Synthesis of new sugar-based surfactants and evaluation of their hemolytic activities

Article abstract of DOI:10.1021/jo051904b

The synthesis of four sugar-based surfactants derived from glucose and (R)-12-hydroxystearic acid is described. The surfactants have a hydroxy group in the hydrophobic part, which is either free or acylated using acetyl chloride, hexanoyl chloride, or myristoyl chloride. Three of the synthesized surfactants are water-soluble and are evaluated with respect to their CMCs and hemolytic activities. The fourth surfactant has limited water solubility and is not further included in the study. The investigated surfactants are all hemolytic close to their respective CMC indicating that their use in parenteral formulations may be limited. Nevertheless, surfactants having the proposed structure appear as promising alternatives to existing solubilizing agents for pharmaceutical applications.

Full text of DOI:10.1021/jo051904b

SCHEME 1. Retrosynthetic outline
Synthesis of New Sugar-Based Surfactants and
Evaluation of Their Hemolytic Activities
Kristina Neimert-Andersson,† Sven Sauer,† Olaf Panknin,†
Tessie Borg,† Erik So¨derlind,‡ and Peter Somfai*,†
KTH Chemical Science and Engineering, Organic Chemistry,
S-100 44 Stockholm, Sweden, and
AstraZeneca R&D Mo¨lndal S-431 83 Mo¨lndal, Sweden
somfai@kth.se
ReceiVed September 10, 2005
synthesis of a new class of dicephalic8 surfactants, as well as
an investigation of the hemolytic properties of these surfactants.
Recent studies of poly(ethylene oxide) surfactants of acylated
(R)-12-hydroxystearic acid have revealed exceptional properties
of these surfactants: good solubilization capacity combined with
low cell damaging activity toward erythrocytes and Caco-2 cell
monolayers.7 The surfactants 1-4 (Scheme 1) were suggested
because they have the hydrophobic part in common with this
group of surfactants and also some commercially available
surfactants intended for pharmaceutical use.9 Furthermore, the
recent interest within the pharmaceutical industry to replace the
poly(ethylene oxide) group with other hydrophilic groups,
preferably from renewable sources, led us to choose a sugar
group as the hydrophilic part.
We and others have previously reported that glucamide-type
surfactants might have limited water solubility.10-13 We rea-
soned that the solubility might be increased if the tendency of
the surfactants to crystallize could be decreased.14 Another
possible reason for poor solubility in water is an imbalance
between the hydrophobic and the hydrophilic part of the
surfactant. A large hydrophobic group needs to be balanced by
a sufficiently large water-soluble head group. To meet both of
The synthesis of four sugar-based surfactants derived from
glucose and (R)-12-hydroxystearic acid is described. The
surfactants have a hydroxy group in the hydrophobic part,
which is either free or acylated using acetyl chloride, hexa-
noyl chloride, or myristoyl chloride. Three of the synthesized
surfactants are water-soluble and are evaluated with respect
to their CMCs and hemolytic activities. The fourth surfactant
has limited water solubility and is not further included in
the study. The investigated surfactants are all hemolytic close
to their respective CMC indicating that their use in parenteral
formulations may be limited. Nevertheless, surfactants having
the proposed structure appear as promising alternatives to
existing solubilizing agents for pharmaceutical applications.
Many drug candidates suffer from low water solubility;
therefore, one of the major uses of surfactants is as solubilizers
in pharmaceutical formulations. Especially at the stage of
pharmacological evaluation, the use of surfactants as solubilizers
has great advantages compared to chemical modifications of
the drug candidate.1 Nonionic surfactants are most commonly
employed in these applications due to their generally lower
toxicity compared to anionic and cationic surfactants.1-5 Yet,
existing poly(ethylene oxide)-based surfactants for drug delivery
often suffer from other major drawbacks. Available products
consist of complex mixtures of many different components
giving rise to large batch-to-batch variations, complicated
chemical analyses, and product specification issues. Although
some of them possess low hemolytic activities,6,7 they may cause
severe side effects, among which histamine release might be
the most acute.1 Therefore, there is a need for new, nontoxic
surfactants of well-defined composition to be used in pharma-
ceutical formulations. In this paper, we wish to report the
(2) von Rybinski, W.; Hill, K. In NoVel Surfactants. Preparation,
Applications, and Biodegradability, 2nd ed.; Holmberg, K., Ed.; Marcel
Dekker: New York, 2003; Vol. 114, pp 35-93.
(3) Lawrence, M. J. Chem. Soc. ReV. 1994, 23, 417-424.
(4) Macia´n, M.; Seguer, J.; Infante, M. R.; Selve, C.; Vinardell, M. P.
Toxicology 1996, 106, 1-9.
(5) Bevinakatti, H. S.; Mishra, B. K. Annu. Surf. ReV. 1999, 2, 1-50.
(6) So¨derlind, E. PCT Int. Appl. WO 03039511, 2003.
(7) von Corswant, C.; Hult, K.; So¨derlind, E.; Viklund, F. PCT Int. Appl.
WO 2004089869, 2004.
(8) Sommerdijk, N. A. J. M.; Hoeks, T. L.; Booy, K. J.; Feiters, M. C.;
Nolte, R. J. M.; Zwanenburg, B. Chem. Commun. 1998, 743-744.
(9) Both Solutol HS15 and Cremophor EL contain mainly ethoxylated
12-hydroxystearic acid.
(10) Neimert-Andersson, K.; Blomberg, E.; Somfai, P. J. Org. Chem.
2004, 69, 3746-3752.
(11) Burczyk, B. In NoVel Surfactants. Preparation, Applications, and
Biodegradability, 2 ed.; Holmberg, K., Ed.; Marcel Dekker: New York,
2003; Vol. 114, pp 129-192.
(12) Syper, L.; Wilk, K. A.; Sokolowski, A.; Burczyk, B. Prog. Colloid
Polym. Sci. 1832, 110, 199-203.
* Corresponding author. Phone: (+46)-8-790 69 60. Fax: (+46)-8-791 23
33.
† KTH, Chemical Science and Engineering, Organic Chemistry.
‡ AstraZeneca R&D.
(13) Zhang, T.; Marchant, R. E. J. Colloid Interface Sci. 1996, 177, 419-
426.
(1) Attwood, D.; Florence, A. T. Surfactant Systems: Their chemistry,
pharmacy and biology; Chapman and Hall: London, 1983.
(14) So¨derman, O.; Johansson, I. Curr. Opin. Coll. Interface Sci. 2000,
4, 391-401.
10.1021/jo051904b CCC: $33.50 © 2006 American Chemical Society
Published on Web 03/25/2006
J. Org. Chem. 2006, 71, 3623-3626
3623

SCHEME 2. Preparation of the Surfactant Head Groupa
SCHEME 3. Synthesis of Surfactants 1-4a
a Reaction conditions: (a) (R)-12-hydroxy stearic acid, EDC, CH2Cl2,
64%; (b) acetyl chloride, pyridine, CH2Cl2, 93%; (c) hexanoyl chloride,
pyridine, CH2Cl2, 94%; (d) myristoyl chloride, pyridine, CH2Cl2, 93%; (e)
H2, Pd/C, MeOH, 98%; (f) H2, Pd/C, HOAc, MeOH, 100%.
a Reaction conditions: (a) MsCl, pyridine, 0 °C f rt, CH2Cl2, 98%; (b)
aq NH4OH, THF, 100 °C, 86%; (c) (COCl)2, DMSO, Et3N, -78 °C, 78%;
(d) Ti(OiPr)4, NaBH3CN, MeOH, 88% over two steps.
these requirements, dicephalic surfactants with a sugar-based
head group were suggested. We planned to synthesize the hydro-
philic head group A from two suitably protected monosaccha-
rides and then couple A with (R)-12-hydroxystearic acid.15 Acyl-
ation of the 12-hydroxy group and a global deprotection would
then complete the synthesis.
Synthesis of the Surfactant Head Group. Glucoside 516 was
transformed, via mesylate 6,17 into the corresponding amine 7
(Scheme 2). Reductive amination between aldehyde 8, available
from 5, with amine 7 then gave the desired amine 9 in 88%
yield.
Coupling between Head Group and Tail Group. With a
short and efficient procedure for the preparation of dimer 9,
we focused on the coupling between this head group and the
hydrophobic tail group (R)-12-hydroxy stearic acid. Although
there are several coupling reagents available for this transforma-
tion,18 our previous experiences from surfactant synthesis had
shown the importance of avoiding tedious purification steps.
Thus, the coupling reaction between 9 and fatty acid with EDC19
provided surfactant precursor 10 in good yield (Scheme 3). The
12-hydroxy group was further derivatized employing selected
acid chlorides (acetyl chloride, hexanoyl chloride, and myristoyl
chloride) to yield derivatives 11-13, respectively. Global depro-
tection of 10-13 was accomplished using catalytic hydro-
genolysis to give surfactants 1-4 in nearly quantitative yields.
Surface Chemical Evaluation. Determination of CMC. The
CMCs of surfactants 1-3 were determined using a colored
probe (Eosin Y) according to a previously published procedure.20
The aqueous solubility of surfactant 4 was limited and was,
therefore, excluded from the measurements.
FIGURE 1. Absorbance curve for surfactant 1, measured in saline.
TABLE 1. CMC for Surfactants 1-3
entry
surfactant
CMC salinea (error limits) (mM)
1
2
3
1
2
3
0.26 (0.17-0.35)
0.16 (0.12-0.4)
0.20 (0.15-0.28)
a NaCl 9 g/L.
the tangent at the inflection point, respectively. The CMC was
obtained by fitting a sigmoidal function, represented by the solid
line, to the data and calculating the intersection from the fitted
function parameters. The same procedure was carried out for
surfactants 2 and 3 (not presented), and the resulting CMCs for
surfactants 1-3 are given in Table 1 together with the corres-
ponding estimated error limits.21 The CMC was determined in
saline (NaCl 9 g/L) to provide a CMC value under physiologi-
cally relevant conditions for the comparison with the concentra-
tions at which hemolysis occurs. The CMC obtained in the
presence of electrolytes is generally lower than in pure H2O,
although this effect is only minor for sugar-based surfactants.22
Preliminary tests using pure aqueous solutions confirmed that
the electrolyte effect on the CMCs for the present surfactants
is marginal.
Figure 1 shows how the CMC of surfactant 1 dissolved in
saline was extracted from the data points. The CMC is defined
as the intersection between the two dashed lines in Figure 1,
representing the absorbance in the absence of surfactant and
(15) The enantiomeric purity of 12-hydroxy stearic acid was determined
to be >95% in analogy with the method described in: Sonnet, P. E.; Hayes,
D. J. Am. Oil Chem. Soc. 1995, 72, 1069-1071.
(16) Ishikawa, T.; Shimizu, Y.; Kudoh, T.; Saito, S. Org. Lett. 2003, 5,
3879-3882.
(17) Kobertz, W. R.; Bertozzi, C. R. J. Org. Chem. 1996, 61, 1894-
1897.
(18) Klausner, Y. S.; Bodansky, M. Synthesis 1972, 453-463.
(19) 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.
(20) Patist, A.; Bhagwat, S. S.; Penfield, K. W.; Aikens, P.; Shah, D. O.
J. Surfact. Deterg. 2000, 3, 53-58.
The CMC values obtained here are in the same range as
previously reported CMCs for dicephalic surfactants with sugar-
based head groups: 0.02-0.84 mM.11,23 Other surfactants with
the same number of glucose residues such as alkyl-â-D-mal-
(21) The limiting values were determined by setting the correlation
coefficient >0.99.
3624 J. Org. Chem., Vol. 71, No. 9, 2006

tosides (CnG2, n ) 10-14) have a wider range of CMC values
spanning the CMCs reported here.24 However, those CMCs
depend strongly on the surfactant hydrocarbon chain length.
Commonly, the CMC drops dramatically with increased
hydrocarbon chain length (typically a factor of 3 for each added
methylene carbon for nonionic surfactants); thus, it is expected
that surfactant 3 has the lowest CMC and surfactant 1 the
highest.25 However, when the number of carbon atoms in the
hydrophobic chain exceeds 16 this effect is not necessarily very
pronounced.26 Furthermore, previous studies of surfactants
derived from acylated 12-hydroxystearic acid have shown that
the CMC depends only slightly on the chain length of the acyl
group.27 Hence, it is reasonable to assume that the CMCs for
the three surfactants are within the same order of magnitude.
Although the CMCs obtained for surfactants 1-3 are in the
same range as other sugar-based dicephalic surfactants, they
are surprisingly high in comparison to the CMCs for poly-
(ethylene oxide)-based surfactants with the same hydrophobic
part (approximately 1-5 µM).27 The CMC for a sugar-based
surfactant is expected to be somewhat larger than for the poly-
(ethylene oxide) counterpart, but here the difference is unex-
pectedly large. The reason for this unexpected property is
presently unknown and requires further studies. It has previously
been shown that the size of the sugar head group does not
influence the CMC;14 thus, the bulky head group is expected to
have a minor effect on the aggregation behavior.
Hemolytic Activity. The haemolytic activity was assessed
as previously described.24 Hemolysis is believed to occur
through partitioning of the surfactant into the outer cell
membrane, followed by formation of surfactant-lipid mixed
micelles and lysis, with cell leakage as a result.28-30 Surfactant
structure is therefore believed to play an important role for the
hemolytic activity. It is commonly reported that the hemolytic
activity increases as the CMC of the surfactant decreases, the
increased hydrophobic character of the surfactant being the
reason. Others have reported that bulkier surfactants display
lower hemolytic activities compared to less bulkier ones.31 The
hemolysis curves for surfactants 1-3 are presented in Figure
2. The relative hemolytic activity of each surfactant is character-
ized by the CH50 value, i.e., the surfactant concentration that
causes 50% hemolysis. Surfactants 1 and 2 have similar
hemolytic activity with CH50 values of 0.8 and 0.7 mM,
respectively. Surfactant 3 appears slightly less hemolytic, CH50
) 1.2 mM. It was previously demonstrated that the hemolytic
activity for poly(ethylene oxide) 12-acyloxystearates decreases
when the number of carbon atoms in the acyloxy group increases
and is diminished when the number of carbon atoms exceeds
12.27 Yet, in the present case this trend is not easily seen. To
FIGURE 2. Hemolysis curves for surfactants 1-3. Percent hemolysis
curves for surfactants 1 (O), 2 (4), and 3 (0).
our knowledge, there are only a few previous studies in the
literature describing hemolytic activities of sugar surfactants.32-35
Comparing the concentrations at which compounds 1-3 cause
severe hemolysis (0.6-0.7 mM) to the hemolytic concentrations
for the previously reported sugar surfactants with similar CMCs
(1-1.5 mM),32 it is obvious that surfactants 1-3 are only
slightly more hemolytic at lower concentrations. Yet, a prereq-
uisite for solubilization is that micelles are present in the
solution. It is therefore illustrative to compare the CMC with
the concentration at which hemolysis becomes substantial for
each surfactant. Previously studied sugar surfactants with C8
or C10 alkyl groups are hemolytic already at premicellar
concentrations, which makes them less suited as solubilizers
for drug formulations. Similarly to known sugar surfactants with
C12 alkyl groups, surfactants 1-3, having CMCs in the range
of 0.12-0.4 in saline (Table 1), are hemolytic at concentrations
close to their respective CMC. Although the CMCs from Table
1 are recorded at a slightly lower temperature (24 °C) than the
hemolysis measurements (37 °C) the effect of temperature on
CMC is regarded to be of minor importance.36
To assess the usefulness of these surfactants as solubilizers
in pharmaceutical formulations, it is also important to consider
the capacity to solubilize poorly soluble substances. It was
outside the scope of the present study to investigate the
solubilization capacity. However, it has been shown in several
studies that the hydrocarbon chain length is the surfactant
property that has the strongest impact on the capacity to
solubilize substances.32,37 Having considerably larger hydro-
phobic groups than the previously studied sugar surfactants, this
class of surfactants is expected to have a higher solubilization
capacity. In solubilization studies using surfactants with the same
hydrophobic group there are strong indications that the solu-
bilization capacity of the present surfactants should be in the
same range as for commonly used surfactants such as Solutol,
(22) Jin, X.; Zhang, S.; Yang, J.; Lu, R. Tenside Surf. Det. 2004, 41,
126-129.
(23) Griffiths, P. C.; Whatton, M. L.; Abbott, R. J.; Kwan, W.; Pitt, A.
R.; Howe, A. M.; King, S. M.; Heenan, R. K. J. Colloid Interface Sci.
1999, 215, 114-123.
(24) So¨derlind, E.; Karlsson, L. Eur. J. Pharm. Biopharm. 2006, in press.
(25) Lindman, B. In Handbook of Applied Surface and Colloid Chemistry;
Holmberg, K., Ed.; Wiley: Chichester, 2002; Vol. 1, pp 421-443.
(26) Patist, A. In Handbook of Applied Surface and Colloid Chemistry;
Holmberg, K., Ed.; Wiley: Chichester, 2002; Vol. 2, p 239-249.
(27) Viklund, F. Ph.D. Thesis, Royal Institute of Technology, 2003.
(28) Jones, M. N. Int. J. Pharm. 1999, 177, 137-159.
(29) Kondo, T. AdV. Colloid Interface Sci. 1976, 6, 139-172.
(30) Shalel, S.; Streichman, S.; Marmur, A. J. Colloid Interface Sci. 2002,
255, 265-269.
(32) So¨derlind, E.; Wollbratt, M.; von Corswant, C. Int. J. Pharm. 2003,
252, 61-71.
(33) Isomaa, B.; Ha¨gerstrand, H.; Paatero, G. Biochim. Biophys. Acta
1987, 899, 93-103.
(34) Isomaa, B.; Ha¨gerstrand, H.; Paatero, G.; Engblom, A. C. Biochim.
Biophys. Acta 1986, 860, 510-524.
(35) Reinhart, T.; Bauer, K. H. Pharmazie 1995, 50, 403-407.
(36) Claesson, P. M.; Kjellin, U. R. M. In Encyclopedia of Surface and
Colloid Science; Hubbard, A. T., Ed.; Marcel Dekker: New York, 2002;
pp 4909-4925.
(31) Ohnishi, M.; Sagitani, H. J. Am. Oil Chem. Soc. 1993, 70, 679-
684.
(37) Yalkowsky, S. H. Solubilization by surfactants; Oxford University
Press: New York, 1999.
J. Org. Chem, Vol. 71, No. 9, 2006 3625

Brij, and Triton.7 In conclusion, surfactants 1-3 are equally or
less hemolytic in relation to CMC than previously reported sugar
surfactants, but they are expected to have a higher solubilization
capacity. Still the differences in hemolytic activity between the
three investigated surfactants are marginal, and the influence
of a C2-C6 acyloxy group in the hydrophobic part is not
significant. In comparison to commercially available surfactants
such as Solutol, Brij, and Triton, surfactants 1-3 are more
hemolytic, and their use in pharmaceutical formulations is
therefore limited. However, surfactants with this type of structure
appear as promising alternatives to existing solubilizing agents.
A less hemolytic surfactant with unchanged micellar properties
is desired, which may be obtained by exchanging the acyloxy
group. To compensate for the increased hydrophobicity of such
surfactants the head group structure needs to be modified, e.g.,
by introducing larger sugar groups.
69.9, 55.2, 54.6, 49.5, 47.3, 37.5, 33.2, 31.8, 29.7, 29.64, 29.59,
29.54, 29.50, 29.42, 29.37, 25.7, 25.6, 25.5, 22.6, 14.1; IR (neat)
2926, 1647, 1454, 1072, 737, 698 cm-1; [R]D +45.0 (c 1.00, CH2-
Cl2); HRMS (FAB+) calcd for C74H97NNaO12 (M + Na) 1214.6909,
found 1214.6907.
(12R)-12-Acetoxystearylbis(methyl 2,3,4-tri-O-benzyl-6-deoxy-
r-D-glucopyranoside)amine (11). To a cooled solution of alcohol
10 (150 mg, 126 µmol) in dry CH2Cl2 (10 mL) were added
successively pyridine (204 µL, 2.52 mmol) and acetyl chloride (90
µL, 1.26 mmol). After being stirred for 2 h at rt, the mixture was
quenched with HCl (0.1 M). The phases were separated, and the
aqueous phase was extracted with CH2Cl2 (2 × 7 mL). The
combined organic phases were washed with H2O and brine, dried
(MgSO4), and concentrated in vacuo. The resulting yellow vitreous
solid was subjected to flash chromatography (pentane/EtOAc 5:1
f 3:1 f 2:1) to give 11 in 93% yield (145 mg, 118 µmol) as a
colorless syrup: 1H NMR (CDCl3, 400 MHz) δ 7.19-7.35 (m,
30H) 5.01-4.54 (m, 13H), 4.47 (d, J ) 3.6 Hz, 1H), 4.45 (d, J )
3.6 Hz, 1 H), 4.02-3.99 (m, 1H), 3.96 (t, J ) 9.3 Hz, 1H), 3.95 (t,
J ) 9.2 Hz, 1H), 3.77 (td, J ) 9.8, 1.8 Hz, 1H), 3.59-3.54 (m,
2H), 3.46 (dd, J ) 9.6, 3.5 Hz, 1H), 3.43 (dd, J ) 9.6, 3.6 Hz,
1H), 3.19 (s, 3H), 3.18 (s, 3H), 3.24-3.09 (m, 4H), 2.22 (mc, 2H),
2.04 (s, 3H), 1.55-1.22 (m, 28H), 0.88 (t, J ) 6.8 Hz, 3H); 13C
NMR (CDCl3, 125 MHz) δ 173.5, 171.1, 138.8, 138.6, 138.44,
138.40, 138.2, 138.1, 128.7, 128.61, 128.58, 128.53, 128.4, 128.24,
128.22, 128.20, 128.15, 128.0, 127.9, 127.8, 127.6, 97.8, 97.7, 82.3,
81.9, 79.8, 79.7, 79.2, 77.4, 76.0, 75.9, 75.0, 74.6, 74.2, 73.5, 73.4,
71.8, 70.1, 55.3, 54.8, 49.4, 47.5, 34.31, 34.29, 33.4, 31.9, 29.79,
29.75, 29.7, 29.6, 29.4, 25.7, 25.5, 25.4, 22.7, 21.5, 14.2; IR (neat)
2960, 1732, 1649, 1090, 737, 698 cm-1; [R]D +52.5 (c 1.04, CH2-
Cl2); HRMS (FAB+) calcd for C76H99NNaO13 (M + Na) 1256.7015,
found 1256.7019.
Experimental Section
General Methods. The general experimental procedures have
been published before.10 The study was approved by the Animals
Ethics Committee of Gothenburg, ethics approval no. 120200.
Bis(methyl 2,3,4-tri-O-benzyl-6-deoxy-r-D-glucopyranoside)-
amine (9). Aldehyde 8 (1.36 g, 2.94 mmol) and amine 7 (1.36 g,
2.94 mmol) in MeOH (45 mL) was added Ti(OiPr)4 (1.75 mL, 5.88
mmol) and the mixture was stirred for 3 h at rt. NaBH3CN (278
mg, 4.41 mmol) was added to the solution, and the mixture was
stirred for 2 days at rt. The reaction was quenched by the addition
of H2O (100 mL) and diluted with Et2O (50 mL). The inorganic
precipitate was filtered off and washed thoroughly with aq NH4-
OH and Et2O. The filtrate was collected, and the phases were
separated. The organic layer was dried (Na2SO4) and concentrated
to give 9 in 88% yield (2.34 g, 2.57 mmol). An analytical sample
was purified with preparative HPLC, and the remaining material
was taken to the next step without further purification: 1H NMR
(400 MHz, CDCl3) δ 7.45-7.27 (m, 30H), 5.02 (d, J ) 10.8 Hz,
2H), 4.92 (d, J ) 11.1 Hz, 2H), 4.87 (d, J ) 10.8 Hz, 2H), 4.83
(d, J ) 12.2 Hz, 2H), 4.69 (d, J ) 12.2 Hz, 2H), 4.66 (d, J ) 11.1
Hz, 2H), 4.56 (d, J ) 3.5 Hz, 2H), 4.02 (t, J ) 9.6 Hz, 2H), 3.81-
3.73 (m, 2H), 3.50 (dd, J ) 9.6, 3.7 Hz, 2H), 3.44 (t, J ) 9.6 Hz,
2H), 3.38 (s, 6H), 2.89 (dd, J ) 12.3, 2.5 Hz, 2H), 2.75 (dd, J )
12.3, 7.1 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 138.7, 138.3,
138.2, 128.40, 128.37, 128.35, 128.03, 128.00, 127.8, 127.7, 127.6,
97.8, 82.0, 80.1, 79.6, 75.8, 75.0, 73.3, 69.9, 55.0, 50.5; IR (neat)
2914, 1454, 1360, 1072, 737, 698 cm-1; [R]D +62.3 (c 1.06, CH2-
Cl2); HRMS (FAB+) calcd for C56H63NNaO10 (M + Na) 932.4350,
found 932.4354.
(12R)-12-Hydroxystearylbis(methyl 2,3,4-tri-O-benzyl-6-deoxy-
r-D-glucopyranoside)amine (10). To a solution of amine 9 (1.05
g, 1.15 mmol) in CH2Cl2 (20 mL) were added (R)-12-hydroxystearic
acid (415 mg, 1.38 mmol) and EDC (265 mg, 1.38 mmol), and the
reaction mixture was stirred for 1 day at rt. The mixture was washed
with 2 M HCl (50 mL), H2O (2 × 50 mL), and brine, dried
(MgSO4), and concentrated in vacuo. The resulting pale yellow wax
was adsorbed on silica (CH2Cl2) and purified by flash chromatog-
raphy (pentane/EtOAc 4:1 f 2:1 f1 :1) to give 10 in 64% yield
(872 mg, 0.736 mmol): 1H NMR (CDCl3, 500 MHz) δ 7.34-7.20
(m, 30H), 5.00-4.55 (m, 12H), 4.47 (d, J ) 3.5 Hz, 1H), 4.45 (d,
J ) 3.5 Hz, 1H), 4.02-3.99 (m, 1H), 3.96 (t, J ) 9.5 Hz, 1H),
3.95 (t, J ) 9.5 Hz, 1H), 3.77 (t, J ) 9.6 Hz, 1H), 3.59-3.55 (m,
3H), 3.45 (t, J ) 10.0 Hz, 1H), 3.44 (t, J ) 10.5 Hz, 1H), 3.19 (s,
3H), 3.18 (s, 3H), 3.16-3.09 (m, 4H), 2.22 (t, J ) 7.0 Hz, 2H),
1.57-1.23 (m, 28H), 0.89 (t, J ) 6.8 Hz, 3H); 13C NMR (100
MHz, CDCl3) δ 173.3, 138.7, 138.5, 138.3, 138.2, 138.0, 137.9,
128.5, 128.44, 128.41, 128.35, 128.2, 128.07, 128.06, 128.04,
128.02, 127.98, 127.9, 127.7, 127.6 127.5, 97.6, 97.5, 82.2, 81.8,
79.7, 79.5, 79.0, 75.8, 75.7, 74.8, 74.0, 73.31, 73.25, 72.0, 71.6,
(12R)-12-Hydroxystearylbis(methyl 6-deoxy-r-D-glucopyra-
noside)amine (1). Compound 10 (1.88 g, 1.58 mmol) was dissolved
in dry MeOH (90 mL), and to this solution was added Pd/C (10 wt
%, 310 mg). The solvent was degassed at -78 °C, and a hydrogen
gas balloon was then connected to the reaction flask. After 48 h at
rt, the reaction mixture was filtered through a small plug of Florisil
to remove the catalyst, and the filtrate was concentrated. This
afforded surfactant 1 as a waxy solid in 98% yield (1.01 g, 1.55
mmol): 1H NMR (400 MHz, MeOD): δ 4.64 (d, J ) 3.5 Hz, 1H),
4.62 (d, J ) 3.8 Hz, 1H), 3.98 (d, J ) 14.4 Hz, 1H), 3.90 (dd, J )
13.7, 1.6 Hz, 1H), 3.78-3.70 (m, 1H), 3.69-3.61 (m, 3H), 3.61-
3.54 (m, 2H), 3.53-3.44 (m, 1H), 3.42-3.34 (m, 2H), 3.33 (s,
3H), 3.31 (s, 3H), 3.10 (t, J ) 9.1 Hz, 1H), 3.03 (t, J ) 9.3 Hz,
1H), 2.60-2.39 (m, 2H), 1.68-1.54 (m, 2H), 1.48-1.22 (m, 26H),
0.90 (t, J ) 6.5 Hz, 3H); 13C NMR (125 MHz, MeOD): δ 177.0,
101.0, 75.0, 74.5, 73.8, 73.5, 73.3, 72.5, 72.3, 71.8, 55.5, 55.4, 51.8,
49.8, 38.4, 34.0, 33.0, 30.8, 30.71, 30.66, 30.61, 30.51, 30.49, 30.45,
26.74, 26.71, 23.6, 14.4; IR (neat) 3367 (br), 2926, 1624, 1049
cm-1; [R]D +92.9 (c 0.51, MeOH); HRMS (FAB+) calcd for
C32H61NNaO12 (M + Na) 674.4092, found 674.4099.
Acknowledgment. The Centre for Surfactants Based on
Natural Products (SNAP) and the Swedish Research Council
are acknowledged for financial support.
Supporting Information Available: Experimental data for
compounds 2-4, 7, 8, 12, 13, determination of CMC and
1
haemolytic activity, and copies of H and 13C NMR spectra. This
material is available free of charge via the Internet at http://
pubs.acs.org.
JO051904B
(38) Bauer, K. J. Clin. Chem. Clin. Biochem. 1981, 19, 971-976.
3626 J. Org. Chem., Vol. 71, No. 9, 2006