Synthesis of myo-inositol 1,2,3-tris- and 1,2,3,5-tetrakis(dihydrogen phosphate)s as a tool for the inhibition of iron-gall-ink corrosion

Article abstract of DOI:10.1016/j.carres.2006.02.029

Two myo-inositol phosphates, myo-inositol 1,2,3-tris(dihydrogen phosphate) and myo-inositol 1,2,3,5-tetrakis(dihydrogen phosphate), have been synthesised in several steps from myo-inositol (in Chem. Abstr.: d-myo-inositol) in the form of their sodium salt

Full text of DOI:10.1016/j.carres.2006.02.029

Carbohydrate Research 341 (2006) 897–902
Note
Synthesis of myo-inositol 1,2,3-tris- and 1,2,3,5-tetrakis(dihydrogen
phosphate)s as a tool for the inhibition of iron-gall-ink corrosion
a,b
Martin Sala, Jana Kolar,a Matija Strlicˇb and Marijan Kocˇevarb,*
ˇ
aNational and University Library, Leskosˇkova 12, SI-1000 Ljubljana, Slovenia
bFaculty of Chemistry and Chemical Technology, University of Ljubljana, Asˇkercˇeva 5, SI-1000 Ljubljana, Slovenia
Received 11 November 2005; received in revised form 16 February 2006; accepted 23 February 2006
Available online 13 March 2006
Abstract—Two myo-inositol phosphates, myo-inositol 1,2,3-tris(dihydrogen phosphate) and myo-inositol 1,2,3,5-tetrakis(dihydro-
gen phosphate), have been synthesised in several steps from myo-inositol (in Chem. Abstr.: D-myo-inositol) in the form of their
sodium salts. They were shown to prevent iron-gall-ink decay in cellulose items at the same level as phytic acid dodecasodium salt.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: myo-Inositol phosphates; Synthesis; Antioxidant activity; Iron-gall-ink corrosion; Paper stabilisation
1. Introduction
of ferrous ions with hydroperoxides. Since it represents
only a modest health hazard, it has been recently pro-
posed as a preventive antioxidant for iron-gall-ink-con-
taining cellulose.8
One of the most important inks in the history of the wes-
tern world is called iron gall ink; it is named after the
two colour-forming ingredients: gallic acid from the tan-
nins and iron ions. Unfortunately, these components
induce severe damage or even the complete destruction
of numerous historical artifacts, and significant efforts
are devoted to the development of processes that would
increase their stability.1,2 The two main reasons for iron-
gall-ink corrosion have been identified as acid hydrolysis
and oxidation, catalysed by ferrous ions. Acid hydro-
lysis of cellulose is prevented by deacidification, whereas
oxidative decay is usually inhibited by the addition of
antioxidants. The only antioxidant that has been used
for the prevention of ink decay is the iron chelating
agent myo-inositol hexakis(dihydrogen phosphate) (phy-
tic acid),3 a naturally occurring antioxidant,4–6 which
theoretically doubles the lifetime of iron-containing
paper, though its mode of action is still not completely
clear.7 Its anion (phytate) apparently occupies all the
available coordination sites, thus preventing the reaction
Unfortunately, due to the poor solubility of phytate in
non-aqueous media, it cannot be used for water-sensi-
tive items, such as bound books. We have therefore
decided to investigate other myo-inositol derivatives that
might exhibit the same effect on the stabilisation of the
paper items, but contain free hydroxy groups, which
might be easily derivatised to give less polar compounds,
which would consequently be soluble in non-aqueous
solvents. Previously it was shown that a 1,2,3-grouping
of myo-inositol phosphates inhibited the production of
hydroxy radicals (HOÅ) in the iron-catalysed Haber–
Weiss reaction.9 It also prevented the iron-catalysed oxi-
dation of ascorbic acid and the peroxidation of arachi-
donic acid.10 On this basis it was concluded that such
pattern might be essential for the properties of phytate.11
To establish whether they might stabilise cellulose
containing iron gall ink and consequently to confirm the
above conclusion, we have decided to compare the effects
of sodium salts of myo-inositol 1,2,3-tris(dihydrogen
phosphate) 7 (Scheme 1), 1,2,3,5-tetrakis(dihydrogen
phosphate) 10 and phytic acid on the stabilisation of
paper items. Compound 7 has been previously synthesised
*
Corresponding author. Fax: +386 1 2419 220; e-mail: Marijan.
Kocevar@fkkt.uni-lj.si
0008-6215/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2006.02.029

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898
Scheme 1. Reagents and conditions: (a) DIBALH, À20 ꢁC, CH2Cl2 (76% yield); (b) BnBr, NaH, Bu4NI, DMF (70%); (c) HCl, MeOH, D (93%); (d)
1. (BnO)2PN(i-Pr)2, 1H-tetrazole, CH2Cl2; 2. m-CPBA (for 6 90%, for 9 93%); (e) H2/1 bar, Pd/C (10%), MeOH/H2O (19:1), then ion-exchange
(quantitatively for 7 and 10).
from myo-inositol in several steps in the form of monoso-
dium tetra(cyclohexylammonium) myo-inositol-1,2,3-
trisphosphate,9 and derivative 10 as an octapotassium
salt of myo-inositol-1,2,3,5-tetrakisphosphate.12
lower quantities of DIBALH and, as a consequence,
longer reaction times were employed. Moreover, lower-
ing the quantity of the solvent also resulted in a lower
yield. The compound 3 was benzylated with benzyl bro-
mide in the presence of sodium hydride as a base, and
tetrabutylammonium iodide as a catalyst at the remain-
ing free hydroxy group to give 4, which was further
hydrolysed under acidic conditions to obtain previously
described22 tribenzyl derivative 5. The latter was phos-
phorylated by a modified method from the literature,24
employing treatment with dibenzyl N,N-diisopropyl-
phosphoramidite in the presence of 1H-tetrazole,
followed by an oxidation with m-chloroperbenzoic acid
(m-CPBA) in CH2Cl2 yielding tris(dibenzyl phosphate) 6
(90% yield). The complete removal of all benzyl groups
was accomplished by hydrogenolysis in the presence of
Pd/C (10%) in a mixture MeOH/H2O 19:1, then the
deprotected 6 was run through an ion-exchange column
(50X-8-100 Na+ form). Finally, fractions containing the
product were combined and lyophilised to give triso-
dium salt of trisphosphate 7 as a white powder. The
overall yield for the eight steps from the starting myo-
inositol (1) was 25% (in the calculation the best yields
from the literature15,16,20 were taken for the synthesis
of 2). The obtained yield is much higher than that
obtained for the synthesis of the previously mentioned
sodium tetra(cyclohexylammonium) salt of myo-inosi-
tol-1,2,3-trisphosphate, which was synthesised from 1
in seven steps, but with a very low overall yield (below
4%).9,25
2. Results and discussion
Our idea was to start from a single intermediate, which
would enable (by the application of selective protecting
groups)13,14 the synthesis of both products in the form of
sodium salts in order to exclude the effect of the cation
on accelerated ageing tests (phytic acid is also commer-
cially available as dodecasodium salt). myo-Inositol
1,3,5-orthoformate and its derivatives have been widely
used as precursors for the synthesis of variously substi-
tuted inositol phosphates.12,15–23 The selective protec-
tion or deprotection of the hydroxy groups of inositol
orthoformate was achieved either by the enzymatic16,18
or chemical methods.12,15,17–20,23 We decided to start
from the previously known 2-O-tert-butyldimethylsilyl
derivative 2,15 which can be prepared in several steps
from myo-inositol (1).15,16,20 Compound 2 contains
three different orthogonal sets14 of protecting groups
and, thus, allows us to transform it selectively into phos-
phates 7 and 10.
Treatment of 2 with an excess (5 equiv) of diiso-
butylaluminium hydride (DIBALH) in dichloromethane
(CH2Cl2)21,22 at À20 ꢁC, gave selectively derivative 3 in
a 76% yield. At À60 ꢁC the reaction did not take place
at all, but at 0 ꢁC or at room temperature the cleavage
was not selective and the TBDMS group was also
partially eliminated. The same situation occurred when
The synthesis of the myo-inositol 1,2,3,5-tetrakisphos-
phate 10 from 2, via the previously known deprotected
derivative 8,19 which was treated in a similar way as

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M. Sala et al. / Carbohydrate Research 341 (2006) 897–902
899
compound
5
with dibenzyl N,N-diisopropylphos-
for the stabilisation of water-sensitive items that are
endangered by corrosive iron gall inks.
phoramidite in the presence of 1H-tetrazole in CH2Cl2,
was followed by the addition of m-CPBA to give
1,2,3,5-tetrakis(dibenzyl phosphate) 9; further hydro-
genation and ion-exchange resulted in pentasodium salt
10 with an overall yield of 44% for six steps (in compar-
ison with the previous synthesis of the octapotassium
salt of myo-inositol 1,2,3,5-tetrakisphosphate 10 from
myo-inositol in six steps with a 42% overall yield).12
To establish the potential stabilising effect during the
iron-gall-ink-induced decay of paper, the samples con-
taining iron gall ink were treated with aqueous solutions
of sodium salts of either of the two myo-inositol deriva-
tives, 7 and 10, or phytate.26 Sodium salts were used
instead of the usually employed calcium and ammonium
salts,3 due to the poorly defined composition of the
latter. After accelerated ageing, the degree of polymeri-
sation (DP) was determined using viscometry. The rate
constant was obtained, according to Ekenstam,27 as
the slope of (1/DPt À 1/DP0) over time t, where DPt
and DP0 are the degrees of polymerisation at time t
and 0, respectively. The results presented in Figure 1
demonstrate a significant improvement in the cellulose
stability after the treatment with phytate or with com-
pounds 7 and 10. While the paper treated with phytate
was 13 4 times more stable than the deacidified
control, the effect obtained with the treatments using
compounds 7 and 10 was 6 1 and 15 7 times,
respectively.
3. Experimental
Melting points were determined on a Kofler micro-hot-
stage and are uncorrected. 1H (300 MHz), 31P (121 MHz)
and 13C NMR (75 MHz) spectra were recorded with a
1
Bruker Avance DPX 300 spectrometer. In all the H
NMR spectra TMS was used as an internal reference,
in the 13C NMR spectra the residual solvent signal
was used as an internal reference (CDCl3, triplet at
77.0 ppm) unless otherwise stated. All 31P spectra were
referenced to 85% phosphoric acid. All 31P and 13C
1
NMR spectra were H decoupled unless otherwise sta-
ted. The coupling constants (J) are given in hertz. IR
spectra were obtained with a Perkin–Elmer Spectrum
1000 spectrophotometer. Mass spectra were recorded
with a VG-Analytical AutoSpec Q instrument. Elemen-
tal analyses (C, H, N) were performed with a Perkin–
Elmer 2400 CHN Analyser. Column chromatography
was performed with Silica Gel 60 (E. Merck, 60–
63 mm). Thin-layer chromatography was carried out
on Fluka silica-gel TLC cards. The starting compound
2 was prepared as described in the literature.15,16,20
CH2Cl2 was dried over P4O10 and distilled before use.
All other reagents were used as received from commer-
cial suppliers. For the paper-stabilisation studies, puri-
fied cotton linters cellulose sheets (Whatman filter
paper no. 1; 86.0 g mÀ2, degree of polymerisation
(DP): 2630, RSD 0.74%) were used. Model ink contain-
ing tannin (puro, Carlo Erba) (49.2 g LÀ1), gum arabic
(31.4 g LÀ1) and FeSO4 · 7H2O (42 g LÀ1) in deionised
water was applied as 1 cm broad lines to model paper
using a Roland plotter DXY 990 with a 0.6 mm pen at
a speed of 5 cm sÀ1. The samples were immersed in
In conclusion, we have presented a new and efficient
synthesis of two myo-inositol derivatives (7 and 10) that
inhibit cellulose degradation in the range similar to that
of phytate. Due to the presence of hydroxy groups,
which might be transformed to form derivatives soluble
in non-aqueous solvents, compounds 7 and 10 in their
suitably derivatised forms might have a strong potential
aqueous solutions of Ca(HCO3)2 (0.01 mol LÀ1
,
2 · 15 min). Apart from one sample, which was used
as a control, the dry papers were immersed in
0.01 mol LÀ1 solutions of chelator (phytate or 7 or 10,
2 · 15 min). All samples were aged according to ISO
Standard 5630/3 conditions (80 ꢁC and 65% RH) in a
Vo¨tsch VC 0020 ageing oven. Viscometric determina-
tions of the degree of polymerisation (DP) were per-
formed according to the standard procedure (SCAN-
CM 15:88), using 1 mol LÀ1 cupriethylenediamine sol-
vent (Carlo Erba), with the typical RSD below 0.8%.
DP was calculated from the intrinsic viscosity using
the equation DP0.85 = 1.1 · [g].28
3.1. 4,6-Di-O-benzyl-2-O-tert-butyldimethylsilyl-1,3-O-
methylene-myo-inositol (3)
Figure 1. Graph showing the changes of 1/DPt À 1/DP0 over time
during accelerated ageing at 80 ꢁC and 65% relative humidity. All the
samples were deacidified with Ca(HCO3)2 and treated with 7, 10 or
phytate; the control was only deacidified.
To a cooled (À20 ꢁC) solution of 2 (1.00 g, 2.1 mmol) in
anhydrous CH2Cl2 (25 mL) DIBALH (10 mL of 1 M

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900
solution in CH2Cl2, 10 mmol) was added under an Ar
atmosphere. After 1 h of stirring the mixture was poured
into a cooled (À20 ꢁC) solution of potassium tartrate
(60 g in 100 mL of water) and saturated aqueous NH4Cl
(80 mL). Ethyl acetate (200 mL) was added and the mix-
ture was stirred for 1 h at room temperature. Layers
were separated and the aqueous layer was additionally
extracted with ethyl acetate (2 · 80 mL), combined or-
ganic layers were dried over Na2SO4, filtered and evap-
orated under reduced pressure. The residue was purified
by column chromatography on silica gel with CH2Cl2/
ethyl acetate (15:1) to give 3 as a bright-yellow oil
(760 mg, 76%). IR (neat): m 3567, 2953, 2928, 2857,
3.3. Preparation of 4,5,6-tri-O-benzyl-myo-inositol (5)22
A solution of 4 (1.00 g, 1.7 mmol) in methanol (30 mL)
and concentrated aqueous HCl (4 mL) was refluxed for
3 h, then it was evaporated, water (10 mL) was added to
the residue and the mixture was extracted with CH2Cl2
(3 · 20 mL). The combined organic layers were dried
over Na2SO4, filtered and evaporated under reduced
pressure. The product was obtained as a white solid
(722 mg, 93%): mp (from MeOH/H2O) 118–120 ꢁC; IR
(KBr): m 3379 br, 2922, 1497, 1454, 1360 cmÀ1 1H
;
NMR (CDCl3): d 7.33 (m, 15H, 3 · Ph), 4.95 (d, 2H, J
11.3 Hz, 4- and 6-CHAHBPh), 4.92 (s, 2H, 5-CH2Ph),
4.76 (d, 2H, J 11.3 Hz, 4- and 6-CHAHBPh), 4.17 (dt,
1H, J 1.8 and 2.8 Hz, 2-H), 3.80 (dd, 2H, J 9.4 and
9.5 Hz, 4-H, 6-H), 3.54 (ddd, 2H, J 2.8, 4.4 and
9.5 Hz, 1-H, 3-H), 3.49 (t, 1H, J 9.4 Hz, 5-H), 3.55 (d,
1H, J 1.8 Hz, 2-OH), 3.40 (d, 2H, J 4.4 Hz, 1-OH, 3-
OH); 13C (CDCl3): d 138.4, 138.3, 128.5, 128.3, 127.8,
127.75, 127.70, 127.6, 83.2, 81.7, 75.5, 75.4, 71.9, 71.3;
EI-MS: m/z 359 [(MÀCH2Ph)+, 23], 107 (22), 92 (39),
91 (100). Anal. Calcd for C27H30O6: C, 71.98; H, 6.71.
Found: C, 71.83; H, 6.92.
1
1497, 1463, 1455 cmÀ1; H NMR (CDCl3): d 7.28 (m,
10H, 2 · Ph), 5.63 (d, 1H, J 4.6 Hz, HAHBCO2), 4.69
(d, 2H, J 12.0 Hz, PhCHAHB), 4.64 (d, 1H, J 4.6 Hz,
HAHBCO2), 4.63 (t, 1H, J 1.6 Hz, 2-H), 4.59 (d, 2H, J
12.0 Hz, PhCHAHB), 4.24 (m, 2H, 1-H, 3-H), 4.00–
3.94 (m, 3H, 4-H, 5-H, 6-H), 3.00 (d, 1H, J 10.6 Hz,
5-OH), 0.90 (s, 9H, t-Bu), 0.10 (s, 6H, 2 · Me); 13C
(CDCl3): d 138.0, 128.3, 127.5, 127.3, 85.4, 81.2, 75.4,
71.9, 68.8, 64.0, 25.7, 17.9, À4.8; EI-MS: m/z 485
[(MÀH)+, 1], 181 (100), 92 (78); HRMS (EI) calcd for
C27H38O6Si (M+) 486.2438, found 486.2446.
3.4. 4,5,6-Tri-O-benzyl-myo-inositol 1,2,3-tris(dibenzyl
phosphate) (6)
3.2. 4,5,6-Tri-O-benzyl-2-O-tert-butyldimethylsilyl-1,3-
O-methylene-myo-inositol (4)
To a mixture of triol 5 (200 mg, 0.44 mmol) and 1-H-tet-
razole (360 mg, 5.1 mmol) in MeCN (30 mL) N,N-diiso-
propyl dibenzyl phosphoramidite (720 mg, 2.28 mmol)
in CH2Cl2 (10 mL) was added. After 240 min of stirring
at room temperature the reaction mixture was cooled to
À40 ꢁC and m-CPBA (80–85%, 600 mg, 2.8 mmol) in
CH2Cl2 (10 mL) was added. The resulting solution was
stirred at 0 ꢁC for 240 min, then the reaction mixture
was diluted with CH2Cl2 (60 mL), washed with Na2SO3
(10%, 2 · 40 mL), saturated NaHCO3 (2 · 30 mL),
water (30 mL) and saturated aqueous NaCl solution
(30 mL). The organic phase was dried over Na2SO4, fil-
tered and evaporated under reduced pressure. The crude
product thus obtained was purified by column chroma-
tography on silica gel with petroleum benzine (boiling
point 40–60 ꢁC)/CH2Cl2/ethyl acetate (3:10:3) to give 6
(492 mg, 90%) as a bright-yellow oil. IR (neat): m 3466
To a stirred solution of 3 (1.00 g, 2.1 mmol) in DMF
(8 mL), 60% sodium hydride (140 mg, 3.5 mmol) and
tetrabutylammonium iodide (20 mg, 0.07 mmol) were
added at room temperature. After 5 min of stirring benz-
yl bromide (650 lL, 5 mmol) was added dropwise and
the mixture was stirred for 1 h at room temperature.
The reaction was quenched with water (150 mg, 8 mmol)
and evaporated, then water (10 mL) was added and the
mixture was extracted with CH2Cl2 (3 · 20 mL), com-
bined organic layers were dried over Na2SO4, filtered
and evaporated under reduced pressure. The residue
was purified by column chromatography on silica gel
with petroleum benzine (boiling point 40–60 ꢁC)/ethyl
acetate (15:1) to give 4 as a bright-yellow oil (830 mg,
70%). IR (neat): m 3342 br, 2953, 2928, 2857, 1725,
1
1497, 1454 cmÀ1; H NMR (CDCl3): d 7.29 (m, 15H,
1
3 · Ph), 5.33 (d, 1H, J 4.7 Hz, HAHBCO2), 4.77 (d,
1H, J 4.7 Hz, HAHBCO2), 4.61 (s, 2H, 5-CH2Ph), 4.60
(d, 2H, J 12.0 Hz, 4- and 6-CHAHBPh), 4.53 (d, 2H, J
12.0 Hz, 4- and 6-CHAHBPh), 4.24 (t, 1H, J 1.8 Hz, 2-
H), 4.08 (dd, 2H, J 1.8 and 1.8 Hz, 1-H, 3-H), 3.93
(dd, 2H, J 1.8 and 4.6 Hz, 4-H, 6-H), 3.64 (t, 1H, J
4.6 Hz, 5-H), 0.93 (s, 9H, t-Bu), 0.12 (s, 6H, 2 · Me);
13C (CDCl3): d 138.4, 137.9, 128.4, 128.3, 127.9, 127.7,
127.6, 85.4, 82.1, 79.2, 74.5, 72.9, 71.7, 64.4, 25.8, 18.1,
À4.7 (one signal is hidden); EI-MS: m/z 575 [(MÀH)+,
0.2], 181 (42), 91 (100); HRMS (EI) calcd for
C34H44O6Si (M+) 576.2907, found 576.2926.
br, 3066, 3033, 2951, 2894, 1497, 1456 cmÀ1; H NMR
(CDCl3): d 7.35–7.10 (m, 45H, 9 · Ph), 5.40 (td, 1H, J
2.3 and 8.4 Hz, 2-H), 5.13–4.74 (m, 18H, 9 · PhCH2),
4.41 (dddd, 2H, J 2.2, 2.3, 9.6 and 9.6 Hz, 1-H, 3-H),
3.92 (dd, 2H, J 9.4 and 9.6 Hz, 4-H, 6-H), 3.52 (t, 1H,
J 9.4 Hz, 5-H); 13C (CDCl3): d 138.0, 137.9, 135.9 (d,
J 7 Hz), 135.8 (d, J 7 Hz), 135.7 (d, J 7 Hz), 128.44,
128.43, 128.39, 128.34, 128.32, 128.28, 128.23, 128.22,
128.0, 127.92, 127.88, 127.7, 127.6 (two s), 127.5, 82.3
(m), 79.4 (d, J 5 Hz), 77.7 (m), 76.1, 75.9 (dd, J 3 and
6 Hz), 75.5, 69.6 (d, J 5 Hz), 69.40 (d, J 5 Hz), 69.38
(d, J 6 Hz); 31P NMR (121 MHz, CDCl3): d 2.75 (2P),

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M. Sala et al. / Carbohydrate Research 341 (2006) 897–902
901
1.93 (1P); FAB+-MS: m/z 1231.5 [(M+H)+], 1141.3,
181; HRMS (ESI) calcd for C69H70O15P3 (M+H)+
1231.3928, found 1231.3930.
9.6 Hz, 1-H, 3-H), 4.00 (dd, 2H, J 9.4 and 9.6 Hz, 4-
H, 6-H); 13C (CDCl3): d 138.3, 136.4 (d, J 8 Hz), 136.3
(d, J 7 Hz), 136.2 (d, J 7 Hz) 136.0 (d, J 7 Hz), 128.93,
128.91, 128.87, 128.82, 128.80, 128.77, 128.75, 128.6,
128.5, 128.47, 128.45, 128.13, 128.10, 127.9, 127.8,
74.5, 69.6 (d, J 5 Hz), 69.4 (d, J 5 Hz, two C), 69.2 (d,
J 5 Hz), 79.3 (m), 77.6 (m, two C), 77.1 (m), 75.2 (m,
two C); 31P NMR (121 MHz, CDCl3): d 2.61 (2P),
2.31 (1P), 2.10 (1P); FAB+-MS m/z 1401.9 [(M+H)+,
23], 307.1, 181; HRMS (ESI) calcd for C76H77O18P4
(M+H)+ 1401.4060, found 1401.4070. Anal. Calcd for
C76H76O18P4: C, 65.14; H, 5.47. Found: C, 65.12; H,
5.69.
3.5. Trisodium salt of myo-inositol 1,2,3-tris(dihydrogen
phosphate) (7)
A mixture of 6 (492 mg, 0.4 mmol) in methanol/water
(19:1, 20 mL), and Pd/C (10%, 100 mg) was stirred
under a H2 atmosphere for 12 h at room tempera-
ture. The catalyst was removed by filtration and the
filtrate was concentrated under reduced pressure at
room temperature. The residue was dissolved in water
(1 mL) and applied to a column of cation-exchange resin
(Dowex 50-X8, mesh 20–50, Na+ form) that was eluted
with water. Fractions containing the product were com-
bined and lyophilised to give 7 quantitatively as a white
solid: mp >300 ꢁC; IR (neat): m 3423 br, 1656 br, 1198 br
3.7. Pentasodium salt of myo-inositol 1,2,3,5-tetrakis-
(dihydrogen phosphate) (10)
A mixture of 9 (620 mg, 0.4 mmol) in methanol/water
(19:1, 20 mL), Pd/C (10%, 150 mg) was stirred under a
H2 atmosphere for 12 h at room temperature. The
catalyst was removed by filtration and the filtrate
concentrated under reduced pressure at room tempera-
ture. The residue was dissolved in water (1 mL) and
applied to a column of cation-exchange resin (Dowex
50-X8, mesh 20–50, Na+ form) that was eluted with
water. Fractions containing the product were combined
and lyophilised to give 10 quantitatively as a white solid:
mp >300 ꢁC; IR (neat): m 3424 br, 1647 br, 1198 br, 1050
cmÀ1
;
1H NMR (D2O, referenced to DMSO at
2.71 ppm): d 4.94 (td, 1H, J 2.5 and 9.9 Hz, 2-H), 4.06
(m, 2H, 1-H, 3-H), 3.84 (dd, J1 ꢀ J2 ꢀ 9.5 Hz, 4-H,
6-H), 3.44 (t, J 9.4 Hz, 5-H); 13C (D2O, referenced to
DMSO at 39.39 ppm): d 76.4 (m), 75.9 (m), 74.8, 72.8
(m); 31P NMR (121 MHz, D2O): d 4.06 (2P), 3.79
(1P); FABÀMS: m/z 485 [(C6H11Na3O15P3)À; free
acid+3Na+À4H+], 463 [(C6H12Na2O15P3)À; free
acid+2Na+À3H+], 441 [(C6H13NaO15P3)À; free acid+
Na+À2H+], 419 [(C6H14O15P3)À; free acidÀH+], 181.
Anal. Calcd for C6H12Na3O15P3 · 3H2O: C, 13.34; H,
3.36. Found: C, 13.71; H, 3.62.
br cmÀ1 1H NMR (D2O, referenced to DMSO at
;
2.71 ppm): d 4.75 (td, 1H, J 2.6 and 9.9 Hz, 2-H), 3.93
(m, 2H, 1-H, 3-H), 3.87–3.71 (m, 3H, 4-H, 5-H, 6-H);
13C (75 MHz, D2O, referenced to DMSO at 39.5 ppm):
d 80.2 (m), 76.1 (m), 75.6 (m), 72.3 (m); 31P NMR
(121 MHz, D2O): d 6.28 (1P), 4.85 (1P), 4.59 (2P);
FABÀMS: m/z 609 [(C6H10Na5O18P4)À; free acid+
5Na+À6H+], 587 [(C6H11Na4O18P4)À; free acid+
4Na+À5H+], 565 [(C6H12Na3O18P4)À; free acid+3Na+À
4H+], 543 [(C6H13Na2O18P4)À; free acid+2Na+À3H+],
521 [(C6H14NaO18P4)À; free acid+Na+À2H+], 499
[(C6H15O18P4)À; free acidÀH+]. Anal. Calcd for
C6H11Na5O18P4 · 3H2O: C, 10.85; H, 2.58. Found: C,
11.06; H, 2.91.
3.6. 4,6-Di-O-benzyl-myo-inositol 1,2,3,5-tetrakis-
(dibenzyl phosphate) (9)
To a mixture of tetrol 8 (200 mg, 0.54 mmol) and
1-H-tetrazole (470 mg, 6.7 mmol) in MeCN (10 mL),
N,N-diisopropyl dibenzyl phosphoramidite (1.20 g,
3.46 mmol) in CH2Cl2 (10 mL) was added. After
240 min of stirring at room temperature the reaction
mixture was cooled to À40 ꢁC, and m-CPBA (80–85%,
1.00 g, 4.64 mmol) in CH2Cl2 (10 mL) was added. The
resulting solution was stirred at 0 ꢁC for 240 min, then
the reaction mixture was diluted with CH2Cl2 (60 mL),
washed with Na2SO3 (10%, 2 · 40 mL), saturated NaH-
CO3 (2 · 30 mL), water (30 mL) and saturated aqueous
NaCl solution (30 mL). The organic phase was dried
over Na2SO4, filtered and evaporated under reduced
pressure. The crude product thus obtained was purified
by column chromatography on silica gel with petroleum
benzine (boiling point 40–60 ꢁC)/CH2Cl2/ethyl acetate
(5:5:3) to give 9 (620 mg, 93%) as a bright-yellow oil.
IR (neat): m 3426 br, 3064, 3033, 2951, 2893, 1497,
Acknowledgements
The authors gratefully acknowledge the support of
the European Commission, the Fifth Framework
Programme (EVK4-CT-2001-0049) and the support
of the Ministry of Higher Education, Science and
Technology of the Republic of Slovenia, as well as
Slovenian Research Agency (P1-0230 and P1-0153).
1455 cmÀ1
;
1H NMR (CDCl3): d 7.36–6.95 (m, 50H,
Dr. B. Kralj and Dr. D. Zigon (Center for Mass Spec-
ˇ
10 · Ph), 5.49 (td, 1H, J 2.2 and 8.4 Hz, 2-H), 5.14–
4.60 (m, 20H, 10 · PhCH2), 4.52 (dt, 1H, J 9.4 and
9.4 Hz, 5-H), 4.44 (dddd, 2H, J 2.0, 2.2, 9.6 and
troscopy, ‘Jozˇef Stefan’ Institute, Ljubljana, Slovenia)
are gratefully acknowledged for mass spectroscopy
measurements.

ˇ
M. Sala et al. / Carbohydrate Research 341 (2006) 897–902
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