New deuterated oligo(ethylene glycol) building blocks and their use in the preparation of surface active lipids possessing labeled hydrophilic tethers

Article abstract of DOI:10.1021/jo701979z

(Chemical Equation Presented) For the introduction of additional analysis protocols of tethered molecules, a method is presented to prepare functionalized, deuterated oligo(ethylene glycols) from ethylene glycol-d ₄. Partial oligomerization of ethylene glycol-d₄ and conversion to ditosylates is accompanied by coupling reactions to prepare doubly benzyl protected oligo(ethylene glycols) with two to five repeating units. The tetramer bearing 16 deuteria was elaborated at both ends to eventually prepare 2,3-di-O-phytanyl-sn-glycerol-1-tetraethylene glycol-D,L-α-lipoic acid ester (DPTL), which bears a fully deuterated tetra(ethylene glycol) spacer group. Through linking of functionalized components, an analogue of DPTL possessing an octa(ethylene glycol) spacer group was prepared, both in deuterated and unlabeled form.

Full text of DOI:10.1021/jo701979z

New Deuterated Oligo(ethylene glycol) Building Blocks and Their
Use in the Preparation of Surface Active Lipids Possessing Labeled
Hydrophilic Tethers
Robert J. Faragher and Adrian L. Schwan*
Department of Chemistry, UniVersity of Guelph, Guelph, Ontario, Canada N1G 2W1
schwan@uoguelph.ca
ReceiVed September 13, 2007
For the introduction of additional analysis protocols of tethered molecules, a method is presented to
prepare functionalized, deuterated oligo(ethylene glycols) from ethylene glycol-d4. Partial oligomerization
of ethylene glycol-d4 and conversion to ditosylates is accompanied by coupling reactions to prepare
doubly benzyl protected oligo(ethylene glycols) with two to five repeating units. The tetramer bearing
16 deuteria was elaborated at both ends to eventually prepare 2,3-di-O-phytanyl-sn-glycerol-1-tetraethylene
glycol-D,L-R-lipoic acid ester (DPTL), which bears a fully deuterated tetra(ethylene glycol) spacer group.
Through linking of functionalized components, an analogue of DPTL possessing an octa(ethylene glycol)
spacer group was prepared, both in deuterated and unlabeled form.
Introduction
Poly(ethylene glycol) (PEG) and oligo(ethylene glycol)
(OEG) linkers are particularly useful in the area of surface
modification and analysis.9,10,15 The binding of tethered sub-
strates to surfaces has facilitated the evolution of tethered bilayer
lipid membranes (tBLMs)16-18 which serve as viable and
popular models for the biological membrane, enabling the study
of membrane proteins18-21 and ion transport mechanisms.12,17
The concept calls for a molecule(s) that tethers the lipid to a
metal surface, yet incorporates a spacer region between the
bilayer and the metal substrate. Optimally, the tether is
hydrophilic and can counteract the hydrophobic nature of the
metal surface. The substrate for study is then introduced and
self-assembles through interaction with the immobilized lipid.
Linker technology1-3 has found a home in many fields
including organic synthesis,4 drug delivery,5,6 and interfacial
chemistry7-10 including molecule immobilization techniques.7,11-14
Ethylene glycol-based polymers and oligomers have proved very
popular for these purposes because of water solubility, nontox-
icity, and low cost.2,6
* Address correspondence to this author. Fax: (519)766-1499. Phone: (519)-
824-4120, ext. 53061.
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10.1021/jo701979z CCC: $40.75 © 2008 American Chemical Society
Published on Web 01/17/2008
J. Org. Chem. 2008, 73, 1371-1378
1371

Faragher and Schwan
SCHEME 1. Possible Approaches to DPTL, 1
2,3-Di-O-phytanyl-sn-glycerol-1-tetraethylene glycol-D,L-R-
lipoic acid ester (DPTL, 1) represents a popular substrate for
the studies noted above.12,20,22-26 Not only does DPTL feature
a tetra(ethylene glycol) unit as the requisite hydrophilic tether,
but it also advertises nonhydrolyzable ether linkages throughout
and two phytanyl chains which embrace guest molecules. Until
now, DPTL has been prepared and utilized without concern for
isotope incorporation.25,26 If DPTL were to feature a deuterated
tether, one could call on neutron reflectivity measurements27 to
assess the amount of water that resides in the tethered section
of the membrane.28 Moreover the development of isotopically
labeled oligo(ethylene glycol) linkers in general would facilitate
structural analysis by other techniques including IR,29 NMR,30
and mass spectrometry.31,32
The previous preparation of DPTL, which parallels retrosyn-
thetic path A of Scheme 1,25 does not mesh well with any
reasonable plan for deuterium incorporation principally because
20 equiv of tetra(ethylene glycol) (EG4) were employed to
incorporate the tether. We also sought to improve other steps,
such as the double phytanylation reaction, which occurred in
49% previously.25 Finally, we held the view that alternative path
B should be evaluated as it introduces the labeled component
at a later stage of the overall synthesis.
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In this paper, we outline the synthesis of small useful
deuterated oligoisomeric building blocks from ethylene glycol-
d4 (EG-d4) and also incorporate an EG4-d16 derivative for the
preparation of DPTL-d16 and its analogue with an octameric
tether. An experimental description (only) of our preparation
of nondeuterated DPTL, developed with the option of facile
extension to the labeled manifold, has already been published.26
Despite the large number of available protocols for OEG linker
methods,26,33-37 applications toward deuterated substrates have
not been demonstrated.
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1372 J. Org. Chem., Vol. 73, No. 4, 2008

New Deuterated Oligo(ethylene glycol) Building Blocks
reduction events.40,41 Adopting that protocol would mean we
would have no use for the significant amount of EG-d4
recovered during the aforementioned distillation. Hence we
sought to develop a method to monobenzylate EG-d4, thereby
exploiting the excess available deuterated starting material.
Whereas many monofunctionalization protocols typically rely
on an excess of the bifunctional reactant, this was unacceptable
due to the high cost. After experimental evaluation of a number
of methods, the use of Ag2O, BnBr, and CH2Cl2 was adopted
for its convenience.42 In particular, the absence of a water
workup would permit recovery of unreacted EG-d4. Under the
optimized conditions, the targeted 2-d4 was isolated (50%) in
addition to starting material (8%) and doubly benzylated EG-
d4 (16%). Given that the latter could be converted to EG-d4
through hydrogenation (H2, 10% Pd/C, EtOAc), the yield of
3-d8 was 65% once corrected for recovered starting material
from the two sources.
SCHEME 2. Assembly of EG4-d16 Derivatives
At this point, methods were explored for the reaction of 2-d4
with ditosylate 3-d8. The Williamson-like protocol of powdered
KOH in DMSO forwarded by Johnstone and Rose,43 which is
used for alkylation procedures targeting ether containing phos-
pholipids,44 also proved amenable to the chemistry at hand. The
tosic acid elimination that occurred during trials of other
conditions was not observed and doubly benzylated 6-d16 was
cleanly provided in 99% yield (Scheme 2).
Results and Discussion
The lone preparation of deuterated EG-d4 oligomers was
outlined by Schnabel.38 As outlined in that paper, EG-d4 was
converted to numerous oligomers upon heating to 190 °C in
the presence of 1.2 mol % of I2. The mixture was subjected to
fractional distillation and numerous perdeuterated EG oligomers
were obtained including EG4-d16, which was isolated in 8%
yield; there is, however, no mention of the absolute scale of
the reaction.38 To ensure a complete separation of EG3-d12 and
EG5-d20 from the target molecule, it was felt that significantly
large amounts of EG-d4 would be required.39 Moreover the
distillation had the potential to be exasperatingly slow, perhaps
requiring numerous repetitions, to achieve but an 8% yield or
be unsuccessful in the worst case scenario! Finally, we were
concerned about our ability to be certain that EG4-d16 was
completely free of other oligomers.
For these reasons, an alterative procedure was developed. The
EG-d4 monomer would be heated for a shorter period of time
to access larger amounts of smaller oligomers and distillation
in combination with functional group manipulations would
complete the separation. The initial target under these conditions
was a derivatized dimer that could then be extended by
substitution reactions. To this end, the following treatment was
performed. In a typical protocol, 6.4 g of EG-d4 was heated at
160-170 °C for 7.5 h in the presence of 1.2% (mol) of I2. The
heat was reduced and the pot was subjected to vacuum
distillation to recover 3.84 g of unreacted monomer. The
remaining pot constituents were subjected to tosylation condi-
tions. The result was three ditosylated compounds (3-d8, 4-d12,
5-d16) which could be separated by flash chromatography
(Scheme 2).
A quantitative hydrogenative deprotection of 6-d16 to EG4-
d16 was carried out under the conditions previously employed,
and provided EG4-d16 of suitable purity for subsequent chem-
istry. The synthetic pathway from EG-d4 to EG4-d16 occurred
with only a 44% loss of consumed EG-d4 over 5 steps45 and
demonstrates the first preparation of gram quantities of the useful
precursor EG4-d16.
The successful double alkylation procedure and the isolation
of additional ditosylated compounds prompted us to evaluate
the chemistry for other small oligomers of EG-d4. The ditosy-
lates (Scheme 2) were reacted with either BnOH or 2-d4 and in
all cases but one, the yields of elongated product approached
or exceeded 90%. The low yielding reaction involved the
ditosylate of EG-d4 where elimination chemistry dominated the
process. Notwithstanding those results, successful reactions of
ditosylates 3-d8, 4-d12, and 5-d16 offer deuterated dibenzyl
protected oligomers of EG-d4 possessing 2-5 repeating units.
The efficient deprotective hydrogenation of dibenzylated com-
pounds EG-d4 and EG4-d16 suggests the general applicability
of the reaction for other oligomers. Higher doubly tosylated
oligomers may be prepared more efficiently by longer heating
in the original oligomerization reaction, or a more efficient
method may involve debenzylation and further functionalization
of the products of Table 1. Compounds with linker chains longer
(40) Bird, I.; Farmer, P. B. J. Labelled Compd. Radiopharm. 1989, 27,
199-216.
(41) Campbell, J. B. J. Chem. Soc., Perkin Trans. 1 1983, 1213-1217.
(42) Bouzide, A.; Sauve, G. Tetrahedron Lett. 1997, 38, 5945-5948.
(43) Johnstone, R. A. W.; Rose, M. E. Tetrahedron 1979, 35, 2169-
2173.
(44) (a) Wang, Z.; Schwan, A. L.; Lairson, L. L.; O’Donnell, J. S.; Byrne,
G. F.; Foye, A.; Holm, B. A.; Notter, R. H. Am. J. Physiol. 2003, 285,
L550-L559. (b) Chang, Y.; Wang, Z.; Notter, Robert, H.; Wang, Z.; Qu,
L.; Schwan, A. L. Bioorg. Med. Chem. Lett. 2004, 14, 5983-5986.
(45) This value arises in the following manner: 52% losses occur in the
two steps providing ditosylate 3-d8 and 35% losses occur making 3-d4. Since
these components each deliver one-half of the required four EG units to
6-d16, those losses become 26% and 17.5%, respectively. The total losses
are therefore 43.5% before the final two near-quantitative steps completing
the preparation of EG4-d16.
The subsequent plan was to take dimeric ditosylate 3-d8 and
react it at each end with a monoprotected EG-d4 such as 2-d4.
Benzyl-protected 2-d4 has previously been prepared in good
yield by reacting BnOH and BrCH2COOH followed by deute-
rium incorporation by ester enolate exchange and LiAlD4
(37) Waterhouse, J. E.; Harbottle, R. P.; Keller, M.; Kostarelos, K.;
Coutelle, C.; Jorgensen, M. R.; Miller, A. D. ChemBioChem 2005, 6, 1212-
1223.
(38) Schnabel, R. J. Labelled Compd. Radiopharm. 1992, 31, 91-94.
(39) At the time of these experiments, no oligomeric forms of EG-d4
were commercially available.
J. Org. Chem, Vol. 73, No. 4, 2008 1373

Faragher and Schwan
SCHEME 3. Functionalization of Glycerol
TABLE 1. General Preparation for Doubly Benzylated
Perdeuterated OEG’s
no.
n
y
Xa
product
yield (%)
1
2
3
4
5
6
2
1
3
2
4
3
0
1
0
1
0
1
2
3
3
4
4
5
EG2-d8-2Bn
EG3-d12-2Bn
EG3-d12-2Bn
6-d16
6-d16
EG5-d20-2Bn
89
32b
91
99
91
98
a X ) (n + 2y). b Only EG3-d12-2Bn was recovered from a mixture of
three products. On scrutiny of the 1H NMR of the crude reaction mixture,
the other two products appeared to possess unsaturation.
the chemical stability and fluidity of a molecule compared to
conventional linear fatty alkyl options.55
The direct linking of diphytanyl glycerol (15) and compounds
9-11 was attempted under a number of conditions. It was
quickly established that TBDMS-protected 10 readily degraded
under a variety of basic conditions and was ineffective.56
Mesylate 9 proved unreactive to the reaction conditions and
the coupled material was eventually achieved by using NaH
and tosylate 11 in THF. However, the reaction was slow and
incomplete even after 7 days, but afforded 16 in 72% based on
consumed starting material (Scheme 3).
CHART 1. Some Functionalized EG4 Derivatives
The synthetic approach to this juncture, based on retrosyn-
thetic path B of Scheme 1, assembled the tether and glycerol
components of DPTL in an efficient and partially convergent
manner, one amenable to label incorporation. However, since
the last step was sluggish, we turned our focus fully toward
path A (Scheme 1), on which we had been simultaneously
working. It should be noted that notwithstanding the attachment
of the tether to the glycerol component, pathway B is still viable
for DPTL preparation. Since a number of steps had been
optimized and improved, particularly the double diphytanylation,
incorporation of labeled material early in the reaction sequence,
as retrosynthetic path A requires, was viewed as a satisfactory
approach. Scheme 4 shows the steps eventually chosen for this
protocol, both in the unlabeled26 and in the labeled form. The
full explanation of the methods follows.
than five units can be accessed through coupling reactions
presented herein (vide infra) or the oligomeric diols can be
extended by using already demonstrated protocols.35,46,47
For eventual construction of DPTL, the EG4-d16 would
require further adaptation by way of a monofunctionalization.48
As such, known EG4 derivatives 7,37,49 8,36 9,50 10,34 and 1149
(Chart 1) were prepared as potential building blocks for DPTL
construction by adapting and in some cases improving the yields
or atom efficiencies of past procedures. Given these options
for bifunctional EG4 linkers, attention was turned toward the
elaboration of the glycerol portion and introduction of the
hydrophobic phytanyl groups. Phytanyl mesylate (12) was
prepared from phytanol by adapting a literature protocol (95%).51
The mesylate was then employed for the double alkylation of
benzyl glycerol (13), using powdered KOH/DMSO, to afford
the desired benzyl diphytanyl glycerol (14) in 86-95% yield
after optimization. Concluding with a reductive debenzylation
(H2, 10% Pd/C, quant.), this preparation of diphytanyl glycerol
(15) represents a significant improvement over other meth-
ods.51,52 This particular disubstituted glycerol, which is naturally
occurring in the lipid membranes of H. cutirubrum,53,54 has been
sought for a variety of reasons, as phytanyl chains improve both
Enantiopure 17 ((S)-solketal, (S)-(+)-1,2-isopropylidene-
glycerol) or its mesylate could serve as a protected glycerol for
tether attachment. The nucleophilic attack by monobenzyl
derivative 7 on the mesylate proved unsuitable but solketal
performed efficiently as a nucleophile with the optimized KOH/
DMSO conditions affording 18 in 87% yield. Repetition of the
57
protocol with 9-d16 was equally effective, offering 18-d16 in
90% yield. Cleavage of the isopropylidene in 18 was not trivial
and many reagents brought about breakdown of the polyether
tether. The diol was eventually freed by using 1.0 M HCl in
MeOH (74-78%), an outcome comparable in our hands to the
Dowex reagent previously employed.58 The phytanyl groups
(46) Zalipsky, S. Bioconjugate Chem. 1995, 6, 150-165.
(47) Burkett, B. A.; Chan, T. H. Synthesis 2004, 1007-1010.
(48) It was felt that employing one end of EG4 as a nucleophile under
harsh basic conditions may bring about its breakdown. Hence monopro-
tection schemes of commercial EG4 (protiated form) were investigated for
eventual creation of electrophilic EG4 derivatives.
(49) Richard, A.; Marchi-Artzner, V.; Lalloz, M.-N.; Brienne, M.-J.;
Artzner, F.; Gulik-Krzywicki, T.; Guedeau-Boudeville, M.-A.; Lehn, J.-
M. Proc. Natl. Acad. Sci. (U.S.A.) 2004, 101, 15279-15284.
(50) Azzam, T.; Peppas, N. A.; Slomkowski, S.; Domb, A. J. Polym.
AdV. Technol. 2002, 13, 788-797.
(51) Eguchi, T.; Arakawa, K.; Terachi, T.; Kakinuma, K. J. Org. Chem.
1997, 62, 1924-1933.
(52) (a) Aoki, T.; Poulter, C. D. J. Org. Chem. 1985, 50, 5634-5636.
(b) Kamikawa, T.; Nogawa, K.; Yamagiwa, Y. Glycoconjugate J. 1993,
10, 235-239.
(53) Joo, C. N.; Kates, M. Biochim. Biophys. Acta, 1969, 176, 278-
297.
(54) Kates, M.; Palameta, B.; Yengoyan, L. S. Biochemistry 1965, 4,
1595-1599.
(55) Raguse, B.; Braach-Maksvytis, V.; Cornell, B. A.; King, L. G.;
Osman, P. D. J.; Pace, R. J.; Wieczorek, L. Langmuir 1998, 14, 648-659.
(56) A few trials with the mesylate of diphytanyl glycerol and a
monoproptected EG4 derivative gave no reaction and this option was
discarded.
(57) The monobenzylation of EG4-d16 using the conditions of Scheme
2 occurs in 47% yield, but after recovery of starting material and reduction
of a small amount of doubly benzylated EG4-d16, the effective yield was
93%.
1374 J. Org. Chem., Vol. 73, No. 4, 2008

New Deuterated Oligo(ethylene glycol) Building Blocks
SCHEME 4. Preparation of DPTL and DPTL-d16
SCHEME 5. Preparation of 21 and 21-d32
were introduced to diol 19 through the agency of KOH/DMSO,
affording fully functionalized glycerol derivative 16 in about
75% yield, a 26% improvement over the previous report, despite
employing less alkylating agent.58
Quantitative hydrogenation readied the tethered material (20)
for esterification with lipoic acid. With use of unlabeled 20,
the coupling was achieved in 73% after exposure to 1.25 equiv
of lipoic acid and 1.3 equiv of carbodiimide coupling agent
EDC‚HCl. Interestingly, this reaction was stirred for 14 h at
room temperature followed by reflux conditions for an additional
18 h. When 20-d16 was converted into 1-d16 and the reaction
was stirred 16 h at rt followed by reflux conditions for 72 h,
DPTL with the deuterated linker (1-d16) was isolated in 93%
yield!
The NMR spectra of 1-d16, though not fully diagnostic of
the assigned structure, were nevertheless consistent. Further
characterization was found in the IR with strong bands at C-D
stretching frequencies of 2182 and 2082 cm-1. The electrospray
mass spectrum was also consistent, depicting peaks at m/z 1034
((M + H)+) and 1051 ((M + NH4)+). A small peak possessing
ca. 20% of the intensity of the (M + H)+ peak was observed at
m/z 1033 and is predicted based on the enrichment of the original
EG-d4 (98.3%), but more importantly, indicates no substantial
loss of deuterium during the preparation.
Given this successful synthesis and the valuable coupling
chemistry of some small EG mesylates and tosylates, we sought
to prepare an octameric analogue of DPTL, both unlabeled and
possessing a fully deuterated octameric EG linker. Specifically,
diphytanyl glycerol octaethylene glycol lipoates (DPOL) 21 and
21-d32 were targeted for IR spectroscopy and neutron reflectivity
analysis of water transportation/encapsulation across biomimetic
membranes. As with the EG4 linker of DPTL, the EG8 tether
is expected to demonstrate an affinity for water, but EG
oligomers of five or more units are known to coil in a helical
fashion with a 7/2 coil parameter and not extend linearly.59
The synthetic plan was based closely on the preparation of
1. A successful octameric linker was prepared through tosylation
of 20 and a Williamson connection to monofunctionalized 7
(Scheme 5). The tosylation was efficient (95%), but the coupling
was lower yielding. The KOH/DMSO conditions could not be
effectively applied and 23 was instead obtained in 74% yield
with NaH/THF. The deuterated version affording 23-d32 pro-
ceeded at 60%. After debenzylation (96%), lipoic acid conden-
sation was again performed with EDC‚HCl. The final reactions
were very sluggish and although DPOL (21) could be obtained
in 77% yield, the 21-d32 reaction required additional reactants
and heating for 7 days for a 60% yield.
Consistent with the bonds within each compound, DPOL (21)
did not contain bands from 2200 to 2050 cm-1 but DPOL-d32
did possess characteristic C-D stretching frequencies at 2182
and 2082 cm-1. As well, the mass spectral data confirmed that
21 and 21-d32 were prepared and 21-d32 contained the required
32 deuterons. An examination of the spectrum from 21 with EI
provided a (M + H)+ peak at m/z 1194 and a (M + NH4)+
signal at m/z 1211. The mass spectrum of 21-d32 did not possess
intense M+ or (M + H)+ peaks compared to a dominant (M +
NH4)+ signal of m/z 1243. However, expansion of the (M +
H)+ region showed that the (M + H - 1)+ peak was 41% of
the (M + H)+intensity, proving that no losses of deuterium
occurred during the synthesis.
Conclusions
Whereas synthetic applications of OEG-containing materials
to linker technology are well established, a protocol for the
preparation of a selection of deuterated oligo(ethylene glycol)
synthetic precursors is introduced herein. The materials are
suitable components for elaboration using the methods described
and are expected to mesh well with already published protocols
for nonlabeled analogues.35,40,41,46,47 The methods demonstrated
are high yielding and are broadly applicable to a variety of fields
(58) Schiller, S.; Naumann, R.; Knoll, W. EP 1364948, 2003.
(59) (a) Harder, P.; Grunze, M.; Dahint, R.; Whitesides, G. M.; Laibinis,
P. E. J. Phys. Chem. B 1998, 102, 426-436. (b) Valiokas, R.; Oestblom,
M.; Svedhem, S.; Svensson, S. C. T.; Liedberg, B. J. Phys. Chem. B 2000,
104, 7565-7569. (c) Vanderah, D. J.; Meuse, C. W.; Silin, V.; Plant, A. L.
Langmuir 1998, 14, 6916-6923.
J. Org. Chem, Vol. 73, No. 4, 2008 1375

Faragher and Schwan
of 2-d4 (2 equiv, 2.70 g, 17.3 mmol) and 3-d8 (1 equiv, 3.65 g,
8.64 mmol) in dry DMSO (20 mL) was added. The cooling bath
was removed and the mixture was stirred for 48 h at rt and then
24 h at 40 °C. After cooling, H2O (100 mL) was added and the
mixture was extracted with EtOAc (4 × 100 mL). The combined
organics were washed with H2O (7 × 100 mL) and brine and dried
over MgSO4. Concentration in vacuo yielded 6-d16 as an oil, 3.35
g (99%), which was used directly in the next step. Spectral data:
1H NMR (400 MHz, CDCl3) δ 7.34-7.27 (m, 10H), 4.56 (s, 4H);
2H NMR (61 MHz, CDCl3) δ 3.68 (s, 16H); 13C NMR (75 MHz,
CDCl3) δ 137.72, 127.57, 126.87, 126.75, 72.27, 68.95 (pent, JCD
) 21.3 Hz), 67.91 (pent, JCD ) 21.5 Hz); IR (neat) (cm-1) 3088,
3063, 3030, 2932, 2854, 2183, 2082.
related to linker technology and may provide new opportunities
for mass spectrometry-based pharmacokinetics of tethered drugs
and for proteomics.31
To exhibit the usefulness of the labeled building blocks,
monobenzylated tetra(ethylene glycol) (7) was functionalized
to prepare labeled and unlabeled DPTL, a popular surface active
agent for membrane biomimetic studies. The chemistry achieved
herein shows that two synthetic approaches represented in
Scheme 1 are viable for the preparation of DPTL. A derivative
of DPTL containing an octameric OEG linker has also been
synthesized, both in unlabeled and d32 form. As a part of this
study we have improved the published preparation of DPTL
(1). Our unlabeled material possesses purity and surface activity
adequate for use in a number of surface studies26,60,61 and the
labeled analogue was equally useful.62
Preparation of Tetra(ethylene glycol)-d16 (EG4-d16). To a
round-bottomed flask was added 6-d16 (4.54 g, 11.6 mmol) and
10% Pd/C (1.0 g) and EtOAc (40 mL). The suspension was
degassed (3×) then hydrogen was introduced under balloon pressure
(15 to 16 psi) and the reaction was placed into a pre-equilibrated
oil bath at 40 °C for 3 days. Then the mixture was filtered through
Celite, which was washed liberally with EtOH (400 mL), and the
combined organics were concentrated in vacuo yielding 2.40 g
(99%) of EG4-d16 as an oil.38 Spectral data for EG4-d16: 1H NMR
Experimental Section
The general procedures have been published elsewhere.63 The
experimental procedures for the preparation of nonlabeled DPTL
has been published previously.26 Procedures for most nondeuterated
compounds are found in the Supporting Information. EG-d4 (98.3%
D) was purchased from C-D-N Isotopes.
Conversion of Ethylene Glycol-d4 to Higher Oligomers. To a
round-bottomed flask was added EG-d4 (6.4 g) and iodine (1.2 mol
%). A Dean Stark apparatus was attached and the mixture was
placed into a pre-equilibrated oil bath (160-170 °C) for 7.5 h. The
mixture was allowed to cool and then starting material was distilled
off (38-40 °C, 0.15 mmHg) to give 3.84 g of EG-d4.
Distosylates. To the distillation pot was added dry CH2Cl2 (35
mL) and TsCl (7.84 g, 41.1 mmol). The mixture was cooled to
-30 °C and powdered KOH (4 equiv, 2.31 g, 41.1 mmol) was
added portionwise. The mixture was slowly warmed to rt and stirred
overnight. H2O (100 mL) and enough CH2Cl2 (200 mL) were added
to dissolve solid material, followed by Na2S2O3 (aq) (50 mL). The
mixture was extracted with CH2Cl2 (2 × 40 mL) and the combined
extracts were washed with Na2S2O3 (50 mL), H2O (50 mL), and
brine (50 mL) and dried over MgSO4. The solvent was evaporated
in vacuo yielding a solid (∼6.5 g) that was chromatographed (flash
conditions (20-60% EtOAc/hexanes). Yields are based on recov-
ered EG-d4: 3-d8 (3.89 g, 48%), 4-d12 (680 mg, 11%), and 5-d16
(139 mg, 2.7%). The ditosylate of EG-d4 was sometimes obtained
when distillation times were minimized. See the Supporting
Information for characterization data.
Monobenzylated EG-d4 (2-d4). To a flame-dried round-bottomed
flask was added EG-d4 (1.14 g, 17.3 mmol), dry CH2Cl2 (30 mL),
and Ag2O (1.5 equiv, 5.99 g, 25.8 mmol) and the mixture was
heated to 40 °C. Then benzyl bromide (1 equiv, 2.95 g, 17.3 mmol)
was added neat and the reaction was stirred overnight. The mixture
was filtered through a small pad of silica gel, which was washed
liberally with EtOAc, and the combined organics were concentrated
in vacuo to yield an oil. Flash chromatography (10-50% EtOAc/
hexanes then EtOH) yielded doubly benzylated EG-d4 (676 mg,
16%), 2-d4 (1.34 g, 50%), and EG-d4 (91 mg, 8%). See the
Supporting Information for characterization data.
2
(400 MHz, CDCl3) δ 4.15-3.37 (br, 2H); H NMR (61 MHz,
CDCl3) δ 3.69 (s, 4H), 3.66 (s, 8H), 3.60 (s, 4H); 13C NMR (100
MHz, CDCl3) δ 70.93 (pent, JCD ) 21.0 Hz), 68.71 (pent, JCD
)
21.5 Hz), 68.35 (pent, JCD ) 21.4 Hz), 59.66 (pent, JCD ) 21.5
Hz); IR (neat) (cm-1) 3405 (br), 2930, 2205, 2084.
General Procedure for the Preparation of Dibenzyl Perdeu-
terated Oligomeric EG’s (Table 1). To a flame-dried round-
bottomed flask was added KOH (5 equiv) and dry DMSO, and the
suspension was stirred for 30 to 60 min. The mixture was then
cooled in an ice bath for 5 min followed by the addition of a solution
of 2-d4 or benzyl alcohol (2.0 equiv), and ditosylated OEG’s (1.0
equiv) in DMSO was added over 5 min. The mixture was allowed
to warm to rt for 1-3 days and then warmed at 40 °C for 1-3
days. See the Supporting Information for isolation and purification
procedures and for characterization data.
Preparation of 13-Phenyl-3,6,9,12-tetraoxatridecan-1-ol-d16
(7-d16, monobenzylated EG4-d16). To a flame-dried round-bot-
tomed flask was added EG4-d16 (1.01 g, 4.81 mmol), Ag2O (1.5
equiv, 1.65 g, mmol), and dry CH2Cl2 (50 mL), and the mixture
was placed into a pre-equilibrated oil bath at 40 °C. The mixture
was allowed to reflux while freshly distilled BnBr (828 mg, 4.84
mmol) was added and the resulting mixture was stirred overnight.
The mixture was filtered through a small plug of silica gel, which
was washed liberally with EtOH (250 mL), and the combined
organics were concentrated in vacuo yielding an oil. Flash chro-
matography (30% EtOAc/hexanes to 30% EtOH/EtOAc, Rf 0.1
(EtOAc)) yielded 7-d16 in 93% after correction for recovered EG4-
d16 and reductive debenzylation of 6-d16. Spectral data for 7-d16:
1H NMR (400 MHz, CDCl3) δ 7.35-7.28 (m, 5H), 4.56 (s, 2H),
2.24 (br s, 1H); 2H NMR (61 MHz, CDCl3) δ 3.74-3.56 (m, 16H);
13C NMR (100 MHz, CDCl3) δ 137.6, 127.6, 126.9, 126.8, 72.3,
71.0 (pent, JCD ) 21.6 Hz), 68.9 (pent, JCD ) 21.1 Hz), 67.9 (pent,
JCD ) 21.5 Hz), 59.9 (pent, JCD ) 21.6 Hz); IR (neat) (cm-1) 3455
(br), 3031, 2857, 2186, 2082. Anal. Calcd for C15H8D16O5: C 59.98,
H 8.05. Found :C 59.99, H 7.96.
Doubly Benzylated Tetra(ethylene glycol)-d16 (6-d16). To a
flame-dried round-bottomed flask was added KOH (5 equiv, 2.42
g, 43.2 mmol) and dry DMSO (30 mL) and the suspension was
stirred for 1 h. The mixture was cooled with ice water and a solution
1-Phenyl-2,5,8,11-tetraoxatridecan-13-yl Methanesulfonate-
16 (9-d16). To a flame-dried round-bottomed flask was added 7-d16
d
(1.48 g, 4.92 mmol), Et3N (1.8 equiv, 0.895 g, 8.85 mmol, 1.23
mL), and dry CH2Cl2 (10 mL). The mixture was cooled to -30 °C
and mesyl chloride (1.5 equiv, 0.845 g, 7.38 mmol) was added
over 5 min. The mixture was allowed to slowly warm to rt. After
2.75 h, sat. NH4Cl(aq) (30 mL) and H2O (20 mL) were added and
the mixture was extracted with EtOAc (3 × 25 mL). The combined
organics were washed with sat. NH4Cl(aq), sat. NaHCO3(aq), sat. NH4-
Cl(aq), and brine, dried over MgSO4, and then concentrated in vacuo
to yield 9-d16 (1.73 g, 97%) as an oil that was used without further
purification. Spectral data for 9-d16: 1H NMR (400 MHz, CDCl3)
(60) Becucci, L.; Guidelli, R.; Karim, C. B.; Thomas, D. D.; Veglia, G.
Biophys. J. 2007, 93, 2678-2687.
(61) Becucci, L.; Santucci, A.; Guidelli, R. J. Phys. Chem. B,2007, 111,
9814-9820.
(62) Kunze, J.; Leitch, J.; Schwan, A. L.; Faragher, R. J.; Naumann, R.;
Knoll, W.; Dutcher, J. R.; Lipkowski, J. Manuscript in preparation.
(63) Faragher, R. J.; Alberico, D.; Schwan, A. L. Tetrahedron 2005, 61,
1115-1125.
1376 J. Org. Chem., Vol. 73, No. 4, 2008

New Deuterated Oligo(ethylene glycol) Building Blocks
2
δ 7.29-7.18 (m, 5H), 4.50 (s, 2H), 3.06 (s, 3H); H NMR (61
19.46, 19.40, 19.36; IR (neat) (cm-1) 3064, 3031, 2953, 2925, 2867,
MHz, CDCl3) δ 4.36 (s, 2H), 3.75 (s, 2H), 3.68-3.61 (m, 12H);
13C NMR (100 MHz, CDCl3) δ 137.8 127.7, 127.0, 126.9, 72.3,
68.9 (br pent, JCD ) 21.5 Hz), 68.3 (pent, JCD ) 22.3 Hz), 68.0
(pent, JCD ) 21.1 Hz), 67.3 (pent, JCD ) 21.5 Hz), 36.8.
2181, 2081; [R]24 -0.308 (CH2Cl2, c 14.6). Anal. Calcd for
D
C58H94D16O7: C 74.47, H 11.85. Found: C 74.28, H 11.61.
(14S,23R,27R)-19,23,27,31-Tetramethyl-14-[[(7R,11R)-3,7,11,-
15-tetramethylhexadecyl]oxy]-3,6,9,12,16-pentaoxadotriacontan-
1-ol-d16 (20-d16). To a round-bottomed flask was added 16-d16 (1.65
g, 1.76 mmol), EtOAc (60 mL), and 10% Pd/C (0.400 g), and the
solution was degassed (3×). Then hydrogen gas was introduced
under balloon pressure (15-16 psi) and the mixture was warmed
at 40 °C for 13 h. The mixture was filtered through Celite, which
was washed liberally with EtOAc, and the combined organics were
concentrated in vacuo. Flash chromatography (30% EtOAc/hexanes
to EtOAc, Rf 0.1 (50% EtOAc/hexanes)) yielded 20-d16 as an oil,
1.43 g (96%). Spectral data: 1H NMR (400 MHz, CDCl3) δ 3.59-
3.45 (m, 9H), 2.51 (br s, 1H), 1.64-1.47 (m, 6H), 1.40-1.00 (m,
42H), 0.86 (br d, J ) 6.6 Hz, 18H), 0.84 (v br d, J ) 6.6 Hz, 12
H); 2H NMR (61 MHz, CDCl3) δ 3.70-3.56 (br s, 16H); 13C NMR
(100 MHz, CDCl3) δ 77.6, 77.7, 71.3 (pent, JCD ) 21.3 Hz), 71.0,
70.54, 70.49, 69.4, 69.3 (pent, JCD ) 20.8 Hz), 68.3, 60.3 (pent,
JCD ) 21.3 Hz), 37.0, 36.9, 36.8, 36.7, 36.4, 36.3, 29.4, 29.3, 27.5,
24.4, 24.1, 24.0, 22.34, 22.25, 19.4, 19.3; IR (neat) (cm-1) 3476
(br), 2954, 2930, 2868, 2183, 2082; [R]24D -0.511 (CH2Cl2, c 9.22).
Anal. Calcd for C51H88D16O7: C 72.46, H 12.40. Found: C 72.38,
H 12.31.
(4R)-2,2-Dimethyl-4-(15-phenyl-2,5,8,11,14-pentaoxapentadec-
1-yl)-1,3-dioxolane-d16 (18-d16). To a flame-dried round-bottomed
flask was added powdered KOH (2.5 equiv, 0.642 g, 11.5 mmol)
and dry DMSO (30 mL) and the suspension was allowed to stir
for 30 min. The mixture was cooled in an ice bath and a solution
of 9-d16 (1 equiv, 1.73 g, 4.58 mmol) and 17 (1 equiv, 0.605 g,
4.58 mmol) in dry DMSO (25 mL) was added. The mixture was
then warmed to rt and stirred for 18 h and then warmed at 40 °C
for 18 h. H2O (100 mL) was added and the solution was extracted
with EtOAc (4 × 50 mL) and the combined organics were washed
with H2O (6 × 50 mL) and brine, dried over MgSO4, and
concentrated in vacuo to yield an oil, 1.71 g (90%), suitable for
use in the next step. A small sample was purified from flash
chromatography (20-50% EtOAc/hexanes), Rf 0.50 (1:1 EtOAc:
hexanes). Spectral data for 18-d16: 1H NMR (400 MHz, CDCl3) δ
7.37-7.28 (m, 5H), 4.59 (s, 2H), 4.30 (app quint, J ) 6.0 Hz,
1H), 4.07 (dd, J ) 8.3, 6.4 Hz, 1 H), 3.74 (dd, J ) 8.3, 6.4 Hz, 1
H), 3.59 (dd, J ) 10.0, 5.8 Hz, 1 H), 3.50 (dd, J ) 10.0, 5.5 Hz,
1H), 1.44 (s, 3H), 1.38 (s, 3H); 2H NMR (61 MHz, CDCl3) δ 3.63
(br s, 16H); 13C NMR (100 MHz, CDCl3) δ 137.6, 127.4, 126.7,
126.6, 108.2, 73.8, 72.1, 71.3, 69.2 (pent, JCD ) 21.6 Hz), 68.8
(pent, JCD ) 21.3 Hz), 67.8 (pent, JCD ) 21.3 Hz), 65.9, 25.9, 24.6;
(3R)-(14S,23R,27R)-19,23,27,31-Tetramethyl-14-[[(7R,11R)-
3,7,11,15-tetramethylhexadecyl]oxy]-3,6,9,12,16-pentaoxadotria-
cont-1-yl-ester-1,2-dithiolane-3-pentanoate-d16 (1-d16, DPTL-d16).
To a flame-dried round-bottomed flask was added lipoic acid (2
equiv, 0.409 g, 1.98 mmol), EDC‚HCl (2.5 equiv, 0.475 g, 2.48
mmol), DMAP (cat, 26.7 mg), and dry CH2Cl2 (10 mL). Then a
solution of 20-d16 (1 equiv, 0.837 g, 0.990 mmol) and Et3N (2.5
equiv, 0.251 g, 2.48 mmol) in dry CH2Cl2 (15 mL) was added and
the mixture was stirred at rt for 24 h and warmed at 40 °C for 3
days. Saturated NH4Cl(aq) (20 mL) and H2O (20 mL) were added
and the solution was extracted with CH2Cl2 (4 × 50 mL). The
combined organics were washed with sat. NH4Cl(aq), H2O, sat.
NaHCO3(aq), H2O, and brine, dried over MgSO4, and concentrated
in vacuo. Flask chromatography (20-50% EtOAc/hexanes, Rf 0.13
in 50% EtOAc/hexanes) yielded 1-d16 as an oil, 0.952 g (93%).
Spectral data: 1H NMR (400 MHz, CDCl3) δ 3.60-3.45 (m, 9H),
3.23-3.16 (m, 2H), 2.51-2.40 (m, 1H), 2.35 (t, J ) 7.5 Hz, 2H),
1.93-1.82 (m, 1H), 1.71-1.03 (m, 55H), 0.86 (br d, J ) 6.6 Hz,
18H), 0.84 (v br d, J ) 6.6 Hz, 12H); 2H NMR (61 MHz, CDCl3)
δ 4.08 (s, 2H), 3.50 (s, 14H); 13C NMR (75 MHz, CDCl3) δ 172.7,
77.6, 71.0, 70.6, 70.5, 69.43, 69.38 (br pent, JCD ) 21.1 Hz), 68.3,
67.9 (pent, JCD ) 21.6 Hz), 62.3 (pent, JCD ) 21.5 Hz), 55.8, 39.8,
39.0, 38.0, 37.1, 37.0, 36.9, 36.8, 36.74, 36.4, 36.3, 34.2, 33.5, 32.4,
29.5, 29.4, 28.3, 27.6, 24.4, 24.2, 24.1, 24.0, 22.4, 22.3, 19.41,
IR (neat) (cm-1) 3063, 3030, 2986, 2934, 2864, 2184, 2082; [R]24
D
+5.96 (CH2Cl2, c 14.2); MS(EI) m/z (%) 414 (M+, 4), 399 (27),
272 (80), 257 (32), 229 (100), 185 (10), 173 (13), 161 (10), 145
(20), 132 (27), 101 (31), 91 (64), 84 (77); HRMS calcd for
C21H18D16O7 414.3293, found 414.3299.
(2S)-17-Phenyl-4,7,10,13,16-pentaoxaheptadecane-1,2-diol-
16 (19-d16). To a round-bottomed flask was added 18-d16 (1.45 g,
d
3.50 mmol) and MeOH (30 mL) and the mixture was cooled to
-40 °C. Then a solution of freshly prepared 1 M HCl in MeOH
(31.1 mL, precooled to -40 °C) was added over 2 min and the
mixture was slowly warmed over 4 h after which time the mixture
was concentrated in vacuo to yield an oil. Flash chromatography
(EtOAc to 7:1 EtOAc:EtOH, Rf 0.55 in 9:1 EtOAc/EtOH) yielded
19-d16 as an oil, 0.970 g (74%). Spectral data: 1H NMR (400 MHz,
CDCl3) δ 7.37-7.28 (m, 5H), 4.58 (s, 2H), 3.87-3.83 (m, 1H),
3.72-3.54 (m, 4 H); 2H NMR (61 MHz, CDCl3) δ 3.67 (br s, 16H);
13C NMR (75 MHz, CDCl3) δ:137.2, 127.4, 126.7, 126.6, 72.1,
71.0 (br), 69.4 (br), 68.7 (br pent, JCD ) 21 Hz), 67.6 (br pent, JCD
) 21 Hz), 62.0; IR (neat) (cm-1) 3311 (br), 3036, 2929, 2864,
2186, 2083.
(16S,25R,29R)-1-Phenyl-21,25,29,33-tetramethyl-16-[[(7R,-
11R)-3,7,11,15-tetramethylhexadecyl]oxy]-2,5,8,11,14,18-hexaox-
atetratriacontane-d16 (16-d16). To a flame-dried round-bottomed
flask was added powdered KOH (5 equiv, 0.710 g, 12.5 mmol)
and dry DMSO (25 mL) and the suspension was stirred for 30 min.
The mixture was then cooled in an ice bath and a solution of 19-
d16 (1 equiv, 0.937 g, 2.50 mmol) and phytanyl mesylate (12) (3
equiv, 2.82 g, 7.50 mmol) in dry DMSO (25 mL) was added and
the mixture was allowed to warm to rt and stirred at rt for 18 h
and at 40 °C for 3 days. H2O (100 mL) was added and the aqueous
mixture was extracted with EtOAc (5 × 30 mL) and the combined
organics were washed with H2O (6 × 50 mL) and brine, dried over
MgSO4, and concentrated in vacuo. Flash chromatography (20%
EtOAc:hexanes, Rf 0.45 (25% EtOAc/hexanes)) yielded 16-d16 as
an oil, 1.68 g (74%). Spectral data: 1H NMR (400 MHz, CDCl3)
δ 7.34-7.27 (m, 5H), 4.56 (s, 2H), 3.62-3.43 (m, 9H), 1.63-
1.47 (m, 6H), 1.38-1.01 (m, 44H), 0.86 (br d, J ) 6.6 Hz, 18 H),
0.84 (v br d, J ) 6.6 Hz. 12H); 2H NMR (61 MHz, CDCl3) δ 3.64
(br s, 16H); 13C NMR (75 MHz, CDCl3) δ 138.0, 127.9, 127.3,
127.1, 77.7, 72.8, 71.1, 70.7, 70.6, 69.5, 69.4 (pent, JCD ) 21.0
Hz), 68.4, 68.3 (pent, JCD ) 21.4 Hz), 39.1, 37.2, 37.1, 37.0, 36.9,
36.8, 36.5, 36.4, 32.4, 29.5, 29.4, 27.6, 24.5, 24.2, 24.1, 22.4, 22.3,
19.35; IR (neat) (cm-1) 2953, 2926, 2867, 2182, 2082, 1737; [R]24
D
-0.359 (CH2Cl2, c 9.22); MS(TOF ES) m/z (%) 1051 ((M +
NH4)+), 1033 ((M)+); HRMS C59H104D16NO8S2 calcd 1033.9194,
found 1033.9158. Anal. Calcd for C59H100D16O8S2: C 68.55, H
11.31. Found: C 68.61, H 11.11.
(16S,25R,29R)-19,23,27,31-Tetramethyl-1-p-toluenesulfonate-
14-[[(7R,11R)-3,7,11,15-tetramethylhexadecyl]oxy]-3,6,9,12,16-
pentaoxadotriacontane-d16 (22-d16). To a flame-dried round-
bottomed flask was added 20-d16 (1 equiv, 0.564 g, 0.668 mmol),
TsCl (1.95 equiv, 0.248 g, 1.30 mmol), and dry CH2Cl2 (45 mL).
The mixture was cooled to -30 °C and powdered KOH (3.2 equiv,
0.120 g, 2.14 mmol) was added portionwise and the mixture was
allowed to warm to rt overnight and was stirred vigorously for 3
days. H2O (100 mL) was added and the mixture was extracted with
CH2Cl2 (4 × 50 mL). The combined organics were washed with
H2O (40 mL) and brine, dried over MgSO4, and concentrated in
vacuo. Flash chromatography (25-75% EtOAc/hexanes, Rf 0.13
in 50% EtOAc/hexanes) yielded 22-d16 as a slightly yellow oil,
0.634 g (95%). Spectral data: 1H NMR (400 MHz, CDCl3) δ 7.80
(d, J ) 8.4 Hz, 2H), 7.34 (d, J ) 8.4 Hz, 2H), 3.56-3.44 (m, 9H),
2.45 (s, 3H), 1.56-1.49 (m, 6H), 1.37-1.03 (m, 42H), 0.86 (br d,
J. Org. Chem, Vol. 73, No. 4, 2008 1377

Faragher and Schwan
2
J ) 6.7 Hz, 18H), 0.84 (v br d, J ) 6.7 Hz, 12H); H NMR (61
29.6, 27.9, 24.7, 24.4, 24.3, 22.6, 22.5, 19.7, 19.60, 19.55, 19.5;
MHz, CDCl3) δ 4.14 (s, 2H), 3.67 (s, 2H), 3.62 (s, 8H), 3.56 (s,
4H); 13C NMR (75 MHz, CDCl3) δ 144.2, 132.9, 129.4, 127.6,
77.6, 71.0, 70.6, 69.5, 69.3 (pent, JCD ) 21.6 Hz), 68.4, 68.2 (pent,
JCD ) 21.5 Hz), 67.4 (pent, JCD ) 21.6 Hz), 39.0, 37.2, 37.1, 36.9,
36.8, 36.44, 36.35, 32.4, 29.5, 29.4, 27.6, 24.4, 24.1, 24.0, 22.4,
22.3, 21.2, 19.44, 19.37, 19.31; IR (neat) (cm-1) 3030, 2954, 2926,
IR (neat) (cm-1) 3479 (br), 2954, 2926, 2868, 2182, 2082; [R]24
D
-0.160 (CH2Cl2, c 4.96); MS(ESI) m/z (%) 1055 ((M + NH4)+),
1038 ((M + H)+); HRMS calcd for C59H92D32NO11 1055.1183,
found 1055.1232.
(3R)-(26S,35R,39R)-31,35,39,51-Tetramethyl-26-[[(7R,11R)-
3,7,11,15-tetramethylhexadecyl]oxy]-3,6,9,12,15,18,21,24,28-non-
aoxatetratetracontan-1-ylester-1,2-dithiolane-3-pentanoate-d32
(21-d32). To a flame-dried round-bottomed flask was added lipoic
acid (2.0 equiv, 58.0 mg, 0.280 mmol), EDC‚HCl (2.5 equiv, 67.0
mg, 0.350 mmol), DMAP (cat, 3 mg), and dry CH2Cl2 (5 mL). A
solution of 24-d32 (1.0 equiv, 0.145 g, 0.140 mmol) and Et3N (2.5
equiv, 35 mg, 0.350 mmol) in dry CH2Cl2 (10 mL) was added and
the mixture was stirred at rt for 24 h and refluxed for 3 days. Then
an additional amount of lipoic acid (45 mg) and EDC‚HCl (55 mg)
was added and stirring was continued at reflux for 4 days. Saturated
NH4Cl(aq) (10 mL) and H2O (10 mL) were added and the aqueous
solution was extracted with CH2Cl2 (4 × 25 mL). The combined
2867, 2186, 2083, 1598; [R]24 -0.441 (CH2Cl2, c 3.54). Anal.
Calcd for C58H94D16O9S: C 69.69, H 11.09. Found: C 69.61, H
11.12.
D
(28S,27R,41R)-33,37,41,45-Tetramethyl-1-phenyl-28-[[(7R,-
11R)-3,7,11,15-tetramethylhexadecyl]oxy]-2,5,8,11,14,17,20,23,-
26,30-decaoxahexatetracontane-d32 (23-d32). To a flame-dried
round-bottomed flask was added NaH (4.0 equiv, 81.0 mg, 2.03
mmol), which was washed with hexanes (2 × 25 mL), and then
dry THF (10 mL) was added. The suspension was cooled to
-78 °C and a solution of 22-d16 (0.506 g, 0.506 mmol) and 7-d16
(0.152 g, 0.506 mmol) in dry THF (20 mL) was added dropwise.
The mixture was slowly warmed to rt and stirred for 3 days at rt
and then warmed at 40 °C for 3 h. H2O (20 mL) was added and
the mixture was extracted with EtOAc (4 × 25 mL) and the
combined organics were washed with H2O (20 mL) and brine, dried
over MgSO4, and concentrated in vacuo. Flash chromatography
(20-75% EtOAc/hexanes then 50% EtOH/EtOAc, Rf 0.1 (EtOAc))
yielded 23-d32 as an oil, 0.346 g (60%). Spectral data: 1H NMR
(400 MHz, CDCl3) δ 7.34-7.27 (m, 5H), 4.56 (s, 2H), 3.61-3.43
(m, 9H), 1.37-0.98 (m, 42H), 0.86 (br d, J ) 6.6 Hz, 18H), 0.84
organics were washed with sat. NH4Cl(aq), H2O, sat. NaHCO3(aq)
,
H2O, and brine, dried over MgSO4, and concentrated in vacuo. Flash
chromatography (1:1 EtOAc:hexanes then 1:1 EtOAc:EtOH) yielded
21-d32 as a yellow oil, 98 mg (60% after recovery of 24-d32 (28
mg)). Spectral data for 21-d32: 1H NMR (400 MHz, CDCl3) δ
3.64-3.42 (m, 9H), 3.21-3.08 (m, 2H), 2.47 (app pent, J ) 6.3
Hz, 0.5H), 2.45 (app pent, J ) 6.3 Hz, 0.5H), 2.35 (t, J ) 7.4 Hz,
2H), 1.91 (app hextet, J ) 6.9 Hz, 1H), 1.71-1.42 (m, 13H), 1.41-
1.01 (m, 42H), 0.86 (br d, J ) 6.7 Hz, 18H), 0.84 (v br d, J ) 6.7
Hz, 12H); 2H NMR (61 MHz, CDCl3) δ 4.18 (s, 2H), 3.59 (s, 30H);
13C NMR (75 MHz, CDCl3) δ 173.3, 77.8, 71.3, 70.81, 70.76, 69.8,
69.6 (pent, JCD ) 21.5 Hz), 68.9, 68.8, 68.2 (br pent, JCD ) 22.0
Hz), 62.6 (pent, JCD ) 22.4 Hz), 56.2, 40.1, 39.3, 38.4, 37.4, 37.29,
37.28, 37.24, 37.2, 37.1, 37.0, 36.64, 36.56, 34.5, 33.8, 32.7, 29.8,
29.72, 29.69, 28.6, 27.9, 24.7, 24.5, 24.4, 24.3, 22.6, 22.5, 19.7
19.6, 19.54, 19.52; IR (neat) (cm-1) 2953, 2925, 2867, 2181, 2082,
2
(v br d, J ) 6.6 Hz, 12H); H NMR (61 MHz, CDCl3) δ 3.58 (br
s, 32 H); 13C NMR (75 MHz, CDCl3) δ 138.1, 128.1, 127.5, 127.3,
77.7, 72.9, 71.2, 70.7, 69.7, 69.5 (br pent, JCD ) 21.4 Hz), 68.6
(br), 68.4 (pent, JCD ) 21.6 Hz), 39.2, 37.3, 37.2, 37.1, 37.0, 36.9,
36.6, 36.5, 32.6, 29.7, 29.6, 27.8, 24.6, 24.3, 24.2, 22.54, 22.45,
19.57, 19.51; IR (neat) (cm-1) 3090, 3066, 3030, 2955, 2930, 2865,
2180, 2082; [R]24 -0.161 (CH2Cl2, c 4.77). Anal. Calcd for
D
1736; [R]24 -0.284 (CH2Cl2, c 2.75); ES MS (+) m/z (%) 1243
C66H94D32O11: C 70.29, H 11.26. Found: C 70.48, H 11.05.
(26S,35R,39R)-31,35,39,51-Tetramethyl-26-[[(7R,11R)-3,7,11,-
15-tetramethylhexadecyl]oxy]-3,6,9,12,15,18,21,24,28-nonaox-
atetratetracontan-1-ol-d32 (24-d32). To a round-bottomed flask was
added 23-d32 (0.295 g, 0.265 mmol), EtOAc (20 mL), and 10%
Pd/C (75 mg), and the mixture was degassed (3×). Then hydrogen
gas was introduced under balloon pressure (15-16 psi) and the
mixture was warmed at 40 °C for 2.5 h. The mixture was filtered
over Celite, which was washed liberally with EtOAc, and combined
organics were concentrated in vacuo. Flash chromatography (EtOAc
to 9:1 EtOAc:EtOH), Rf 0.5 (9:1 EtOAc:EtOH), yielded 24-d32 as
an oil, 0.265 g (95%). Spectral data: 1H NMR (400 MHz, CDCl3)
δ 3.60-3.40 (m, 9H), 3.11 (br s, 1H), 1.60-1.53 (m, 2H), 1.49
(app heptet, J ) 6.6 Hz, 4H), 1.34-1.02 (m, 42H), 0.83 (br d, J )
6.6 Hz, 18H), 0.81 (v br d, J ) 6.6 Hz, 12H); 2H NMR (61 MHz,
CDCl3) δ 3.60 (br s, 32H); 13C NMR (75 MHz, CDCl3) δ 77.2,
71.5 (pent, JCD ) 21.6 Hz), 71.3, 70.9, 70.8, 69.9, 69.5 (br pent,
JCD ) 21.2 Hz), 68.8 (br), 60.8 (pent, JCD ) 21.6 Hz), 39.3, 37.4,
37.32, 37.30, 37.2, 37.1, 37.0, 36.7, 36.6, 32.7, 29.8, 29.74, 29.72,
D
((M + NH4)+); HR TOF ES MS(+) C67H100D32O12S2 ((M + H)+),
calcd 1226.1247, found 1226.1199; C67H104D32NO12S2 ((M +
NH4)+), calcd 1243.1513, found 1243.1506. Anal. Calcd for
C67H100D32O12S2: C 65.64, H 10.85. Found: C 66.20, H 10.44.
Acknowledgment. The authors are indebted to the Natural
Sciences and Engineering Research Council for funding this
project. The authors also thank Dr. Julia Kunze, Prof. Jacek
Lipkowski, and the Lipkowski group for their guidance and their
confidence in us. R.J.F. thanks the Ontario Government for a
graduate scholarship.
Supporting Information Available: Additional experimental
procedures and copies of 1H and 13C NMR spectra for nondeuterated
and selected deuterated compounds. This material is available free
of charge via the Internet at http://pubs.acs.org.
JO701979Z
1378 J. Org. Chem., Vol. 73, No. 4, 2008