Synthetic epoxy-mycolic acids

Article abstract of DOI:10.1016/j.tet.2014.06.089

We report the synthesis of single enantiomers of epoxy-mycolic acids containing an α-methyl-trans-alkene or a cis-cyclopropane with structures that match those of major isomers of such molecules present in complex mixtures in Mycobacteria such as Mycobact

Full text of DOI:10.1016/j.tet.2014.06.089

Tetrahedron 70 (2014) 7322e7335
Contents lists available at ScienceDirect
Tetrahedron
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Synthetic epoxy-mycolic acids
*
Dakhil Z. Al Kremawi, Juma’a R. Al Dulayymi, Mark S. Baird
School of Chemistry, Bangor University, Gwynedd LL57 2UW, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
We report the synthesis of single enantiomers of epoxy-mycolic acids containing an
a-methyl-trans-
Received 30 April 2014
Received in revised form 12 June 2014
Accepted 20 June 2014
alkene or a cis-cyclopropane with structures that match those of major isomers of such molecules
present in complex mixtures in Mycobacteria such as Mycobacterium fortuitum or Mycobacterium
smegmatis
Available online 2 July 2014
Ó 2014 Elsevier Ltd. All rights reserved.
Keywords:
Mycolic acid
Environmental
Mycobacteria
Epoxy
1. Introduction
often a cyclopropane or an alkene and the distal group is a cyclo-
propane (
a
-MA), an
b
a
-methoxy-
b
-methyl fragment (methoxy-MA)
Mycolic acids (MAs), 1 (Fig. 1), are major constituents of the cell
envelope of Mycobacterium tuberculosis and other mycobacteria,
some of which are pathogenic to animals and humans.1e3 Their
structure and biosynthesis has been reviewed,4 and a number of
structural and stereochemical relationships examined.5 Their
presence is thought to be linked to the resistance of these organ-
isms to most current antibiotics and other chemotherapeutic
agents.6
or an -keto-
a
-methyl fragment (keto-MA).2,3 In 1981, Daffe et al.
ꢀ
reported the identification of a new kind of mycolic acid in Myco-
bacterium fortuitum containing an -methyl epoxy-group at the
a
distal position and an alkene at the proximal position (2, R¼H)
(Scheme 1).9 Minnikin et al. later described the presence of similar
molecules in M. fortuitum, Mycobacterium farcinogenes, Mycobac-
terium senegalense, ‘Mycobacterium peregrinum’, and Mycobacte-
rium smegmatis;10e12 in these cases the major isomers had a cis-
alkene at the proximal position, but there was a minor component
(ca. 30% by NMR spectroscopy) (2, R¼Me) containing a proximal
a-
methyl-trans-alkene; the major isomer of the latter contained 78
carbons; the epoxy-MA had carbon skeletons similar to those in
methoxy-, keto- or a
-MA described earlier.10
Fig. 1. The typical structure of a mycolic acid.
The two stereocentres in the
a and b-positions relative to the
carboxylic group have both been found to be in the R-configuration
for all the mycolic acids examined, irrespective of the other func-
tional groups.7,8 In each case ‘aed’ represent long alkyl chains, and
generally each Mycobacterium contains a mixture of several ho-
mologues. In the common classes of MA, the proximal group is
* Corresponding author. Tel.: þ44 1248382374; fax: þ44 1248370528; e-mail
Scheme 1. (i) Acetolysis; (ii) saponification; (iii) oxidative cleavage; (iv) methylation.
address: chs028@bangor.ac.uk (M.S. Baird).
http://dx.doi.org/10.1016/j.tet.2014.06.089
0040-4020/Ó 2014 Elsevier Ltd. All rights reserved.

D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
7323
Epoxy-MAs are also present in Mycobacterium chitae,13,14 ‘My-
cobacterium giae’,13 M. peregrinum,11e13 Mycobacterium porcinum
and M. senegalense,15 and in a mutant strain of M. tuberculosis.16 In
the final case, these included epoxy-MA with a cis-cyclopropane at
the proximal position. Epoxy-mycolic acids have also been detected
directly by MALDI-TOF mass spectrometry; the major isomers
containing a trans-alkene at the proximal position are reported to
be C78 and C80 molecules.16e18 Studies using M. smegmatis have
identified the function of the protein MSMEG0913 in adding the
methyl branch adjacent to both an alkene and a cyclopropane at the
proximal position of epoxy-mycolates to produce the trans-homo-
logues,18 and examined other aspects of the biochemistry of such
species.19e22 The relative and absolute stereochemistry of epoxy-
and keto mycolic acids containing an
a
-methyl-trans-cyclopropane
unit,29,30 of cis-alkene mycolic acids,31 and of hydroxy- and keto
mycolic acids containing an (R)-
now report in full the synthesis of two stereoisomeric epoxy-
mycolic acids containing an (R)- -methyl-trans-alkene at the
a
-methyl-trans-alkene unit.32 We
a
proximal position; these have the chain lengths reported for one
mycolic acid in M. fortuitum,4,5 and the total carbon number is
consistent with those observed for one component of a mixture
from M. smegmatis by MALDI mass spectrometry.17,18 This has been
reported briefly earlier.33 We also report the synthesis of an epoxy-
mycolic acid containing a cis-cyclopropane.
2. Results and discussion
mycolates containing a proximal cis- or
a-methyl-trans-alkene
has been probed by two methods (Scheme 1).23 Firstly, opening of
the epoxide 2 by acetolysis, then saponification and oxidative
cleavage of both the derived 1,2-diol and the alkene leads to three
products, including (R)-ester 3.
The aldehyde 13 was first prepared from the known aldehyde
10,28,34,35 with sulfone 11 (see Supplementary data) and base in
a modified Julia-Kocienski reaction, followed by hydrogenation to
give 12. Deprotection and oxidative cleavage of the acetal 12 led to
13 (Scheme 4).
Secondly, reductive ring-opening of the epoxide 2 followed by
oxidative cleavage of the proximal alkene, saponification and
methylation led to the two acids 6 and 7 (Scheme 2). The latter was
shown to have R,R-stereochemistry by comparison to a model
compound. On this basis the authors assigned all the stereocentres
in the epoxy-mycolic acid as R.23 However, it seems clear in fact that
the result actually suggests the epoxy fragment is R,S,S as in 8 rather
than R,R,R as in 9, the priorities in the epoxide being different from
those in the ring-opened alcohol.
Scheme 4. (i) 10, LiN(SiMe3)2 (LiBSA), THF, ꢁ10 ꢃC (67%); (ii) H2, Pd/C, ethanol, (92%);
(iii) periodic acid, dry ether (77%).
AWittig reaction and then reduction with DIBAL led to the trans-
alcohol 14 (Scheme 5). Asymmetric epoxidation using Sharpless
conditions provided the two diastereoisomers 15 and 16.36,37 The
two epoxides showed ½a D22
of þ18.1 and ꢁ21.2, respectively. The
ꢀ
literature value for (2R,3R)-dodecyloxiranyl-methanol is ꢁ25.5.38
Scheme 2. (i) Reduction; (ii) oxidative cleavage; (iii) saponification; (iv) methylation.
What is arguably most interesting is that the methyl group ad-
jacent to the epoxide is in the R-configuration, whereas that adja-
cent to the hydroxyl, methoxy or keto-groups at the distal position
of the corresponding mycolic acids is of S-configuration. It is at-
tractive to propose that the various types of mycolic acid are formed
through a formal intermediate carbocation, formed by methylation
of a cis-alkene by SAM (Scheme 3). Methylation from the Re or Si
face of the alkene at the alkylated carbon could then lead to a di-
vergence in stereochemistry.
Scheme 5. (i) Ph3P]CHCOOMe, toluene (65%); (ii) DIBAL, CH2Cl2 (95%); (iii) L-
(þ)-diethyl tartrate, Ti(Oi-Pr)4, t-BuOOH, CH2Cl2, ꢁ20 ꢃC (75%); (iv) PCC, CH2Cl2 (59%,
18), (60%, 17); (v) D-(ꢁ)-diethyl tartrate, Ti(Oi-Pr)4, t-BuOOH, CH2Cl2, ꢁ20 ꢃC (67%).
Oxidation of each alcohol led to the corresponding aldehyde.
The aldehyde 18 was chain extended by reaction with the sulfone
19 (see Supplementary data) and base, followed by saturation of the
Scheme 3. Possible formal mechanism for production of S- and R-methyl branches by
methylation of a cis-alkene by SAM.
derived alkene using di-imide. The derived bromide 20, ½a D22
ꢁ13.1
ꢀ
We have reported the synthesis of an
methoxymycolic acids with either absolute stereochemistry at the
cis-cyclopropane or -methyl-
-methoxy fragment,26 and of keto
mycolic acids.27,28 We have also reported the synthesis of methoxy
a
-mycolic acid,24,25 of
(c 1.2, CHCl3) ([M]D ꢁ76) {molecular rotation, [M]D ¼ (molecular
weightꢂspecific rotation)/100}, was then converted into the cor-
responding sulfone 21. In the same manner, diastereoisomer 17 was
converted into 22 (Scheme 6). The molecular rotations of the two
a
b

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D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
diastereomeric sulfones 21 and 22 were ꢁ58 and þ43, respectively.
This may provide an approximate value for the contribution of this
chiral unit to the molecular rotations of mycolic acids containing
these fragments.
Scheme 8. (i) LiBSA, ꢁ10 ꢃC (61%); (ii) H2, Pd/C, IMS, THF (93%); (iii) LiAlH4, THF (91%);
(iv) NBS, Ph3P, CH2Cl2 (96%); (v) 1-phenyl-1H-tetrazole-5-thiol, K2CO3, acetone (90%);
(vi) Mo7O24(NH4)6$4H2O, H2O2, THF/IMS (92%).
Scheme 6. (i) LiBSA, THF, ꢁ10 ꢃC (71%); (ii) KO2CN]NCO2K, AcOH, THF, MeOH (93%);
(iii) 1-phenyl-1H-tetrazole-5-thiol, acetone, K2CO3 (82%); (iv) H2O2, Mo7O24(N-
H4)6$4H2O, IMS (industrial methylated spirit), THF (67%).
The NMR spectra of the isomers 21 and 22 (see Supplementary
data), and of each pair of precursors were very similar. However, in
each case, those of the series leading to 21 showed a double triplet
for the epoxide hydrogen adjacent to the methylene group at
(J 2.2, 5.7 Hz), with a coupling constant of around 2.2 Hz to the
second epoxide hydrogen, a double doublet at 2.41 (J 2.2, 7.0 Hz);
d 2.72
d
apparently the coupling constants between the former hydrogen
and the two diastereotopic methylene hydrogens are equal. The
methyl group adjacent to the epoxide appeared as a doublet at
In the 13C NMR spectrum, the two epoxide carbons appeared at
63.8 and 58.8. In the series leading to 22, the corresponding hy-
drogen signals appeared at 2.66 and 2.45, with approximately
similar coupling constants, while the methyl signal appeared at
d 1.0.
d
d
d
0.91ꢁ0.92. In this case the epoxide carbons appeared at ca.
d 63.7
and 57.4. The 1H NMR spectra for 21 and 22 each showed minor
impurities corresponding to the other diastereoisomer, probably
arising from a small amount of epimerization of the aldehyde 13.
Scheme 9. (i) LiBSA, THF, ꢁ10 ꢃC (89%); (ii) H2, Pd/C, IMS, THF (95%); (iii) HF$pyridine,
In order to obtain the a-methyl-trans-alkene unit the sulfone 26
pyridine, THF (80%); (iv) Ac2O, pyridine, toluene (98%); (v) HIO4, Et2O (64%).
was first prepared from lactone 23 (Scheme 7):39
Scheme 7. (i) NaOMe, MeOH; (ii) H2SO4, MeOH, reflux (85% for two steps) (iii) Ph3P,
NBS, NaHCO3, CH2Cl2 (88%) (iv) 1-phenyl-1H-tetrazole-5-thiol, K2CO3, acetone (90%);
(v) Mo7O24(NH4)6$4H2O, H2O2, THF/IMS (91%).
Chain extension of the aldehyde 27, prepared as described ear-
lier,28,34,35 with the sulfone 26 and base, followed by saturation of
the derived mixture of alkenes and then conversion into the sulfone
31 was achieved by standard methods (Scheme 8).
Reaction of the sulfone 31 with aldehyde 3228,31 and base, fol-
lowed by saturation of the alkenes produced, led to the acetal 33.
This could be transformed into aldehyde 36 by changing the pro-
tecting group to acetate followed by oxidative cleavage (Scheme 9).
Finally, coupling of 36 and 21 in the presence of base led to the
protected epoxy-mycolic acid 37, using the method described
earlier.28 Compound 37 could be deprotected to 38 (Scheme 10). In
Scheme 10. (i) KBSA, 1,2-dimethoxyethane, ꢁ5 ꢃC (26%); (ii) LiOH, THF, H2O, MeOH,
45 ꢃC (70%).

D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
7325
the same way 39 was obtained from 22. Compound 38 showed
a MALDI mass ion corresponding to one homologue of the natural
mixture.18 The specific rotation of compound 38 corresponded to
a molecular rotation of ꢁ66, while that of 39 was þ72. The proton
NMR spectrum of 38 showed signals for the two epoxide hydro-
gens at
and two methyl doublets at
drogens appeared as a characteristic double triplet at
double doublet at 5.24, with a coupling of 15.2 Hz between them.
The carbons of the epoxide appeared at
64.0 and 59.0 in the 13C
d
2.73 (1H, dt, J 2.2, 5.3 Hz) and 2.43 (1H, dd, J 2.2, 7.3 Hz)
1.0 and 0.94. The trans-alkene hy-
5.33 and
d
d
Scheme 12. (i) PPTS, CH2Cl2, 3,4-dihydro-2H-pyran (84%); (ii) LiAlH4, THF (92%); (iii)
PCC, CH2Cl2 (54%).
d
NMR spectrum. As in the case of the intermediates leading to 38
and 39, while the two epoxide hydrogens and the methyl adjacent
to the epoxide of 38 appeared at the positions described above,
the corresponding proton signals for 39 appeared at
d 2.68, 2.47,
and 0.92; the epoxide carbons appeared at 63.9 and 57.6. The
d
proton spectra of these two compounds are reproduced in the
Supplementary data. The signals for 38 visually correspond well
(Supplementary data) with those reported by Laval et al. for
a fraction of natural trans-alkene containing epoxy-MA.18 Epoxy-
mycolates present in M. smegmatis are reported to show a dou-
ble doublet at
signals at
1.02 and 0.92.18 An earlier paper reports the chemical
shifts as 2.39 and 2.70, with the signal for the methyl adjacent to
the epoxide appearing at 0.98 and that adjacent to the alkene at
63.7 and
d 2.43 and a broad triplet at d 2.72 and methyl
d
d
d
d
0.92; the epoxide carbons are reported to appear at d
58.6.10,40 The shape and position of the signal for the epoxide
hydrogen adjacent to the chain methylene group for 38 is very
similar to that shown for the corresponding proton in Mycobac-
terium confluentis and M. smegmatis.41
This method produces an epoxy-MA 38 with the same chain
lengths as those reported for one natural example, and molecular
rotations for fragments, which are consistent with those reported.
Moreover, by simple variation, the method can be adjusted to
provide a trans-alkene containing epoxy-MA of any necessary chain
length and varying absolute stereochemistry.
In the second part of this work, a cis-cyclopropane containing
epoxy-mycolic acid,16,17,40 was prepared. The epoxy-sulfones 42
and 43 were first prepared from aldehydes 18 and 17 using a similar
method to that above (Scheme 11).
Scheme 13. (i) LiBSA, THF, ꢁ10 ꢃC (89%); (ii) LiAlH4, THF (80%); (iii) tBuPh2SiCl, Et3N,
CH2Cl2 (95%); (iv) PPTS, MeOH/THF 50 ꢃC (82%); (v) KO2CN]NCO2K, AcOH, THF, MeOH
(98%); (vi) PCC, CH2Cl2 (98%).
A second coupling of 42 and 51, followed again by saturation of
the alkene provided 52, which was deprotected and oxidized to 53.
In the same way 43 was converted into 54 (Scheme 14).
Scheme 11. (i) LiBSA, THF, ꢁ10 ꢃC (63%); (ii) KO2CN]NCO2K, AcOH, THF, MeOH (96%);
(iii) 1-phenyl-1H-tetrazole-5-thiol, acetone, K2CO3 (71%); (iv) H2O2, Mo7O24(N-
H4)6$4H2O, IMS, THF (84%).
Scheme 14. (i) LiBSA, THF, ꢁ10 ꢃC (89%); (ii) KO2CN]NCO2K, AcOH, THF, MeOH (80%);
(iii) TBAF, THF (91%); (iv) PCC, CH2Cl2 (76%).
The cis-cyclopropane was introduced using the aldehyde 47
prepared from the butyrate 44 (Scheme 12):42
Coupling of 47 with 26 and base, followed by hydrogenation of
the derived alkene mixture and functional group modification
provided the chain extended aldehyde 51 (Scheme 13):
The molecular rotation of the aldehyde 53 was ꢁ81, compared
to the diastereomer 54, at þ60. These values correspond reasonably
well with those for the two epoxide fragments 21 and 22, reflecting
the modest contribution of the cis-cyclopropane to the molecular
rotation.

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D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
In order to achieve the coupling to form the complete mycolic
epoxide fragments such as 21 and 22 may be estimated from the
present results as ꢁ60 and þ45 (see Supplementary data). In the
case of the methyl ester of 59 and 60, the contribution form the cis-
cyclopropane is expected to be very small (as seen above), the
chirality arising only from differences in the two substituents, both
involving very long chains. Using a notional value of 0 for this, the
MD values for the two compounds can be estimated as ꢁ20
(ꢁ60þ40) and þ85 (þ45þ40) based on the sum of the epoxide and
hydroxy acid contributions; the two methyl esters gave experi-
mental values of ꢁ24 and þ62. A more detailed analysis of the
contributions of the synthetic fragments to the [M]D will be pre-
sented elsewhere.
acid, the known alcohol 55,31 was first transformed into the sulfone
57 (Scheme 15):
3. Conclusion
Although first described relatively late in the understanding of
mycolic acids in mycobacteria,9 epoxy-mycolic acids have been
identified in a large number of organisms. As with many individual
mycolic acids, the specific chain lengths are often not fully identi-
fied; however, although the absolute stereochemistry of some
groups present in MA even now remains uncertain that of epoxy-
MA has been well defined at least from one organism.23 This pa-
per describes the synthesis of epoxy-MA of that stereochemistry,
Scheme 15. (i) NBS, PPh3, CH2Cl2 (60%); (ii) 1-phenyl-1H-tetrazole-5-thiol, acetone,
K2CO3 (95%); (iii) H2O2, Mo7O24(NH4)6$4H2O, IMS, THF (90%).
Coupling of aldehyde 53 to sulfone 57 provided the protected
epoxy-mycolic acid 58, which was deprotected to the free acid 59.
In the same way, compound 54 was converted into 60. This cor-
responds to the formula of one of three isomers reported to be
present in the epoxy-MA fraction of M. smegmatis (Scheme 16).18
containing either a proximal a-methyl-trans-alkene or a cis-cyclo-
propane. Synthetic mycolic acids corresponding to the three major
classes present in pathogenic mycobacteria such as M. tuberculosis
have been shown to elicit strong and differential responses in as-
says to determine their effect on the immune system.44,45 They also
behave as antigens to antibodies in the serum of patients with
active tuberculosis, albeit with modest sensitivity and specificity in
standard ELISA assays.46 Studies of the effects of epoxy-MA in
a range of assays to determine their immune system effects are on-
going. In a preliminary study to determine whether they bind to
antibodies in the serum of patients with active tuberculosis using
a standard ELISA approach, there was no difference in the average
response with 10 TB-positive and 40 TB-negative samples from
samples taken in several countries where TB is indigenous when
compound 39 was used as the antigen.47 This is perhaps not un-
expected, as these MA are not significant components of M.
tuberculosis.
4. Experimental section
4.1. General
Chemicals used were obtained from commercial suppliers
(Sigma, Aldrich, and Alfa Aeser) or prepared from them by the
methods described. Solvents, which were required to be dry, e.g.,
ether, tetrahydrofuran were dried over sodium wire and benzo-
phenone under nitrogen, while dichloromethane was dried over
calcium hydride. Petroleum spirit (petrol) was of boiling point
40e60 ꢃC. All reagents and solvents used were of reagent grade
unless otherwise stated. Silica gel (Merck 7736) and silica gel plates
used for column chromatography and thin layer chromatography
were obtained from Aldrich; separated components were detected
using variously UV light, I2 and phosphomolybdic acid solution in
IMS followed by charring. Anhydrous magnesium sulfate was used
to dry organic solutions. Infra-red (IR) spectroscopy was carried out
on a PerkineElmer 1600 FTIR spectrometer as liquid films or KBr
disc (solid). Melting points were measured using a Gallenkamp
melting point apparatus. NMR spectroscopy was carried out on
Scheme 16. (i) LiBSA, THF, ꢁ2 ꢃC (68%); (ii) KO2CN]NCO2K, AcOH, THF, MeOH (92%);
(iii) HF$pyridine, pyridine, THF (56%); (iv) LiOH, THF, MeOH 45 ꢃC (76%).
The proton NMR spectrum of 59 corresponded to that re-
ported.40 Thus the epoxide protons appeared at
d 2.73 (2.73 in the
natural mixture) and 2.43 (2.42), the methyl adjacent to the ep-
oxide at 1.00 (1.01), and the cyclopropane protons at 0.65ꢁ0.69
(0.65), 0.56 (0.57), ꢁ0.32 (ꢁ0.32).40
The molecular rotation of hydroxy acid 59 was ꢁ97, while that of
the diastereoisomer 60 was þ144. Those of the precursor methyl
esters were ꢁ23 and þ61, respectively. The molecular rotations of
individual functional groups in natural mixtures of mycolic acids
and in model compounds have been identified by Quemard et al.43
In general [M]D in such systems where groups of chiral centres are
separated by long carbon chains are approximately additive; the
individual values for the R,R-centres of the 2-hydroxy acid (ester)
fragment in mycolates is estimated as þ40, the ReCH]CHCHCH3e
Bruker Avance 400 or 500 spectrometers. [a] values were recor-
D
ded in CHCl3 on a POLAAR 2001 optical activity polarimeter. Mass
spectra were recorded on a Bruker MALDI-TOF MS) to an accuracy
of 2 d.p.; accurate mass values were obtained on a Bruker Microtof
LCeMS.
fragment as ꢁ25 (for 30% content). The figure for the
a-methyl-

D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
7327
14.1; nmax: 2924, 2853, 2360, 1730, 1656, 1465, 1270, 1173,
1038 cmꢁ1
In general, for those compounds synthesised in two stereo-
chemistries, the experimental details are presented here for only
one series; the details for the other series are provided in
Supplementary data.
.
4.1.3. (E)-(R)-4-Methyleicos-2-en-1-ol 14. DIBAL-H (64.8 mL,
64.8 mmol,1 M in hexane) was added to a stirred solution of methyl
(E)-(R)-4-methyleicos-2-enoate (8.47 g, 25.9 mmol) in dry
dichloromethane (250 mL) at ꢁ60 ꢃC under nitrogen. The mixture
was stirred overnight at room temperature and then quenched by
adding satd aq ammonium chloride (30 mL) at ꢁ30 ꢃC, then
allowed to reach room temperature and stirred for 0.5 h. Sub-
sequently, hydrochloric acid (5%) was added until the solution be-
came acidic. The organic layer was separated and the aqueous layer
was extracted with dichloromethane (3ꢂ150 mL). The combined
organic layers were dried and evaporated to give a pale yellow oil;
column chromatography eluting with petrol/ether (5:2) gave
a white solid, the title compound 14 (7.4 g, 95%), mp: 34e35 ꢃC
4.1.1. (S)-2,2-Dimethyl-4-((R)-1-methylheptadecyl)-[1,3]dioxola-
ne. Lithium bis(trimethylsilyl)amide (50 mL, 52 mmol, 1.06 M)
was added dropwise with stirring to (R)-3-((S)-2,2-dimethyl-
[1,3]dioxolan-4-yl)-butyraldehyde 1028,34,35 (5.42 g, 31.5 mmol)
and 5-(tetradecane-1-sulfonyl)-1-phenyl-1H-tetrazole 11 (see
Supplementary data) (16.6 g, 40 mmol) in dry tetrahydrofuran
(250 mL) under nitrogen at ꢁ2 ꢃC. The mixture was allowed to
reach room temperature and stirred for 16 h then quenched
with water (100 mL) and petrol/ether (1:1, 2ꢂ100 mL). The
combined organic layers were washed with satd aq sodium
chloride (2ꢂ100 mL), dried and evaporated to give a thick oil.
Chromatography on silica gel eluting with petrol/ether (20:1)
gave an oil, (S)-2,2-dimethyl-4-((E/Z)-(R)-1-methylheptadec-3-
enyl)[1,3]dioxolane (7.42 g, 67%) as a mixture of two isomers
in ratio ca. 2:1. Palladium on charcoal (10%, 0.5 g) was added to
a stirred solution of the alkenes (6.40 g, 18.1 mmol) in ethanol
(100 mL). The mixture was stirred under hydrogen at atmo-
spheric pressure. When no more hydrogen was absorbed it was
filtered through a bed of Celite and washed with warm ethyl
acetate (100 mL). The filtrate was evaporated at 14 mmHg to
[Found (M)þ: 310.3296, C21H42O requires: 310.3235], ½a D26
ꢁ15 (c
ꢀ
1.4, CHCl3), which showed dH (500 MHz, CDCl3): 5.62e5.57 (2H, m),
4.09 (2H, d, J 5.1 Hz), 2.17e2.07 (1H, m), 1.31e1.26 (31H, br s), 0.98
(3H, d, J 6.9 Hz), 0.88 (3H, t, J 7.0 Hz); dC (125 MHz, CDCl3): 139.4,
127.0, 63.9, 36.8, 36.3, 31.9, 29.8, 29.7, 29.67, 29.6, 29.3, 27.3, 22.7,
20.3, 14.1; nmax: 3448, 2954, 2924, 2854, 1644, 1462, 1377 cm-1.
4.1.4. [(2R,3R)-3-((R)-1-Methylheptadecyl)oxiranyl]methanol
15. Titanium tetraisopropoxide in dry dichloromethane (3.4 M,
give the title compound 12 as a colourless oil (5.9 g, 92%), ½a D22
ꢀ
0.28 mL, 0.96 mmol) was added to a stirred solution of
D-
þ17.6 (c 0.625, CHCl3) [Found (MþH)þ: 355.3582, C23H47O2 re-
quires: 355.3571], which showed dH (500 MHz, CDCl3): 3.99 (1H,
t, J 6.6 Hz), 3.86 (1H, br q, J 6.9 Hz), 3.59 (1H, br t, J 7.6 Hz),
1.56e1.51 (1H, m), 1.4 (3H, s), 1.35 (3H, s), 1.31e1.26 (30H, br s),
0.96 (3H, d, J 6.6 Hz), 0.88 (3H, t, J 6.3 Hz); dC (125 MHz, CDCl3):
108.5, 80.4, 67.8, 36.5, 32.7, 31.9, 29.9, 29.7, 29.65, 29.6, 29.4,
27.0, 26.6, 25.5, 22.7, 15.6, 14.1; nmax: 2984, 2923, 2854, 1466,
(ꢁ)-diethyl tartrate (0.23 mL, 1.13 mmol) in dry dichloromethane
ꢃ
ꢁ
(100 mL) under nitrogen at ꢁ20 C in the presence of 4 A molecular
sieves (0.5 g). The mixture was stirred at ꢁ20 ꢃC for 0.5 h then tert-
butyl hydroperoxide in dry dichloromethane (3.3 M, 4.8 mL,
16 mmol) was added dropwise and the mixture was stirred for
another 0.5 h. To this solution, (E)-(R)-4-methyl-eicos-2-en-1-ol
(2.5 g, 8.1 mmol) in dry dichloromethane (10 mL) was added
dropwise. After stirring at the same temperature for 4.5 h, the re-
action was left at ꢁ20 ꢃC overnight, then quenched with water
(10 mL) and allowed to reach room temperature. After stirring for
50 min, a solution of sodium hydroxide (30%) in satd aq sodium
chloride (6 mL) was added. The mixture was stirred for 0.5 h, the
organic layer was separated and the aqueous layer was re-extracted
with dichloromethane (3ꢂ15 mL). The combined organic layers
were dried and evaporated to give a thick oil; chromatography
eluting with petrol/ether (5:2) gave the title compound 15 as
a white solid (1.74 g, 67%), mp: 35e37 ꢃC [Found (MþH)þ: 327.3274,
1378, 1214, 1161, 1066 cmꢁ1
.
4.1.2. Methyl (E)-(R)-4-methyleicos-2-enoate.
(a) Periodic acid (11.5 g, 60.8 mmol) was added to a stirred solution
of dioxolane 12 (9.0 g, 25 mmol) in dry ether (250 mL) under
nitrogen at room temperature. The mixture was stirred for 16 h,
then filtered through a bed of Celite and washed with ether.
The solvent was evaporated to give a residue. Column chro-
matography eluting with petrol/ether (10:1) gave (R)-2-
methyloctadecanal 13 as
a
colourless oil (5.4 g, 77%),33
½
a 2D5
ꢀ
ꢁ11.4 (c 1.07, CHCl3), which showed dH (500 MHz,
C
21H43O2 requires: 327.3258], ½a D28
þ18.1 (c 0.8, CHCl3), which
ꢀ
CDCl3): 9.6 (1H, d, J 1.9 Hz), 2.34e2.27 (1H, m), 1.71e1.64 (1H,
m), 1.34e1.25 (29H, br s), 1.08 (3H, d, J 7.25 Hz), 0.87 (3H, t, J
6.95 Hz); dC (125 MHz, CDCl3): 205.3, 46.3, 31.9, 30.5, 29.7,
29.66, 29.63, 29.6, 29.5, 29.4, 26.9, 22.7, 14.1, 13.3; nmax: 2925,
showed dH (500 MHz, CDCl3): 3.9 (1H, ddd, J 2.5, 5.6, 12.6 Hz), 3.6
(1H, ddd, J 4.5, 7.0, 12.0 Hz), 2.94e2.92 (1H, m), 2.76 (1H, dd, J 2.2,
7.3 Hz), 1.53e1.48 (1H, m), 1.43e1.25 (31H, br m, including br s at
1.25), 0.92 (3H, d, J 7.0 Hz), 0.88 (3H, t, J 6.6 Hz); dC (125 MHz,
CDCl3): 61.9, 60.6, 57.0, 35.3, 34.5, 31.9, 29.9, 29.7, 29.63, 29.6, 29.3,
2853, 2699, 1730, 1465.5, 1376 cmꢁ1
.
(b) Methyl (triphenylphosphoranylidene) acetate (6.0 g,
18 mmol) was added in portions to a stirred solution of al-
dehyde 13 (4.69 g, 16.6 mmol) in toluene (75 mL) at 10 ꢃC.
The mixture was allowed to reach room temperature and
stirred for 24 h. The solvent was evaporated and the residue
was heated under reflux with petrol/ether (1:1, 150 mL) for
10 min. The precipitate was filtered and washed with petrol/
ether (10:1, 150 mL). The filtrate was evaporated to give
a residue. Chromatography on silica gel eluting with petrol/
ethyl acetate (20:1) gave the title compound as a colourless
oil (3.6 g, 65%) [Found (MþH)þ: 339.3269, C22H43O2 requires:
26.8, 22.7, 15.8, 14.1; nmax: 3431, 2922, 2852, 1384 cmꢁ1
.
4.1.5. [(2S,3S)-3-((R)-1-Methylheptadecyl)oxiranyl]methanol
16. Titanium tetraisopropoxide in dry dichloromethane (3.4 M,
0.28 mL, 0.96 mmol) was added to a stirred solution of
L
-(þ)-diethyl
tartrate (0.23 mL, 1.113 mmol) in dry dichloromethane (70 mL)
ꢃ
ꢁ
under nitrogen at ꢁ20 C in the presence of 4 A molecular sieves
(0.5 g). The mixture was stirred at ꢁ20 ꢃC for 0.5 h then tert-butyl
hydroperoxide in dry dichloromethane (3.3 M, 4.8 mL, 16 mmol)
was added dropwise and the mixture was stirred for another 0.5 h.
To this solution, (E)-(R)-4-methyl-eicos-2-en-1-ol (2.5 g, 8.1 mmol)
in dry dichloromethane (10 mL) was added dropwise. After stirring
at the same temperature for 4.5 h, the mixture was left at ꢁ20 ꢃC for
16 h in the freezer, then quenched with water (10 mL) and allowed
to reach room temperature. After stirring for 50 min, a solution of
sodium hydroxide (30%) in satd aq sodium chloride (6 mL) was
339.3258], ½a 2D4
ꢁ18.6 (c 1.5, CHCl3), which showed dH
ꢀ
(500 MHz, CDCl3): 6.86 (1H, dd, J 7.9, 15.5 Hz), 5.77 (1H, dd, J
1.0, 15.5 Hz), 3.72 (3H, s), 2.28 (1H, sept., J 7 Hz), 1.39e1.25
(30H, m, including br s at 1.25), 1.03 (3H, d, J 6.7 Hz), 0.87
(3H, t, J 6.9 Hz); dC (125 MHz, CDCl3): 167.3, 155.0, 119.1, 51.3,
36.5, 36.0, 31.9, 29.7, 29.63, 29.6, 29.5, 29.3, 27.2, 22.7, 19.4,

7328
D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
added. After a further 0.5 h, the organic layer was separated and the
aqueous layer was extracted with dichloromethane (3ꢂ15 mL). The
combined organic layers were dried and evaporated to give a thick
oil; column chromatography eluting with petrol/ether (5:2) gave
a white solid, the title compound 16 (2.0 g, 75%), mp: 48e49 ꢃC
[Found (MþH)þ: 327.3258, C21H43O2 requires: 327.3258],
requires: 579.41], ½a D26
ꢁ13.1 (c 1.2, CHCl3), which showed dH
ꢀ
(500 MHz, CDCl3): 3.41 (2H, t, J 7.0 Hz), 2.71 (1H, dt, J 2.2, 5.4 Hz),
2.41 (1H, dd, J 1.9, 7.0 Hz), 1.85 (2H, pent., J 6.9 Hz), 1.54e1.22 (53H,
br m, including br s at 1.26),1.0 (3H, d, J 6.0 Hz), 0.88 (3H, t, J 6.6 Hz);
dC (125 MHz, CDCl3): 63.8, 58.8, 36.0, 34.0, 33.8, 32.8, 32.3, 31.9,
29.9, 29.7, 29.63, 29.6, 29.56, 29.54, 29.53, 29.5, 29.4, 29.36, 28.8,
28.2, 27.2, 26.1, 22.7, 22.6, 17.3, 14.1; nmax: 2919, 2850, 1462, 1377,
½
a 2D2
ꢀ
ꢁ21.2 (c 1.56, CHCl3), which showed dH (500 MHz, CDCl3): 3.88
(1H, ddd, J 2.2, 5.7, 12.6 Hz), 3.58e3.53 (1H, m), 2.94 (1H, br pent., J
2.5 Hz), 2.68 (1H, dd, J 2.6, 7.3 Hz), 2.59 (1H, br t, J 6.3 Hz), 1.38e1.19
(31H, br m, including br s at 1.23), 0.98 (3H, d, J 6.6 Hz), 0.85 (3H, t, J
6.6 Hz); dC (125 MHz, CDCl3): 61.8, 60.6, 58.5, 35.4, 33.6, 31.9, 29.8,
29.6, 29.59, 29.58, 29.5, 29.3, 27.1, 22.6, 17.1, 14.0; nmax: 3430, 2918,
1116 cmꢁ1
.
4.1.9. 5-(13-[(2S,3S)-3-((R)-1-Methylheptadecyl)oxiranyl]tridecane-
1-sulfonyl)-1-phenyl-1H-tetrazole 21.
2849, 1463, 1384, 1071 cmꢁ1
.
(i) (2S,3S)-2-(13-Bromotridecyl)-3-((R)-1-methylheptadecyl)-
oxirane 20 (0.8 g, 1.4 mmol) was added with vigorous stirring
to 1-phenyl-1H-tetrazole-5-thiol (0.25 g, 1.43 mmol) and an-
hydrous potassium carbonate (0.390 g, 2.86 mmol) in acetone
(50 mL). The mixture was heated under reflux for 2.5 h when
the inorganic salts were filtered off and washed with acetone;
the solution was evaporated to a small bulk and the residue
extracted between dichloromethane (30 mL) and water
(30 mL). The aqueous layer was extracted with dichloro-
methane (2ꢂ20 mL). The combined organic phases were
washed with water (25 mL), dried and evaporated to give
a solid. Chromatography on silica gel eluting with petrol/ethyl
acetate (10:1) gave a white solid, 5-(13-[(2S,3S)-3-((R)-1-
methyl-heptadecyl)oxiranyl]tridecylsulfanyl)-1-phenyl-1H-
tetrazole (0.77 g, 82%), mp: 41e43 ꢃC [Found (MþH)þ:
4.1.6. (2S,3R)-3-((R)-1-Methylheptadecyl)-oxirane-2-carbaldehyde
17. Alcohol 15 (1.23 g, 3.76 mmol) in dichloromethane (15 mL) was
added to a stirred suspension of pyridinium chlorochromate (2.0 g,
7.5 mmol) in dichloromethane (100 mL) at room temperature.48
The mixture was stirred vigorously for 3 h, diluted with ether
(100 mL), filtered through a bed of Celite, then washed well with
ether and the filtrate evaporated to give a residue. Chromatography
on silica gel eluting with petrol/ether (5:2) gave a white solid, the
title compound 17 (0.72 g, 60%), mp: 40e42 ꢃC, ½a D28
ꢁ63.5 (c 1.06,
ꢀ
CHCl3), which showed dH (500 MHz, CDCl3): 9.02 (1H, d, J 6.3 Hz),
3.14 (1H, dd, J 1.9, 6.3 Hz), 3.05 (1H, dd, J 1.9, 6.6 Hz), 1.55e1.48 (1H,
m), 1.43e1.22 (30H, br m, including br s at 1.26), 0.95 (3H, d, J
6.9 Hz), 0.88 (3H, t, J 6.6 Hz); dC (125 MHz, CDCl3): 198.6, 61.3, 57.9,
35.3, 34.4, 31.9, 29.74, 29.7, 29.64, 29.6, 29.5, 29.3, 26.8, 22.7, 15.6,
14.1; nmax: 2918, 2851, 1741, 1384 cmꢁ1, and recovered starting
material (0.25 g).
655.5341, C40H71N4OS requires: 655.5343], ½a D20
ꢁ12.5 (c 1.09,
ꢀ
CHCl3), which showed dH (500 MHz, CDCl3): 7.60e7.52 (5H, m),
3.40 (2H, t, J 7.6 Hz), 2.71 (1H, dt, J 2.2, 5.7 Hz), 2.41 (1H, dd, J
2.2, 7.3 Hz), 1.82 (2H, br pent., J 7.6 Hz), 1.54e1.26 (53H, br m,
including br s at 1.26), 1.0 (3H, d, J 6.3 Hz), 0.88 (3H, t, J 6.7 Hz);
dC (125 MHz, CDCl3): 154.5, 133.8, 130.0, 129.7, 123.9, 63.8, 58.8,
36.0, 33.8, 33.4, 32.3, 31.9, 29.9, 29.7, 29.66, 29.64, 29.63, 29.6,
29.56, 29.53, 29.5, 29.4, 29.3, 29.1, 29.0, 28.6, 27.2, 26.1, 22.7,
4.1.7. (2R,3S)-3-((R)-1-Methylheptadecyl)-oxirane-2-carbaldehyde
18. Alcohol 16 (1.96 g, 6.01 mmol) in dichloromethane (15 mL) was
added to a stirred suspension of pyridinium chlorochromate (3.9 g,
18 mmol) in dichloromethane (100 mL) at room temperature. The
mixture was stirred vigorously for 3 h then diluted with ether
(100 mL), filtered through a bed of Celite, then washed with ether
and the filtrate evaporated to give a residue. Chromatography on
silica gel eluting with petrol/ether (5:2) gave a white solid, the title
17.3, 14.1; nmax: 2954, 2924, 2854, 1501, 1462, 1377 cmꢁ1
.
(ii) Ammonium molybdate (VI) tetrahydrate (0.60 g, 0.53 mmol) in
H2O2 (35%, w/w,1.5 mL) was added to a stirred solution of 5-(13-
[(2S,3S)-3-((R)-1-methylheptadecyl)oxiranyl]tridecylsulfanyl)-
1-phenyl-1H-tetrazole (0.78 g, 1.19 mmol) in THF (15 mL) and
IMS (25 mL) at 12 ꢃC and stirred at rt for 2 h. Further ammo-
nium molybdate (VI) tetrahydrate (0.60 g, 0.53 mmol) in ice
cold H2O2 (35%, w/w, 1.5 mL) was added and the mixture was
stirred at rt 18 h, then poured into water (75 mL) and extracted
with dichloromethane (3ꢂ40 mL). The combined organic
phases were washed with water (2ꢂ25 mL), dried and evap-
orated to give a solid. Chromatography on silica gel eluting
with petrol/ethyl acetate (10:1) gave a white solid of the title
compound 21 (0.70 g, 67%), mp: 45e47 ꢃC [Found (MþNa)þ:
compound 18 (1.2 g, 59%), mp: 31e32 ꢃC, ½a D20
þ53.5 (c 1.22, CHCl3),
ꢀ
which showed dH (500 MHz, CDCl3): 9.02 (1H, d, J 6.3 Hz), 3.19 (1H,
dd, J 1.9, 6.3 Hz), 3.02 (1H, dd, J 1.9, 7.0 Hz), 1.51e1.46 (1H, br pent., J
6.6 Hz), 1.41e1.22 (30H, br m), 1.06 (3H, d, J 6.6 Hz), 0.88 (3H, t, J
6.7 Hz); dC (125 MHz, CDCl3): 198.5, 61.2, 59.0, 35.3, 33.3, 31.9, 29.7,
29.68, 29.64, 29.62, 29.6, 29.5, 29.4, 27.0, 22.7, 16.9, 14.1; nmax: 2954,
2924, 2854, 1734, 1462, 1377 cmꢁ1. Starting material (0.55 g) was
recovered.
4.1.8. (2S,3S)-2-(13-Bromotridecyl)-3-((R)-1-methylheptadecyl)oxir-
ane 20. Lithium bis(trimethylsilyl)amide (5.4 mL, 5.7 mmol,
1.06 M) was added dropwise with stirring to aldehyde 18 (0.95 g,
2.9 mmol) and 5-(12-bromo-dodecane-1-sulfonyl)-1-phenyl-1H-
tetrazole 19 (see Supplementary data) (1.74 g, 3.80 mmol) in dry
tetrahydrofuran (50 mL) under nitrogen at ꢁ10 ꢃC. The mixture was
allowed to reach room temperature, stirred for 1 h, then quenched
with water (7 mL) and petrol/ether (1:1, 40 mL). The organic layer
was separated and the aqueous layer was re-extracted with petrol/
ether (1:1, 2ꢂ20 mL). The combined organic layers were washed
with satd aq sodium chloride (2ꢂ20 mL), dried and evaporated to
give a thick oil. Chromatography on silica gel eluting with petrol/
ether (20:1) gave a white solid (E/Z)-(2S,3S)-2-(13-bromotridec-1-
enyl)-3-((R)-1-methylheptadecyl)oxirane (1.16 g, 71%), as a 1.6:1
mixture of two isomers. Hydrogenation was carried out with
dipotassium azodicarboxylate as before. Chromatography eluting
with petrol/ether (20:1) gave a white solid,þthe title compound 20
(0.64 g, 93%), mp: 42e44 ꢃC [Found (MþNa) : 579.36, C33H65NaBrO
709.5018, C40H70N4NaO3S requires: 709.5061], ½a D20
ꢁ8.5 (c
ꢀ
0.97, CHCl3); dH (500 MHz, CDCl3): 7.72e7.69 (2H, m),
7.66e7.59 (3H, m), 3.73 (2H, t, J 7.9 Hz), 2.72 (1H, dt, J 2.2,
5.7 Hz), 2.41 (1H, dd, J 2.2, 7.0 Hz), 1.99e1.93 (2H, m), 1.56e1.26
(53H, br m, including br s at 1.26), 1.0 (3H, d, J 6.3 Hz), 0.88 (3H,
t, J 6.6 Hz); dC (500 MHz, CDCl3): 153.5,133.1, 131.4,129.7, 125.0,
63.8, 58.8, 56.0, 36.0, 33.8, 32.3, 31.9, 29.9, 29.7, 29.64, 29.63,
29.6, 29.55, 29.53, 29.5, 29.4, 29.3, 29.2, 28.9, 28.1, 27.2, 26.1,
22.7, 21.9, 17.3, 14.1; nmax: 2918, 2851, 1498, 1464, 1344,
1153 cmꢁ1
.
4.1.10. 5-(13-[(2R,3R)-3-((R)-1-Methylheptadecyl)-oxiranyl]-tride-
cane-1-sulfonyl)-1-phenyl-1H-tetrazole 22. Ammonium molybdate
(VI) tetrahydrate (0.4 g, 0.322 mmol) in ice cold H2O2 (35% w/w,
1 mL) was added to a stirred solution of 5-(13-[(2R,3R)-3-((R)-1-
methylheptadecyl)oxiran-yl]-tridecylsulfanyl)-1-phenyl-1H-

D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
7329
tetrazole (see Supplementary data) (0.47 g, 0.72 mmol) in THF
(10 mL) and IMS (15 mL) at 12 ꢃC and stirred at rt for 2 h. Further
ammonium molybdate (VI) tetrahydrate (0.40 g, 0.32 mmol) in ice
cold H2O2 (35%, w/w, 1 mL) was added and the mixture was stirred
at rt for 18 h, then poured into water (50 mL) and extracted with
dichloromethane (3ꢂ25 mL). The combined organic phases were
washed with water (2ꢂ15 mL), dried and evaporated to give a solid;
chromatography on silica gel eluting with petrol/ethyl acetate
(10:1) gave a white solid, the title compound 22 (0.34 g, 69%), mp:
41e42 ꢃC [Found (MþH)þ: 687.5243, C40H71N4O3S requires:
2ꢂ50 mL). The combined organic layers were washed with satd aq
sodium chloride (2ꢂ80 mL), dried and evaporated to give a thick
oil. Chromatography on silica gel eluting with petrol/ethyl acetate
(20:1) gave a thick oil, methyl (E,Z)-(R)-18-((S)-2,2-dimethyl[1,3]
dioxolan-4-yl)-nonadec-15-enoate (4.4 g, 61%) as a mixture of two
isomers in ratio 2:1. Palladium 10% on carbon (1 g) was stirred
with the alkenes (4.40 g, 10.7 mmol) in ethanol (100 mL) and THF
(20 mL) under hydrogen for 2 h until no more hydrogen was
absorbed. The solution was filtered through a bed of Celite and the
solvent was evaporated to give a white solid, the title compound
28 (4.15, 93%), mp: 36e38 ꢃC [Found (MþNa)þ: 435.3387,
687.5241], ½a 2D0
þ6.25 (c 1.3, CHCl3); dH (500 MHz, CDCl3):
ꢀ
7.72e7.68 (2H, m), 7.64e7.57 (3H, m), 3.72 (2H, t, J 7.9 Hz), 2.66 (1H,
dt, J 1.9, 5.7 Hz), 2.45 (1H, dd, J 2.3, 7.3 Hz), 1.98e1.91 (2H, m),
1.58e1.25 (53H, br m, including br s at 1.25), 0.91 (3H, d, J 6.6 Hz),
0.87 (3H, t, J 6.6 Hz); dC (125 MHz, CDCl3): 153.5, 133.0, 131.4, 129.6,
125.0, 63.7, 57.4, 56.0, 35.8, 34.6, 32.2, 31.9, 29.9, 29.7, 29.6, 29.57,
29.55, 29.52, 29.5, 29.47, 29.4, 29.3, 29.1, 28.8, 28.1, 26.8, 26.1, 22.6,
21.9, 15.9, 14.1; nmax: 2921, 2853, 1500, 1463, 1377, 1344, 1153,
C
25H48NaO4 requires: 435.3450], ½a D20
þ11.3 (c 1.50, CHCl3), which
ꢀ
showed dH (500 MHz, CDCl3): 4.0 (1H, br q, J 6.3 Hz), 3.86 (1H, br
q, J 7.3 Hz), 3.66 (3H, s), 3.59 (1H, br t, J 7.6 Hz), 2.30 (2H, t, J
7.6 Hz), 1.61 (1H, pent., J 7.3 Hz), 1.57e1.53 (2H, m), 1.40 (3H, s),
1.35 (3H, s), 1.28e1.21 (27H, br s), 1.10e1.06 (1H, m), 0.96 (3H, d, J
6.6 Hz); dC (125 MHz, CDCl3): 174.3, 108.5, 80.4, 67.8, 51.4, 36.5,
34.1, 32.7, 29.8, 29.64, 29.62, 29.6, 29.57, 29.4, 29.2, 29.1, 27.0, 26.6,
25.5, 24.9, 15.6; nmax: 2922, 2853, 1736, 1463, 1377, 1213, 1169,
1049 cmꢁ1
.
1051 cmꢁ1
.
4.1.11. Methyl
15-(1-phenyl-1H-tetrazole-5-sulfonyl)-pentadeca-
noate 26.
4.1.13. (R)-18-((S)-2,2-Dimethyl[1,3]dioxolan-4-yl)-nonadecan-1-ol
29. (R)-18-((S)-2,2-Dimethyl[1,3]dioxolan-4-yl)nonadecanoic acid
methyl ester (4.0 g, 9.7 mmol) in THF (30 mL) was added dropwise
over 15 min to a suspension of lithium aluminium hydride (0.560 g,
14.5 mmol) in THF (100 mL) at rt. The mixture was heated under
reflux for 1 h, then cooled to rt and quenched carefully with freshly
prepared satd aq sodium sulfate decahydrate (10 mL) until a white
precipitate was formed, followed by the addition of magnesium
sulfate (10 g). The mixture was stirred vigorously for 10 min and
then filtered through a bed of Celite and washed with THF (100 mL).
The filtrate was evaporated to give a residue, which was purified by
chromatography on silica gel eluting with petrol/ethyl acetate (2:1)
to give a white solid, tþhe title compound 29 (3.4 g, 91%), mp:
56e57 ꢃC [Found (MþH) : 385.3678, C24H49O3 requires: 385.3678],
(i) Methyl 15-bromopentadecanoate (see Supplementary data)
(20.6 g, 61.5 mmol) was added with vigorous stirring to 1-
phenyl-1H-tetrazole-5-thiol (10.95 g, 61.49 mmol) and an-
hydrous potassium carbonate (17.0 g, 123 mmol) in acetone
(250 mL). The mixture was heated under reflux for 2.5 h
then worked up and purified as before to give methyl 15-(1-
phenyl-1H-tetrazole-5-ylsulfanyl)pentadecanoatþe as a white
solid (24 g, 90%), mp: 62e64 ꢃC [Found (MþNa) : 455.2448,
C
23H36N4NaO2S requires: 455.2451], which showed dH
(500 MHz, CDCl3): 7.75e7.60 (5H, m), 3.67 (3H, s), 3.39 (2H,
t, J 7.3 Hz), 2.30 (2H, t, J 7.6 Hz), 1.82 (2H, quintet, J 7.4 Hz),
1.62 (2H, quintet, J 7.4 Hz), 1.47e1.41 (2H, m), 1.32e1.25 (18H,
m); dC (125 MHz, CDCl3): 174.3, 154.5, 133.8, 130.1, 129.8,
123.9, 51.4, 34.1, 33.4, 29.6, 29.56, 29.5, 29.4, 29.3, 29.2, 29.1,
29.0, 28.6, 25.0; nmax: 2916, 2850, 1742, 1499, 1472, 1250,
½
a 1D8
ꢀ
þ17.6 (c 1.10, CHCl3), which showed dH (500 MHz, CDCl3): 3.99
(1H, dd, J 3.6, 7.9 Hz), 3.86 (1H, br q, J 6.9 Hz), 3.63 (2H, t, J 6.6 Hz),
3.59 (1H, t, J 7.9 Hz), 2.1 (1H, s), 1.59e1.51 (4H, m), 1.39 (3H, s), 1.34
(3H, s), 1.32e1.21 (28H, br m, including br s at 1.25), 1.11e1.03 (1H,
m), 0.95 (3H, d, J 6.9 Hz); dC (125 MHz, CDCl3): 108.5, 80.4, 67.8,
63.0, 36.5, 32.8, 32.7, 29.8, 29.64, 29.63, 29.6, 29.58, 29.4, 27.0, 26.6,
25.7, 25.5, 15.6; nmax: 3448, 2961, 2923, 2852, 1465, 1377, 1155,
1171 cmꢁ1
.
(ii) A solution of ammonium molybdate (VI) tetrahydrate (30.9 g,
25.0 mmol) in H2O2 (35% w/w, 70 mL) was added to a stirred
solution of methyl 15-(1-phenyl-1H-tetrazole-5-ylsulf-anyl)
pentadecanoate (24.0 g, 55.5 mmol) in THF (300 mL) and IMS
(500 mL) at 12 ꢃC and stirred at rt for 2 h. Further ammonium
molybdate (VI) tetrahydrate (13.0 g, 10.5 mmol) in H2O2 (35%,
w/w, 35 mL) was added and the mixture was stirred at rt for
18 h, then worked up and purified as before to give the title
compound 26 as a white solid (23.6 g, 91%), mp: 72e73 ꢃC
[Found (MþNa)þ: 487.2343, C23H36N4NaO4S requires:
487.2349], which showed dH (500 MHz, CDCl3): 7.71e7.68 (2H,
m), 7.63e7.58 (3H, m), 3.73 (2H, distorted t, J 8.2 Hz), 3.67 (3H,
s), 2.30 (2H, t, J 7.6 Hz), 1.98e1.92 (2H, m), 1.64e1.58 (2H, m),
1.52e1.46 (2H, m), 1.34e1.25 (18H, m); dC (125 MHz, CDCl3):
174.3, 153.5, 133.0, 131.4, 129.9, 129.7, 125.0, 124.98, 56.0, 51.4,
34.1, 29.54, 29.53, 29.51, 29.5, 29.4, 29.2, 29.15, 28.9, 28.1, 25.0,
21.9; nmax: 2918, 2948, 1729, 1497, 1464, 1343, 1255, 1199,
1056 cmꢁ1
.
4.1.14. (S)-4-((R)-18-Bromo-1-methyloctadecyl)-2,2-dimethyl-[1,3]
dioxolane 30. N-Bromosuccinimide (2.04 g, 11.5 mmol) was added
in portions over 15 min to a stirred solution of (R)-18-((S)-2,2-
dimethyl[1,3]dioxolan-4-yl)nonadecan-1-ol (3.4 g, 8.9 mmol), tri-
phenylphosphine (2.89 g, 11.1 mmol) and sodium hydrogen
carbonate (0.2 g) in dichloromethane (70 mL) at 0 ꢃC. The mixture
was stirred at rt for 1 h, then quenched with satd aq sodium meta-
bisulfite (50 mL). The organic layer was separated and the aqueous
layer was re-extracted with dichloromethane (2ꢂ50 mL). The
combined organic extracts were washed with water (50 mL), dried
and evaporated to give a residue. This was heated under reflux for
30 min with ether (150 mL) and then filtered and washed with
petrol/ethyl acetate (5:1, 50 mL). The filtrate was evaporated and
the residue was purified by column chromatography eluting with
petrol/ethyl acetate (5:1) to give a colourless oil, the title compound
30 (3.8 g, 96%) [Found Mþ: 447.2831, C24H47Br79O2 requires:
1157 cmꢁ1
.
4.1.12. Methyl
(R)-18-((S)-2,2-dimethyl-[1,3]dioxolan-4-yl)-non-
adecanoate 28. Lithium bis(trimethylsilyl)amide (27.8 mL,
29.5 mmol,1.06 M) was added dropwise with stirring to (R)-3-((S)-
2,2-dimethyl-[1,3]dioxolan-4-yl)-butyraldehyde 2728,34,35 (3.0 g,
17 mmol) and sulfone 26 (10.5, 22.7 mmol) in dry THF (150 mL)
under nitrogen at ꢁ10 ꢃC. The mixture was allowed to reach rt and
stirred for 1 h, then quenched with water (80 mL) and petrol/ethyl
acetate (1:1, 80 mL). The organic layer was separated and the
aqueous layer was re-extracted with petrol/ethyl acetate (1:1,
447.2832], ½a 1D8
þ16.5 (c 1.1, CHCl3), which showed dH (500 MHz,
ꢀ
CDCl3): 3.98 (1H, dd, J 6.0, 7.6 Hz), 3.85 (1H, q, J 7.3 Hz), 3.58 (1H, t, J
7.6 Hz), 3.38 (2H, t, J 6.9 Hz), 1.84 (2H, pent., J 7.0 Hz), 1.59e1.51 (1H,
m), 1.44e1.40 (2H, m), 1.38 (3H, s), 1.33 (3H, s), 1.31e1.2 (27H, br m,
including br s at 1.25), 1.0e1.03 (1H, m), 0.95 (3H, d, J 6.6 Hz); dC
(125 MHz, CDCl3): 108.4, 80.4, 67.8, 36.5, 33.7, 32.8, 32.77, 29.8,

7330
D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
29.6, 29.57, 29.5, 29.4, 28.7, 28.2, 27.0, 26.6, 25.5, 15.6; nmax: 2985,
2921, 2851, 1470, 1377, 1369, 1250, 1216, 1160, 1056 cmꢁ1
Column chromatography eluting with petrol/ethyl acetate (20:1)
.
gave a colourless oil, the title compound 33 (3.53 g, 95%) [Found
(MþNa)þ: 943.8484, C58H116NaO5Si requires: 943.8489],
½ ꢀ
a 2D0
4.1.15. 5-[(R)-18-((S)-2,2-Dimethyl-[1,3]dioxolan-4-yl)nonadecane
sulfonyl]-1-phenyl-1H-tetrazole 31.
þ4.41 (c 1.62, CHCl3), which showed dH (500 MHz, CDCl3): 4.0 (1H,
dd, J 6.3, 7.6 Hz), 3.92e3.90 (1H, m), 3.87 (1H, br q, J 7.0 Hz), 3.65
(3H, s), 3.60 (1H, br t, J 7.9 Hz), 2.52 (1H, ddd, J 3.8, 7.3, 11.0 Hz),
1.59e1.53 (2H, m), 1.49e1.42 (2H, m), 1.40 (3H, s), 1.35 (3H, s),
1.29e1.22 (77H, br m, including br s at 1.26), 0.96 (3H, d, J 6.7 Hz),
0.88 (3H, t, J 7.3 Hz), 0.86 (9H, s), 0.047 (3H, s), 0.023 (3H, s); dC
(125 MHz, CDCl3): 175.1, 108.5, 80.4, 73.2, 67.8, 51.9, 51.6, 36.5, 33.7,
32.7, 31.9, 29.9, 29.8, 29.7, 29.67, 29.65, 29.6, 29.57, 29.55, 29.4,
29.35, 27.8, 27.5, 27.0, 26.6, 25.75, 25.5, 23.7, 22.7, 18.0, 15.6,
14.1, ꢁ4.37, ꢁ4.9; nmax: 2924, 2853, 1740, 1464, 1377, 1368, 1253,
(i) (S)-4-((R)-18-Bromo-1-methyloctadecyl)-2,2-dimethyl-[1,3]
dioxolane (3.8 g, 8.5 mmol) was added with vigorous stirring to
1-phenyl-1H-tetrazole-5-thiol (1.5 g, 8.5 mmol) and anhydrous
potassium carbonate (2.34 g, 17.0 mmol) in acetone (100 mL).
The mixture was heated under reflux for 2.5 h, then worked up
and purified by chromatography on silica gel eluting with
petrol/ethyl acetate (8:2) to give a yellow oil, 5-[(R)-18-((S)-
2,2-dimethyl[1,3]dioxolan-4-yl)nonadecylsulfan-yl]-1-phenyl-
1H-tetrazole (4.2 g, 90%) [Found (MþH)þ: 545.3860,
1165, 1067 cmꢁ1
.
C
31H53N4O2S requires: 545.3884], ½a D20
þ12.6 (c 1.46, CHCl3),
ꢀ
4.1.17. Methyl (2R,3R,23R)-23-((S)-2,2-dimethyl[1,3]-dioxolan-4-yl)-
2-docosyl-3-hydroxytetracosanoate 34. The ester 33 (3.85 g,
4.17 mmol) was dissolved in dry THF (50 mL) in a dry poly-ethylene
vial under nitrogen at rt and stirred. Pyridine (1.5 mL) and hydrogen
fluoride-pyridine complex (4 mL) were added and the mixture was
stirred for 17 h at 40 ꢃC, then poured slowly to a satd aq NaHCO3
until no more carbon dioxide was liberated and the product was
extracted with petrol/ethyl acetate (1:1, 3ꢂ50 mL). The combined
organic layers were washed with brine and dried. The solvent was
evaporated and the crude product was purified by column chro-
matography eluting with petrol/ethyl acetate (20:1) to give a white
solid, the title compound 34 (2.7 g, 80%), mp: 56e58 ꢃC [Found
which showed dH (500 MHz, CDCl3): 7.58e7.49 (5H, m), 3.98
(1H, dd, J 6.3, 7.5 Hz), 3.85 (1H, q, J 7.0 Hz), 3.58 (1H, t, J 7.6 Hz),
3.37 (2H, t, J 7.3 Hz),1.80 (2H, pent., J 7.3 Hz),1.58e1.50 (1H, m),
1.45e1.41 (2H, m), 1.38 (3H, s), 1.30 (3H, s), 1.29e1.2 (27H, br m,
including br s at 1.24), 1.11e1.02 (1H, m), 0.94 (3H, d, J 6.6 Hz);
dC (125 MHz, CDCl3): 154.4, 133.8, 129.9, 129.7, 123.8, 108.4,
80.3, 67.7, 36.4, 33.4, 32.7, 29.8, 29.6, 29.55, 29.5, 29.46, 29.4,
29.1, 29.0, 28.6, 26.9, 26.6, 25.5, 15.5; nmax: 2983, 2924, 2853,
1598, 1500, 1464, 1379, 1245, 1064 cmꢁ1
.
(ii) Ammonium molybdate (IV) tetrahydrate (4.0 g, 3.3 mmol) in
ice cold H2O2 (35% w/w, 10 mL) was added to a stirred solution
of the above tetrazole (4.0 g, 7.3 mmol) in IMS (100 mL) and
THF (10 mL) at 12 ꢃC and stirred at rt for 2 h. Further ammo-
nium molybdate (IV) tetrahydrate (4.0 g, 3.3 mmol) in ice cold
H2O2 (35% w/w, 10 mL) was added and the mixture was stirred
at rt for 18 h, then worked up and purified by chromatography
on silica gel eluting with petrol/ethyl acetate (8:2) to give
a white solid, the title compound 31 (3.9 g, 92%), mp: 52e54 ꢃC
[Found (MþNa)þ: 599.3632, C31H52N4NaO4S requires:
(MþNa)þ: 829.7631, C52H102NaO5 requires: 829.7624], ½a D25
þ13.3
ꢀ
(c 1.07, CHCl3), which showed dH (500 MHz, CDCl3): 4.0 (1H, dd,
J 6.3, 7.9 Hz), 3.87 (1H, br q, J 7.3 Hz), 3.71 (3H, s), 3.65 (1H, br s), 3.60
(1H, br t, J 7.6 Hz), 2.43 (1H, dt, J 5.4, 10.4 Hz), 1.73e1.67 (1H, m),
1.60e1.53 (2H, m), 1.47e1.43 (2H, m), 1.40 (3H, s), 1.35 (3H, s),
1.31e1.21 (77H, br m), 0.96 (3H, d, J 6.7 Hz), 0.88 (3H, t, J 6.6 Hz); dC
(125 MHz, CDCl3): 176.2, 108.5, 80.4, 72.3, 67.8, 51.5, 50.9, 36.5, 35.7,
32.7, 31.9, 29.9, 29.7, 29.66, 29.62, 29.6, 29.55, 29.53, 29.5, 29.4,
29.35, 27.4, 27.0, 26.6, 25.7, 25.5, 22.7, 15.6, 14.1; nmax: 3369, 2953,
599.3606], ½a 2D0
þ12.5 (c 1.10, CHCl3), which showed dH
ꢀ
(500 MHz, CDCl3): 7.70e7.68 (2H, m), 7.64e7.58 (3H, m), 4.0
(1H, dd, J 6.3, 7.9 Hz), 3.87 (1H, q, J 7.0 Hz), 3.73 (2H, t, J 7.9 Hz),
3.60 (1H, t, J 7.9 Hz), 1.98e1.92 (2H, m), 1.58e1.54 (1H, m),
1.52e1.47 (2H, m), 1.40 (3H, s), 1.35 (3H, s), 1.33e1.22 (27H, br
m, including br s at 1.26), 1.11e1.07 (1H, m), 0.96 (3H, d, J
6.7 Hz); dC (125 MHz, CDCl3): 153.6, 133.2, 131.4, 129.7, 125.1,
108.5, 80.4, 67.8, 56.1, 36.5, 32.8, 29.9, 29.64, 29.61, 29.6, 29.5,
29.4, 29.2, 28.9, 28.1, 27.0, 26.6, 25.5, 22.0, 15.6; nmax: 2921,
2922, 2853, 1709, 1461, 1377, 1188, 1164 cmꢁ1
.
4.1.18. Methyl (2R,3R,23R)-3-acetoxy-23((S)-2,2-dimethyl-[1,3]diox-
olan-4-yl)-2-docosyltetracosanoate 35. A mixture of acetic anhy-
dride (10 mL) and anhydrous pyridine (10 mL) was added to stirred
solution of the methyl (2R,3R, 23R)-23-((S)-2,2-dimethyl[1,3]diox-
olan-4-yl)-2-docosyl-3-hydroxytetracosanoate (2.6 g, 3.2 mmol) in
dry toluene (35 mL) at rt and stirred for 18 h, then diluted with
toluene (10 mL) and the solvent was evaporated. Column chro-
matography eluting with petrol/ethyl acetate (10:1) gave a white
solid, the title compound 35 (2.7 g, 98%), mp: 51e52 ꢃC [Found
2853, 1460, 1377, 1149, 1066 cmꢁ1
.
4.1.16. Methyl (2R,3R,23R)-3-(tert-butyldimethylsilanyloxy)-23-((S)-
2,2-dimethyl[1,3]dioxolan-4-yl)-2-docosyl-tetracosanoate
33. Lithium bis(trimethylsilyl)amide (9.0 mL, 9.6 mmol, 1.06 M)
was added dropwise with stirring to methyl (R)-2-[(R)-1-(tert-
butyldimethylsilanyloxy)-3-oxopropyl]tetracosanoate 32 (3.5 g,
6.15 mmol)28,31 and sulfone 31 (4.26 g, 7.38 mmol) in dry THF
(50 mL) under nitrogen at ꢁ10 ꢃC. The mixture was allowed to
reach rt and stirred for 2 h, then quenched with water (50 mL) and
petrol/ethyl acetate (1:1, 50 mL). The aqueous layer was re-
extracted with petrol/ethyl acetate (1:1, 2ꢂ50 mL). The combined
organic layers were washed with satd aq sodium chloride
(2ꢂ50 mL), dried and evaporated to give a thick oil. Chromatog-
raphy eluting with petrol/ethyl acetate (20:1) gave a colourless oil,
methyl (E/Z)-(2R,3R,23R)-3-(tert-butyldimethylsilanyloxy)-23-((S)-
2,2-dimethyl[1.3]dioxolan-4-yl)-2-docosyltetracos-5-enoate (4.4 g,
89%) as a mixture of two isomers in ratio 2:1. Palladium on carbon
(10%, 1.5 g) was added to a stirred solution of the alkenes (4.0 g,
4.0 mmol) in IMS (30 mL) and THF (10 mL) under hydrogen at-
mosphere. Hydrogenation was carried out for 2 h then the mixture
was filtered through a bed of Celite and the solvent was evaporated.
(MþNa)þ: 871.7758, C54H104NaO6 requires: 871.7730], ½a D25
þ15.4 (c
ꢀ
1.10, CHCl3), which showed dH (500 MHz, CDCl3): 5.08 (1H, br dq,
J 4.1, 8.2 Hz), 4.0 (1H, dd, J 6.3, 7.9 Hz), 3.87 (1H, br q, J 7.6 Hz), 3.68
(3H, s), 3.60 (1H, br t, J 7.6 Hz), 2.61 (1H, ddd, J 4.4, 6.9, 11.0 Hz), 2.03
(3H, s), 1.64e1.21 (80H, br m, including br s at 1.25),1.40 (3H, s),1.35
(3H, s), 1.11e1.04 (1H, m), 0.96 (3H, d, J 6.6 Hz), 0.88 (3H, t, J 6.6 Hz);
dC (125 MHz, CDCl3): 173.6, 170.3, 108.5, 80.4, 74.1, 67.8, 51.5, 49.6,
36.5, 32.7, 31.9, 31.7, 29.9, 29.7, 29.64, 29.6, 29.5, 29.42, 29.4, 29.34,
28.1, 27.5, 27.0, 26.6, 25.5, 24.98, 22.7, 21.0, 15.6, 14.1; nmax: 2953,
2923, 2854, 1748, 1462, 1377, 1235, 1161 cmꢁ1
.
4.1.19. Methyl (2R,3R,23R)-3-acetoxy-2-docosyl-23-methyl-24-oxo-
tetracosanoate 36. Periodic acid (1.8 g, 7.9 mmol) was added to
a stirred solution of ester 35 (2.7 g, 3.2 mmol) in dry ether (70 mL)
at rt under nitrogen. The mixture was stirred for 16 h, then filtered
through a bed of Celite and washed with ether. The solvent was
evaporated and the crude product was purified by column chro-
matography eluting with petrol/ethyl acetate (7:1) to give a white
solid, the title compound 36 (1.6 g, 64%), mp: 41e43 ꢃC, ½a D25
þ4.90
ꢀ

D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
7331
(c 1.02, CHCl3), which showed dH (500 MHz, CDCl3): 9.61 (1H, d, J
2.2 Hz), 5.08 (1H, br dt, J 3.8, 7.9 Hz), 3.68 (3H, s), 2.61 (1H, ddd, J 4.5,
7.0, 11.1 Hz), 2.37e2.29 (1H, m), 2.03 (3H, s), 1.72e1.21 (80H, br m,
including br s at 1.25), 1.09 (3H, d, J 7.0 Hz), 0.88 (3H, t, J 6.6 Hz); dC
(125 MHz, CDCl3): 205.4,173.6,170.3, 74.1, 51.5, 49.6, 46.3, 31.9, 31.7,
30.5, 29.72, 29.4, 29.39, 29.34, 28.1, 27.5, 26.9, 25.0, 22.7, 21.0, 14.1,
carried out with dipotassium azodicarboxylate (2.50 g, 12.9 mmol)
as before; chromatography eluting with petrol/ethyl acetate (20:1)
gave a white solid, the title compound 41 (1.0 g, 96%), mp: 44e46 ꢃC
[Found (MþNa)þ: 551.3796, C31H61Br79NaO requires: 551.3798],
½
a 2D4
ꢀ
ꢁ8.1 (c 1.05, CHCl3), which showed dH (500 MHz, CDCl3): 3.40
(2H, t, J 7 Hz), 2.71 (1H, dt, J 2.2, 5.4 Hz), 2.41 (1H, dd, J 1.9, 7 Hz),
1.88e1.82 (3H, m),1.54e1.24 (48H, br m, including br s at 1.26), 0.99
(3H, d, J 6.3 Hz), 0.88 (3H, t, J 7 Hz); dC (125 MHz, CDCl3): 63.8, 58.8,
36.0, 33.9, 33.8, 32.8, 32.2, 31.9, 29.9, 29.7, 29.65, 29.63, 29.61, 26.0,
29.52, 29.5, 29.4, 29.3, 28.7, 28.2, 27.2, 26.1, 22.7, 17.2, 14.2, 14.1;
13.3; nmax: 2923, 2852, 1745, 1465, 1371, 1236, 1165, 1022 cmꢁ1
.
4.1.20. Methyl (E)-(2R,3R,23R)-3-acetoxy-23-methyl-37-[(2S,3S)-3-
((R)-1-methylheptadecyl)oxiranyl]-2-docosyl-heptatri acont-24-
enoate 37. Potassium bis(trimethylsilyl)amide (0.350 mL,
0.176 mmol, 0.5 M) was added dropwise with stirring to aldehyde
36 (0.088 mg, 0.113 mmol) and sulfone 21 (0.093 mg, 0.135 mmol)
in dry 1,2-dimethoxyethane (7 mL) under nitrogen at ꢁ5 ꢃC. The
mixture was allowed to reach 10 ꢃC, then quenched with water
(5 mL) and petrol/ethyl acetate (20:1, 20 mL) was added. The
aqueous layer was re-extracted with petrol/ethyl acetate (20:1,
2ꢂ15 mL). The combined organic layers were washed with satd aq
sodium chloride (2ꢂ15 mL), dried and evaporated. Column chro-
matography eluting with petrol/ethyl acetate (20:1) gave a white
solid, the title compound 37 (37 mg, 26%), mp: 34e35 ꢃC [Found
nmax: 2924, 2853, 1465, 1376 cmꢁ1
.
4.1.23. 5-(11-((2S,3S)-3-((R)-Octadecan-2-yl)oxiran-2-yl)undecyl
sulfonyl)-1-phenyl-1H-tetrazole 42.
(i) Bromide 41 (1.0 g, 1.9 mmol) was added with vigorous stirring
to 1-phenyl-1H-tetrazole-5-thiol (0.37 g, 2.1 mmol) and an-
hydrous potassium carbonate (0.52 g, 3.8 mmol) in acetone
(35 mL). The mixture was heated under reflux for 2.5 h, then
worked up and purified as before to give a white solid, 5-
(11-((2S,3S)-3-((R)-octadecan-2-yl)oxiran-2-yl)undecyl-thio)-
1-phenyl-1H-tetrazole (0.84 g, 71%), mp: 39e40 ꢃC [Found
(MþH)þ: 627.5033, C38H67N4OS requires: 627.5035], ½ ꢀD ꢁ4.8
(c 0.99, CHCl3), which showed dH (500 MHz, CDCl3): 7.60e7.53
(5H, m), 3.39 (2H, t, J 7.3 Hz), 2.71 (1H, dt, J 2.2, 5.7 Hz), 2.41(1H,
dd, J 2.2, 7.3 Hz), 1.82 (1H, pent., J 7.3 Hz), 1.54e1.22 (50H, m,
including br s at 1.26), 0.99 (3H, d, J 6.3 Hz), 0.88 (3H, t, J
6.6 Hz); dC (125 MHz, CDCl3): 154.5, 133.8, 130.0, 129.7, 123.9,
63.8, 58.8, 36.0, 33.8, 33.4, 32.2, 31.9, 29.9, 29.7, 29.65, 29.63,
29.6, 29.52, 29.5, 29.4, 29.3, 29.1, 29.0, 28.6, 27.2, 26.1, 22.7, 17.2,
a 18
(MþNa)þ: 1260.2128, C83H160NaO5 requires: 1260.2158], ½ ꢀD ꢁ2.0
a 21
(c 1.0, CHCl3), which showed dH (500 MHz, CDCl3): 5.33 (1H, br dq, J
6.7, 15.5 Hz), 5.24 (1H, dd, J 7.6, 15.5 Hz), 5.11e5.07 (1H, m), 3.68
(3H, s), 2.71 (1H, dt, J 2.2, 5.4 Hz), 2.62 (1H, ddd, J 4.1, 6.6, 10.7 Hz),
2.40 (1H, dd, J 5.1, 7.3 Hz), 2.03 (3H, s), 1.99e1.94 (2H, m), 1.69e1.08
(134H, br m, including br s at 1.26), 1.00 (3H, d, J 6.0 Hz), 0.94 (3H, d,
J 7 Hz), 0.89 (6H, t, J 6.6 Hz); dC (125 MHz, CDCl3): 173.6,170.3,136.5,
128.4, 74.1, 63.8, 58.8, 51.5, 49.6, 37.2, 36.7, 36.0, 33.8, 32.6, 32.3,
31.9, 31.7, 29.9, 29.8, 29.7, 29.66, 29.65, 29.6, 29.55, 29.53, 29.5,
29.46, 29.43, 29.4, 29.35, 29.1, 28.1, 27.5, 27.3, 27.2, 26.1, 25.0, 22.7,
14.1; nmax: 2923, 2852, 1500, 1466, 1385, 1243, 1073 cmꢁ1
.
(ii) Ammonium molybdate (VI) tetrahydrate (0.70 g, 0.57 mmol) in
ice cold H2O2 (35% w/w, 3 mL) was added to a stirred solution
of the above tetrazole (0.79 g, 1.25 mmol) in THF (10 mL) and
IMS (25 mL) at 12 ꢃC and stirred at rt for 2 h. Further ammo-
nium molybdate (VI) tetrahydrate (0.3 g, 0.24 mmol) in ice cold
H2O2 (35% w/w, 2 mL) was added and the mixture was stirred
at rt 18 h, then worked up and purified as before to give a white
solid, the title compound 42 (0.70 g, 84%), mp: 42e44 ꢃC
[Found (MþH)þ: 659.4907, C38H67N4O3S requires: 659.4928],
21.0, 20.9, 17.3, 14.1; nmax: 2919, 2851, 1737, 1470, 1238 cmꢁ1
.
4.1.21. (E)-(2R,3R,23R)-3-Hydroxy-23-methyl-37-[(2S, 3S)-3-((R)-1-
methylheptadecyl)-oxiranyl]-2-docosyl-heptatriacont-24-enoic acid
38. Lithium hydroxide monohydrate (31.8 mg, 0.759 mmol) was
added to a stirred solution of ester 37 (31.4 mg, 0.0253 mmol) in
THF (4 mL), methanol (0.5 mL) and water (0.5 mL) at rt. The mixture
was stirred at 45 ꢃC overnight, then cooled to rt and a mixture of
petrol/ethyl acetate (7:2, 5 mL) was added. The mixture was acid-
ified to pH 1 with potassium hydrogen sulfate. Further petrol/ethyl
acetate (7:2, 10 mL) was added and the organic layer was separated.
The aqueous layer was re-extracted with petrol/ethyl acetate (7:2,
2ꢂ10 mL). The combined organic layers were dried and evaporated.
The crude product was crystallized from petrol/ethyl acetate (10:1,
15 mL) and left for 30 min at room temperature then at 0 ꢃC for
15 min to give white crystals ofþthe title compound 38 (22 mg, 72%),
mp: 71e73 ꢃC [Found (MþNa) : 1204.1912, C80H156NaO4 requires:
½
a 2D0
ꢀ
ꢁ14.2 (c 0.79, CHCl3), which showed dH (500 MHz, CDCl3):
7.71e7.69 (2H, m), 7.63e7.58 (3H, m), 3.73 (2H, t, J 7.9 Hz), 2.71
(1H, dt, J 2.2, 5.7 Hz), 2.41 (1H, dd, J 2.2, 7.0 Hz), 1.99e1.92 (2H,
m), 1.58e1.22 (49H, m, including br s at 1.26), 1.0 (3H, d, J
6.3 Hz), 0.88 (3H, t, J 6.7 Hz); dC (125 MHz, CDCl3): 153.6, 133.1,
131.4, 129.7, 125.1, 63.8, 58.8, 56.1, 36.0, 33.8, 32.2, 31.9, 29.9,
29.7, 29.63, 29.6, 29.5, 29.45, 29.43, 29.4, 29.3, 29.2, 28.9, 28.1,
27.2, 26.1, 22.7, 21.9, 17.2, 14.1; nmax: 2923, 2853, 1463, 1342,
1152 cm1.
1204.1896], ½a 2D0
ꢁ5.5 (c 0.74, CHCl3), dH (500 MHz, CDCl3): 5.33
ꢀ
(1H, td, J 6.3,15.2 Hz), 5.24 (1H, dd, J 7.6,15.2 Hz), 3.74e3.70 (1H, m),
2.73 (1H, dt, J 2.2, 5.3 Hz), 2.49e2.45 (1H, m), 2.43 (1H, dd, J 2.2,
7.3 Hz), 2.11e2.01 (2H, m), 1.96 (2H, q, J 6.7 Hz), 1.78e1.06 (134H, br
m, including br s at 1.26), 1.0 (3H, d, J 6.3 Hz), 0.94 (3H, d, J 6.7 Hz),
0.89 (6H, t, J 6.6 Hz); dC (125 MHz, CDCl3): 178.7, 136.5, 128.4, 72.1,
64.0, 59.0, 50.7, 37.2, 36.7, 36.0, 35.5, 33.8, 32.6, 32.2, 31.9, 29.9, 29.8,
29.7, 29.6, 29.53, 29.5, 29.4, 29.36, 29.1, 27.3, 27.2, 26.1, 25.7, 22.7,
4.1.24. ((1S,2R)-2-(Tetrahydro-2H-pyran-2-yloxy)methyl)-cyclo-
propyl butyrate 45. 3,4-Dihydro-2H-pyran (7.81 g, 92.9 mmol) and
pyridinium-p-toluene sulfonate (0.58 g, 2.32 mmol) were added to
a
stirred solution of ((1S,2R)-2-(hydroxymethyl)cyclopropyl)
methyl butyrate42 (8.0 g, 46 mmol) in dry CH2Cl2 (150 mL) under
nitrogen at rt. The reaction was stirred for 3 h and worked up with
satd aq NaHCO3 (20 mL). The organic layer was separated and the
aqueous layer was extracted with CH2Cl2 (2ꢂ50 mL). The combined
organic layers were dried and evaporated; column chromatography
on silica gel eluting with petrol/ethyl acetate (10:1) to give a col-
ourless oil, the title compound 45 as a mixture of diastereoisomers
(10.0 g, 84%) [Found (MþNa)þ: 279.1594, C14H24NaO4 requires:
21.0, 17.3, 14.1; nmax: 3368, 2922, 2851, 1686, 1463, 1048 cmꢁ1
.
4.1.22. (2S,3S)-2-(11-Bromoundecyl)-3-((R)-octadecan-2-yl)oxirane
41. Lithium bis(trimethylsilyl)amide (5.23 mL, 5.54 mmol, 1.06 M)
was added dropwise to a stirred solution of aldehyde 18 (1.0 g,
3.0 mmol) and sulfone 40 (1.58 g, 3.69 mmol) in dry tetrahydro-
furan (36 mL) under nitrogen at ꢁ10 ꢃC. The mixture was allowed to
reach room temperature and stirred for 1 h, then worked up and
purified as before to give (2S,3S)-2-((E/Z)-11-bromoundec-1-enyl)-
3-((R)-octadec-an-2-yl)oxirane (1.03 g, 63%). Hydrogenation was
279.1567], ½a 2D0
þ2.01 (c 1.19, CHCl3), which showed dH (500 MHz,
ꢀ
CDCl3): 4.61 (1H, t, J 3.8 Hz), 4.53 (1H, t, J 4.1 Hz), 4.16 (1H, td, J 2.2,
3.5 Hz), 4.14 (1H, dd, J 2.2, 7.6 Hz), 4.04e3.97 (2H, m), 3.85e3.75
(3H, m), 3.63e3.6 (1H, m), 3.51e3.43 (3H, m), 3.32 (1H, br dd, J 7.6,

7332
D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
10.8 Hz), 2.26 (2H, t, J 7.3 Hz), 2.25 (2H, t, J 7.6 Hz), 1.82e1.77 (2H,
m), 1.70e1.46 (14H, m), 1.28e1.22 (4H, m), 0.91 (6H, t, J 7.3 Hz),
0.85e0.79 (2H, m), 0.28 (1H, q, J 5.4 Hz), 0.25 (1H, q, J 5.4 Hz); dC
(125 MHz, CDCl3): 173.6, 173.6, 98.7, 98.21, 94.5, 67.1, 67.0, 64.5,
64.45, 62.2, 61.9, 36.1, 30.6, 30.57, 30.5, 25.4, 25.3, 19.6, 19.5, 19.3,
18.3, 15.6, 15.3, 14.4, 14.2, 13.5, 8.5, 8.3; nmax: 2942, 2874, 1735, 1458,
step without further analysis; (c) Triethylamine (1.38 mL,
13.7 mmol) was added dropwise at 0 ꢃC to a stirred solution of 48
(4.50 g, 11.4 mmol) in dry dichloromethane (50 mL) under nitrogen.
After stirring for 10 min, tert-butyl diphenylchlorosilane (3.44 g,
12.5 mmol) was added followed by the addition of 4-
dimethylaminopyridine (29 mg). The mixture was then stirred for
5 h at rt followed by quenching with water (10 mL). The organic
layer was separated and the aqueous layer was extracted with
dichloromethane (3ꢂ30 mL). The combined organic layers were
dried and concentrated to give the crude product; chromatography
eluting with petrol/ethyl acetate (5:1) gave a colourless oil (6.9 g,
95%), which was used for next step without further analysis; (d) A
solution of pyridinium-p-toluene sulfonate (1.36 g, 5.42 mmol) in
methanol (10 mL) was added to a stirred solution of the above si-
lane (6.9 g, 10.9 mmol) in THF (40 mL) and stirred at 50 ꢃC over-
night. Satd aq NaHCO3 (10 mL) and water (25 mL) were added and
extracted with ethyl acetate (3ꢂ40 mL). The combined organic
layers were dried and the solvent was evaporated. Column chro-
matography eluting with petrol/ethyl acetate (6:1) gave a colour-
less oil, ((1R,2R)-2-((E/Z)-16-(tert-butyldiphenylsilyloxy)hexadec-
1-enyl)cyclopropyl)methanol 49 (4.9 g, 82%); (e) Hydrogenation
was carried out with dipotassium azodicarboxylate as before and
the product was purified by column chromatography eluting with
petrol/ethyl acetate (2:1) to give a colourless oil of the title com-
pound 50 (4.8 g, 98%) [Found (MþNa)þ: 573.4099, C36H58NaO2Si
1374, 1259, 1183, 1026 cmꢁ1
.
4.1.25. ((1S,2R)-2-((Tetrahydro-2H-pyran-2-yloxy)methyl)-cyclo-
propyl) methanol 46. ((1S,2R)-2-((Tetrahydro-2H-pyran-2-yloxy)
methyl)cyclopropyl butyrate (10.0 g, 39 mmol) in tetrahydrofuran
(50 mL) was added dropwise over 15 min to a suspension of lithium
aluminium hydride (2.28 g, 58.5 mmol) in tetrahydrofuran
(200 mL) at room temperature. The mixture was heated under
reflux for 1 h, then worked up and purified as before to give a col-
ourless oil, the title compound 46 as a mixture of diastereoisomers
(6.7 g, 92%) [Found (MþNa)þ: 209.1, C10H18NaO3 requires: 209.1],49
½
a 2D0
ꢀ
þ17.7 (c 1.19, CHCl3), which showed dH (500 MHz, CDCl3):
4.64e2.62 (2H, m), 4.18 (1H, dd, J 5.7, 11.1 Hz), 3.93e3.85 (4H, m),
3.82e3.78 (1H, m), 3.53e3.46 (2H, m), 3.37 (1H, t, J 11 Hz), 3.24 (1H,
dd, J 10.4, 12.0 Hz), 3.19 (1H, dd, J 10.7, 12.0 Hz), 3.09 (1H, t, J
10.8 Hz), 2.8 (1H, br s), 1.82e1.75 (1H, m), 1.74e1.62 (3H, m),
1.6e1.46 (9H, m), 1.37e1.29 (2H, m), 1.28e1.20 (2H, m), 0.8e0.75
(2H, m), 0.19e0.14 (2H, m); dC (125 MHz, CDCl3): 98.8, 98.2, 67.9,
67.7, 62.9, 62.6, 62.5, 62.1, 30.5, 30.4, 25.2, 25.1, 19.6, 19.2, 18.4, 18.37,
14.9, 14.5, 8.1, 8.05; nmax: 3435, 2924, 2854, 1456, 1377, 1118,
requires: 573.4098], ½a D22
þ7.47 (c 1.07, CHCl3), which showed dH
ꢀ
1021 cmꢁ1
.
(500 MHz, CDCl3): 7.70e7.68 (4H, m), 7.45e7.37 (6H, m), 3.68e3.64
(3H, including t at d 3.67 (J 6.3 Hz)), 3.59 (1H, dd, J 7.9, 11.0 Hz), 1.57
4.1.26. (1S,2R)-2-((Tetrahydro-2H-pyran-2-yloxy)methyl)cyclo-
propanecarbaldehyde 47. (1S,2R)-2-((Tetrahydro-2H-pyran-2-
(2H, pent, J 7 Hz),1.49e1.23 (29H, m), 1.12e1.10 (1H, m), 1.06 (9H, s),
0.92e0.84 (1H, m), 0.71 (1H, dt, J 4.5, 8.2 Hz), ꢁ0.019 (1H, br q, J
5.4 Hz); dC (125 MHz, CDCl3): 135.5, 134.2, 129.4, 127.5, 64.0, 63.3,
32.6, 30.2, 29.7, 29.65, 29.63, 29.6, 29.55, 29.4, 28.5, 26.8, 25.7, 19.2,
18.1, 16.1, 9.5; nmax: 3368, 3072, 2924, 2853, 1746, 1593, 1463, 1428,
yloxy)methyl)cyclopropyl)methanol (6.48 g, 34.79 mmol) in
dichloromethane (15 mL) was added to a stirred suspension of
pyridinium chlorochromate (18.7 g, 87.0 mmol) in dichloro-
methane (250 mL) at room temperature. The mixture was stirred
vigorously for 3 h then worked up as before and purified by chro-
matography on silica gel eluting with petrol/ethyl acetate (1:1) to
give a colourless oil, the title compound 47 as a mixture of di-
1111, 1030 cmꢁ1
.
4.1.28. (1R,2S)-2-(16-(tert-Butyldiphenylsilyloxy)hexadecyl)-cyclo-
propanecarbaldehyde 51. ((1R,2S)-2-(16-(tert-Butyldiphenylsily-
astereoisomers (3.5 g, 54%), ½a D18
ꢀ
þ19.3 (c 1.15, CHCl3), which
loxy)hexadecyl)cyclopropyl)methanol (1.2 g, 2.2 mmol) in
dichloromethane (15 mL) was added to a stirred suspension of
pyridinium chlorochromate (1.17 g, 5.44 mmol) in dichloromethane
(30 mL) at room temperature.48 The mixture was stirred vigorously
for 3 h then worked up as before; chromatography on silica eluting
with petrol/ethyl acetate (1:1) gave a colourless oil, the title com-
showed dH (500 MHz, CDCl3): 9.4 (1H, t, J 4.7 Hz), 9.38 (1H, t, J
5.1 Hz), 4.59e4.58 (1H, m), 4.45e4.43 (1H, m), 4.11 (1H, dd, J 2.2,
5.7 Hz), 3.83e3.76 (1H, m), 3.75e3.72 (1H, m), 3.71e3.56 (1H, m),
3.48e3.42 (2H, m), 3.35e3.30 (1H, m), 2.01e1.91 (2H, m), 1.83e1.68
(3H, m), 1.65e1.60 (2H, m), 1.53e1.46 (8H, m), 1.30e1.24 (2H,
m),1.23e1.17 (2H, m), 0.54e0.49 (1H, m), 0.17e0.15 (1H, m); dC
(125 MHz, CDCl3): 200.2, 200.1, 98.7, 98.1, 65.2, 65.1, 62.2, 61.7, 30.4,
pound 51 (1.18 g, 98%), ½a D23
þ48.6 (c 1.11, CHCl3), which showed dH
ꢀ
(500 MHz, CDCl3): 9.35 (1H, d, J 5.7 Hz), 7.69e7.67 (4H, m),
7.44e7.36 (6H, m), 3.66 (2H, t, J 6.6 Hz), 1.89e1.84 (1H, m),
1.63e1.24 (33H, m, including br s at 1.26), 1.05 (9H, s); dC (125 MHz,
CDCl3): 201.8, 135.6, 134.2, 129.4, 127.5, 64.0, 32.6, 30.0, 29.7, 29.63,
30.3, 26.8, 26.78, 25.2, 23.5, 23.0, 19.4, 19.0, 13.9, 12.0, 11.96; nmax
:
2944, 2871, 1704, 1371, 1201, 1172, 1120, 1061 cmꢁ1
.
4.1.27. ((1R,2S)-2-(16-(tert-Butyldiphenylsilyloxy)hexadecyl)cyclo-
propyl)methanol 50. (a) Lithium bis(trimethylsilyl)amide (18.0 mL,
28.7 mmol, 1.06 M) was added dropwise with stirring to aldehyde
47 (2.94 g, 15.95 mmol) and ester 26 (8.88 g, 20.7 mmol) in dry THF
(100 mL) under nitrogen at ꢁ10 ꢃC. The mixture was allowed to
reach rt and stirred for 1.5 h, then worked up as before and purified
by chromatography eluting with petrol/ethyl acetate (7:1) to give
a colourless oil, methyl (E/Z)-16-((1R,2R)-2-((tetrahydro-2H-pyran-
2-yloxy)methyl)cyclopropyl)hexadec-15-enoate (6.0 g, 89%), which
was used for the next step without further analysis; (b) the above
ester (6 g, 14.19 mmol) in tetrahydrofuran (25 mL) was added
dropwise over 15 min to a suspension of lithium aluminium hy-
dride (0.810 g, 21.3 mmol) in tetrahydrofuran (150 mL) at room
temperature. The mixture was heated under reflux for 1 h, then
worked up as before and purified by chromatography on silica gel
eluting with petrol/ethyl acetate (2:1) to give a colourless oil, (E/Z)-
16-((1R,2R)-2-((tetrahydro-2H-pyran-2-yloxy)-methyl)cyclopropyl)
hexadec-15-en-1-ol 48 (4.5 g, 80%), which was used for the next
29.61, 29.5, 29.4, 29.2, 28.2, 27.8, 26.9, 25.8, 24.8, 19.2, 14.7; nmax
:
3072, 2925, 2854, 1704, 1463, 1428, 1111 cmꢁ1
.
4.1.29. tert-Butyl-(16-((1S,2R)-2-(12-((2S,3S)-3-((R)-octadecan-2-
yl)-oxiran-2-yl)dodecyl)cyclopropyl)hexadecyloxy)diphenylsilane
52. Lithium bis(trimethylsilyl)amide (1.54 g, 1.63 mmol, 1.06 M)
was added dropwise with stirring to aldehyde 51 (0.50 g,
0.91 mmol) and sulfone 42 (0.72 g, 1.09 mmol) in dry THF (30 mL)
under nitrogen at ꢁ10 ꢃC. The mixture was allowed to reach rt and
stirred for 1.5 h, then quenched with NH4Cl (5 mL) and petrol/ethyl
acetate (1:1, 20 mL) at 0 ꢃC. The organic layer was separated and the
aqueous layer was re-extracted with petrol/ethyl acetate (1:1,
2ꢂ20 mL). The combined organic layers were dried and the solvent
was evaporated. Column chromatography eluting with petrol/ethyl
acetate (20:1) to give a colourless oil, tert-butyl-[16-((1S,2R)-2-{(E/
Z)-12-[(2S,3S)-3-((R)-1-methylheptadecyl)oxiranyl]dodec-1-enyl}
cyclopropyl)hexadecyloxy]diphenylsilane (0.8 g, 89%). Hydrogena-
tion was carried out with potassium azodicarboxylate as before and

D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
7333
the product was purified by column chromatography eluting with
C
34H69Br79NaO3Si requires: 655.4092], ½a 2D2
ꢀ
þ7.8 (c 1.06, CHCl3),
petrol/ethyl acetate (20:1) to give a white semi solid, the title
which showed dH (500 MHz, CDCl3): 4.10e4.07 (1H, m), 3.68 (3H, s),
3.46e3.42 (2H, m), 2.54 (1H, ddd, J 3.8, 5.7, 9.5 Hz), 2.09e2.02 (1H,
m), 1.97 (1H, ddd, J 3.5, 7.9, 11.4 Hz), 1.67e1.22 (42H, br m, including
compound 52 (0.64 g, 80%) [Found (MþNa)þ: 1005.8743,
C
67H118NaO2Si requires: 1005.8793], ½a D20
ꢁ4.9 (c 0.85, CHCl3),
ꢀ
t
which showed dH (500 MHz, CDCl3): 7.68 (4H, dd, J 1.3, 7.9 Hz),
7.43e7.36 (6H, m), 3.65 (2H, t, J 6.6 Hz), 2.72 (1H, dt, J 2.2, 5.7 Hz),
2.41(1H, dd, J 1.9, 6.9 Hz), 1.60e1.22 (85H, br m, including br s at
1.25), 1.05 (9H, s), 1.0 (3H, d, J 6.0 Hz), 0.89 (3H, t, J 6.7 Hz),
0.67e0.64 (2H, m), 0.56 (1H, br dt, J 4.1, 8.2 Hz), ꢁ0.32 (1H, q, J
5.1 Hz); dC (125 MHz, CDCl3):135.6, 134.2, 129.4, 127.5, 64.0, 63.9,
58.9, 36.0, 33.8, 32.6, 32.3, 31.9, 30.2, 29.9, 29.74, 29.7, 29.63, 29.6,
29.58, 29.5, 29.4, 29.36, 28.7, 27.2, 26.9, 26.1, 25.8, 22.7, 19.2, 17.3,
br s at 1.26), 0.9e0.86 (12H, m, including s at 0.88 for the Bu and
a triplet at 0.89 with J 5.7 Hz), 0.11 (3H, s), 0.08 (3H, s); dC (125 MHz,
CDCl3): 174.1, 71.3, 51.6, 51.5, 36.8, 31.9, 29.7, 29.64, 29.61, 29.6,
29.55, 29.4, 29.35, 28.0, 26.5, 25.7, 22.7, 18.0, 14.1, 14.0, ꢁ4.6, ꢁ4.8;
nmax: 2924, 2854, 1741, 1463, 1254, 1072 cme1
.
4.1.32. Methyl (R)-2-[(R)-1-(tert-butyldimethylsilanyloxy)-3-(1-
phenyl-1H-tetrazole-5-sulfonyl)propyl]tetracosanoate 57.
15.8, 14.1, 10.9; nmax: 3072, 2924, 2853, 1464, 1111 cmꢁ1
.
(i) (R)-2-((R)-3-Bromo-1-(tert-butyl-dimethylsilanyloxy)-pro-
pyl]-
4.1.30. 16-((1S,2R)-2-{12-[(2S,3S)-3-((R)-1-Methylheptadecyl)oxir-
anyl]dodecyl}cyclopropyl)hexadecanal 53.
tetracosanoic acid methyl ester (0.7 g, 1.1 mmol) was added
with vigorous stirring to 1-phenyl-1H-tetrazole-5-thiol (0.21 g,
1.2 mmol) and anhydrous potassium carbonate (0.3 g,
2.2 mmol) in acetone (30 mL). The mixture was heated under
reflux for 2.5 h, then worked up and purified as before to give
a colourless oil, methyl (R)-2-[(R)-1-(tert-butyldimethyl-sila-
nyloxy)-3-(1-phenyl-1H-tetrazole-5-ylsulfanylpropyl]tetraco-
sanoate (0.76 g, 95%) [Found (MþNa)þ: 753.5174,
(i) Tetra-n-butyl ammonium fluoride (0.97 mL, 0.97 mmol, 1 M in
THF) was added to a stirred solution of silane 52 (0.64 g,
0.65 mmol) in dry THF (30 mL) at 0 ꢃC under nitrogen. The
mixture was allowed to reach rt and stirred overnight, then
cooled to 5 ꢃC and quenched with satd aq NH4Cl (5 mL) and the
product extracted with ethyl acetate (3ꢂ50 mL), then washed
with brine (20 mL), dried over MgSO4 and the solvent was
evaporated. Column chromatography eluting with petrol/ethyl
acetate (6:1) gave a white solid, 16-((1S,2R)-2-{12-[(2S,3S)-3-
((R)-1-methylheptadecyl)oxiranyl]dodecyl}-cyclopropyl)-hex-
adecan-1-ol (0.44 g, 91%), mp: 60e63 ꢃC [Found (MþH)þ:
C41H74N4NaO3SSi requires: 753.5143],
½
a 2D2
ꢀ
ꢁ9.9 (c 0.82,
CHCl3), which showed dH (500 MHz, CDCl3): 7.61e7.51 (5H, m),
4.07 (1H, dt, J 4.1, 6.3 Hz), 3.66 (3H, s), 3.49e3.43 (1H, m),
3.40e3.34 (1H, m), 2.59 (1H, ddd, J 4.8, 7.0, 11.4 Hz), 2.14e2.07
(1H, m), 2.01e1.93 (1H, m), 1.59e1.21 (42H, br m, including br s
at 1.25), 0.89e0.87 (12H, m, including s at 0.88 for tBu and t at
0.87 with J 4.1 Hz), 0.07 (3H, s), 0.05 (3H, s); dC (125 MHz,
CDCl3)): 174.4, 154.2, 133.7, 130.1, 129.8, 123.8, 72.0, 51.5, 51.46,
33.1, 31.9, 29.7, 29.64, 29.63, 29.6, 29.5, 29.4, 28.6, 27.8, 27.1,
25.7, 22.7, 17.9, 14.1, ꢁ4.4, ꢁ4.9; nmax: 2924, 2853, 1738, 1504,
745.7781, C51H101O2 requires: 745.7796], ½a D25
ꢁ6.6 (c 1.07,
ꢀ
CHCl3), which showed dH (500 MHz, CDCl3): 3.64 (2H, t, J
6.6 Hz), 2.72 (1H, dt, J 2.2, 5.4 Hz), 2.41 (1H, dd, J 2.2, 7.3 Hz),
1.60e1.23 (86H, br m, including br s at 1.26),1.0 (3H, d, J 6.0 Hz),
0.88 (3H, t, J 7.0 Hz), 0.69e0.64 (2H, m), 0.56 (1H, dt, J 4.1,
8.2 Hz), ꢁ0.32 (1H, q, J 5.1 Hz); dC (125 MHz, CDCl3): 63.9, 63.1,
58.9, 36.0, 33.8, 32.8, 32.3, 31.9, 30.2, 29.9, 29.72, 29.7, 29.63,
29.6, 29.58, 29.5, 29.4, 29.35, 28.7, 27.2, 26.5, 26.1, 25.7, 22.7,
1466, 1254, 1085 cmꢁ1
.
(ii) Ammonium molybdate (VI) tetrahydrate (0.57 g, 0.46 mmol) in
ice cold H2O2 (35% w/w, 1.5 mL) was added to a stirred solution
of the above ester (0.75 g, 1.02 mmol) in IMS (15 mL) and THF
(2 mL) at 12 ꢃC and stirred at rt for 2 h. Further ammonium
molybdate (VI) tetrahydrate (0.30 g, 0.22 mmol) in ice cold
H2O2 (35% w/w, 1 mL) was added and the mixture was stirred
at rt for 18 h, then worked up as before; column chromatog-
raphy eluting with petrol/ethyl acetate (6:1) gave a white solid,
the title compound 57 (0.71 g, 90%), mp: 65e67 ꢃC [Found
(MþNa)þ: 785.5025, C41H74N4NaO5SSi requires: 785.5041],
17.3, 15.8, 14.1, 10.9; nmax: 3418, 2925, 2854, 1464, 1112 cmꢁ1
.
(ii) The above alcohol (0.44 g, 0.59 mmol) in dichloromethane
(10 mL) was added to a stirred suspension of pyridinium
chlorochromate (0.3 g, 1.47 mmol) in dichloromethane (30 mL)
at rt. The mixture was stirred vigorously at rt for 2 h, then
poured into petrol/ethyl acetate (10:1, 30 mL), filtered through
a bed of silica and Celite then washed with petrol/ethyl acetate
and the filtrate was evaporated to give a residue. Column
chromatography on silica gel eluting with petrol/ethyl acetate
(8:1) gave a white solid, the title compound 53 (0.33 g, 76%),
½
a 2D0
ꢀ
ꢁ9.6 (c 0.82, CHCl3), which showed dH (500 MHz, CDCl3):
7.71e7.70 (2H, m), 7.65e7.59 (3H, m), 4.16e4.12 (1H, m),
3.81e3.77 (2H, m), 3.68 (3H, s), 2.52 (1H, ddd, J 3.8, 7.6,
11.4 Hz), 2.23e2.07 (2H, m), 1.61e1.22 (42H, br m, including br
s at 1.25), 0.89e087 (12H, m, including s at 0.88 for the tBu and
t at 0.87 with J 3.2 vHz), 0.10 (3H, s), 0.06 (3H, s); dC (125vMHz,
CDCl3): 174.1, 153.4, 133.0, 131.5, 129.7, 125.0, 123.8, 70.9, 51.7,
51.6, 51.3, 31.9, 29.7, 29.64, 29.6, 29.54, 29.5, 29.4, 29.35, 27.6,
27.4, 26.2, 25.7, 25.6, 22.7, 17.9, 14.1, ꢁ4.5, ꢁ5.1; nmax: 2925,
mp: 49e51 ꢃC, ½a 2D1
ꢁ11 (c 0.7, CHCl3), which showed dH
ꢀ
(500 MHz, CDCl3): 9.77 (1H, t, J 1.6 Hz), 2.72 (1H, dt, J 1.9,
5.4 Hz), 2.44e2.40 (2H, m), 1.66e1.22 (84H, br m including br s
at 1.26), 1.0 (3H, d, J 6 Hz), 0.88 (3H, t, J 6.6 Hz), 0.69e0.64 (2H,
m), 0.56 (1H, dt, J 4.1, 8.2 Hz), ꢁ0.32 (1H, q, J 5.1 Hz); dC
(125 MHz, CDCl3): 202.9, 63.9, 58.9, 43.9, 36.0, 33.8, 32.3, 31.9,
30.2, 29.9, 29.73, 29.7, 29.66, 29.63, 29.6, 29.5, 29.4, 29.35, 29.2,
28.7, 27.2, 26.5, 26.1, 22.7, 22.1, 17.3, 15.8, 14.1, 10.9; nmax: 2922,
2854, 1739, 1463, 1498, 1343, 1154, 1080 cmꢁ1
.
2851, 1731, 1463, 1372, 1231, 1115 cmꢁ1
.
4.1.33. Methyl (R)-2-[(R)-1-(tert-butyldimethylsilanyloxy)-19-((1S,
2R)-2-{12-[(2S,3S)-3-((R)-1-methylheptadecyl)oxiranyl]dodecyl}cy-
clopropyl)nonadecyl]tetracosanoate 58. Lithium bis(trimethyl-silyl)
amide (0.21 mL, 0.27 mmol, 1.06 M) was added dropwise with
stirring to aldehyde 53 (0.12 g, 0.16 mmol) and sulfone 57 (0.14 g,
0.19 mmol) in dry tetrahydrofuran (10 mL) under nitrogen at ꢁ2 ꢃC.
The mixture was allowed to reach rt and stirred for 1.5 h, then
worked up as before and purified by chromatography on silica gel
eluting with petrol/ethyl acetate (20:1) to give methyl (R)-2-[(E/Z)-
(R)-1-(tert-butyldimethylsilanyloxy)-19-((1S,2R)-2-{12-[(2S, 3S)-3-
((R)-1-methylheptadecyl)oxiranyl]dodecyl}cyclopropyl)nonadec-
3-enyl]tetracosanoate (0.14 g, 68%). Hydrogenation was carried out
4.1.31. Methyl (R)-2-[(R)-3-bromo-1-(tert-butyldimethylsilanyloxy)
propyl]tetracosanoate 56. N-Bromosuccinimide (1.21 g, 6.83 mmol)
was added in portions over 15 min to a stirred solution of methyl
(R)-2-[(R)-1-(tert-butyldimethylsilanyloxy)-3-hydroxypropyl]-tet-
racosanoate (3.0 g, 5.3 mmol),31 triphenylphosphine (1.72 g,
6.56 mmol) and sodium hydrogen carbonate (0.3 g) in dichloro-
methane (50 mL) at 0 ꢃC. The mixture was stirred at rt for 1 h, then
worked up and purified as before to give a pale yellow thick oil of
the title compound 56 (2.0 g, 60%) [Found (MþNa)þ: 655.4085,

7334
D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
with dipotassium azodicarboxylate as before; chromatography
eluting with petrol/ethyl acetate (20:1) gave a semi solid, the title
compound 58 (0.13 g, 92%) [Found (MþNa)þ: 1305.2684,
References and notes
1. Minnikin, D. E. In The Biology of the Mycobacteria; Standford, J., Ed.; Academic:
San Diego, 1982; p 95.
2. Watanabe, M.; Aoyagi, Y.; Ridell, M.; Minnikin, D. E. Microbiology 2001, 147,
1825e1837.
3. Watanabe, M.; Aoyagi, Y.; Mitome, H.; Fujita, T.; Naoki, H.; Ridell, M.; Minnikin,
D. E. Microbiology 2002, 148, 1881e1902.
C
85H168NaO4Si requires: 1304.2604], ½a D24
ꢁ6.95 (c 1.15, CHCl3); dH
ꢀ
(500 MHz, CDCl3): 3.92e3.89 (1H, m), 3.66 (3H, s), 2.72 (1H, dt, J 2.2,
5.4 Hz), 2.53 (1H, ddd, J 3.8, 7.3, 11 Hz), 2.41 (1H, dd, J 2.2, 7.3 Hz),
1.70e1.22 (133H, br m, including br s at 1.26), 1.0 (3H, d, J 6.0 Hz),
0.88 (6H, t, J 7.0 Hz), 0.86 (9H, s), 0.66e0.64 (2H, m), 0.56 (1H, dt, J
4.1, 8.2 Hz), 0.05 (3H, s), 0.02 (3H, s), ꢁ0.32 (1H, q, J 5.1 Hz); dC
(125 MHz, CDCl3): 175.1, 73.2, 63.8, 58.9, 51.6, 51.2, 36.1, 33.8, 33.7,
32.3, 31.9, 30.2, 29.9, 29.8, 29.7, 29.7, 29.6, 29.5, 29.44, 29.4, 28.7,
27.8, 27.5, 27.2, 26.1, 25.8, 23.7, 22.7, 22.6, 18.0, 17.3, 15.8, 14.1, 10.9,
ꢀ
ꢀ
4. Asselineau, C.; Asselineau, J.; Laneelle, G.; Laneelle, M.-A. Prog. Lipid Res. 2002,
41, 501e523.
ꢀ
ꢀ
5. Marrakchi, H.; Laneelle, M.-A.; Daffe, M. Chem. Biol. 2014, 21, 67e85.
6. Barry, C. E.; Lee, R. E.; Mdluli, K.; Sampson, A. E. Prog. Lipid Res.1998, 37, 143e179.
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ꢀ
ꢀ
9. Daffe, M.; Laneelle, M.-A.; Puzo, G.; Asselineau, C. Tetrahedron Lett. 1981, 22,
4515e4516.
ꢁ4.4, ꢁ4.9; nmax: 2924, 2853, 1741, 1464, 1377, 1258, 1170 cmꢁ1
.
10. Minnikin, D. E.; Minnikin, S. M.; Goodfellow, M. Biochim. Biophys. Acta 1982,
712, 616e620.
11. Minnikin, D. E.; Minnikin, S. M.; O’Donnell, A. G.; Goodfellow, M. J. Microbiol.
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Gen. Microbiol. 1984, 130, 363e367.
4.1.34. (R)-2-[(R)-Hydroxy-19-((1S,2R)-2-{12-[(2S,3S)-3-((R)-1-
methylheptadecyl)oxiranyl]dodecyl}cyclopropyl)nonadecyl]tetracosa-
noic acid 59.
13. Minnikin, D. E.; Minnikin, S. M.; Parlett, J. H.; Goodfellow, M.; Magnusson, M.
Arch. Microbiol. 1984, 139, 225e231.
(i) Ester 58 (0.18 g, 0.14 mmol) was dissolved in dry THF (15 mL) in
a dry poly-ethylene vial under nitrogen at rt and stirred. Pyr-
idine (0.2 mL) and hydrogen fluoride-pyridine complex
(1.6 mL) were added and the mixture was stirred for 17 h at
40 ꢃC, then worked up as before and purified by chromatog-
raphy eluting with petrol/ethyl acetate (9:1) to give
a white solid, methyl (R)-2-[(R)-1-hydroxy-19-((1S,2R)-2-{12-
[(2S,3S)-3-((R)-1-methylheptadecyl)oxiranyl]dodecyl}cyclo-
propyl)nonadecyl]tetracosanoate (90 mg, 56%), mp: 47e49 ꢃC
[Found (MþNa)þ: 1190.1755, C79H154NaO4 requires:
14. Ausina, V.; Luqion, M.; Margarit, I. J. Gen. Microbiol. 1985, 131, 2237e2239.
ꢀ
15. Luquin, M.; Laneelle, M.-A.; Ausina, V.; Barcelo, G. M.; Belda, F.; Alonso, C.;
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ꢀ
ꢀ
16. Dinadayala, P.; Laval, F.; Raynaud, C.; Lemassu, A.; Laneelle, M.-A.; Laneelle, G.;
ꢀ
Daffe, M. J. Biol. Chem. 2003, 278, 7310e7319.
ꢀ
ꢀ
17. Laval, F.; Laneelle, M.-A.; Deon, C.; Monsarrat, B.; Daffe, M. Anal. Chem. 2001, 73,
4537e4544.
18. Laval, F.; Haites, R.; Movahedzadeh, F.; Lemassu, A.; Wong, C. Y.; Stoker, N.;
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Kremer, L.; Besra, G. S.; Hatfull, G. F.; Jacobs, W. R. mBio 2013, 4 e00222-13.
20. Wheeler, P. R.; Besra, G. S.; Minnikin, D. E.; Ratledge, C. Biochim. Biophys. Acta
1993, 1167, 182e188.
1190.1739], ½a 2D1
ꢁ2.0 (c 0.54, CHCl3), which showed dH
ꢀ
(500 MHz, CDCl3): 3.71 (3H, s), 3.67e3.65 (1H, m), 2.72 (1H, dt,
J 2.2, 5.4 Hz), 2.47e2.40 (2H, m, including dd at 2.41, J 1.9,
7.0 Hz), 1.74e1.22 (134H, br m, including br s at 1.26), 1.0 (3H, d,
J 6.3 Hz), 0.88 (6H, t, J 7.0 Hz), 0.69e0.64 (2H, m), 0.56 (1H, dt, J
4.1, 7.9 Hz), ꢁ0.32 (1H, q, J 5.1 Hz); dC (125 MHz, CDCl3): 176.2,
72.3, 63.9, 58.7, 51.5, 50.9, 36.0, 35.7, 33.8, 32.3, 31.9, 30.2, 29.9,
29.7, 29.7, 29.63, 29.61, 29.6, 29.53, 29.5, 29.42, 29.4, 28.7, 27.4,
27.2, 26.1, 25.7, 22.7,17.3,15.8,14.1,10.9; nmax: 3472, 2924, 2853,
21. George, K. M.; Yuan, Y.; Sherman, D. R.; Barry, C. E. J. Biol. Chem. 1995, 270,
27292e27298.
22. Slayden, A. R.; Lee, E. R.; Armour, W. J.; Cooper, M. A.; Orme, M. I.; Brennan, J. P.;
Besra, S. G. Antimicrob. Agents Chemother. 1996, 40, 2813e2819.
ꢀ
23. Lacave, C.; Laneelle, M.-A.; Montrozier, H.; Rols, M.-P.; Asselineau, C. Eur. J. Bi-
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1&SID¼X13GBh6V1SEeTxZSEYt&page¼4&doc¼34&cacheurlFromRightClick¼
no.
1727, 1464, 1377, 1166 cmꢁ1
.
(ii) Lithium hydroxide monohydrate (43 mg, 1.02 mmol) was
added to a stirred solution of the above ester (80 mg,
0.068 mmol) in THF (4 mL), methanol (0.5 mL) and water
(0.7 mL) at rt. The mixture was stirred at 45 ꢃC overnight, then
cooled to rt and a mixture of petrol/ethyl acetate (7:2, 10 mL)
was added. The mixture was acidified to pH 1 with potassium
hydrogen sulfate and worked up as before. Column chroma-
tography eluting with petrol/ethyl acetate (7:2) gave a white
solid, the title compound 59 (60 mg, 76%), mp: 60e63 ꢃC
[Found (MþNa)þ: 1176.1544, C78H152NaO4 requires:
30. Koza, G.; Muzael, M.; Schubert-Rowles, R. R.; Theunissen, C.; Al Dulayymi, J. R.;
Baird, M. S. Tetrahedron 2013, 69, 6285e6296.
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678e684.
32. Koza, G.; Rowles, R. R.; Theunissen, C.; Al Dulayymi, J. R.; Baird, M. S. Tetrahe-
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1176.1583], ½a 2D4
ꢀ
ꢁ8.4 (c 0.9, CHCl3), which showed dH
:
3.73e3.70 (1H, m), 2.73 (1H, dt, J 2.2, 5.7 Hz), 2.48e2.44 (1H,
m), 2.43 (1H, dd, J 2.2, 7.3 Hz), 1.77e1.70 (1H, m), 1.63e1.22
(134H, br m, including br s at 1.26), 1.0 (3H, d, J 6.0 Hz), 0.88
(6H, t, J 6.6 Hz), 0.69e0.65 (2H, m), 0.56 (1H, dt, J 4.1, 8.2 Hz),
ꢁ0.32 (1H, q, J 5.1 Hz); dC: 179.0, 72.1, 64.0, 59.0, 50.7, 36.0,
35.5, 33.8, 32.2, 31.9, 30.2, 29.9, 29.7, 29.6, 29.5, 29.42, 29.4,
28.7, 27.3, 27.2, 26.1, 25.7, 22.7, 17.3, 15.8, 14.1, 10.9; nmax: 3375,
2917, 2849, 1683, 1465, 1381, 1266, 1070 cmꢁ1
.
40. Yuan, Y.; Barry, C. E. Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 12828e12833.
ꢀ
41. Secanella-Fandos, S.; Luquin, M.; Perez-Trujillo, M.; Julian, E. J. Chromatogr., B
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42. Coxon, C. D.; Al Dulayymi, J. R.; Baird, M. S.; Knobl, S.; Roberts, E.; Minnikin, D.
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ꢀ
ꢀ
ꢀ
ꢀ
We thank the Government of Iraq for the award of a grant to DK.
44. Vander Beken, S.; Al Dulayymi, J. R.; Naessens, T.; Koza, G.; Maza-Iglesias, M.;
Rowles, R. R.; Theunissen, C.; De Medts, J.; Lanckacker, E.; Baird, M. S.; Grooten,
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Supplementary data
45. Verschoor, J. A.; Baird, M. S.; Grooten, J. Prog. Lipid Res. 2012, 51, 325e339.
46. Beukes, M.; Lemmer, Y.; Deysel, M.; Al Dulayymi, J. R.; Baird, M. S.; Koza, G.;
Iglesias, M. M.; Rowles, R. R.; Theunissen, C.; Grooten, J.; Toschi, G.; Roberts, V.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2014.06.089.

D.Z. Al Kremawi et al. / Tetrahedron 70 (2014) 7322e7335
7335
V.; Pilcher, L.; Van Wyngaardt, S.; Mathebula, N.; Balogun, M.; Verschoor, J. A.
Chem. Phys. Lipids 2011, 164, 175.
47. Baird, M. S.; Jones, A.; Gwenin, C. D.; Ramsay, A. Unpublished results. The re-
sults of this study will be described in detail elsewhere, in comparison with
those for a series of other mycolic acids.
48. Akihiro, K.; Takeshi, O.; Hideo, I.; Takashi, T. Chem. Lett. 1987, 1491e1494.
49. The enantiomer has recently been reported: Shimomura, S.; Oyama, S.;
Nakano, K.; Hasegawa, M.; Toshima, H. Biosci. Biotechnol. Biochem. 2013, 77,
1353e1357.