Polyhydroxy fatty acids derived from sophorolipids

Article abstract of DOI:10.1007/s11746-007-1054-4

Starting from 17-hydroxyoleic acid, which is readily available from acid alcoholysis of sophorolipids, several new polyhydroxy fatty acids have been synthesized. These compounds contain from 2 to 4 hydroxy groups, in some instances combined with other fun

Full text of DOI:10.1007/s11746-007-1054-4

J Amer Oil Chem Soc (2007) 84:463–471
DOI 10.1007/s11746-007-1054-4
ORIGINAL PAPER
Polyhydroxy Fatty Acids Derived from Sophorolipids
Jonathan A. Zerkowski Æ Daniel K. Y. Solaiman
Received: 7 November 2006 / Accepted: 5 March 2007 / Published online: 3 April 2007
ꢀ AOCS 2007
Abstract Starting from 17-hydroxyoleic acid, which is
readily available from acid alcoholysis of sophorolipids,
several new polyhydroxy fatty acids have been synthe-
sized. These compounds contain from 2 to 4 hydroxy
groups, in some instances combined with other functional
groups. The added hydroxy groups can be incorporated in
the C18 chain in a variety of geometries, for example
spaced widely throughout the chain at C1, C8, and C17.
This regiochemical control will be of use in structure/
function studies involving materials constructed from
these hydroxy fatty acids. A further benefit is that the
hydroxy groups can be present in protected or free states.
The principal reactions used to introduce extra hydroxy
groups are selenium oxide-mediated allylic hydroxylation,
osmium-catalyzed dihydroxylation, and borohydride
reduction of a carboxylic ester. These new compounds are
expected to be of use in a number of areas, but particu-
larly as building blocks for polymers or components of
lubricant formulations.
Introduction
Hydroxylated fatty acids (HFA) are the objects of a great
deal of study due to their potential for application in a
number of technologies. On the bulk scale, these include
building blocks for polymers, especially polyurethanes
and polyesters, lubricants, and grease thickeners [1–3 and
references therein]. More specialized uses are as compo-
nents in slow-release polymers for drug delivery [4],
building blocks in biosurfactants [5], humectants [6],
solubilizers [7], and monolayers compatible with bio-
macromolecules [8]. The principal HFA that has attracted
attention over the years has been ricinoleic acid, although
lesquerolic acid has recently emerged as an alternative
[9]. Unfortunately, both of these compounds have limi-
tations. Ricinoleic acid is associated with toxic byproducts
from the castor bean source, but a different kind of lim-
itation is structural: both ricinoleic and lesquerolic acids
possess their hydroxy functional group roughly in the
middle of the alkanoic chain. This geometry is not nec-
essarily a drawback, but it does limit the range of options
in structure/function studies that can be applied during an
effort to fine-tune the properties of materials constructed
from these HFA.
Keywords Biorenewables Á Fatty alcohols Á Hydroxy
fatty acids Á Sophorolipids
Fortunately, there are other HFA that are available from
biorenewable sources. Fermentation of fats and oils by
yeasts such as Candida bombicola can provide glycolipids
in good yields. For example, sophorolipids are disaccha-
rides with a lipid chain that is hydroxylated at the x or
x – 1 positions. Isolation of this HFA is easy with acid
treatment [10]. Molecule 1 is an isomer of ricinoleic acid
that has the important advantage of possessing three sites
that can be used for chemical derivatization (carboxy,
olefin, and hydroxy) that are widely spaced throughout the
chain. This geometry should impart alternative properties
Mention of trade names or commercial products in this publication is
solely for the purpose of providing specific information and does not
imply recommendation or endorsement by the US Department of
Agriculture.
J. A. Zerkowski (&) Á D. K. Y. Solaiman
Fats, Oils and Animal Coproducts Research Unit,
US Department of Agriculture, Agricultural Research Service,
Eastern Regional Research Center, 600 East Mermaid Ln.,
Wyndmoor, PA 19038, USA
e-mail: jonathan.zerkowski@ars.usda.gov
123

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J Amer Oil Chem Soc (2007) 84:463–471
Diols 2a and 2b
to materials constructed from this chain. A polyester con-
structed from 1, for example, would not contain the six-
carbon side chain that a polymer from ricinoleic acid would
have; glass-transition temperatures, among other proper-
ties, of two such polymers should be quite different. Our
goal was to show how the abundant bioderived starting
material 1 can be altered into a number of polyhydr-
oxylated fatty acids and alcohols—diols, triols, and
tetrols—with the OH groups distributed in a range of
geometries, and in some cases with other functional groups
present that can be reacted further. The hydroxy groups
themselves can be incorporated either free or in masked
(‘‘protected’’) style, allowing for their use in a selective
fashion. This latter point represents an important difference
with HFA that are prepared through microbial routes; while
a great deal of elegant work has appeared, and regio- and
stereoselectivity are likely to be good, the tolerance of
biosynthetic pathways to bulky protecting groups might be
low, so chemical routes such as those presented here will
remain a necessary complement to microbial methods [11].
We expect that these polyfunctional compounds will find
use in a number of the technological applications listed
above, especially as polymer building blocks.
A solution of SeO2 (275 mg, 2.5 mmol) and tBuOOH
(3 mL of a 5–6 M solution in decane, 15–18 mmol) was
prepared in 10 mL CH2Cl2 at room temperature and stirred
for 20 min. To this solution was then added 1 (1.44 g,
4.6 mmol) in another 10 mL CH2Cl2. Glacial acetic acid
was added (10 lL). The reaction was allowed to proceed
for 48 h, then solvent was removed on the rotary evapo-
rator, 100 mL EtOAc was added, and extraction was per-
formed three times with Na2S2O3 solution (approx. 1 M,
100 mL each). Solvent was again removed on the rotary
evaporator, and the residue was chromatographed on silica
gel with 1:1 hexane/ethyl acetate. Diols 2a (Rf = 0.4) and
2b (Rf = 0.3) were obtained in a combined yield of 66%
(495 and 504 mg respectively); 309 mg starting material
was also recovered.
Diol 3a and Ketone 3b
Molecule 1 (1.05 g, 3.3 mmol) was dissolved in 10 mL
MeOH and 3 mL water, LiOHÁH2O (282 mg, 6.6 mmol)
was added, and the mixture was heated at 45 ꢁC for 18 h.
MeOH was removed on the rotary evaporator, 50 mL
saturated citric acid solution was added, and the resulting
suspension was extracted with 1:1 EtOAc/Et2O
(2 · 50 mL). Approximately half (0.5 g, 1.7 mmol) of the
free acid thus obtained after removal of organic solvent
was dissolved in 10 mL tetrahydrofuran (THF), and N,
N-diisopropylethylamine (DIEA) (366 lL, 2.1 mmol) fol-
lowed by benzotriazol-1-yloxytris(pyrrolidino) phospho-
nium hexafluorophosphate (PyBOP) (983 mg, 1.9 mmol)
were added. The mixture was stirred for 30 min under N2,
then NaBH4 (65 mg, 1.7 mmol) was added. After another
30 min, another portion of NaBH4 (30 mg, 0.9 mmol) was
added, and stirring was continued for another 2 h. Solvent
was removed on the rotary evaporator, and the residue was
taken up in 100 mL EtOAc and extracted with 2% HCl,
then H2O. Solvent was again removed and the crude was
chromatographed on silica gel with 1:1 hexane/ethyl ace-
tate (Rf = 0.5) to afford 3a, 203 mg [42% (75% allowing
for recovered starting material, 218 mg, 0.7 mmol)]. To
form 3b, 3a (190 mg, 0.7 mmol) was dissolved in 10 mL
CH2Cl2, and tert-butyldiphenylsilyl chloride (tBDPSCl,
182 mg, 0.7 mmol), 4-dimethylaminopyridine (DMAP,
10 mg, 0.1 mmol), and NEt3 (102 lL, 0.7 mmol) were
added. The reaction was stirred under N2 for 36 h at room
temperature, then concentrated, applied to a silica gel
column, and eluted with 3:1 hexane/ethyl acetate (Rf = 0.6)
to afford the mono-protected diol (305 mg, 87%). This
compound (280 mg, 0.5 mmol) was then dissolved in
Experimental Procedures
General
Compound 1 was prepared, as previously reported, from
sophorolipids [10], which were in turn prepared using
oleic acid and glucose as carbon sources [12]. Chemicals
and reagents were obtained commercially from Sigma-
Aldrich (St. Louis, MO) and Lancaster Synthesis (Alfa
Aesar, Ward Hill, MA). All solvents and reagents were
used as received. Silica gel used for column chroma-
tography was obtained from Fisher Scientific (Fairlawn,
NJ). NMR spectra were recorded at room temperature in
CDCl3 on either a Varian Associates (Walnut Creek, CA)
Gemini 200 MHz or Inova 400 MHz instrument; HMQC
and COSY experiments were used to aid in assignments.
LCMS data were recorded on a Waters/Micromass
(Milford, MA) ZMD instrument with APCI, using an
elution gradient of 40:60 water/acetonitrile to 100%
acetonitrile over 30 min (or minor variations on those
conditions) on a 2.1 · 150 mm Waters Symmetry C18
3.5 l column. GCMS data were collected with a Hew-
lett-Packard (Agilent, Wilmington, DE) HP 5890 instru-
ment using an HP DB-5 column (30 m · 0.25 mm
· 0.25 lm) and an HP 5972 mass detector (EI). The
heating profile was: initial temperature 80 ꢁC, hold
1 min; heat at 10 ꢁC/min to 230 ꢁC; hold 10 min. See
Table 1 for spectroscopic data.
˚
10 mL CH2Cl2, and 3-A molecular sieves and pyridinium
dichromate (PDC, 300 mg, 0.8 mmol) were added. The
123

J Amer Oil Chem Soc (2007) 84:463–471
465
Table 1 Spectra of products
Compound 13C NMRa,b
1H NMRb
Mass specc
2a
23.6(C18), 25.0(C3), (25.4, 25.8, C6, C15),
29.2 (3), 29.4, 29.5, 32.2, 34.2(C2),
37.3(C7), 39.4(C16), 51.6(Me), 68.3(C17),
73.3(C8), 132.3, 133.1(C9,10), 174.5(C1)
1.20 (d, 3H, 6.2 Hz, H18), 1.33 (br s, 16H), 351 (+ Na+), 311 (loss of H2O),
1.52–1.73 (m, 4H), 2.02 (m, 2H, H11), 2.32
(t, 2H, 7.4 Hz, H2), 3.68 (s, 3H, Me), 3.80
(m, 1H, H17), 4.04 (m, 1H, H8), 5.43 (dd,
1H, 15.8, 6.6 Hz, H9), 5.60 (m, 1H, H10)
293 (loss of 2 H2O)
2b
23.7(C18), 25.1(C3), (25.7, 25.9, C6 and C15), 1.17 (d, 3H, 6.9 Hz, H18), 1.29 (br s, 16H),
29.1, 29.3 (3), 29.7, 32.3, 34.3(C2),
37.4(C12), 39.5(C16), 51.7(Me), 68.3(C17),
73.4(C11), (132.4, 133.3, C9, C10),
174.6(C1)
1.40 – 1.63 (m, 4H), 2.00 (q, 2H, 6.7 Hz,
H8), 2.29 (t, 2H, 7.5 Hz, H2), 3.65 (s, 3H,
Me), 3.77 (m, 1H, H17), 4.01 (q, 1H,
6.6 Hz, H11), 5.42 (dd, 1H, 15.4, 7.1 Hz,
H10), 5.60 (m, 1H, H9)
3a
3b
23.7(C18), 26.0 (2, C8, C11), 27.4(C3), 29.4, 1.17 (d, 3H, 6.4 Hz, H18), 1.29 (br s, 14H), 285, 267 (loss of H2O), 249 (loss
29.5, 29.6, 29.7, 29.8, 29.9 (3), 33.0(C2),
39.6(C16), 63.3(C1), 68.4(C17), 130.1 (2,
C9,10)
1.42 (m, 4H), 1.55 (m, 4H), 2.00 (m, 4H,
H8, H11), 3.62 (t, 2H, 6.6 Hz, H1), 3.77 (m,
1H, H17), 5.34 (m, 2H, H9, H10)
of 2 H2O)
19.3(tBu-C), 23.9(C18), 25.9, 27.0 (3, tBu),
(27.2, 27.3, C8,11), 29.2 (2), 29.4, 29.5,
29.6, 29.7, 29.8, 32.7(C2), 43.9(C16),
64.1(C1), 127.7(Ar), 129.6(Ar), (129.8,
130.2, C9, C10), 134.3(Ar), 135.7(Ar),
209.4(C17)
1.08 (s, 9H, tBu), 1.30 (br s, 16H), 1.59 (m, 521, 443 (loss of C6H6), 365 (loss
4H), 2.04 (m, 4H, H8, H11), 2.15 (s, 3H,
H18), 2.44 (t, 2H, 7.5 Hz, H16), 3.68 (t, 2H,
6.5 Hz, H1), 5.38 (m, 2H, H9, H10), 7.43
(m, 6H, Ar), 7.70 (m, 4H, Ar)
of 2 C6H6)
4
23.6(C1, C18), 25.9, 27.3*, 29.2 (2), 29.3*,
29.6, 29.8*, 32.6(C8, C11), 39.4(C3, C16),
68.3(C2, C17), 130.0*, 130.4(C9, C10)
1.20 (d, 6H, 6.0 Hz, H1, H18), 1.31 (br s,
12H), 1.43 (m, 4H), 1.60 (m, 4H), 2.00 (m,
4 H, H8, H11), 3.81 (m, 2H, H2, H17), 5.40
(m, 2H, H9, H10)
285, 267 (loss of H2O), 249 (loss
of 2 H2O)
5
23.6(C18), 25.0(C3), 25.8, 26.0, 29.1, 29.2,
29.5, 29.6, 29.7 (2), 31.3 (2, C8, C11),
34.2(C2), 39.4(C16), 51.6(Me), 68.2(C17),
74.7 (2, C9, C10), 174.5(C1)
1.21 (d, 3H, 6.2 Hz, H18), 1.34 (br s, 16H), 347, 329 (loss of H2O), 311 (loss
1.45 (m, 4H), 1.55–1.8 (m, 4H), 2.33 (t, 2H,
7.6 Hz, H2), 3.62 (m, 2H, H9, H10), 3.69 (s,
3H, Me), 3.82 (m, 1H, H17)
of 2 H2O), 293 (loss of 3 H2O)
5b
20.1(C18), 25.1(C3), 25.4, 26.2 (2), 29.2, 29.4, 1.26 (d, 3H, 6.2 Hz, H18), 1.30 (br s, 16H), 437, 419 (loss of H2O), 311 (loss
29.5, 29.6, 29.7, 31.4 (2, C8, C11),
1.40 (m, 4H), 1.49 (m, 2H), 1.60 (m, 2H),
2.29 (t, 2H, 7.5 Hz, H2), 3.56 (m, 2H, H9,
H10), 3.65 (s, 3H, Me), 4.75 (hex, 1H,
6.4 Hz, H17), 5.13 (s, 2H, Bn), 7.35 (m, 5H,
Ar)
of 2 H2O and C7H6)
34.3(C2), 36.0(C16), 51.7(Me), 69.5(C17),
74.9 (2, C9, C10), 75.8(Bn), (128.5 (2),
128.6, 128.9 (2), 135.6, 6 Ar), 174.6(C1)
6
19.4(tBu-C), 23.3, 24.9, 25.3, 25.8(C3), 27.2 1.09 (br s, 21H, tBu, H18), 1.11–1.36 (m,
800 (+ Na+), 760 (loss of H2O),
559 (+ Na+, loss of tBDPS)
(3, tBu), 29.2, 29.4, 29.6, 32.2, 32.9(C2),
38.2(C7), 39.6(C16), 63.2(C1), 69.7(C17),
74.8(C8), 127.5(Ar), (129.5, 131.3, C9,
C10), 132.9(Ar-C), 134.7(Ar), 136.0(Ar)
18H), 1.36–1.63 (m, 4H), 1.84 (m, 2H,
H11), 3.64 (t, 2H, 6.6 Hz, H1), 3.85 (m, 1H,
H17), 4.08 (m, 1H, H8), 5.16–5.46 (m, 2H,
H9, H10), 7.31–7.46 (m, 12 H, Ar), 7.65–
7.74 (m, 8H, Ar)
9a
9b
17.8(C18), 25.0(C3), 25.6, 26.1, 26.3 (2, acet), 1.34 (br s, 14H), 1.38–1.67 (m, 6H), 1.42 (s, 385, 367 (loss of H2O), 327 (loss
28.8, 29.2, 29.3, 29.6, 29.7 (2), 34.2(C2),
37.2(C14), 51.6(Me), 73.1(C15), 78.1 (2,
C9, C10), 107.4(acet), 126.9(C17),
134.4(C16), 174.4(C1)
6H, acet), 1.71 (d, 3H, 6.2 Hz, H18), 2.32 (t,
2H, 7.2 Hz, H2), 3.68 (s, 3H, Me), 3.96–
4.11 (m, 3H, H9, H10, H15), 5.48 (ddt, 1H,
15.4, 6.9, 1.5 Hz, H16), 5.67 (dq, 1H, 15.4,
6.2 Hz, H17)
of H2O and acetonide), 309 (loss
of 2 H2O, acetonide), 291
25.0(C3), 25.3, 26.1, 26.3 (2, acet), 28.8, 29.2, 1.35 (br s, 16H), 1.44 (s, 6H, acet), 1.47–1.74
29.3, 29.6, 29.7 (3), 34.2(C2), 37.0(C15),
51.6(Me), 73.3(C16), 78.1 (2)(C9, C10),
107.4(acet), 114.7(C18), 141.4(C17),
174.4(C1)
(m, 6H), 2.32 (t, 2H, 7.3 Hz, H2), 3.69 (s,
3H, Me), 4.03 (m, 2H, H9, H10), 4.13 (m,
1H, H16), 5.12 (dt, 1H, 10.2, 1.4 Hz, H18
cis to H17), 5.24 (dt, 1H, 17.2, 1.4 Hz, H18
trans to H17), 5.89 (ddd, 1H, 17.2, 10.3,
6.2 Hz, H17)
9c
25.0(C3), 26.1, 26.3 (2, acet), 28.8, 29.1, 29.2, 1.36 (br s, 16H), 1.44 (s, 6H, acet), 1.48–1.68
29.3, 29.6, 29.7 (3), 32.2(C15), 34.2(C2),
51.6(Me), 64.0(C18), 78.1 (2, C9, C10),
107.4(acet), 129.1(C17), 133.5(C16),
174.4(C1)
(m, 4H), 2.07 (m, 2H, H15), 2.32 (t, 2H,
7.4 Hz, H2), 3.69 (s, 3H, Me), 4.05 (m, 2H,
H9, H10), 4.11 (d, 2H, 6.4 Hz, H18), 5.68
(m, 2H, H16, H17)
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J Amer Oil Chem Soc (2007) 84:463–471
Table 1 continued
Compound 13C NMRa,b
1H NMRb
Mass specc
10a
10b
12
20.2(C18), 21.3(Ac), 21.6(Ac), 25.1, 25.5 (2), 1.18 (d, 3H, 6.2 Hz, H18), 1.30 (br s, 14 H), 429 (loss of H2O), 387 (loss of
26.1, 29.2, 29.4(2), 29.6, 30.9, 33.1(C2),
34.3(C8), 36.0(C16), 51.7(Me), 69.6,
71.2(C9, C17), 74.5, 75.0(C10, C11),
(171.1, 172.5, Ac), 174.6(C1)
1.41–1.52 (m, 4H), 1.52–1.66 (m, 4H), 2.01
(s, 3H, Ac), 2.10 (s, 3H, Ac), 2.29 (t, 2H,
7.5 Hz, H2), 3.27 (m, 1H, H10), 3.45 (m,
1H, H9), 3.65 (s, 3H, Me), 4.74 (m, 1H,
H11), 4.87 (hex, 1H, 6.2 Hz, H17)
CH3CO2H), 369 (loss of
CH3CO2H and 2 H2O), 309
(loss of 2 CH3CO2H and 2 H2O)
20.2(C18), 21.4(Ac), 21.6(Ac), 25.1, 25.5(2), 1.19 (d, 3H, 6.5 Hz, H18), 1.28 (br s, 14H),
25.6, 29.2(2), 29.5(2), 31.1, 33.8(C2),
34.3(C8), 36.0(C16), 51.7(Me), (71.2, 72.0,
C9, C17), (75.0, 75.2, C10, C11), (171.1,
171.4, Ac), 174.6(C1)
1.42 (m, 4H), 1.60 (m, 4H), 2.03 (s, 3H,
Ac), 2.08 (s, 3H, Ac), 2.29 (t, 2H, 7.4 Hz,
H2), 3.38 (t, 1H, 5.2 Hz, H10), 3.53 (m, 1H,
H9), 3.66 (s, 3H, Me), 4.87 (hex, 1H,
6.2 Hz, H17), 4.99 (m, 1H, H11)
19.4(tBu-C), 23.3(C18), 25.3, 25.8, 26.2, 26.3 1.08 (br s, 12H, tBu, H18), 1.38 (br s, 20 H), 598, 580 (loss of H2O), 503 (loss
(2, acet), 27.1 (3, tBu), 28.8, 29.5, 29.6 (2),
29.8 (m), 32.9(C2), 39.5(C16), 63.2(C1),
69.7(C17), 78.2 (2, C9, C10), 107.4(acet),
127.5(Ar), 129.5(Ar-C), 134.7(Ar),
136.0(Ar)
1.46 (s, 6H, acet), 1.60 (m, 6H), 3.66 (t, 2H,
6.6 Hz, H1), 3.84 (hex, 1H, 5.6 Hz, H17),
4.03 (m, 2H, H9, H10), 7.38 (m, 6H, Ar),
7.70 (m, 4H, Ar)
of C6H5 + H2O), 461 (loss of
C6H5, H2O, and acetonide), 383
(loss of 2 C6H5, H2O, and
acetonide)
13a
13b
13c
a
19.6(C18), 25.0(C3), 25.6, 26.1, 26.2 (2, acet), 1.15 (d, 3H, 6.2 Hz, H18), 1.28 (br s, 16H), 403, 385 (loss of H2O), 367 (loss
28.7, 29.1, 29.2, 29.5, 29.7 (3), 33.3(C2),
34.1(C15), 51.5(Me), 70.9(C17), 76.1(C16),
78.1 (2, C9, C10), 107.4(acet), 174.5(C1)
1.39 (s, 6H, acet), 1.41–1.69 (m, 6H), 2.28
(t, 2H, 7.4 Hz, H2), 3.30 (m, 1H, H16 or
H17), 3.54 (m, 1H, H16 or H17), 3.64 (s,
3H, Me), 3.98 (m, 2H, H9, H10)
of 2 H2O), 345 (loss of H2O and
acetonide), 327 (loss of 2 H2O
and acetonide)
25.1(C3), 25.7, 26.2 (2, acet), 26.4, 28.9, 29.3, 1.29 (br s, 18H), 1.39 (s, 6H, acet), 1.45 (m,
29.4, 29.7 (2), 29.8 (3), 33.4(C2),
34.3(C16), 51.7(Me), 67.0(C18), 72.5(C17),
78.2 (2, C9, C10), 107.5(acet), 174.6(C1)
4H), 1.58 (m, 2H), 2.28 (t, 2H, 7.4 Hz, H2),
3.41 (dd, 1H, 11.0, 7.5 Hz, H18), 3.60–3.72
(m, 2H, H17, H18), 3.65 (s, 3H, Me), 3.99
(m, 2H, H9, H10)
16.9(C18), 25.1(C3), 25.7, 26.3, 26.4 (2, acet), 1.20 (d, 3H, 6.5 Hz, H18), 1.30 (br s, 16H),
28.9, 29.3, 29.4, 29.7, 29.8 (2), 31.9,
33.5(C2), 34.3(C15), 51.7(Me), 71.1(C17),
75.1(C16), 78.2 (2, C9, C10), 107.5(acet),
174.6(C1).
1.40–1.71 (m, 6H), 1.42 (s, 6H, acet), 2.31
(t, 2H, 7.3 Hz, H2), 3.55–3.72 (m, 2H, H16,
H17), 3.67 (s, 3H, Me), 4.02 (m, 2H, H9,
H10)
In carbon spectra, numbers in parentheses indicate the number of peaks that are closely overlapped at the indicated chemical shift; ‘‘m’’
indicates a larger number of peaks that cannot be distinguished. Overlapped peaks in the aromatic units of tBDPS are not enumerated. Asterisks
indicate minor peaks from the cis isomer
b
Me = methyl ester; acet = acetonide; Ac = acetyl group; Ar = aromatic; Bn = CH2 of benzyl. ‘‘Hn’’ indicates protons attached to Carbon n
c
Unless otherwise indicated, the first peak listed is MH+. Blank entries indicate that the peaks are the same as observed for the preceding isomer,
with only minor differences in relative intensities
slurry was stirred under N2 at room temperature, with a
CaSO4 drying tube affixed to the flask. After 18 h, TLC
showed that no starting material remained, so the slurry
was filtered through celite, concentrated on the rotary
evaporator, and chromatographed on silica gel with 3:1
hexane/ethyl acetate (Rf = 0.8) to yield ketone 3b (256 mg,
92%).
sieves. The catalyst (benzylidene-bis(tricyclohexylphos-
phine)dichlororuthenium, ‘‘Grubbs’ 1st-generation cata-
lyst’’, 60 mg) was added, dissolving immediately to give a
purple solution. The solution was refluxed for 90 min, over
the course of which the color changed from purple to
brownish. After the mixture cooled to RT, the solvent was
removed under a gentle N2 stream, then the residue was
taken up in 3:1 hexane/ethyl acetate and chromatographed
on a silica gel column. Diol 4 was obtained in 89% theo-
retical yield (63 mg, 0.2 mmol, Rf = 0.3), allowing for the
production of other metathesis products at equilibrium,
since 1 mol of nonsymmetrical olefin A:B can only give
0.25 mol A:A (such as compound 4), 0.5 mol A:B, and
0.25 mol B:B.
Diol 4
Compound 1 (314 mg, 1.0 mmol) was dissolved in 10 mL
˚
CH2Cl2 that had been dried over activated 3-A molecular
sieves, and the solution was stirred under N2 in a round
bottom flask fitted with a drying tube filled with CaSO4 and
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J Amer Oil Chem Soc (2007) 84:463–471
Triol 5
467
filtrate was evaporated, then applied to a silica gel column
and eluted with 4:1 hexane/ethyl acetate to give molecule
7, 0.95 g, 91% (Rf = 0.8).
To a suspension of 1 (1.7 g, 5.4 mmol) in 50 mL 1:1 water/
tBuOH at 0 ꢁC was added methanesulfonamide (530 mg,
5.6 mmol) and AD-mix-a reagent (commercially available
from Aldrich, a mixture of chiral ligand and osmium oxi-
dant, 6.5 g). The mixture was stirred overnight and allowed
to warm to room temperature, then solid Na2S2O3 (approx
2.5 g) was added until the color changed from yellow to
tan. The reaction was extracted with EtOAc (2 · 75 mL)
and CHCl3 (2 · 75 mL), the organic layers combined and
concentrated to dryness on the rotary evaporator, and the
residue was chromatographed on silica gel in ethyl acetate
to yield 5 (1.79 g, 96%, Rf = 0.5).
Bromide 7 (675 mg, 1.5 mmol) was dissolved in 3 mL
toluene and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)
(330 lL, 2.3 mmol) was added. A CaSO4 drying tube was
attached to the flask, and the mixture was heated under N2 at
60–65 ꢁC for 24 h, then another 100 lL DBU was added
and heating was continued for a further 48 h. Solvent was
removed on the rotary evaporator, and the residue was
chromatographed on silica with 4:1 hexane/diethyl ether to
afford 8 (363 mg, 66%, Rf = 0.6) and unreacted 7 (93 mg,
0.21 mmol). For the final step, a procedure analogous to
that used for preparation of 2 was followed, with molecule 8
(220 mg, 0.6 mmol), SeO2 (34 mg, 0.3 mmol), and tBu-
OOH (0.24 mL of a 5–6 M solution in decane) in 10 mL
CH2Cl2. Careful chromatography on silica gel with either
2:1 hexane/ethyl acetate or 5% MeOH in CHCl3
(Rf’s = 0.4, 0.35, 0.3 in both solvent systems) afforded
three products 9b, a, and c (24, 78, and 19 mg, respectively,
see ‘‘Results and Discussion’’ for structures) for a total
yield of 53% as well as unreacted 8 (76 mg, 0.21 mmol).
Triol 6
Diol 2a (200 mg, 0.6 mmol) was dissolved in 5 mL pyri-
dine, and tBDPSCl (419 mg, 1.5 mmol), DMAP (43 mg,
0.4 mmol), and imidazole (48 mg, 0.7 mmol) were added.
The reaction was heated to 50–55 ꢁC for 48 h. TLC showed
no remaining starting material. Solvent was removed on the
rotary evaporator, and the residue was applied to a short
silica gel column and eluted with 3:1 hexane/ethyl acetate
(Rf = 0.9) to give the doubly-protected ester (450 mg,
93%). A portion of this material (220 mg, 0.3 mmol) was
hydrolyzed with LiOHÁH2O as for 3a. The resulting free
acid (140 mg, 0.2 mmol) was dissolved in 10 mL THF,
then DIEA (37 lL, 0.2 mmol) and PyBOP (103 mg,
0.2 mmol) were added. After 30 min, NaBH4 (11 mg,
0.3 mmol) was added, followed by the same amount after
another 30 min. Workup was the same as for 3a, with
chromatography in 2:1 hexane/ethyl acetate yielding
91 mg, 65% (Rf = 0.5) from the free acid, 40% from 2a.
Tetrol 10
Diol 2b (310 mg, 1.0 mmol) was dissolved in 5 mL pyri-
dine, and DMAP (45 mg, 0.4 mmol) and acetic anhydride
(Ac2O, 1.5 mL) were added. The reaction was stirred under
N2 at room temperature. After a few minutes, a yellow
color developed. The reaction continued for 3 h, at which
point TLC showed no starting material, so the solvent was
removed on the rotary evaporator, and the crude mixture
was dried under a nitrogen stream for 2 h, then placed on
the vacuum line overnight. It was then dissolved in 10 mL
1:1 H2O/tBuOH, and methanesulfonamide (100 mg) and
AD-mix-a (1.4 g) were added. The reaction was stirred for
24 h and worked up as for compound 5 above. Silica gel
chromatography in 1:1 hexane/ethyl acetate afforded two
closely eluting spots (Rf’s = 0.3 and 0.2) 10a (197 mg) and
10b (174 mg) for a total yield of 88%.
Triol 9
Triol 5 (1.35 g, 3.9 mmol) was suspended in 7 mL 2,2-
dimethoxypropane and 15 mL CH2Cl2. On the addition of
pyridinium p-toluenesulfonate (PPTS) (230 mg, 0.9 mmol)
all the suspended material dissolved in less than a minute.
The reaction was stirred under N2 at RT for 20 h, the
solvent was removed on the rotary evaporator, and the
residue chromatographed on silica gel with 3:1 hexane/
ethyl acetate to yield 1.41 g, 94% (Rf = 0.3). This 17-hy-
droxy 9,10-acetonide (0.91 g, 2.4 mmol) and triphenyl-
phosphine (1.24 g, 4.7 mmol) were dissolved in 50 mL
1,2-dichloroethane, then a solution of 1,2-dibromotetra-
chloroethane (1.54 g, 4.7 mmol) and triethylamine
(1.31 mL, 9.2 mmol) in 3 mL 1,2-dichloroethane was ad-
ded. The reaction was stirred at room temperature under N2
for 30 min, then filtered through a glass frit. The precipitate
was washed twice with 2 mL of 1,2-dichloroethane. The
Tetrol 12
Compound 1 (1.2 g, 3.8 mmol) was converted to its tBDPS
ether as for 3b and 6. After workup, silica gel chroma-
tography with 3:1 hexane/ethyl acetate afforded 1.72 g
tBDPS-protected 1 (3.2 mmol, 84 %, Rf = 0.9). This
compound was hydrolyzed with LiOHÁH2O as for 3a, and
after workup was chromatographed in 9:1 CHCl3/MeOH to
afford 1.1 g (2.0 mmol) free acid (Rf = 0.4). A portion of
this material (823 mg, 1.5 mmol) was dissolved in 20 mL
THF, and DIEA (320 lL, 1.8 mmol), N,N-diisopropylcar-
bodiimide (DIC, 263 lL, 1.7 mmol), and 1-hydrox-
123

468
J Amer Oil Chem Soc (2007) 84:463–471
ybenzotriazole hydrate (HOBt, 257 mg, 1.7 mmol) were
added. After 10 min, NaBH4 (120 mg, 3.2 mmol) was
added. After another 30 min, the same amount of NaBH4
was added again. The mixture was stirred for a further 2 h,
after which it was concentrated on the rotary evaporator,
stirred with concentrated citric acid solution (caution: gas
evolution), and extracted with 100 mL EtOAc. Column
chromatography on silica gel with 2:1 hexane/ethyl acetate
(Rf = 0.8) yielded 11 (262 mg, 33% from the tBDPS free
acid (57% allowing for recovered starting material 347 mg,
0.7 mmol), or 17% from 1).
allylic hydroxylation with selenium dioxide and t-butyl
hydroperoxide [13]. This route gave two isomers in equal
amounts as expected, the C8,C17 and the C11,C17 diols,
which could be separated from each other by column
chromatography on silica gel. Their identity was deter-
mined by mass spectrometry of fragments resulting from
oxidative cleavage with KMnO4/NaIO4. With LCMS,
mono-methyl nonanedioate was observed only in the
cleavage products from molecule 2b, and hydroxynonanoic
acid from 2a. Portions of the crude cleavage products were
also dissolved in methanol and treated with EDC and
DMAP to form the methyl esters, which were analyzed by
GCMS, showing dimethyl nonanedioate for 2b and methyl
hydroxynonanoate from 2a. Although in our hands this
allylic hydroxylation route always left some starting
material unreacted, it gave reasonable yields and was
straightforward, and the possibility of separating the two
resulting diol isomers may be useful.
Monoprotected diol 11 (150 mg, 0.3 mmol), AD-mix-a
(406 mg) and methanesulfonamide (27 mg, 0.3 mmol)
were combined in 10 mL 1:1 tBuOH/H2O and worked up
as for 5 above, then purified by column chromatography in
ethyl acetate to give the singly-protected tetrol (151 mg,
94%, Rf = 0.6). A portion of this material (50 mg,
0.1 mmol) was reacted with 1 mL 2,2-dimethoxypropane
and 25 mg PPTS in 5 mL CH2Cl2 to give triprotected tetrol
12 after chromatography in 2:1 hexane/ethyl acetate
(44 mg, 83%, Rf = 0.6).
Concerning these compounds, as well as most of the
ones which follow, a note about stereochemistry is war-
ranted. Compound 1 is chiral, with L configuration [12, 14,
and references therein]. The added hydroxy groups at C8
and C11 in 2a and 2b are not introduced stereoselectively,
so diastereomers are created. Separation of these diastere-
omers could well be difficult, requiring extensive HPLC
usage, and we have not attempted to do so. NMR spectra of
these compounds do not appear to be made more compli-
cated by the existence of the compounds as diastereomers.
We propose that this is because the chiral centers are
widely spaced, from the chain midsection to near its end,
and the flexibility of the methylene chain precludes favored
or fixed conformations of one diastereomer versus another.
Regioisomers, on the other hand, such as 2a and 2b and
others below, have been separated.
Tetrol 13
Molecule 8 (200 mg, 0.5 mmol) was reacted with 0.8 g
AD-mix-a and 50 mg methanesulfonamide and worked up
as for 5 to afford the tetrol. TLC in 9:1 CHCl3/MeOH
indicated one principal product and two minor ones, which
could be separated from each other by chromatography on
silica gel (13a, b, and c Rf’s = 0.5, 0.45, 0.4) for yields of
116, 47, and 26 mg (88% total).
Results and Discussion
The second route converted the carboxylic unit of 1 to a
primary alcohol by reduction of an activated ester formed
in situ [15]. Other methods such as using LiAlH4 for
reduction of a methyl ester may be feasible, but we sought
milder and easier-to-handle reagents that would be com-
Synthesis of Diols
Three methods were used to introduce a second hydroxy
group to the skeleton of 1 (Fig. 1). The first was to perform
O
Fig. 1 Synthetic routes used to
convert molecule 1 into
dihydroxy compounds. See text
for abbreviations
O
MeO
SeO
2
MeO
OH
OH
combined yield 66%
2a
2b
OH
1
tBuOOH
O
+
MeO
OH
OH
1) LiOH,
MeOH/H O
2
2) PyBOP,
DIEA, THF
HO
3) NaBH
4
Grubbs' 1st-gen
catalyst
3a
OH
O
42%
1) tBDPSCl,
DMAP, NEt
2) PDC, mol sieves
OH
4
3
tBDPS-O
89%
OH
3b
80%
123

J Amer Oil Chem Soc (2007) 84:463–471
469
Fig. 2 Synthetic routes used to
obtain trihydroxy compounds.
See text for abbreviations
O
OH
OR
5a: R = H
5b: R = Bn
(via 1 + BnBr, Ag O)
AD-mix-α
MeSO NH
1
MeO
2
2
2
5
OH
96%
1) tBDPSCl, DMAP, imidazole
2) LiOH, MeOH/H O
2
HO
2a
O-tBDPS
O-tBDPS
3) PyBOP, DIEA, THF
6
40% overall
4) NaBH
4
Br
1) 2,2-dimethoxypropane, PPTS
2) BrCl C Cl Br,
DBU, Δ
5
7
H CO
3
2
2
2
O
PPh , DIEA
3
O
O
86%, 2 steps
SeO
2
9b =
OH
tBuOOH
H CO
OH
R
8
combined
yield 53%
H CO
3
OH
3
O
O
O
O
O
9c =
O
9a
66%
R
Synthesis of Triols
patible with other functional groups in the molecule. Using
the protocols outlined in Ref. [15], for example, reduction
of a carboxylic acid (as its activated ester) in the presence
of an alkyl ester is possible. The reagent used to form an
HOBt ester, PyBOP, is not cheap, but the conversion to the
primary alcohol was conveniently performed with NaBH4.
The alkene was not reduced, and the 17-OH did not need to
be protected. To give an example of the kind of further
manipulations that can be performed with a diol like 3a, we
selectively protected the primary alcohol as a tBDPS ether
and oxidized the secondary alcohol to a ketone. By analogy
with some polyhydroxylated fatty acids that have been
produced microbially, a ketone of this sort could be a
useful intermediate in studying the formation of bicyclic
compounds that may have anti-cancer activity [16, 17].
Had the 17-OH been protected prior to reduction, the
opposite pattern of monoprotection of the diol could have
been obtained (as it was for the preparation of 6 and 12,
below). The third route to a diol was olefin metathesis of 1
using Grubbs’ first generation catalyst [18]. This route af-
fords a mixture of trans and cis isomers in the ratio of
about 5:1 as determined by both LCMS and NMR. The
other possible metathesis products—dimethyl 1,18 octa-9-
decenoate and the ‘‘reconstituted’’ HFA methyl ester
1—are also obtained, but are easily separated from the diol
by column chromatography. In fact, this method can be
thought of as an alternative ‘‘elaidization’’ route for 1 that
avoids toxic selenium or thiophenol. While 3 and 4 are
structurally similar in that their hydroxy groups are at the
far ends of the chain from each other, it is worth noting that
the primary hydroxy group of 3 can be chemoselectively
derivatized.
Several strategic options exist for introducing two new
hydroxy groups to 1 in a variety of geometries (Fig. 2).
The simplest is to use a dihydroxylation catalyst. We
chose to work with Sharpless’ asymmetric dihydroxyla-
tion (AD) reagents for ease, since the conditions are mild
and the materials are conveniently commercially avail-
able [19]. The asymmetric aspect is not of course par-
ticularly relevant to oleic acid derivatives, since cis
olefins are known to give poor stereoselectivity [19, 20].
Enantioenriched 9,10-dihydroxystearates have however
been obtained from methyl oleate through HPLC sepa-
ration of diastereomers formed with chiral auxiliaries
after osmium-catalyzed dihydroxylation [20]. Molecule
5a was produced in essentially quantitative yield. The
C17-OH does not need to be protected, but we have also
performed the reaction on the C17 benzyl ether (giving
5b).
Another likely strategy is to combine the individual
steps that were used for production of diols. For example,
we intended to subject the allylicly hydroxylated 2a to the
reduction conditions used to produce 3. Protection of both
hydroxy groups of 2a seemed judicious, however, since the
possibility for cyclization existed if either the C8 or C17
groups were to intramolecularly react with the HOBt ester.
Intermolecular esterification was also a possibility. The bis-
tBDPS ether was prepared, then hydrolyzed to the free
carboxylic acid, and reduced to give doubly-protected
primary alcohol 6.
Finally, more elaborate multistep schemes can be em-
ployed to generate triols with added functionality. A key
123

470
J Amer Oil Chem Soc (2007) 84:463–471
Fig. 3 Synthetic routes used to
obtain tetrahydroxy compounds.
See text for abbreviations
O
OH OAc
OH
OAc
1) Ac O, DMAP
2
2b
MeO
2) AD-mix-α, MeSO NH
2
2
10
88%
1) tBDPSCl, DMAP, imidazole
2) LiOH, MeOH/H O
2
HO
1
OtBDPS
11
3) DIC, HOBt, DIEA, THF
17% overall
4) NaBH
4
O
O
1) AD-mix-α, MeSO NH
2
2
HO
2) 2,2-dimethoxypropane, PPTS
12
OtBDPS
78%, 2 steps
O
O
O
HO
OH
AD-mix-α, MeSO NH
2
2
MeO
8
13a, plus 2 isomers
88% combined
Synthesis of Tetrols
motivation was to attain the ability to place hydroxy
groups widely spaced throughout the molecule. Molecule
5a was protected as the acetonide, then converted to the
C17 bromide. Elimination with strong base DBU gave the
olefin in several isomeric forms: GCMS showed three
closely eluting peaks, one major and two minor, all with
correct mass for 8, and NMR of the crude mixture indi-
cated the presence of terminal alkene. We propose that 8
is formed predominantly as trans x – 1 alkene along with
some cis x – 1 and terminal isomers, although they could
not be preparatively separated with column chromatog-
raphy. However, when olefin 8 was hydroxylated with
selenium dioxide as in the preparation of 2, three isomeric
products were obtained in the ratio of 64:20:16, and this
time they could be separated on silica gel and identified
by NMR. In accord with our proposal about 8, the
major product 9a was the trans x – 1 C15-OH product.
Its identity was determined based on 1H-1H coupling
(JH16/H17 = 15.4 Hz), but in addition the calculated value
of the chemical shift for C18 (17.3 ppm from ChemDraw
version 5.0) agrees with the observed (17.8 ppm), while
that calculated for the cis version is 11.3 ppm. The
x-olefin C16-OH (9b) and the trans x – 1 olefin C18-OH
(9c) were minor products. The former is clearly identified
by its terminal alkene pattern in 1H NMR, and the latter
by its lack of a terminal methyl group. The trans ste-
reochemistry of 9c is harder to be sure about, but again
calculated 13C chemical shifts agree better with trans
(C15: 33.3 ppm, observed 32.2) than with cis (C15:
calculated 27.3). We cannot explain why no cis isomers
were observed in the product distribution of 9, except to
suggest that since cis 8 was present in minor relative
amounts, derivatives of it would afford only trace amounts
that could not be observed on the scale we used.
Combining the individual steps used to prepare diols and
triols is again a productive strategy for obtaining higher
hydroxylated molecules (Fig. 3). AD was relied upon
heavily since it efficiently introduces two hydroxy groups.
Diol 2b was diprotected as the acetate, then subjected to
AD conditions to give 10. Two isomers were isolated in
roughly 1:1 ratio (53:47). There should of course be several
diastereomers of 10, since the stereocenter at C11 could
exist in either configuration, and stereoselectivity of the
AD reagent at the cis olefin will be poor. We tentatively
propose that the two isomers obtained could be one with an
all-syn arrangement of the oxygens at C9, C10, and C11,
and another with C9 and C10 oxygens anti to the one at
C11. In any case, the existence of these polyhydroxy
compounds as a mixture of stereoisomers should not be
deleterious in most polymer or materials applications.
For the next tetrol, borohydride reduction of the HOBt
ester derived from 1 was performed after first protecting
the C17 hydroxy group with a silyl group. For this example
of the reduction, the HOBt ester was prepared without the
more expensive PyBOP reagent by using a carbodiimide
and HOBt. Yields were not as good as with the PyBOP
reagent. This diol was then subjected to AD conditions, and
finally protected as the acetonide to give 12. The olefinic
diol 8 is also a useful starting point; AD gives the tetrol 13.
As with the preparation of 9, hydroxylation allows sepa-
ration of the isomers, in a ratio of 61:25:14. The predom-
inant isomer 13a is the C16/C17 diol, and by analogy with
our analysis of the isomers of compound 9, since this is the
major isomer we assume it to be trans. The second in
abundance, 13b, is the C17/C18 diol arising from the ter-
minal alkene component of 8, identified by the presence of
123

J Amer Oil Chem Soc (2007) 84:463–471
471
¨
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8. Overs M, Hoffmann F, Schafer HJ, Huhnerfuss H (2000) Infrared
reflection–absorption spectroscopy of racemic and enantioen-
riched methyl 17,18-dihydroxyoctadecanoate at the air–water
interface. Langmuir 16:6995–6998
five CH–O protons (C9, C10, C17, and two on C18), the
absence of a terminal CH3 group, and the peak at 67 ppm
for C18. The least abundant isomer 13c is also a C16/C17
diol, based on NMR data, and we propose that it arose from
the cis alkene, although detailed NMR experiments to
ascertain stereochemistry have not been performed.
9. Narine SS, Kong X (2005), Vegetable oils in production of
polymers and plastics. In: Shahidi F (ed) Bailey’s industrial oil
and fat products, vol 6, 6th edn. Wiley, New Jersey, pp 279–306
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acid. J Am Oil Chem Soc 83:621–628
Acknowledgments We gratefully acknowledge the technical
assistance of Mr. Bun-Hong Lai (chromatography and fermentations),
Mr. Marshall Reed (microbiology), and Dr. Gary Strahan (NMR).
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