Asymmetric Synthesis of Dialkyloxy-3-alkylammonium Cationic Lipids

Article abstract of DOI:10.1021/jo035422g

The cationic diether-linked cytofectin DOTMA (available commercially as a mixture, Lipofectin comprised of DOTMA:DOPE, 1:1) and analogues including DIMRIE and DORIE are frequently used for in vitro and in vivo transfections. Despite this wide usage direct synthetic routes to the optical isomers have received little attention to date. Here we describe strategies to synthesize enantiomers of DOTMA and analogues, including an extremely concise procedure to the trimethylammonium salts. One strategy utilized N-protection, as the imine, with concomitant ether formation and deprotection during the workup. Methylation of the 1-amino-2,3-dialkyloxypropane then generated the trimethylammonium cationic lipids directly. This methodology was extended to synthesize a novel headgroup functionalized lipid. A second route was also developed using an alternative chiral synthon.

Full text of DOI:10.1021/jo035422g

Asym m etr ic Syn th esis of
Dia lk yloxy-3-a lk yla m m on iu m Ca tion ic
Lip id s
and diether-linked glycerol-based lipids are synthesized
and used as a racemic mixture, having been prepared
from racemic 3-(dimethylamino)-1,2-propanediol. Excep-
tions include synthesis of the more synthetically acces-
sible diesters, for example, (R)-DORI, which was pre-
pared from commercially available optically active glycidol
6
Christopher A. Hurley, J ohn B. Wong,
Helen C. Hailes,* and Alethea B. Tabor
in 5 steps, and the diester pcTG201 7, also synthesized
Department of Chemistry, University College London,
0 Gordon Street, London WC1H 0AJ , United Kingdom
7
from glycidol. Furthermore, in his original patent Fel-
2
gner described the synthesis of the diether (S)-DOTMA
in 5 steps from D-mannitol-3,4-acetonide; however, this
route from the chiral pool would not readily afford the
(R)-isomer.8
h.c.hailes@ucl.ac.uk
Received September 29, 2003
The LID vector, a synthetic gene delivery system
comprised of Lipofectin (L), an integrin-targeting peptide
(I), and DNA has previously been shown to have high
Abstr a ct: The cationic diether-linked cytofectin DOTMA
available commercially as a mixture, Lipofectin comprised
(
9
,10
of DOTMA:DOPE, 1:1) and analogues including DIMRIE
and DORIE are frequently used for in vitro and in vivo
transfections. Despite this wide usage direct synthetic routes
to the optical isomers have received little attention to date.
Here we describe strategies to synthesize enantiomers of
DOTMA and analogues, including an extremely concise
procedure to the trimethylammonium salts. One strategy
utilized N-protection, as the imine, with concomitant ether
formation and deprotection during the workup. Methylation
of the 1-amino-2,3-dialkyloxypropane then generated the
trimethylammonium cationic lipids directly. This methodol-
ogy was extended to synthesize a novel headgroup function-
alized lipid. A second route was also developed using an
alternative chiral synthon.
transfection efficiency in vitro and in vivo.
In the
course of our studies investigating the structural features
of DOTMA which have a key bearing on the transfection
9,10
properties of the LID ternary vector
a concise, flexible
synthesis of both enantiomers of the diether-linked
dialkyloxy-3-alkylammonium cationic lipids was re-
quired. Herein we describe the first synthetic route to
both (R)- and (S)-1,2-dialkyloxy-3-trimethylammonium
salts and alternative strategies to access dimethylam-
monium cationic lipids with a stereospecific center at C-2.
The synthesis of stereochemically defined diester-
linked cationic lipids has been carried out with (R)-
glycidol via ring opening and amine formation then
attachment of acyl moieties incorporating protecting
groups where necessary.6 Our aim was to initially
develop a concise synthetic route to both enantiomers of
the diether trimethylammonium cytofectins such as
DOTMA, suitable for analogue preparation, and therefore
we considered using 3-amino-1,2-propanediol 8, which is
commercially available as both isomers, as our starting
material. We envisaged that N-protection, diether forma-
tion, and then quaternization would directly generate the
cationic lipids. Several N-protecting groups were consid-
ered, with a view to removal in the presence of alkene
,7
The use of synthetic cationic lipids in binding poly-
nucleotides and facilitating gene transfer continues to
develop as an alternative to viral-mediated gene delivery.
Since the initial work by Felgner and co-workers on the
1
synthesis of DOTMA 1, the range of synthetic lipids
reported for use as gene delivery vectors has expanded
significantly. Several reagents have become commercially
available, for example, Lipofectin, a coformulation of
DOTMA 1 with naturally available neutral lipid DOPE
,3
2
(Figure 1).2 DOTMA contains a glycerol backbone with
1
1
moieties. Initially, N-Boc protection was carried out to
give N-Boc-3-amino-1,2-propandiol, which has also been
prepared from (R)-glycidol to access the diester lipid
series.7 However, subsequent reaction with NaH and
oleyl mesylate12 led to neighboring alkoxide attack and
N-alkylation. Similar intramolecular reactions at the
N-Boc carbonyl group have been reported during the
two oleyl chains and a trimethylammonium cationic
headgroup. Related diether-linked analogues include
DIMRIE 3 and DORIE 4, possessing C14:0 and C18:1
chain lengths, respectively, and N,N-dimethyl-N-ethan-
4
olamine headgroups. Several diester-linked amphiphiles
have also been reported including DOTAP 5, which was
5
6
designed to be more readily metabolized, and DORI 6.
1
3
synthesis of polymer-supported oxazolidin-2-ones and
Interestingly, although naturally available DOPE is
available in optically active form (R-isomer) most diester-
in the synthesis of oxazolidinones with N-Boc-â-amino
(
7) Nazih, A.; Cordier, Y.; Kolbe, H. V. J .; Heissler, D. Synlett 2000,
635-636.
(8) Eppstein, D. A.; J ones, G. H.; Felgner, P. L.; Roman, R. B. U.S.
*
To whom correspondence should be addressed: Fax: +44 (0)20
679 7463.
1) Felgner, P. L.; Gadek, T. R.; Holm, M.; Roman, R.; Chan, H. W.;
7
(
Patent 689263, published J uly 23, 1986.
Wenz, M.; Northrop, J . P.; Ringold, G. M.; Danielsen, M. Proc. Natl.
Acad. Sci. U.S.A. 1987, 84, 7413-7417.
(9) Hart, S. L.; Arancibia-Carcamo, C. V.; Wolfert, M. A.; Mailhos,
C.; O’Reilly, N. J .; Ali, R. R.; Coutelle, C.; George, A. J . T.; Harbottle,
R. P.; Knight, A. M.; Larkin, D. F. P.; Levinsky, R. J .; Seymour, L. W.;
Thrasher, A. J .; Kinnon C. Hum. Gene Ther. 1998, 9, 575-585.
(10) J enkins, R. G.; Meng, Q.-H.; Hodges, R. J .; Lee, L. K.; Bottoms,
S. E. W.; Laurent, G. J .; Willis, D.; Ayazi Shamlou, P.; MaAnulty, R.
J .; Hart, S. L. Gene Ther. 2003, 10, 1026-1034.
(
2) Miller, A. D. Angew. Chem., Int. Ed. 1998, 37, 1768-1785.
3) Hope, M. J .; Mui, B.; Ansell, S.; Ahkong, Q. F. Mol. Membr. Biol.
(
1
998, 15, 1-14.
4) Felgner, J . H.; Kumar, R.; Sridhar, C. N.; Wheeler, C. J .; Tsai,
Y. J .; Border, R.; Ramsey, P.; Martin, M.; Felgner, P. L. J . Biol. Chem.
(
1
1
1
994, 269, 2550-2561.
(11) Kokotos, G.; Verger, R.; Chiou, A. Chem. Eur. J . 2000, 6, 4211-
(
5) Leventis, R.; Silvius, J . R. Biochim. Biophys. Acta 1990, 1023,
4217.
24-132.
(12) Surles, J . R.; Wykle, R. L.; O’Flaherty, J . T.; Salzer, W. L.;
Thomas, M. J .; Snyder, F.; Piantadosi, C. J . Med. Chem. 1985, 28, 73-
78.
(6) Bennett, M. J .; Malone, R. W.; Nantz, M. H. Tetrahedron Lett.
995, 36, 2207-2210.
1
0.1021/jo035422g CCC: $27.50 © 2004 American Chemical Society
Published on Web 01/07/2004
9
80
J . Org. Chem. 2004, 69, 980-983

F IGURE 1. Lipids used in gene delivery.
SCHEME 1. F or m a tion of
TABLE 1. Da ta for F or m a tion of
1,2-Dia lk yloxy-3-tr im eth yla m m on iu m Sa lts
a
1
,2-Dia lk yloxy-3-tr im eth yla m m on iu m Sa lts
product;
entry
isomer
R
yielda (%)
salt; [R]D b
1
2
3
4
5
6
2R
2S
2R
2S
2R
2S
C14H29
C14H29
C14H27
C14H27
C18H35
C18H35
9a ; 48
9b; 50
11a ; 51
11b; 48
13a ; 44
13b; 50
10a ; +37.7 (0.5)
10b; -41.5 (0.5)
12a ; +14.0 (1)
12b; -12.0 (1)
1a ; +26.4 (0.8)
1b; -25.7 (0.8)
a
Yield for step a. b Optical rotation of 1,2-dialkyloxy-3-trimeth-
ylammonium salts in CHCl3 at 23 °C, concentration c given in
parentheses.
corresponding diether. The addition of HCl during the
workup regenerated the primary amine and enabled the
product 9a to be isolated as the hydrochloride salt in 48%
yield from 8a . The optical rotation of 9a (+10.7; c 0.8,
CHCl
3
) was in excellent agreement with that reported
1
1
by Kokotos (+11.2; c 0.5, CHCl
3
). Finally, quaterniza-
tion with methyl iodide revealed the cationic lipid 10a
in 89% yield (entry 1, Table 1). Using a similar strategy,
the 2S-isomers 9b and 10b were also generated (entry
a
Reagents and conditions: (a) (i) PhCHO, Na2SO4, CH2Cl2, 18
h, (ii) NaH, THF, MsOR, reflux, 72 h, (iii) 1 M HCl/EtOH (1:1), 6
h; (b) MeI, NaOH, 90 °C, 18 h.
2
, Table 1). Alternatively, when using cis-tetradec-11-
alcohols.14 Interestingly, Kokotos has reported the O-
alkylation of N-Boc-3-amino-1,2-propanediol using satur-
ated alkyl halides and a biphasic solvent mixture con-
taining sodium hydroxide for the synthesis of inhibitors
of digestive lipases, but did not report the formation of
any oxazolidinone side products.11 Our previous studies
investigating such diether synthesis had established that
for unsaturated alkyl chains, activation as the mesylate
led to consistently higher yields. Therefore, since mesyl-
ates are not compatible with aqueous basic conditions,
an alternative protecting group was used.
17
enyl mesylate the free amines 11a and 11b were
isolated,m which were converted in a fashion similar to
12a and 12b (entries 3 and 4, Table 1), respectively. The
use of oleyl mesylate12 similarly generated the amines
13a and 13b and (2R)-DOTMA 1a and (2S)-DOTMA 1b
(entries 5 and 6, Table 1). The optical rotation data for
1b (-25.7; c 0.5, CHCl
reported by Felgner for the chloride salt of (2S)-DOTMA
3
(-20; no c value, CHCl ). Overall this is a short, facile
procedure, ideal for accessing saturated and unsaturated
1,2-dialkyloxy-3-trimethylammonium salts, which have
hitherto received little attention in the literature despite
their numerous applications in transfection studies.
Further studies were then undertaken to synthesize
homochiral diether cationic lipids possessing an alterna-
tive group at the head position for applications in the
synthesis of stereochemically defined functionalized lip-
ids. Two strategies were explored: modification of the
homochiral primary amine (such as compound 9a ) and
the use of an alternative glycerol-based building block.
3
) were consistent with that
8
Accordingly, imine N-protection15 was investigated as
shown in Scheme 1. Protection of (2R)-3-amino-1,2-
propanediol 8a was achieved by using benzaldehyde at
room temperature and anhydrous sodium sulfate. Filtra-
tion, concentration, and treatment of the crude imine
directly with NaH and tetradecyl mesylate16 led to the
(
13) Bew, S. P.; Bull, S. D.; Davies, S. G. Tetrahedron Lett. 2000,
1, 7577-7581.
14) Lee, J . W.; Lee, J . H.; Son, H. J .; Choi, Y. K.; Yoon, G. J .; Park,
4
(
M. H. Synth. Commun. 1996, 26, 83-88.
(
15) McCasland, H. J . Am. Chem. Soc. 1951, 73, 3923.
(17) Roosjen, A.; Smisterova, J .; Driessen, C.; Anders, J . T.; Wa-
genaar, A.; Hoekstra, D.; Hulst, R.; Engberts, J . B. F. N. Eur. J . Org.
Chem. 2002, 7, 1271-1277.
(16) Baumann, W. J .; Mangold, H. K. J . Org. Chem. 1964, 29, 3055-
3
057.
J . Org. Chem, Vol. 69, No. 3, 2004 981

SCHEME 2a
SCHEME 3a
a
Reagents and conditions: (a) NaHCO3/dioxane (1:1), 14, 96%;
(b) LiAlH4, THF, 18 h, 95%; (c) MeI, NaOH, 6 h, 64%; (d) TFA/
CH2Cl2 (1:1), 97%.
a
An Eschweiler-Clark reductive methylation of salt 9a
with formaldehyde and formic acid, for subsequent quat-
ernizsation with a third moiety, was first attempted.18
However, an inseparable mixture of N-methylated prod-
ucts was generated. Use of Barbry’s microwave acceler-
Reagents and conditions: (a) NaOH (14.5 equiv), HNMe2‚HCl
(
11.5 equiv), 18 h, 89%; (b) NaH, oleyl mesylate, toluene, 61% for
1a ; (c) MeI, 95% for 1a .
of DOTMA and chain length analogues were prepared,
with transient protection of the NH
2
group as the
ated reductive amination method also led to a mixture
of products.19 Alternative reductive amination procedures
corresponding imine as the key step. This route was then
extended to access a novel headgroup functionalized lipid.
Finally, a second route was developed by using the
alternative chiral synthons (2R)- and (2S)-3-chloro-1,2-
propanediol. These procedures are high yielding for
reactions of this type and are highly versatile, as they
can be adapted to generate cationic lipids with alternative
headgroup moieties. The transfection activities of the
optical isomers are currently under investigation, and the
results will be published elsewhere.
utilizing sodium cyanoborohydride similarly did not lead
to the clean formation of the N,N-dimethylated com-
pound. A route via the amide was then explored to
generate an N-â-aminoethyl-substituted ammonium cat-
ion possessing a secondary amine moiety (Scheme 2). The
salt 9a was converted to the amine in situ and directly
coupled to Boc-Glu-OSu 14 to give 15 in 96% yield.
Subsequent reduction, methylation, and removal of the
protecting group revealed 16, N-methyl-âAE-DMRIE, a
novel pH-sensitive cationic lipid in 57% overall yield from
9
a . This approach is particularly effective because it
Exp er im en ta l Section
permits the synthesis of diverse functional lipids through
the introduction of alternative functional groups at the
terminal N-Me position.
An alternative approach was also investigated com-
mencing from commercially available starting materials,
Gen er a l Meth od s. The mesylates were prepared as previ-
ously reported.1
2,16,17
Dietherification and quaternization of 18a
1
,4,8
and 18b was carried out as previously described.
Rep r esen ta tive P r oced u r e: P r ep a r a tion of (R)-2,3-Bis-
11Z-tetr a d ecen yloxy)p r op a n a m in e (11a ). (2R)-3-Amino-1,2-
propanediol (8a ; 0.32 g, 3.50 mmol) and anhydrous Na SO (2.49
2 4
(
(S)- or (R)-3-chloro-1,2-propanediol, 17a and 17b, respec-
tively (Scheme 3). Conversion of 17a to (R)-3-(N,N-
dimethylamino)propane-1,2-diol (18a ) in 89% yield was
readily achieved through modification of Bhattacharya’s
method,20 utilizing excess sodium hydroxide and di-
methylamine hydrochloride to avoid the formation of bis-
g, 17.5 mmol) were stirred in anhydrous CH
2
3
2
Cl
0 mL) at room temperature for 30 min. Benzaldehyde (0.37 g,
.50 mmol) was added and stirring continued for 18 h. The
2
/MeOH (10:1,
mixture was then filtered and concentrated in vacuo to give the
crude imine in quantitative yields. NaH (60%; 0.40 g, 10.5 mmol)
was stirred in anhydrous THF (40 mL), the imine (0.63 g, 3.50
mmol) was added, and the resulting mixture was stirred for 4
(
2,3-dihydroxypropyl)-N,N-dimethylammonium chloride.
1
2
17
Reaction with oleyl mesylate under anhydrous basic
conditions gave the dietherified product as previously
h. 11Z-Tetradecenyl mesylate (3.07 g, 10.5 mmol) was added
and the mixture was heated at reflux for 72 h. The reaction was
reported.1,4 Quaternization with a range of functionalized
quenched with water (50 mL) and extracted with EtOAc (3 ×
5
0 mL). The combined organic extracts were dried over anhy-
groups can then be carried out. However, for our purposes
we quaternized the amines with methyl iodide to access
drous MgSO
in concentrated HCl/H
temperature for 6 h. The product was extracted with CH Cl (2
4
and concentrated in vacuo. The residue was stirred
2
O (1:1, 50 mL) and EtOH (50 mL) at room
1
a and 1b in near quantitative yield. We also prepared
2
2
the novel C16:1 analogue 19, via an analogous route,
using cis-hexadec-11-enyl mesylate17 (optical rotation
data for 19a +17.4, c 0.67 and 19b -17.1, c 0.67).
In summary, two direct and versatile routes to homo-
chiral dialkoxy alkylammonium cationic lipids from the
chiral pool have been developed. From commercially
available 3-amino-1,2-propane diol 8, both enantiomers
× 75 mL) and the combined organic extracts washed with water
(50 mL) and brine (50 mL) and dried over MgSO . The solvents
4
were removed in vacuo and the product purified by flash column
chromatography (SiO
to give 11a as an oil (0.43 g, 51%) [R]
ν
2
; gradient CHCl
2
to CHCl
2
/MeOH, 10:1)
+7.4 (c 0.81, CHCl );
3
max (CHCl ) 3380, 2934, 2856, 1460 cm ; H NMR δ 0.95 (6H,
22
D
3
-1
1
t, J ) 7.5 Hz), 1.27 (28H, m), 1.55 (4H, m), 2.04 (8H, m), 2.59
(2H, br s), 2.78 (1H, dd, J ) 13.1 and 5.9 Hz), 3.12 (1H, dd, J )
1
3.1 and 3.2 Hz), 3.42-3.51 (6H, m), 3.69 (1H, m), 5.27-5.47
(
(
4H, m); 13C NMR δ 14.3, 20.5, 26.1, 27.1, 29.1, 29.3, 29.4-29.6
(18) Dai-Ho, G.; Mariano, P. S. J . Org. Chem. 1988, 53, 5113-5127.
(19) Barbry, D.; Torchy, S. Synth. Commun. 1996, 26, 3919-3922.
(20) Data for the racemate: Bhattacharya, S.; Subramanian, M. J .
signal overlap), 30.0, 32.5, 43.3, 70.3, 71.2, 71.7, 79.3, 129.3,
+
131.4; m/z HRMS calcd for C31
480.4793; m/z (+ES) 481 (MH , 48%), 69 (100).
H
62
O
2
N (MH) 480.4781, found
+
Chem. Soc., Perkin Trans. 2 1996, 2027-2033.
9
82 J . Org. Chem., Vol. 69, No. 3, 2004

+
Repr esen tative P r ocedu r e: (R)-1-P r opan am in iu m ,N,N,N-
tr im eth yl-2,3-bis(11Z-tetr a d ecen yl-oxy)-, Iod id e (12a ). The
primary amine 11a (100 mg, 0.19 mmol) and powdered sodium
hydroxide (77 mg, 1.94 mmol) were stirred in iodomethane (2.0
(+ES) 627.86 (MH , 100%). Anal. Calcd for C38
78 4 2
H O N : C,
72.79; H, 12.54; N, 4.47. Found: C, 72.61; H, 12.46; N, 4.25.
(R)-[2-(2,3-Tetradecyloxy-propylamino)ethyl]carbamic acid tert-
butyl ester (150 mg, 0.24 mmol) and powdered sodium hydroxide
(20 mg, 0.48 mmol) were stirred in iodomethane (1 mL) at room
temperature for 24 h. Excess CH
CH Cl (25 mL) was added to the resulting residue. Filtration
of the insoluble inorganic salts and concentration of the filtrate
in vacuo gave (R)-(2,3-bis-tetradecyloxy-propyl)[2-tert-butoxy-
carbonyl-N-methylamino-ethyl]-N,N-dimethylammonium, iodide
as a yellow oil (122 mg, 64%), which was used without further
mL) in a sealed tube at 90 °C for 18 h. After cooling, CHCl
mL) was added and the mixture was washed with brine (20 mL)
and dried (MgSO ). The solvents were removed in vacuo to give
2a as an oil (107 mg, 87%); [R]
3
(20
3
I was removed in vacuo and
4
2
2
2
3
1
D
+14.0 (c 1.0, CHCl
) 2934, 2856, 1464 cm ; H NMR δ 0.93 (6H, t, J ) 7.5
Hz), 1.25 (28H, m), 1.53 (4H, m), 2.02 (8H, m), 3.42 (4H, m),
3
); νmax
-
1 1
(CHCl
3
3
.49 (9H, s), 3.56-3.69 (3H, m), 4.04 (2H, m), 5.33 (4H, m); 13
C
2
3
NMR δ 14.4, 20.5, 26.0, 26.2, 27.1, 29.7, 29.1, 29.2-30.0 (signal
overlap), 55.3, 68.1, 69.3, 72.1, 73.5, 129.3, 131.5; m/z HRMS
purification; [R]
D
3
+11.2 (c 6.3, CHCl ); νmax (film) 2923, 2853,
-
1 1
1720 cm ; H NMR δ 0.84 (6H, t, J ) 7.0 Hz), 1.27 (44H, m),
+
calcd for C34
+ES) 523 (M - I , 100%).
R)-[2,3-(Bis-tetr a d ecyloxy-p r op yl-1-ca r ba m oyl)m eth yl]-
H
68
O
2
+
N (M - I) 522.5250, found 522.5234; m/z
1.42 (9H, s), 1.53 (4H, m), 3.00 (3H, s), 3.39-4.11 (19H, br m);
+
(
m/z HRMS calcd for C41
H
85
O
4
N
2
(M - I) 669.6509, found
(
669.6507.
ca r ba m ic Acid ter t-Bu tyl Ester (15). The amine salt 9a (350
mg, 0.67 mmol) and Boc-Glu-OSu (14; 183 mg, 0.67 mmol) were
(R)-(2,3-Bis-tetradecyloxy-propyl)-[2-tert-butoxycarbonyl-N-
methylamino-ethyl]-N,N-dimethylammonium, iodide (40 mg,
stirred vigorously in sat. aqueous NaHCO
, 21 mL) for 1 h. Water (50 mL) was added and the mixture
extracted with EtOAc (3 × 50 mL). The combined organic
extracts were washed with brine (50 mL), dried (Na SO ), and
concentrated in vacuo to give 15 as an oil (410 mg, 96%); [R]
5.4 (c 3.0, CHCl
); νmax (film) 3315, 2922, 2850, 1694, 1658 cm-1;
H NMR δ 0.86 (6H, t, J ) 6.5 Hz), 1.24 (44H, m), 1.43 (9H, s),
.51 (4H, m), 3.37-3.57 (9H, m), 3.70 (2H, d, J ) 5.7 Hz), 5.12
3
solution/dioxane (1:
0.05 mmol) was stirred in TFA/CH
temperature for 6 h. The solvents were removed in vacuo to give
2 2
Cl (1:1, 2 mL) at room
2
2
3
16 (39 mg, 97%); [R]
D
3
+5.4 (c 4.5, CHCl ); νmax (film) 3450, 2924,
-
1 1
2
4
2848, 1650 cm ; H NMR 0.87 (6H, t, J ) 6.6 Hz), 1.25 (44H,
2
2
13
D
m), 1.54 (4H, m), 3.29-4.10 (22H, br m); C NMR δ 14.0, 22.6,
+
3
25.9, 26.0, 29.4-29.9 (signal overlap), 31.9, 53.9, 68.1 (signal
1
overlap), 69.6, 71.0, 72.1, 72.9; m/z HRMS calcd for C36
77 2 2
H O N
+
1
(
[M - (I + TFA)] 569.5985, found 569.5980.
(R)-3-(N,N-Dim eth ylam in o)pr opan e-1,2-diol (18a). HNMe ‚
2
1
3
1H, m), 6.42 (1H, m); C NMR δ 14.1, 22.7, 26.1, 26.2, 28.3,
2
7
9.3-29.6 (signal overlap), 30.0, 31.9, 40.7, 44.4, 70.3, 71.3, 71.9,
HCl (3.23 g, 39.6 mmol) and (2S)-3-chloro-1,2-propanediol (17a ;
0.50 mL, 3.43 mmol) were added to sodium hydroxide (1.98 g,
49.5 mmol) in water (5 mL) at 0 °C in a sealed tube. The tube
was sealed and the reaction mixture warmed to room temper-
ature then stirred for 18 h. Water (5 mL) was added and the
+
+
6.5, 80.0, 155.9, 169.3; m/z (+FAB) 642 (MH , 18%), 585 (MH
t
-
76 5 2
Bu, 100). Anal. Calcd for C38H O N : C, 71.20; H, 11.95; N,
4
.37. Found: C, 71.51; H, 12.24; N, 4.16.
R)-(2,3-Bis-t et r a d ecyloxy-p r op yl)-N,N-d im et h yl-(2-N-
m eth yla m in o-eth yl)a m m on iu m , Iod id e (16). The amide 15
0.20 g, 0.31 mmol) was stirred in anhydrous THF at 0 °C.
LiAlH (1 M in THF, 1.25 mL, 1.25 mmol) was added dropwise
and the resulting mixture was stirred vigorously for 24 h. The
reaction was quenched by the addition of sat. aqueous NH Cl
2 mL). EtOAc (50 mL) was added and the mixture was washed
(
aqueous solution was washed with CHCl
3
(3 × 10 mL). The
and the solvent
evaporated in vacuo to give 18a (0.33 g, 91%) as a yellow oil;
[R]22
+17.1 (c 0.67, CHCl ).
(
combined organic layer was dried over MgSO
4
2
0
4
D
3
4
(
Ack n ow led gm en t. We thank the EPSRC for stu-
dentships to C.A.H. and J .B.W.
with sat. aqueous NaHCO
The organic extract was dried (Na
3
solution (50 mL) and brine (50 mL).
SO ) and concentrated in
2
4
vacuo to give (R)-[2-(2,3-tetradecyloxy-propylamino)ethyl]car-
bamic acid tert-butyl ester as an oil (0.19 g, 95%), which was
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and spectral data for compounds 1, 9, 10, 13, 18, and
intermediates toward 1 and 19, and NMR spectra for com-
pounds 10a , 11a , 12a , 16, and 19a (and intermediates). This
material is available free of charge via the Internet at
http://pubs.acs.org.
2
2
used without further purification; [R]
D
+4.6 (c 1.5, CHCl
film) 3333, 2923, 2853, 1717 cm-1; H NMR δ 0.84 (6H, t, J )
.4 Hz), 1.22 (44H, m), 1.40 (9H, s), 1.49 (4H, m), 2.62-2.70 (4H,
3
); νmax
1
(
6
1
3
m), 3.17 (2H, m), 3.34-3.58 (7H, m), 4.97 (1H, m); C NMR δ
1
4
4.0, 22.6, 26.2, 28.4, 29.3-30.2 (signal overlap), 30.3, 31.9, 40.2,
9.0, 50.8, 70.4, 71.7 (signal overlap), 72.1, 77.7, 79.0, 156.0; m/z
J O035422G
J . Org. Chem, Vol. 69, No. 3, 2004 983