Stereospecific synthesis of D-glycero-D-ido-oct-2-ulose

Article abstract of DOI:10.1007/s007060170088

D-Glycero-D-gulo-heptose reacted with 2,2-dimethoxypropane to give its 2,3:6,7-di-O-isopropylidene derivative. Its base-catalyzed addition to formaldehyde resulted in the formation of 2,3:6,7-di-O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo- heptofuranose. After acid hydrolysis of this aldolization product, a new branched-chain aldose, 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose, was obtained, which was stereospecifically rearranged under the catalytic action of molybdic acid to D-glycero-D-ido-oct-2-ulose.

Full text of DOI:10.1007/s007060170088

Monatshefte fuÈr Chemie 132, 731±737 (2001)
Stereospeci®c Synthesis of
D-Glycero-D-ido-oct-2-ulose
Ã
Â
Â
Zuzana Hricovõniova , Milos Hricovõni, and Ladislav Petrus
Ï
Â
Ï
Institute of Chemistry, Slovak Academy of Sciences, SK-84238 Bratislava, Slovakia
Summary. D-Glycero-D-gulo-heptose reacted with 2,2-dimethoxypropane to give its 2,3:6,7-di-O-
isopropylidene derivative. Its base-catalyzed addition to formaldehyde resulted in the formation
of 2,3:6,7-di-O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo-heptofuranose. After acid
hydrolysis of this aldolization product, a new branched-chain aldose, 2-C-(hydroxymethyl)-D-
glycero-D-gulo-heptose, was obtained, which was stereospeci®cally rearranged under the catalytic
action of molybdic acid to D-glycero-D-ido-oct-2-ulose.
Keywords. D-Glycero-D-ido-oct-2-ulose; Branched-chain aldose; 2-C-(Hydroxymethyl)-D-glycero-
D-gulo-heptose; Mo(VI) Catalysis.
Introduction
Naturally occurring higher sugars, such as D-manno-hept-2-ulose, D-altro-hept-2-
ulose (sedoheptulose), or D-glycero-D-ido-oct-2-ulose, have been of particular
interest in the ®eld of carbohydrate chemistry. The biological activities of these
sugars and their phosphate derivatives, especially their role in intracellular
communication, have been studied [1, 2]. D-Glycero-D-ido-oct-2-ulose occurs in
Craterostigma plantagineum, which belongs to a small group of drought-tolerant
higher plants and plays an important role in the metabolism of plants. Chemical
analysis revealed that this 8-carbon sugar represents almost 90% of carbohydrates in
the fully hydrated leaves. It is metabolized into sucrose during the dehydration
process and is converted back to octulose during the rehydration [3]. Due to its
exceptional adaptation a number of studies have been initiated to understand the
molecular mechanism of desiccation. D-Glycero-D-ido-oct-2-ulose exists in the free
state in plant extracts from which it has been isolated. The con®guration of this rare
1
octulose has been determined by MS and H NMR [4].
Being aware of the known stereospeci®ty in the isomerization reactions of
reducing sugars in the presence of Mo(VI) [5±8], we have utilized the catalytic
effect for the synthesis of some rare saccharides in previous studies [9±12]. It has
been shown that 2-ketoses undergo a molybdic acid-catalyzed stereospeci®c
rearrangement under formation of 2-C-(hydroxymethyl)-aldoses and vice versa. The
thermodynamic equilibrium of these transformations is strongly shifted to the side
Ã
Corresponding author

 Â
Z. Hricovõniova et al.
732
of 2-ketoses [9, 10]. This approach has been used for preparation of some
biologically important saccharides such as hamamelose [10, 11] or sedoheptulose
[12]. The one-step synthesis of D-glycero-D-ido-oct-2-ulose from the 2-C-branched
aldose, 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose, is a further extension of
the aforementioned method and represents an ef®cient preparation of this eight-
carbon saccharide. The details of the synthesis are given herein.
Results and Discussion
It is known that isomerization of aldoses in aqueous solutions in the presence of a
catalytic amount of molybdic acid at enhanced temperatures affords an aldose/
epialdose mixture. This transformation proceeds without production of undesirable
by-products [5±8] thanks to its unusual mechanism [14, 15]. Similar mutual inter-
conversion was observed in the case of 2-ketoses and 2-C-(hydroxymethyl)-aldoses
[9±12]. This evidence extends the application of the Mo(VI) catalysis for the
preparation of other rare saccharides, such as D-glycero-D-ido-oct-2-ulose from an
appropriate 2-C-(hydroxymethyl) branched-chain aldose. The ®rst step in the
synthesis of the 2-C-(hydroxymethyl)-aldose, which leads to the 2-ketose upon
molybdic acid-catalyzed isomerization, was the preparation of a diisopropylidene
derivative of D-glycero-D-gulo-heptose. Thus, transacetalation of D-glycero-D-
gulo-heptose with 2,2-dimethoxypropane in the presence of toluene-4-sulfonic acid
in 1,2-dimethoxypropane at room temperature afforded 2,3:6,7-di-O-isopropyli-
dene-ꢀ-D-glycero-D-gulo-heptofuranose (1) as the major product (79%). Its alkali-
catalyzed addition to formaldehyde gave a 2-C-branched-chain aldose, 2,3:6,7-di-
O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo-heptofuranose (2) in
86% yield. The isopropylidene groups were removed by acid hydrolysis in the
‡
presence of Amberlite IR 120 in the H form. Using this approach, the novel
compound 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose (3) was prepared in
good yield (95%). The synthesis of 3 is shown in Scheme 1. The structures of
compounds 1, 2, and 3 were con®rmed by NMR spectroscopy.
Scheme 1

Synthesis of D-Glycero-D-ido-oct-2-ulose
733
1
Fig. 1. 300 MHz H NMR spectrum of 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose in aqueous
solution at 313 K; four signals in the anomeric region originate from four cyclic forms present in
solution: ꢀf (5.24 ppm), ꢁf (5.07 ppm), ꢁp (4.98 ppm), and ꢀp (4.93 ppm)
The presence of four resonances, with comparable intensities, was observed in
the anomeric region of the 1H NMR spectrum of 3 (Fig. 1). These signals originate
from four cyclic forms present in aqueous solution. The ratio of these forms was
1
determined from the H NMR spectrum and indicates that the ꢀ-pyranose form is
the most abundant (30%) at 40ꢀC, whereas the other three are nearly equally
1
populated: 21% ꢁp, 25% ꢁf, 24% ꢀf. The assignment of all H and 13C NMR
signals was deduced from 2D COSY, HSQC, and HMBC spectra.
The key step of the reaction is a skeletal rearrangement of the 2-C-
(hydroxymethyl) branched-chain aldose 3 to the desired 2-ketose D-glycero-D-
ido-oct-2-ulose (4) (Scheme 2). The isomerization takes place in mild acidic
aqueous solution in the presence of a catalytic amount of molybdic acid at 80ꢀC.
Under these reaction conditions an equilibrium mixture of the starting branched-
chain aldose 3 and the product ketose 4 was formed in a ratio of 1:5 as determined
from the 1H NMR spectrum. The formation of the 2-ketose is in accordance with the
mechanism of an isomerization reaction studied recently [10, 11]. The mechanism
Scheme 2

 Â
Z. Hricovõniova et al.
734
of this transformation proceeds via the formation of catalytically ef®cient dimolyb-
date complexes of the starting 2-C-branched-chain aldose, yielding the dimolybdate
complex of the desired 2-ketose. It has been found that the reaction is reversible as
has been shown in a study with saccharides substituted regiospeci®cally with 13C
[10, 11]. Furthermore, the thermodynamic equilibrium of these interconversions is
strongly shifted to the side of 2-ketoses. It has been also con®rmed that this
isomerization proceeds as an intramolecular process under C-1-C-2-C-3 rearrange-
ment of carbon skeleton of the starting 2-C-branched aldose. In the present case, the
branched-chain aldose 3 in its acyclic form is bound in a catalytically active
dimolybdate complex through its four hydroxyl groups on C-1, C-2, C-3, and C-4 of
its hydrated form. The rearrangement occurs in a transition state under the
formation of the corresponding dimolybdate complex of acyclic D-glycero-D-ido-
oct-2-ulose (4) as shown previously for similar interconversions [11, 12]. During
this transformation, bond formation between C-1 and C-3 with simultaneous
cleavage of the C-2±C-3 bond takes place. Consequently, the pertinent carbon atoms
become the respective C-3, C-2, and C-4 ones in the skeleton of 2-ketose, whereas
the branch CH2OH becomes the C-1 carbon atom. Various forms (cyclic, anhydro,
pyranose, furanose) of D-glycero-D-ido-oct-2-ulose are present in aqueous solution
after its release from the complex. In addition to the desired D-glycero-D-ido-oct-2-
ulose and the starting 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose, the reaction
mixture obtained after the isomerization contained also D-arabinose and 1,3-
dihydroxyacetone. Separation of the reaction mixture into its components was
achieved by chromatography on a cation-exchange resin column in the Ba2‡ form.
The main component thus isolated in 40% yield was D-glycero-D-ido-oct-2-ulose.
Its 13C NMR assignment is given in the experimental part. The recovery of the
starting 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose was 8%. Besides the
expected compounds, signi®cant amounts of D-arabinose and 1,3-dihydroxyacetone
(together 39%) from the reaction mixture were isolated and identi®ed by their NMR
spectra.
It is assumed that the partial retro-aldol reaction of D-glycero-D-ido-oct-2-ulose
is a consequence of a relative high abundance of its acyclic form in solution. Thus,
the 2-ketose is susceptible for the retro-aldol reaction to D-arabinose and 1,3-
dihydroxyacetone. A similar process occurs during the enzymatically catalyzed
aldolization/retro-aldol reaction of D-arabinose-5-phosphate and 1,3-dihydroxy-
acetone-phosphate to D-glycero-D-ido-oct-2-ulose 1,8-bisphosphate and vice versa
[16]. The presence of different forms was evident from 13C NMR spectra in the
fraction containing D-glycero-D-ido-oct-2-ulose. To facilitate the structural assign-
ment the mixture was treated with acid to convert all these forms to the more stable
anhydro forms (Scheme 3). Two structures, (2,7-anhydro-D-glycero-ꢁ-D-ido-
octulofuranose (5) and 2,7-anhydro-D-glycero-ꢀ-D-ido-octulopyranose (6)) were
identi®ed, the ratio of these forms being 2:1 in favour of the ®rst one. The
1
assignment of the H and 13C NMR signals of both forms was performed by
analysis of one- and two-dimensional NMR spectra.
The introduced synthetic approach is a possible route to obtain D-glycero-D-
ido-oct-2-ulose in a simple way. It is hoped that the availability of synthetically
produced D-glycero-D-ido-oct-2-ulose may help to elucidate unknown biochem-
ical pathways.

Synthesis of D-Glycero-D-ido-oct-2-ulose
735
Scheme 3
Experimental
Melting points were measured on a Ko¯er hotstage microscope. The optical rotations were
determined at 20ꢀC with an automatic polarimeter Perkin-Elmer Model 141 using a 10 cm 1 cm3 cell.
NMR spectra were recorded on a Bruker DPX 300 (300.13 MHz) spectrometer equipped with a 5 mm
inverse broadband probe with a shielded z-gradient. The experiments were carried out in aqueous
solution at 40ꢀC and in acetone at 25ꢀC. Chemical shifts were referenced to internal TSP (D2O) and
TMS (acetone). Presaturation of the residual HDO resonance was achieved by low-power irradiation,
and typically 8±16 scans were collected to achieve a good signal/noise ratio in the one-dimensional
spectra. A 5 mm QNP probe was used for the measurements of the 1D 13C NMR spectra. Two-
1
dimensional techniques (COSY, HMBC, HSQC) were used to determine the H and 13C chemical
shifts; the 2D HSQC experiment was performed in the phase-sensitive pure-absorption mode.
Thin-layer chromatography (TLC) was performed on glass plates precoated with silica gel 60
(Aldrich) to monitor the reactions. Detection was effected by spraying the chromatograms with 10%
ethanolic sulfuric acid and heating them to 100ꢀC. Flash column chromatography was performed with
silica gel (40±100 mm, Lachema) eluted with ethyl acetate:petroleum ether ˆ 3:1 (solvent A) or 6:1
(solvent B). Separation of the free sugars was accomplished by column chromatography on Dowex
50 W X8 resin in the Ba2‡ form (200±400 mesh) using water as eluent. Paper chromatography (PC)
was performed in the descending method on the Whatman No. 1 paper using ethyl acetate:
pyridine:water ˆ 8:2:1 as the mobile phase. The spots were made visible by means of alkaline silver
nitrate. All evaporations were carried out under reduced pressure at a bath temperature not exceeding
50ꢀC.
2,3:6,7-Di-O-isopropylidene-D-glycero-ꢀ-D-gulo-heptofuranose (1; C13H22O7)
A reaction mixture of 1 g D-glycero-D-gulo-heptose (4.8 mmol), 80 cm3 1,2-dimethoxyethane, 0.1 g
toluene-4-sulfonic acid monohydrate, and 6 cm3 2,2-dimethoxypropane (49 mmol) was stirred
vigorously for 8 h. Then, 1.5 g drierite were added, and stirring was continued at room temperature
for 24 h until the disappearance of starting material on TLC (solvent A). The reaction mixture was
neutralized by addition of NaHCO3. The neutral mixture was ®ltered with suction and washed with
2 Â 25 cm3 MeOH. A syrupy diisopropylidene derivative afforded by concentration of the ®ltrates
was puri®ed by ¯ash chromatography on silica gel (solvent A). TLC indicated 1 as major product
which was isolated as a syrup. After 24 h at room temperature, 1 crystallized from its solution in
acetone.

 Â
Z. Hricovõniova et al.
736
Yield: 1.1 g (79%); the spectroscopic data of the light yellow solid matched with previously
20
published data [13]; TLC (solvent A): Rf ˆ 0:47; ‰ꢁŠ
ˆ
32:5ꢀ (c ˆ 1, CHCl3); m.p.: 98±99ꢀC; 1H
D
NMR (300 MHz, ꢂ, acetone-d6): 5.30 (H-1), 4.91 (H-3), 4.58 (H-2), 4.15 (H-5), 4.11 (H-4), 4.03 (H-
7), 3.96 (H-6) ppm; 13C NMR (75 MHz, ꢂ, acetone-d6): 112.69 (2,3 CMe2), 109.35 (6,7 CMe2),
101.12 (C-1), 86.96 (C-2), 81.90 (C-3), 78.96 (C-4), 76.58 (C-5), 71.09 (C-6), 67.51 (C-7) ppm.
2,3:6,7-Di-O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo-heptofuranose (2; C14H24O8)
A reaction mixture of 0.9 g 1 (3.1 mmol), 0.82 g K2CO3, 18 cm3 MeOH, and 9 cm3 37% aqueous
formaldehyde (88 mmol) was re¯uxed under Ar at 85ꢀC for 50 h until the disappearance of 1 on TLC
(solvent B). Subsequently, the reaction mixture was neutralized with 10% aqueous H2SO4 and
evaporated. Extraction with 4Â20 cm3 CHCl3 gave a combined fraction that was dried over
anhydrous Na2SO4 overnight. The organic layer was then evaporated to give syrupy 2 which was
puri®ed on a column of silica gel (solvent A). TLC indicated one major product 2 which was isolated
as syrup.
20
D
Yield: 0.85 g (86%); TLC (solvent B): Rf ˆ 0:33; ‰ꢁŠ
ˆ
18:2ꢀ (c ˆ 1, CHCl3); 13C NMR
(75 MHz, ꢂ, acetone-d6): 113.86 (2,3 CMe2 ꢁꢀ), 109.44 (6,7 CMe2 ꢁꢀ), 103.85 (C-1 ꢀ), 99.53 (C-1
ꢁ), 95.87 (C-2 ꢀ), 90.73 (C-2 ꢁ), 84.95 (C-3 ꢀ), 84.22 (C-3 ꢁ), 80.04 (C-4 ꢀ), 76.84 (C-5 ꢀ), 76.26
(C-4 ꢁ), 74.28 (C-6 ꢁ), 71.49 (C-6 ꢀ), 71.38 (C-5 ꢁ), 66.58 (C-7 ꢀ), 62.87 (CH2(C-2) ꢁ), 62.70 (C-7
ꢁ), 62.56 (CH2(C-2) ꢀ) ppm.
2-C-(Hydroxymethyl)-D-glycero-D-gulo-heptose (3; C8H16O8)
‡
A mixture of 0.55 g 2, 15 cm3 H2O, and 4 cm3 Dowex 50 W X4 resin in the H form was stirred at
75ꢀC for 6 h. The resin was ®ltered, washed with 3Â5 cm3 H2O, and the combined ®ltrate was
puri®ed with charcoal and evaporated in vacuum to afford syrupy 3.
20
Yield: 0.39 g (95%); ‰ꢁŠ
ˆ
16:3 ! 17:0ꢀ (c ˆ 1, H2O) (24 h); 13C NMR (75 MHz, ꢂ, D2O):
D
103.53 (C-1 ꢀf), 99.40 (C-1 ꢁf), 99.15 (C-1 ꢀp), 95.65 (C-1 ꢁp), 83.24 (C-2 ꢀf), 82.06 (C-2 ꢁf),
81.38 (C-4 ꢁf), 80.13 (C-4 ꢀf), 75.90 (C-5 ꢀp), 75.33 (C-2 ꢀp), 74.73 (C-3 ꢁf ), 74.52 (C-3 ꢀf),
74.22 (C-2 ꢁp), 73.95 (C-3 ꢁp), 73.95 (C-3 ꢀp), 73.95 (C-6 ꢀf), 73.95 (C-6 ꢀp), 73.03 (C-5 ꢁf),
72.23 (C-6 ꢁp), 71.85 (C-4 ꢁp), 71.47 (C-4 ꢀp), 71.47 (C-5 ꢀf ), 71.47 (C-6 ꢁf), 68.94 (C-5 ꢁp),
66.30 (CH2(C-2) ꢁp), 65.97 (C-7 ꢀf), 65.79 (C-7 ꢁf), 65.79 (CH2(C-2) ꢁf), 65.66 (C-7) ꢀp), 65.33
(C-7 ꢁp), 65.33 (CH2(C-2) ꢀf), 64.18 (CH2(C-2) ꢀp) ppm.
D-Glycero-D-ido-oct-2-ulose (4; C8H16O8)
A mixture of 0.35 g 3 and 18 cm3 0.3% aqueous molybdic acid was heated at 85ꢀC for 8 h. The
composition of the reaction mixture was examined by paper chromatography until the equilibrium
mixture was reached. The cold reaction mixture was stirred with 20 cm3 Amberlite IRA-400 in the
HCO3 form, which was removed by ®ltration after 15 min and washed with 3Â15 cm3 H2O. The
®ltrates were concentrated to a syrup that was separated by column chromatography.
The syrupy residue (0.25 g) containing a complex equilibrium mixture of D-glycero-D-ido-oct-2-
ulose and remaining 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose was applied on a column
(95 cmÂ1.5 cm) of Dowex 50 W X8 (200±400 mesh) in the Ba2‡ form and eluted with water at a
¯ow rate 10 cm3 Á h 1. Tubes were combined according to the chromatographic behaviour of their
contents (PC test). The paper chromatograms indicated that fraction 1 (eluting between 105 and
130 cm3) contained 1,3-dihydroxyacetone together with D-arabinose (35 mg, 14%). Fraction 2
(eluting between 130 and 140 cm3) contained chromatographically pure D-arabinose (62 mg, 25%).
Fraction 3 (eluting between 140 and 150 cm3) contained D-arabinose and D-glycero-D-ido-oct-2-
ulose (15 mg, 6%). Fraction 4 (eluting between 150 and 180 cm3) consisted of chromatographically

Synthesis of D-Glycero-D-ido-oct-2-ulose
737
1
pure title compound (101 mg, 40%). The H NMR spectrum of 4 was identical with that of D-
glycero-D-ido-oct-2-ulose isolated from a natural source [4]; 13C NMR (75 MHz, ꢂ, D2O): 78.97 (C-
3), 78.64 (C-4, C-5), 73.87 (C-7), 72.08 (C-6), 66.11 (CH2 (C-1)), 65.70 (CH2 (C-8)) ppm. Fraction 5
(eluting between 180 and 280 cm3) contained D-glycero-D-ido-oct-2-ulose together with 2-C-
(hydroxymethyl)-D-glycero-D-gulo-heptose (7 mg, 3%), fraction 6 (eluting between 280 and
440 cm3) chromatographically pure 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose (20 mg, 8%).
2,7-Anhydro-D-glycero-ꢁ-D-ido-octulofuranose (5; C8H14O7) and 2,7-anhydro-D-glycero-
ꢀ-D-ido-octulopyranose (6; C8H14O7)
A syrupy mixture obtained by concentration of fraction 4 (100 mg) was dissolved in 3 cm3 aqueous
0.5 M H2SO4 and heated at 80ꢀC for 16 h. After cooling, the reaction mixture was treated with
20 cm3 Amberlite IRA-400 in the HCO3 form which was then removed by ®ltration and washed
with 3Â10 cm3 H2O. The deionized solution was concentrated to a syrup (91 mg; 91%) containing a
mixture of compounds 5 and 6 in a ratio of 2:1 (by NMR).
13C NMR (75 MHz, ꢂ, D2O): 5: 110.85 (C-2), 85.17 (C-7), 79.32 (C-6), 78.02 (C-4), 76.44 (C-3),
74.96 (C-5), 63.06 (C-1), 61.92 (C-8) ppm; 6: 100.67 (C-2), 79.90 (C-4), 74.49 (C-3), 74.43 (C-5),
72.98 (C-7), 66.16 (C-8), 65.45 (C-1), 64.85 (C-6) ppm.
Acknowledgements
This research was supported in part by VEGA grants No. 2/4144/98 and 2/6037/99 awarded by the
Slovak Academy of Sciences.
References
[1] Webber JN (1962) Adv Carb Chem 17: 45
[2] Frankle FP, Kapucinsky M, Macleod JM, Williams JF (1984) Carbohydr Res 125: 177
[3] Bianchi G, Gamba A, Murelli C, Salamini F, Bartels D (1991) Plant J 1: 355
[4] Howarth OW, Pozzi N, Vlahov G, Bartels D (1996) Carbohydr Res 289: 137
Â
[5] Bõlik V (1972) Chem Zvesti 26: 183
Â
[6] Bõlik V (1972) Chem Zvesti 26: 187
Â
[7] Bõlik V (1972) Chem Zvesti 26: 372
Â
[8] Bõlik V, Voelter W, Bayer E (1972) Liebigs Ann Chem 759: 189
Â
[9] Hricovõniova Z, Hricovõni M, Petrusova M, Matulova M, Petrus L (1998) Chem Papers 52: 238
Â
Â
Ï
Â
Â
Ï
     Ï
[10] Hricovõniova-Bõlikova Z, Hricovõni M, Petrusova M, Serianni AS, Petrus L (1999) Carbohydr
Â
Ï
Res 319: 38
Â
Â
Â
[11] Hricovõniova Z, Hricovõni M, Petrus L (1998) Chem Papers 52: 692
Ï
Â
[12] Hricovõniova-Bõlikova Z, Petrus L (1999) Carbohydr Res 320: 31
Â
Â
Â
Ï
[13] Brimacombe JS, Tucker LCN (1968) J Chem Soc C 562
Â
[14] Bõlik V, Petrus L, Farkas V (1975) Chem Zvesti 29: 690
Ï
Ï
[15] Hayes ML, Pennings NJ, Serianni AS, Barker R (1982) J Am Chem Soc 104: 6764
[16] Paoletti F, Williams JF, Horecker BL (1979) Arch Biochem Biophys 198: 614
Received October 17, 2000. Accepted December 4, 2000