dC
(75 MHz, CDCl3) 173.6, 70.3, 65.4, 63.4, 33.2, 33.1, 32.0, 23.5; m/z
(ES) 237.0115 (M+-OH, 99%, C8H14O3Br requires 237.0121).
5.2.2. 3-((Bromopentanoyl)oxy)propane-1,2-diyl bis(hept-6-
enoate) (25)
DCC (2.90 g, 14.1 mmol, 3.0 equiv) and DMAP (242 mg,
1.98 mmol, 0.4 equiv) were sequentially added to a solution of
6-heptenoic acid (1.40 mL, 10.3 mmol, 2.2 equiv) in CH2Cl2
(20 mL, 0.23 M) at 0 °C and stirred for 30 min. A solution of the diol
24 (1.19 g, 4.66 mmol, 1.0 equiv) in CH2Cl2 (35 mL, 0.13 M) was
added to the reaction mixture, which was then stirred at rt for
18 h. The reaction mixture was filtered through celite, washed with
CH2Cl2 (10 mL), and then concentrated in vacuo. The crude residue
was purified by flash column chromatography on silica using 10%
ethyl acetate in petroleum ether as eluent to give the bis-ester
25 (2.04 g, 93%) as a colourless oil; mmax (CDCl3/cmꢀ1) 3065,
2936, 2861, 1740, 1640, 1166 and 646; dH (400 MHz, CDCl3) 5.78