A synthesis of dioctanoyl phosphatidylinositol

Article abstract of DOI:10.1016/j.tetasy.2009.11.026

A synthesis of the naturally occurring enantiomer of phosphatidylinositol is reported. A resolution strategy, using camphor as a chiral auxiliary is employed to obtain the desired, enantiomerically pure, inositol derivative. Dioctanoyl lipid chains are appended to the molecule, which are shorter than the naturally occurring lipid chains, providing the molecule with enhanced water solubility.

Full text of DOI:10.1016/j.tetasy.2009.11.026

Tetrahedron: Asymmetry 20 (2009) 2809–2813
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
A synthesis of dioctanoyl phosphatidylinositol
Thomas S. Elliott a, Joseph Nemeth a, Simon A. Swain b, Stuart J. Conway c,
*
a School of Chemistry and Centre for Biomolecular Sciences, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
b Prosidion Ltd, Watlington Road, Oxford OX4 6LT, UK
c Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
A synthesis of the naturally occurring enantiomer of phosphatidylinositol is reported. A resolution strat-
egy, using camphor as a chiral auxiliary is employed to obtain the desired, enantiomerically pure, inositol
derivative. Dioctanoyl lipid chains are appended to the molecule, which are shorter than the naturally
occurring lipid chains, providing the molecule with enhanced water solubility.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 12 October 2009
Accepted 27 November 2009
Available online 6 January 2010
1. Introduction
O
O
lipid
O
Phosphatidylinositol phosphates(PtdInsPns) are importantphos-
pholipid components of plant, animal and bacterial cell membranes.
These molecules play a central role in cellular signalling1–3 and act
by recruiting their effector proteins to the cell membrane through
interaction with selective inositol phosphate-binding domains.4
The central intracellular role of the PtdInsPns is responsible for their
involvement in a number of disease related processes, including
insulin signalling and pathways involved in several types of
cancers.5,6
O
O
lipid
P
HO
O-Na+
OH
O
O
HO
OH
OH
1
Figure 1. The general structure of phosphatidylinositol (PtdIns, 1). The constitution
of the lipid chains varies depending on the source of the lipid.
Phosphatidylinositol (PtdIns, 1, Fig. 1) is one of the main acidic
phospholipid components of (for example) erythrocyte cells, com-
prising approximately 1% of all lipids, by weight.4 It was first
isolated from the brain7 and subsequently, in a more pure form,
from soy beans.8 The structure of PtdIns was unambiguously as-
signed by degradation and synthetic studies by Ballou and Pizer.9
However, it is only more recently that the true significance of
the PtdInsPns in cellular signalling has been appreciated. PtdIns
is biosynthesised predominantly in the endoplasmic reticulum
and is then delivered to other membranes.10 Perhaps the most
significant role of PtdIns is as the biosynthetic precursor to mono-
phosphorylated phospholipids, phosphatidylinositol 3-phosphate
(PtdIns3P), phosphatidylinositol 4-phosphate (PtdIns4P) and phos-
phatidylinositol 5-phosphate (PtdIns5P),10–12 which are in turn
transformed into the multiply phosphorylated phosphatidylinosi-
tols. PtdIns itself has been implicated as playing a role in bipolar
disorder,10 and is indirectly involved in many other aspects of cel-
lular function and dysfunction through its biochemical relation-
ship with the other PtdInsPns.
occurring compounds, a number of unnatural derivatives, which
are useful chemical probes, have been developed.12–14 The impor-
tant biological activity of PtdIns, coupled with our interest in the
synthesis of inositol-based molecular probes,15–17 phospholipid
analogues18 and PtdInsPns derivatives19 has prompted us to devel-
op a synthesis of PtdIns.19–26 We have a particular interest in
obtaining the dioctanoyl PtdIns derivative that has enhanced water
solubility, which is advantageous for use in biological assays and
crystallisation studies for X-ray analysis.27
2. Results and discussion
The synthesis commenced from myo-inositol, which is a cheap
and readily available starting material. Using a well-documented
series of transformations, we obtained the chiral, non-racemic
camphor derivative 2 in seven steps.19,28–31 The hydroxyl group
at the D-1-position of the ring was protected as the TIPS ether (3,
The important biological action of the PtdInsPns, coupled with
the densely functionalised nature of their structure has led to sig-
nificant interest in their synthesis.12,13 In addition to the naturally
Scheme 1). Other syntheses have employed PMB ethers as the pro-
tecting group at this position, but we have found that the TIPS
group, which has been relatively under utilised in inositol chemis-
try, can be added and deprotected in high yields, often in the
presence of protected phosphate groups. Removal of the camphor
chiral auxiliary and the allyl group was effected simultaneously
* Corresponding author. Tel.: +44 (0)1865 285109; fax: +44 (0)1865 285002.
E-mail address: stuart.conway@chem.ox.ac.uk (S.J. Conway).
0957-4166/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2009.11.026

2810
T. S. Elliott et al. / Tetrahedron: Asymmetry 20 (2009) 2809–2813
The lipid fragment 11 was synthesised in a manner similar to
BnO
O
BnO
OH
OTIPS
O
that reported previously.18,19,28–30,33–35 The synthesis commenced
with benzyl protection of (+)-1,2-O-isopropylidene glycerol 6,
furnishing 7, followed by an acid-catalysed methanolysis of the
isopropylidene acetal (Scheme 2), to give the diol 8. DMAP-cata-
lysed coupling of the free hydroxyl groups with octanoyl chloride
installed the lipid chains of 9. Hydrogenolysis, mediated by Pearl-
man’s catalyst, effected debenzylation of the lipid 9, yielding 10.
The amidite intermediate 11 was obtained by treatment of the
alcohol 10 with benzyloxybis(N,N-diisopropylamino)phosphine.
The amidite 11 was used immediately after preparation, in order
to minimise degradation.
OBn
OAll
OBn
OAll
O
i
O
2
3
ii
BnO
BnO
HO
OH
OTIPS
iii
OBn
OH
OBn
OBn
BnO
With both fragment 5 and fragment 11 in hand, we proceeded to
couple them (Scheme 3). Treatment of the inositol fragment 5 with
the lipid phosphoramidite 11, afforded a presumed P(III) intermedi-
ate, which was not isolated, but oxidised directly using mCPBA to af-
ford the fully protected PtdIns precursor 12. Palladium black-
catalysed hydrogenolysis of 12 afforded PtdIns in moderate yield.
The inclusion of NaHCO3 led to PtdIns 1 being isolated as its sodium
salt, which exists as a colourless solid after lyophilisation.
OBn
OH
5
4
Scheme 1. The synthesis of the inositol fragment 5. Reagents and conditions: (i)
TIPSOTf, Et3N, CH2Cl2, rt, 87%; (ii) PdCl2, MeOH, rt, 81%; (iii) (a) BnBr, NaH, DMF,
0 °C?rt, 68%; (b) TBAF, THF, rt, 88%.
by treatment with PdCl2 in methanol, affording 4. There are several
possible mechanisms for the allyl group deprotection. Some re-
ports suggest that PdCl2 will undergo an anti-Markovnikov meth-
oxypalladation followed by b-alkoxy cleavage, furnishing the
desired hydroxyl group.32 Alternatively, it is reasonable to suggest
that the PdCl2 isomerises the allyl group to the corresponding enol
ether and that a low concentration of HCl is generated, which
catalyses methanolysis of the enol ether. The camphor acetal could
be cleaved by either the Lewis acid action of PdCl2, or the low con-
centration of HCl in methanol, or both. We had previously em-
ployed Wilkinson’s catalyst to isomerise the allyl group to the
corresponding enol ether, followed by treatment with acetyl chlo-
ride in methanol, to cleave the enol ether and the camphor acetal.
The latter conditions provided a yield of only 37%, compared to
that of 81% when using PdCl2 in methanol. Benzylation of the 3-,
4- and 5-position hydroxyl groups was achieved using standard
benzylation conditions, in a 68% yield. This moderate yield can
likely be attributed to the unfavourable steric demands of benzy-
lating on three contiguous hydroxyl groups. In addition, it is unli-
kely that three alkoxide anions will form simultaneously on the
same molecule, due to the disfavoured anionic interactions. The
TIPS ether was removed by treatment with TBAF in THF at room
temperature, to give an 88% yield of the inositol fragment 5.
3. Conclusion
In summary, we report a concise and robust synthesis of the
dioctanoyl derivative of PtdIns. We have demonstrated that the
use of a TIPS ether is a viable protecting group strategy in the syn-
thesis of inositol derivatives.
4. Experimental
4.1. General experimental details
1H NMR spectra were recorded on Bruker DPX250 (250 MHz);
Bruker Avance 300 (300 MHz); Bruker Avance 400 (400 MHz); Bru-
ker Avance II 400 (400 MHz); Bruker DRX500 (500 MHz); Bruker
Avance 500 (500 MHz); or Bruker Avance III (500 MHz) using deu-
terochloroform (unless indicated otherwise) as a reference for
internal deuterium lock. The chemical shift data for each signal
are given as d in units of parts per million (ppm) relative to tetra-
methylsilane (TMS) where dTMS = 0.00 ppm. The multiplicity of
each signal is indicated by: s (singlet); d (doublet); dd (doublet
of doublets); dt (doublet of triplets); ddd (doublet of doublet of
doublets); dddd (doublet of doublet of doublet of doublets); and
m (multiplet). The number of protons (n) for a given resonance sig-
nal is indicated by nH. Coupling constants (J) are quoted in hertz
and are recorded to the nearest 0.1 Hz. Identical proton coupling
constants (J) are averaged in each spectrum and reported to the
nearest 0.1 Hz. The coupling constants are determined by analysis
using Bruker TopSpin software. 13C NMR spectra were recorded on
Bruker Avance 300 (75 MHz) or Bruker Avance III (125 MHz) spec-
trometers using the PENDANT or DEPT Q pulse sequences with
broadband proton decoupling and internal deuterium lock. The
chemical shift data for each signal are given as d in units of parts
per million (ppm) relative to tetramethylsilane (TMS) where
dTMS = 0.00 ppm. Where appropriate, coupling constants (J) are
quoted in hertz and are recorded to the nearest 0.1 Hz. 1H and
13C spectra were assigned using 2D NMR experiments including
COSY, HSQC, HMBC, DEPT-135, HMQC and DEPT Q. 31P NMR spec-
tra were recorded on a Bruker Avance 300 (121 MHz) using broad-
band proton decoupling pulse sequences and deuterium internal
lock. The chemical shift data for each signal are given as d in units
of parts per million (ppm) relative to 85% phosphoric acid as an
external reference. Mass spectra were acquired using electrospray
ionisation on Micromass LCT; Micromass LCT Premier; and Bruker
MicroTOF spectrometers, operating in positive or negative mode,
i
O
O
O
O
HO
BnO
BnO
6
7
ii
O
OH
O
C7H15
O C7H15
iii
OH
BnO
9
8
O
iv
O
O
O
C7H15
O
O
C7H15
O C7H15
v
BnO
O
C7H15
P
HO
N
O
O
10
11
Scheme 2. The synthesis of the lipid amidite fragment x. Reagents and conditions:
(i) NaH, BnBr, DMF, rt, 92%; (ii) concd HCl, MeOH, reflux, 96%; (iii) DMAP, pyridine,
octanoyl chloride, rt, 92%; (iv) Pd(OH)2, H2, THF, rt, 87%; (v) benzyloxybis(N,N-
diisopropylamino)phosphine, 1H-tetrazole, CH2Cl2, rt, 71%.

T. S. Elliott et al. / Tetrahedron: Asymmetry 20 (2009) 2809–2813
2811
O
O
O
C7H15
C7H15
O
C7H15
O C7H15
BnO
OH
O
O
i
ii
O
O
O
O-Na+
OH
OBn
OBn
P
P
BnO
BnO
HO
O
O
OBn
O
O
OBn
OBn
BnO
HO
OBn
OH
OBn
OH
5
12
1
Scheme 3. The synthesis of PtdIns 1 by coupling of fragment 5 with fragment 11 and subsequent hydrogenolysis. Reagents and conditions: (i) (a) 11, 1H-tetrazole, CH2Cl2, rt;
(b) mCPBA, ꢀ78 °C?rt, 52%; (ii) Pd black, H2, NaHCO3, tBuOH, H2O, rt, 64%.
from solutions of methanol, acetonitrile or water. Certain samples
were submitted to the National Mass Spectrometry Centre, Swan-
sea. m/z Values are reported in Daltons and followed by their per-
centage abundance in parentheses. Microanalyses were obtained
on a Carlo Erber EA1110 analyser by the St Andrews University
microanalysis service. Certain samples were submitted to the Ele-
mental Analysis Service, London Metropolitan University, London.
Melting points were determined using an Electrothermal 9100
melting point apparatus or Kofler hot stage microscope and are
uncorrected. Infrared Spectra were obtained from a thin film on so-
dium chloride plates. The spectra were recorded on Perkin Elmer
GX FT-IR or Bruker Tensor 27 spectrometers. Absorption maxima
are reported in wavenumbers (cmꢀ1). Specific Optical Rotations
were measured using Perkin Elmer Model 241 and 341 polarime-
ters, in cells with a path length of 1 dm. The light source was main-
tained at 589 nm. The concentration (c) is expressed in g/100 mL
isomers and petroleum ether to the fraction boiling between 40
and 60 °C.
4.2. (ꢀ)-1
D-5-O-Allyl-2,6-di-O-benzyl-1-O-triisopropylsilyl-3-O-
exo-(l-10,70,70-trimethylbicyclo[2.2.1]hept-20-ylidine)-myo-
inositol 3
To a stirred solution of triisopropylsilane trifluoromethanesul-
fonate (2.26 g, 1.66 mL, 7.98 mmol) in dry CH2Cl2 (3 mL) under
an atmosphere of nitrogen, was added triethylamine (943.8 mg,
1.3 mL, 9.35 mmol). The solution was allowed to stir for 1 h at
rt, turning to a dark orange colour. To this solution was added
a solution of (ꢀ)-1
D
-5-O-allyl-2,6-di-O-benzyl-3-O-exo-(l-10,70,70-
trimethylbicyclo[2.2.1]hept-20-ylidine)-myo-inositol 2 (3.0 g, 5.61
mmol) in dry CH2Cl2 (30 mL). The reaction mixture was stirred at
rt overnight. After this time TLC analysis indicated that the reaction
was complete, so the reaction mixture was diluted with CH2Cl2
(20 mL) and water (50 mL) was added. The layers were separated
and the aqueous phase was extracted with CH2Cl2 (3 ꢂ 20 mL).
The combined organic phases were dried over magnesium sulfate,
filtered and the filtrate was concentrated under vacuum to yield a
dark brown oil. The oil was adsorbed onto silica gel and purified by
silica gel column chromatography eluting with diethyl ether and
(equivalent to g/0.1 dm3). Specific rotations are denoted ½a DT
ꢁ
and
are given in implied units of 10ꢀ1 deg cm2 gꢀ1 (T = ambient tem-
perature in °C). Analytical thin layer chromatography (TLC) was
carried out on Merck Silica Gel 60 F254 aluminium-supported thin
layer chromatography sheets. Visualisation was by absorption of
UV light (kmax 254 or 365 nm), or thermal development after dip-
ping in one of: (a) ethanolic solution of phosphomolybdic acid
(PMA); or (b) aqueous solution of potassium permanganate. Flash
Column chromatography was carried out on Apollo Scientific Ltd
Silica Gel 40–63 micron or Merck Silica Gel 60 (240–400 mesh),
eluting with solvents as supplied, under a positive pressure of com-
pressed air (unless otherwise stated). Anhydrous solvents were ob-
tained under the following conditions: dry acetonitrile was distiled
from calcium hydride in a recycling still; dry N,N-dimethylform-
amide was purchased from SigmaAldrich UK in a SureSeal™ bottle
and used without further purification or was distiled under re-
duced pressure from activated 4 Å molecular sieves and stored
over 4 Å molecular sieves under an N2 atmosphere; dry dimethyl
sulfoxide was pre-dried over activated alumina, then distiled from
calcium hydride and stored over activated 4 Å molecular sieves un-
der an N2 atmosphere; anhydrous 1,4-dioxane was distiled from
sodium and benzophenone in a recycling still and stored over acti-
vated 3 Å molecular sieves under an Ar atmosphere. Anhydrous
dichloromethane, diethyl ether, toluene, hexane and tetrahydrofu-
ran were obtained using a MBRAUN GmbH MB SPS-800 solvent
purification system, where solvent was dried by passage through
filter columns and dispensed under an atmosphere of N2 or Ar
gas. Chemicals were purchased from Acros UK, Sigma Aldrich UK,
Alfa Aesar UK, Fisher UK, Fluka UK, Fluorochem, Merck or TCI-Eur-
ope. Compound 1135 was synthesised using methods similar to
those previously reported.18,19,28–30,33–35 All solvents and reagents
were purified, when necessary, by standard techniques. Where
appropriate and if not stated otherwise, all non aqueous reactions
were performed in a flame-dried flask under an inert atmosphere
of nitrogen or argon, using a double vacuum manifold with the in-
ert gas passing through a bed of activated 4 Å molecular sieves and
self indicating silica gel. Brine refers to a saturated aqueous solu-
tion of sodium chloride. Hexane refers to a mixture of hexane
petroleum ether (2:98) to afford (ꢀ)-1
D-5-O-allyl-2,6-di-O-benzyl-
1-O-triisopropylsilyl-3-O-exo-(l-10,70,70-trimethylbicyclo[2.2.1]hept-
20-ylidine)-myo-inositol 3 (1.12 g, 87%) as a colourless oil: Rf 0.51
(ethyl acetate/hexane 10:90); ½a D25
¼ ꢀ1:5 (c 1.23, CHCl3); mmax
ꢁ
(NaCl plates)/cmꢀ1 2944 (s), 2867 (s), 2363 (w), 1493 (w), 1454
(m), 1390 (m), 1369 (w), 1309 (w), 1246 (w), 1202 (w), 1182
(m), 1114 (s), 1068 (s), 922 (w), 883 (m), 820 (m), 730 (m), 696
(m), 681 (w); 1H NMR (300 MHz; CDCl3) d 7.38–7.12 (10H, m,
ArH), 5.81 (1H, dddd, J 17.2, 10.4, 5.5, 5.5, CHX@CHYHZ), 5.17 (1H,
dd, J 17.2, 1.5, CHX@CHYHZ), 5.03 (1H, d, J 10.4, CHX@CHYHZ),
4.92 (1H, d, J 11.5, OCHAHB-Ph), 4.85 (1H, d, J 11.1, OCHA’HB’-Ph),
4.68 (1H, d, J 11.1, OCHA’HB’-Ph), 4.63 (1H, d, J 11.5, OCHAHB-Ph),
4.27 (1H, dd, J 12.7, 5.5, OCHVHW–CH@CH2), 4.10 (1H, dd, J 2.7,
1.5, H-2) 4.03 (1H, dd, J 12.7, 5.5, OCHVHW–CH@CH2), 3.94 (1H,
dd, J 9.7, 9.7, H-6), 3.83 (1H, dd, J 9.0, 2.7, H-3), 3.67 (1H, dd, J
9.0, 9.0, H-4), 3.44 (1H, dd, J 9.7, 9.0, H-5), 3.21 (1H, dd, J 9.7, 1.5,
H-1), 2.07 (1H, dt, J 13.4, 3.8, camphor ring), 1.89–1.77 (1H, m,
camphor ring), 1.72–1.58 (2H, m, camphor ring), 1.43–1.36 (1H,
m, camphor ring), 1.36–1.25 (1H, m, camphor ring), 1.18–1.09
(1H, m, camphor ring), 0.95–0.93 (21H, m, Si-[CH(CH3)2]3), 0.93
(3H, s, CH-camphor ring), 0.77 (3H, s, CH3-camphor bridge), 0.73
(3H, s, CH3-camphor bridge); 13C NMR (75 MHz; CDCl3) d 139.9,
139.3, 135.8 (CH@CH2), 128.5, 128.4, 127.9, 127.8, 127.7, 127.4,
120.7 (ketal carbon), 116.9 (CH@CH2), 83.7 (inositol ring), 81.9
(inositol ring), 77.9 (inositol ring), 77.2 (inositol ring), 76.4 (inositol
ring), 76.3 (CH2), 75.3 (inositol ring), 74.2 (CH2), 72.1 (CH2), 53.3
(Cq-camphor ring), 48.7 (Cq-camphor ring), 46.7 (CH2), 45.3 (CH),
29.3 (CH2), 27.1 (CH2), 20.7 (CH3), 20.5 (CH3), 18.6 (CH3), 13.3 (CH3),
10.0 (CH);HRMS m/z (ES+) [Found:(M+Na)+ 713.4209. C42H62O6SiNa+
requires M+, 713.4213]; m/z (ES+) 713 ([M+Na]+, 100%); Anal. Calcd
for C42H62O6Si: C, 73.0; H, 9.0. Found: C, 72.7; H, 9.3.

2812
T. S. Elliott et al. / Tetrahedron: Asymmetry 20 (2009) 2809–2813
4.3. (+)-2,6-Bis-O-benzyl-1-O-triisopropylsilyl-myo-inositol 4
(ꢀ)-1 -5-O-Allyl-2,6-di-O-benzyl-1-O-triisopropylsilyl-3-O-
5 ꢂ OCHAHB-Ph), 3.99 (1H, dd, J 9.5, 9.5, H-4), 3.87 (1H, dd, J 9.5,
9.5, H-6), 3.83 (1H, dd, J 2.0, 2.0, H-2), 3.64 (1H, dd, J 9.5, 2.0, H-
1), 3.38 (1H, dd, J 9.5, 9.5, H-5), 3.34 (1H, dd, J 9.5, 2.0, H-3),
0.99–0.93 (21H, m, Si–[CH(CH3)2]3); 13C NMR (100 MHz; CDCl3) d
139.4, 139.3, 139.0, 138.7, 138.4, 128.4, 128.3, 128.2, 128.1,
128.0, 127.97, 127.8, 127.79, 127.7, 127.5, 127.4, 127.3, 127.2,
127.1, 126.9, 84.2, 82.1, 81.9, 80.9, 79.9, 75.9 (CH2), 75.7 (CH2),
75.4 (CH2), 74.6 (CH2), 74.0, 72.9 (CH2), 18.2 (Si–[CH(CH3)2]3),
18.18 (Si–[CH(CH3)2]3), 12.8 (Si–[CH(CH3)2]3); HRMS m/z (ES+)
[Found: (M+Na)+ 809.4204. C50H62O6SiNa requires M+, 809.4208];
m/z (ES+) 804 ([M+NH4]+, 45%), 809 ([M+Na]+, 50%), 845
([M+NH4ꢃMeCN]+, 100%); Anal. Calcd for C50H62O6Si: C, 76.3, H,
7.9; Found: C, 76.4, H, 7.9.
D
exo-(l-1’,7’,7’-trimethylbicyclo[2.2.1]hept-2’-ylidine)-myo-inositol
3 (700 mg, 1.01 mmol) was dissolved in methanol (70 mL), to this
(under an atmosphere of nitrogen) was added PdCl2 (179 mg,
1.01 mmol). The reaction was left to stir at rt for 2 h before the pal-
ladium residues were removed by filtration through CeliteÒ. The fil-
trate was concentrated under vacuum and the residue partitioned
between CH2Cl2 (50 mL) and a solution of H2O2 (15% w/w, 60 mL).
The layers were stirred vigorously together for 30 min before being
separated and the aqueous phase was extracted with CH2Cl2
(3 ꢂ 20 mL). The combined organic layers were washed with a satu-
rated aqueous solution of NaHCO3, brine, then dried over magne-
sium sulfate and filtered. The filtrate was concentrated under
vacuum and the residue purified by silica gel column chromatogra-
phy, eluting with methanol and chloroform (1:99, 2:98 then 3:97),
affording (ꢀ)-2,6-bis-O-benzyl-1-O-triisopropylsilyl myo-inositol 4
(426 mg, 81% yield) as a colourless gum: Rf 0.30 (ethyl acetate);
4.5. (ꢀ)-2,3,4,5,6-Penta-O-benzyl myo-inositol 5
(ꢀ)-2,3,4,5,6-Penta-O-benzyl-1-O-triisopropylsilyl myo-inositol
(136 mg, 0.17 mmol) was dissolved in THF (15 mL). To this solution
was added TBAF (1 M solution in THF, 190 lL, 0.19 mmol), the mix-
½
a 2D5
ꢁ
¼ þ14:8 (c 1.36, CHCl3); mmax (NaCl plates)/cmꢀ1 3405 (s),
ture was stirred at rt and monitored by TLC analysis. After 3 h the
reaction was adjudged to be complete by TLC analysis and was di-
luted with diethyl ether (40 mL) and water (40 mL). The layers were
separated and the aqueous phase was further extracted with diethyl
ether (3 ꢂ 20 mL). The combined organic layers were dried over
magnesium sulfate, filtered and the filtrate concentrated under vac-
uum. The residue was purified by silica gel column chromatography
eluting with ethyl acetate and petroleum ether (20:80 then 30:70)
furnishing (ꢀ)-2,3,4,5,6-penta-O-benzyl myo-inositol 5 (96 mg,
88% yield) as a colourless gum: Rf 0.46 (petroleum ether/ethyl
2943 (s), 1455 (s), 1150 (s), 1061 (s); 1H NMR (400 MHz; CDCl3) d
7.31–7.17 (10H, m, ArH), 5.01 (1H, d, J 11.1, OCHAHB-Ph), 4.88 (1H,
d, J 11.9, OCHA’HB’-Ph), 4.67 (1H, d, J 11.1, OCHAHB-Ph), 4.66 (1H, d,
J 11.9, OCHA’HB’-Ph), 3.83 (1H, dd, J 2.4, 2.4, H-2), 3.83 (1H, dd, J
9.1, 2.4, H-1), 3.71 (1H, dd, J 9.1, 9.1, H-6), 3.68 (1H, ddd, J 9.1, 9.1,
2.4, H-4), 3.42 (1H, ddd, J 9.1, 7.8, 2.4, H-3), 3.30 (1H, ddd, J 9.1,
9.1, 2.4, H-5), 2.49 (1H, d, J 2.4, 4-OH), 2.30 (1H, d, J 2.4, 5-OH),
2.26 (1H, d, J 7.8, 3-OH), 1.20–1.06 (21H, m, Si–[CH(CH3)2]3); 13C
NMR (75 MHz; CDCl3) d 139.3, 139.2, 128.82, 128.8, 128.1, 128.0,
127.8, 82.2, 81.7, 75.8, 75.5, 75.3, 74.9, 74.4, 72.7, 18.7, 13.2; HRMS
m/z (ES+) [Found: (M+H)+ 517.2978. C29H45O6Si+ requires M+,
517.2980]; m/z (ES+) 575 ([M+NH4ꢃMeCN]+, 100%); m/z (ESꢀ) 515
([MꢀH]ꢀ, 100%), 575 ([M+OAc]ꢀ, 80%); Anal. Calcd for C29H44O6Si:
C, 67.4; H, 8.6. Found: C, 67.3; H, 8.5.
acetate 70:30); ½a D25
ꢁ
¼ ꢀ10:9 (c 0.5, CHCl3) [lit.29
½
a 1D8
ꢁ
¼ ꢀ10:0
(c 2.3, CHCl3]; 1H NMR (300 MHz; CDCl3) d 7.42–7.27 (25H, m,
ArH), 5.06–4.70 (10H, m, 5 ꢂ OCHAHB-Ph), 4.09 (1H, dd, J 9.5, 9.5,
inositol ring), 4.06 (1H, dd, J 2.5, 2.5, inositol ring), 3.84 (1H, dd, J
9.5, 9.5, inositol ring), 3.56–3.46 (3H, m, inositol ring), 2.22 (1H, d,
J 6.3, OH); m/z (ES+) 648 ([M+NH4]+, 30%), 653 ([M+Na]+, 100%),
732 ([M+HNEt3]+, 25%). These data are in agreement with the litera-
ture values.29,36
4.4. (+)-2,3,4,5,6-Penta-O-benzyl-1-O-triisopropylsilyl myo-
inositol
(+)-2,6-Bis-O-benzyl-1-O-triisopropylsilyl myo-inositol 4 (128
mg, 0.25 mmol) was dissolved in dry DMF (10 mL) under an atmo-
sphere of nitrogen and then cooled to 0 °C. With vigorous stirring,
sodium hydride (60% dispersion w/w in mineral oil, 40 mg,
0.99 mmol) was added. The resulting slurry was allowed to warm
to rt and stirred for a further 2 h. The slurry was cooled to 0 °C and
4.6. (+)-1D-1-(1,2-Dioctanoyl-sn-glycerol-3-phospho)-2,3,4,5,6-
penta-O-benzyl-myo-inositol 12
To a stirred solution of phosphoramidite 11 (120 mg, 0.206
mmol) in dry CH2Cl2 (5 mL) under an atmosphere of nitrogen
was added 1H-tetrazole (0.43 M solution in acetonitrile, 479
206 mol). This mixture was stirred at rt for 10 min before the
addition of (ꢀ)-2,3,4,5,6-penta-O-benzyl myo-inositol 5 (65 mg,
103 mol) as a solution in CH2Cl2 (2 mL). The reaction solution
lL,
benzyl bromide (170 mg, 117
lL, 0.99 mmol) was added with vig-
l
orous stirring. The reaction mixture was warmed to rt and stirred
overnight. The reaction was judged to be incomplete by TLC anal-
ysis. Therefore, the reaction mixture was cooled to 0 °C and an
additional sodium hydride (60% dispersion w/w in mineral oil,
l
was stirred at rt overnight. TLC analysis indicated that further
equivalents of phosphoramidite 11 (120 mg, 0.206 mmol) were re-
quired and the reaction was stirred at rt for another 3 h before the
addition of more phosphoramidite 11 (120 mg, 0.206 mmol). After
stirring for a further 2 h the reaction mixture was cooled to ꢀ78 °C
40 mg, 0.99 mmol) and benzyl bromide (170 mg, 117 lL, 0.99
mmol) were added and stirred at rt for 5 h. The sodium hydride
was quenched with the addition of water (2 mL). The volatile com-
ponents were removed under vacuum and the residue was parti-
tioned between ethyl acetate (20 mL) and water (20 mL). The
layers were separated and the aqueous phase was extracted with
ethyl acetate (3 ꢂ 15 mL). The combined organic components were
dried over magnesium sulfate, filtered and the filtrate concentrated
under vacuum to yield an orange oil. The oil was adsorbed onto sil-
ica gel and purified by silica gel column chromatography, eluting
with ethyl acetate and hexane (1:99, 2:98 then 3:97) giving (ꢀ)-
2,3,4,5,6-penta-O-benzyl-1-O-triisopropylsilyl myo-inositol (77 mg,
68% yield) as a colourless oil: Rf 0.40 (petroleum ether/diethyl
and mCPBA (60% purity, 178 mg, 618 lmol) added. The reaction
solution was stirred at rt for 20 min before being partitioned be-
tween sodium hydrogen sulfite (10% aq solution, 15 mL) and an
additional CH2Cl2 (5 mL), the layers were separated and the aque-
ous layer was further extracted with CH2Cl2 (3 ꢂ 10 mL). The com-
bined organic layers were washed with a saturated solution of
NaHCO3, and then dried over magnesium sulfate and filtered. The
filtrate was concentrated under vacuum and the residue purified
by silica gel column chromatography eluting with ethyl acetate
and hexane (20:80 then 40:60) to give (+)-1D-1-(1,2-dioctanoyl-
ether 90:10); ½a D25
ꢁ
¼ þ1:8 (c 1.00, CHCl3); mmax (NaCl plates)/cmꢀ1
sn-glycerol-3-phospho)-2,3,4,5,6-penta-O-benzyl-myo-inositol 12 (60
mg, 52% yield) as a colourless oil: Rf 0.66 (ethyl acetate/petroleum
3089 (w), 3064 (w), 3030 (m), 2925 (s), 2866 (s), 2361 (m), 2342
(m), 1947 (w), 1869 (w), 1808 (w), 1734 (w); 1H NMR (300 MHz;
ether 60:40); ½a D20
¼ þ3:2 (c 0.79, CHCl3) as a colourless oil: mmax
ꢁ
CDCl3)
d
7.38–7.05 (25H, m, ArH), 4.91–4.57 (10H, m,
(NaCl plates)/cmꢀ1 3090 (s), 3064 (s), 2954 (s), 2894 (s), 1956

T. S. Elliott et al. / Tetrahedron: Asymmetry 20 (2009) 2809–2813
2813
(w), 1885 (w), 1721 (s), 1313 (s), 1008 (s); 1H NMR (300 MHz;
CDCl3) 7.34–7.11 (30H, m, ArH), 5.06–4.54 (13H, m,
Acknowledgements
d
6 ꢂ OCHAHB-Ph + glycerol CH), 4.28–4.24 (1H, m, inositol ring),
We thank EaStCHEM and CRUK for a studentship (TSE). We are
grateful to Dr. Martin Procter and Dr. Thomas Krulle, Prosidion Ltd,
for helpful discussions and thank Prosidion Ltd for a CASE award
(JN). SJC thanks St Hugh’s College, Oxford, for research support.
We are grateful to the EPSRC mass spectrometry facility for the
provision of some mass spectrometry data.
4.22–3.77 (7H, m, 3 ꢂ inositol ring + 4 ꢂ glycerol CH2), 3.47–3.34
(2H, m, 2 ꢂ inositol ring), 2.26–2.06 (4H, m, 2 ꢂ
aCOCH2), 1.58–
1.39 (4H, m, 2 ꢂ bCOCH2CH2), 1.27–1.10 (16H, m, octanoyl CH2),
0.85–0.75 (6H, m, 2 ꢂ CH3); 13C NMR (125 Hz; CDCl3) d 128.6,
128.5, 128.34, 128.3, 128.27, 128.2, 128.19, 128.15, 128.0, 127.8,
127.77, 127.66, 127.6, 127.57, 127.5, 127.47, 127.4, 83.1, 81.2,
80.4, 79.9, 78.6, 76.3, 76.0 (CH2), 75.9 (CH2), 75.5 (CH2), 75.0
(CH2), 72.7 (CH2), 69.4 (CH2), 69.0 (CH glycerol), 65.5 (CH2 glycerol),
References
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¼ þ2:25
ꢁ
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[a]
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CHXHY-Oct + inositol ring, H-2), 4.06–3.95 (2H, m, glycerol
3
POCHX’HY’), 3.89 (1H, ddd, J 9.6, 1.9, JHP 9.6, inositol ring, H-1),
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9.6, inositol ring, H-4), 3.48 (1H, dd, J 9.6, 1.9, inositol ring, H-
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2
76.2 (d, JCP 5.6, inositol ring, C-1), 73.9 (inositol ring, C-5), 72.2
(inositol ring, C-4), 71.4 (inositol ring, C-6), 71.2 (inositol ring,
2
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3.8, glycerol POCH2), 63.2 (glycerol OCH2-Oct), 34.1 (
aCOCH2)
34.0 ( COCH2), 31.8 (octanoyl chain, CH2), 29.1 (octanoyl chain,
a
CH2), 29.09 (octanoyl chain, CH2), 29.0 (octanoyl chain, CH2),
28.9 (octanoyl chain, CH2), 24.8 (bCOCH2CH2), 24.7 (bCOCH2CH2)
22.6 (octanoyl chain, CH2), 22.5 (octanoyl chain, CH2), 13.8 (octa-
noyl chain, CH3), 13.7 (octanoyl chain, CH3); 31P NMR (121 MHz;
D2O) d ꢀ0.84; HRMS m/z (ESꢀ) [Found: (MꢀNa)ꢀ 585.2690.
C25H46O13P1 requires Mꢀ, 585.2682]; m/z (ESꢀ) 585 ([MꢀNa]ꢀ,
100%). These data are in good agreement with the literature
values.20,24