Two new examples of the rare C→O migration of ethoxycarbonyl groups

Article abstract of DOI:10.1016/S0040-4020(03)00988-8

Two new examples of a carbon→oxygen ethoxycarbonyl group shift are described. Treatment of 3-ethoxycarbonylnitromethyl-1,2-O-isopropylidene-6-O-p-toluenesulfonyl- α-D-allofuranose (4) with Bu₄NF leads to a rearrangement to 5-O-ethoxycarbonyl-1,

Full text of DOI:10.1016/S0040-4020(03)00988-8

Tetrahedron 59 (2003) 6285–6289
Two new examples of the rare C!O migration of
ethoxycarbonyl groups
*
´ ´ ´
Raquel G. Soengas, Juan C. Estevez and Ramon J. Estevez
´ ´ ´
Departamento de Quımica Organica, Facultde de Quımica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
Received 18 November 2002; revised 5 June 2003; accepted 24 June 2003
Abstract—Two new examples of a carbon!oxygen ethoxycarbonyl group shift are described. Treatment of 3-ethoxycarbonylnitromethyl-
1,2-O-isopropylidene-6-O-p-toluenesulfonyl-a-D-allofuranose (4) with Bu4NF leads to a rearrangement to 5-O-ethoxycarbonyl-1,2-O-
isopropylidene-3-nitromethyl-6-O-p-toluenesulfonyl-a-D-allofuranose (8). Similar treatment of ethyl-3-O-benzyl-6-deoxy-6-nitro-D,L-
glycero-D-glucoheptofuronate (12) gives 3-O-benzyl-4-O-ethoxycarbonyl-6-deoxy-6-nitro-D-glucopyranose (16).
q 2003 Elsevier Ltd. All rights reserved.
A wide range of C!C migrations involving alkoxycarbonyl
groups have been reported1 but, in contrast, C!N and C!O
alkoxycarbonyl shifts2 are much less common. The first
C!O alkoxycarbonyl migration, reported in 1972, involved
the migration of an ethoxycarbonyl group in a compound
resulting from the reaction between ethyl nitroacetate and a
1,5-dialdehyde.3 To the best of our knowledge, only one
other example4 has been described and this occurred in the
context of an unusual decarboxylation of b-ethoxycarbonyl-
ketones. We report here two new, closely related C!O
ethoxycarbonyl migrations that were observed during the
course of a project aimed at the synthesis of cyclic a-nitro
acids from sugars by intramolecular Henry reactions
between appropriate sugar derivatives and ethyl nitroace-
tate. More specifically, compounds 4 and 12, upon treatment
with Bu4NF, rearranged to give compounds 8 and 16,
respectively.
methanol, acetic acid and water allowed selective hydro-
lysis of the exocyclic acetonide protecting group. The
resulting unstable mixture of compounds 3 was directly
treated with one equivalent of tosyl chloride at low
temperature to yield the expected tosyl compound 4 (64%
yield for the last two steps), which results from the selective
tosylation of the less hindered hydroxy group at C-6.
Finally, compound 4 was reacted with Bu4NF in order to
promote the intramolecular cyclization leading to bicycle 5.
However, compound 8 was obtained as the only isolable
component of a complex reaction mixture {59% yield,
[a]2D1¼þ9.608 (c, 1.6 in CHCl3)}.
The isomeric nature of compounds 4 and 8 was easily
established from their HRMS data, which indicated the
same molecular formula (C20H28NO12S) from the corre-
sponding (MþþH) peak.
When diacetone-D-glucose derivative 15 was reacted with
ethyl nitroacetate and ammonium acetate in DMF, com-
pound 2 was formed in 26% yield as a 15:1 mixture of
epimers (Scheme 1). As expected,6 the resulting R
configuration at C-3 was controlled by the starting material,
which facilitates attack by the ethyl nitroacetate anion on
the less hindered face of the carbonyl group in ketone 1.
However, the relatively long distance between the methyl-
ene group in ethyl nitroacetate and the stereogenic centers in
compound 1 did not allow full stereocontrol at the carbon
bearing the ethoxycarbonyl and nitro groups.
The structure of 8 was established from its spectroscopic
data. The IR spectrum contains at 1559 and 1357 cm21 two
bands due to the nitro group, and a band at 1746 cm21
,
corresponding to the carbonyl group. The 1H NMR
spectrum contains the expected signals for aromatic protons
of the OTs group: a doublet (2H) at 7.31 ppm and a doublet
(2H) at 7.75 ppm. Additional information about the
structure of compound 8 was obtained from its 13C NMR
spectrum, particularly the signals at 65.01, 68.00 and
75.78 ppm due to the three methylene groups. These signals
clearly indicate the internal displacement of the ethoxycar-
bonyl group.
Subsequent treatment of nitroester 2 with a mixture of
Transformation of compound 4 into 8 might occur in the
following way: the hydroxy group at C-5 in compound 4
takes part in an intramolecular attack on the ethoxycarbonyl
group to give a cyclic intermediate 6. This compound
Keywords: carbohydrates; rearrangement; nitro compounds.
*
Corresponding author. Tel.: þ34-981-563100x14242; fax: þ34-981-
591014; e-mail: qorjec@usc.es
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00988-8

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R. G. Soengas et al. / Tetrahedron 59 (2003) 6285–6289
Scheme 1. Conditions: (i) Ethyl nitroacetate, AcONH4, DMF (26% yield); (ii) CH3OH/CH3CO2H/H2O, 1:1:1; (iii) p-toluenesulfonyl chloride, dry pyridine
(64% yield over the two last steps); (iv) Bu4NF (1 M solution in THF), dry THF (59% yield); (v) K2CO3 1% methanolic solution (43% yield).
readily rearranges to the more stable anionic intermediate 7,
which is finally protonated in the reaction medium.
1373 cm21 two bands due the nitro group and a band at
1748 cm21 corresponding to the carbonyl of the ethox-
ycarbonyl group. The presence of this group was confirmed
1
In an attempt to further confirm the aforementioned
displacement of the ethoxycarbonyl group in compound 4,
compound 8 was treated with 1% methanolic potassium
carbonate solution. Under these conditions compound 9 was
formed in 43% yield as an oil {[a]2D0¼þ32.208 (c, 0.9 in
CHCl3)} as a result of the removal of the ethoxycarbonyl
group at C5 and the displacement of the tosyl group by
methanol. The mass spectrum confirmed the molecular
weight expected for this compound and the IR and 1H NMR
spectra do not show any evidence for the presence of an
ethoxycarbonyl group. Moreover, this compound shows a
NOE between the nitromethylene chain and the hydrogen at
position C2. Therefore, this confirm that the R configuration
at C3 is maintained along the reactions sequence starting
from compound 2.
from the H NMR spectrum, which showed a triplet at
1.29 ppm (J¼7.23 Hz) due to the methyl of the ethoxy
substituent. In addition, the 13C NMR spectrum clearly
shows two signals at 65.07 and 75.35 ppm, the last one
corresponding to the highly deshielded methylene contig-
uous to the nitro group.
A mechanism similar, but slightly more complex, to that
discussed above for the transformation of compound 4 into
compound 8 can be proposed for the rearrangement of
compound 12 to 16: furanose 12a can easily isomerize to
pyranose 12b, which experiences intramolecular attack by
the C-4 hydroxy group on the ethoxycarbonyl group. This
step results in the bicyclic intermediate 14, which
irreversibly opens to the more stable anionic intermediate
15. Protonation of this compound in the reaction medium
yields the unstable rearranged compound 16, which was
finally converted into its stable derivative 17 by protecting
the free hydroxy groups as TBDMS derivatives. The
stereochemistry at the anomeric position of this compound
The second rearrangement described here involved nitro-
acetate derivative 11 (Scheme 2), which was obtained in
40% yield as a 59:41 epimeric mixture when diacetoneglu-
cose derivative 107 was allowed to react with ethyl
nitroacetate under basic conditions.8 Hydrolysis of com-
pound 11 with a 1:1 mixture of trifluoroacetic acid/water
gave the unstable hemiacetal derivative 12a, which was
directly reacted with Bu4NF in order to promote its
intramolecular Henry reaction to compound 13. However,
in this case the only isolable component from the resulting
complex reaction mixture was compound 16, which was
obtained in 26% yield (for the two last steps) as an oil and
was identified from its analytical and spectroscopic data.
The HRMS (CI) shows the molecular formula C16H22NO9
from the (MþþH) peak. The IR spectrum shows at 1560 and
1
was easily established from its H NMR spectrum, which
includes a doublet at 4.83 ppm due to the proton at C1. The
coupling constant for this doublet (J1,2¼11.24 Hz) allowed
us to establish the diaxial disposition of the protons at C1
and at C2.
Migration of the ethoxycarbonyl group in 12 was corrobo-
rated by chemical means in a similar way as for compound
8: treatment of compound 17 with a methanolic K2CO3
solution resulted in the formation of compound 18 in 61%
yield as a solid {mp: 101–1038C (hexane), [a]2D0¼21.338

R. G. Soengas et al. / Tetrahedron 59 (2003) 6285–6289
6287
Scheme 2. Conditions: (i) ethyl nitroacetate, Bu4NF, Et3N, t-BuMe2SiCl (40% yield); (ii) CF3CO2H/H2O, 1:1; (iii) Bu4NF (1 M solution in THF), dry THF
(26% yield over the two last steps); (iv) t-BuMe2SiCl, imidazole, DMF (67% yield); (v) K2CO3 1% aqueous solution, CH3OH (61% yield).
(c, 1 in CHCl3)} due to removal of the ethoxycarbonyl
group at C-4. The structure of compound 18 was confirmed
from its analytical and spectroscopic data. The IR spectrum
does not show evidence of a carbonyl group and has a band
at 3505 cm21 due to the hydroxy group.
Solutions of extracts in organic solvents were dried with
anhydrous sodium sulfate.
1.1.1. 3-Ethoxycarbonylnitromethyl-1,2:5,6-di-O-isopro-
pylidene-a-D-allofuranose (2). Ethyl nitroacetate (1.83 ml,
16.5 mmol) and ammonium acetate (1.65 g, 21.45 mmol)
were added to a solution of compound 1 (3.87 g, 15 mmol)
in DMF (80 ml) and the resulting mixture was stirred at
room temperature for 40 h. The solvent was evaporated in
vacuo, the residue dissolved in dichloromethane (150 ml)
and the solution washed with water (3£100 ml). The organic
layers were dried, filtered and the solvent evaporated. The
residue was submitted to flash column chromatography
(ethyl acetate/hexane, 1:3) to give the title compounds
(1.5 g, 26% yield) as a gum-like mixture of isomers in a 15:1
ratio. [a]2D0¼þ40.208 (c, 1.3 in MeOH). Spectroscopic data
for the main epimer: nmax (NaCl): 3440 (–OH), 1747
(CvO), 1570 (–NO2), 1376 (–NO2). dH (300 MHz,
CDCl3): 1.25–1.44 (m, 9H, –O–CH2–CH3 and 2£–CH3),
1.52 (s, 6H, 2£–CH3), 3.61 (bs, 1H, –OH), 4.03–4.39 (m,
5H), 4.58 (d, 1H, J¼6.4 Hz), 4.82 (d, 1H, J¼3.6 Hz), 5.84
(s, 1H, H2), 5.93 (d, 1H, J1,2¼4.0 Hz, H1). dC (75.3 MHz,
CDCl3): 13.72 (q, –CH3), 24.86 (q, –CH3), 25.60 (q, –CH3),
26.45 (q, –CH3), 26.53 (q, –CH3), 63.16 (t, –CH2–), 67.23
(t, –CH2–), 73.00 (d, –CH–), 80.26 (d, –CH–), 81.23 (s,
–C–), 85.78 (d, –CH–), 89.20 (d, –CH–), 104.43 (d, –CH–),
110.09 (s, –C–), 113.16 (s, –C–), 162.46 (s, CvO). m/z (%):
490 [(Mþ215), 8], 318 (6), 212 (14), 259 (3), 143 (8), 101
(100), 59 (70). HRMS: C15H22NO10 (Mþ215), calcd
376.1244; found 376.1251.
In summary, we report two new examples of rare carbon!
oxygen rearrangements. The chemistry described here also
represents an interesting contribution to the knowledge of
the Henry reaction. The application of this reaction to the
synthesis of sugar amino acids is currently under investi-
gation in our laboratory.9
1. Experimental
1.1. General
Melting points were determined using a Kofler Thermo-
gerate apparatus and are uncorrected. Specific rotations
were recorded on a JASCO DIP-370 optical polarimeter.
Infrared spectra were recorded on a MIDAC FTIR
spectrophotometer. Nuclear magnetic resonance spectra
were recorded on a Bruker WM-300 or a Bruker AMX-500
apparatus, using deuterochloroform solutions containing
tetramethylsilane as internal standard. NMR assignments
were made by a combination of 1D, COSY, NOESY and
DEPT-135 experiments. Mass spectra were obtained on a
Kratos MS 50 TC mass spectrometer by electronic impact
unless otherwise specified. Elemental analyses were
obtained from the Elemental Analysis Service at the
University of Santiago de Compostela. Thin layer chroma-
tography (TLC) was performed using Merck GF-254 type
60 silica gel and ethyl acetate/hexane mixtures as eluants;
the TLC spots were visualized with Hannesian mixture.
Column chromatography was carried out using Merck type
9385 silica gel. Solvents were purified as per Ref. [10].
1.1.2. 3-Ethoxycarbonylnitromethyl-1,2-O-isopropyli-
dene-6-O-p-toluenesulfonyl-a-D-allofuranose (4). Com-
pound 2 (1.2 g, 3.07 mmol) was dissolved in a 1:1:1 mixture
of methanol/water/acetic acid (18 ml) and the solution
stirred at room temperature for 22 h. The solvent was
evaporated in vacuo, the traces of acetic acid were

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R. G. Soengas et al. / Tetrahedron 59 (2003) 6285–6289
co-evaporated with toluene (3£1 ml) and the resulting
unstable compound 3 was immediately dissolved in dry
pyridine (10 ml). Tosyl chloride (0.62 g, 3.37 mmol) was
then added slowly to this cooled (2208C) solution and the
resulting mixture was stirred at 2208C for 10 h. The solvent
was evaporated in vacuo and the residue submitted to flash
column chromatography (ethyl acetate/hexane, 2:3) to give
a mixture of compounds 4 (0.407 g, 64% over the two last
steps) as a clear gum. [a]2D2¼þ29.08 (c, 0.6 in CHCl3).
Spectroscopic data for the main epimer: nmax (NaCl): 3432
(–OH), 1750 (CvO), 1564 (–NO2), 1379 (–NO2). dH
(500 MHz, CDCl3): 1.31–1.33 (m, 6H, –CH3 and –O–
CH2–CH3), 1.63 (s, 3H, –CH3), 2.45 (s, 3H, –CH3), 4.11–
3410 (–OH); 1585 (–NO2), 1376 (–NO2). dH (500 MHz,
CDCl3): 1.32 (s, 3H, –CH3), 1.51 (s, 3H, CH3), 2.58 (bs, 1H,
–OH), 3.41 (s, 3H, –CH3), 3.48–3.51 (m, 1H, H6), 3.61–
0
3.64 (m, 1H, H6 ), 3.79 (d, 1H, J4,5¼8.6 Hz, H4), 4.10–4.12
(m, 1H, H5), 4.58 (d, 1H, J1,2¼3.5 Hz, H2), 4.78 (d, 1H,
0
0
0
J7,7 ¼14.5 Hz, H7), 5.01 (d, 1H, J7,7 ¼14.5 Hz, H7 ), 5.92 (d,
1H, J1,2¼3.5 Hz, H1). m/z (%, CI): 294 [(MþþH), 16], 278
(Mþ215, 12); 236 (100). HRMS (CI): C11H20NO8
(MþþH), calcd 294.1188; found 294.1179.
1.1.5. 3-O-Benzyl-4-O-ethoxycarbonyl-6-deoxy-6-nitro-
D-glucopyranose (16). Compound 11 (0.23 g, 0.57 mmol)
was dissolved in a 1:1 mixture of trifluoroacetic acid/water
(4 ml) and the solution was stirred at room temperature for
9 h. The solvent was evaporated in vacuo, the traces of
acetic acid were co-evaporated with toluene (3£1 ml) and
the resulting unstable compound 12 was immediately
dissolved in dry THF (10 ml). Tetrabutylammonium
fluoride (0.48 ml, 1 M in THF) was added to this solution
and the resulting mixture was stirred at room temperature
for 16 h. The solvent was evaporated in vacuo and the
residue was submitted to flash column chromatography
(ethyl acetate/hexane, 2:3) to give the title compounds
(0.08 g, 26% yield over the two last steps) as a yellow oil.
[a]2D0¼211.88 (c, 1.0 in CHCl3). nmax (NaCl): 3437 (–OH),
1748 (CvO), 1560 (–NO2), 1373 (–NO2). dH (300 MHz,
CDCl3): 1.29 (t, 3H, J¼7.23 Hz, –O–CH2–CH3), 3.68–
3.90 (m, 2H), 4.14–4.22 (m, 3H), 4.44–4.86 (m, 5H), 5.18
(d, 1H, J¼3.6 Hz, H1), 7.32 (s, 5H, 5£Ar-H). dC (75.3 MHz,
CDCl3): 14.15 (q, –CH3), 65.07 (t, –CH2–), 66.61 (d,
–CH–), 72.26 (d, –CH–), 74.76 (d, –CH–), 75.35 (t,
–CH2–), 75.93(t, –CH2–), 79.40(d, –CH–), 92.13(d, –CH–),
127.86 (d, –CH–), 127.94 (d, 2£–CH–), 128.42 (d, 2£–
CH–), 137.88 (s, –C–), 154.51 (CvO). m/z (%, CI): 372
[(MþþH), 10], 217 (24), 91 (100). HRMS (CI):
C16H22NO9 (MþþH), calcd 372.1295; found 372.1291.
0
4.15 (m, 2H, H5 and H6), 4.26–4.34 (m, 3H, H6 and –O–
CH2–CH3), 4.55 (d, 1H, J4,5¼7.4 Hz, H4), 4.81 (d, 1H,
J1,2¼3.7 Hz, H2), 5.85 (d, 1H, J1,2¼3.7 Hz, H1), 5.91 (s, 1H,
H7), 7.35 (d, 2H, J¼8.2 Hz, 2£Ar-H), 7.80 (d, 2H,
J¼8.2 Hz, 2£Ar-H). dC (75.3 MHz, CDCl3): 13.72 (q,
–CH3), 21.69 (q, –CH3), 26.42 (q, –CH3), 26.55 (q, –CH3),
63.34 (t, –CH2–), 67.89 (d, –CH–), 72.24 (t, –CH2–), 78.55
(d, –CH–), 81.28 (s, –C–), 85.49 (d, –CH–), 89.27 (d,
–CH–), 104.25 (d, –CH–), 113.32 (s, –C–), 128.06 (d,
–CH–), 130.00 (d, –CH–), 132.35 (s, –C–), 145.25 (s, –C–),
162.66 (s, CvO). m/z (%): 496 [(Mþ215), 0.5], 290 (2), 155
(60), 91 (100). HRMS (FAB): C20H28NO12S (MþþH), calcd
506.1332; found 506.1330.
1.1.3. 5-O-Ethoxycarbonyl-1,2-O-isopropylidene-3-
nitromethyl-6-O-p-toluenesulfonyl-a-D-allofuranose (8).
Tetrabutylammonium fluoride (0.32 ml, 1 M in THF) was
added to a solution of compound 4 (0.16 g, 0.32 mmol) in
dry THF (5 ml) and the mixture was stirred at room
temperature for 7 h. The reaction mixture was evaporated in
vacuo and the residue submitted to flash column chroma-
tography (ethyl acetate/hexane, 1:2) to give the title
compound (94 mg, 59%) as a clear gum. [a]2D1¼þ9.68 (c,
1.6 in CHCl3). nmax (NaCl): 3446 (–OH), 1746 (CvO),
1559 (–NO2), 1357 (–NO2). dH (500 MHz, CDCl3): 1.27–
1.29 (m, 6H, –O–CH2–CH3 and –CH3), 1.46 (s, 3H, –CH3),
2.42 (s, 3H, –CH3), 4.02 (d, 1H, J4,5¼6.7 Hz, H4), 4.14–
4.18 (m, 3H, –O–CH2–CH3 and H6), 4.47 (d, 1H,
1.1.6. 3-O-Benzyl-1,2-di-O-tert-butyldimethylsilyl-4-O-
ethoxycarbonyl-6-deoxy-6-nitro-b-D-glucopyranose
(17). A solution of compound 16 (0.07 g, 0.19 mmol) in dry
DMF (1.5 ml) was added to a mixture of tert-butyldi-
methylsilyl chloride (0.28 g, 1.89 mmol) and imidazole
(0.22 g, 3.02 mmol) in dry DMF (3 ml). The reaction
mixture was stirred at room temperature for 18 h. The DMF
was evaporated in vacuo and the residue was dissolved in
chloroform (20 ml) and washed with water (3£10 ml). The
organic layer was dried, filtered and evaporated. The residue
was submitted to flash column chromatography (ethyl
acetate/hexane, 1:12) to give the title compound (0.08 g,
67%) as an oil. {[a]2D2¼29.08 (c, 0.6 in CHCl3)}. nmax
(NaCl): 1751 (CvO), 1563 (–NO2), 1373 (–NO2). dH
(500 MHz, CDCl3): 0.04 (s, 3H, –SiCH3), 0.06 (s, 3H,
–SiCH3), 0.08 (s, 3H, –SiCH3), 0.10 (s, 3H, –SiCH3), 0.87
[s, 9H, –SiC(CH3)3], 0.90 [s, 9H, –SiC(CH3)3], 1.19 (t, 3H,
J¼7.0 Hz, –O–CH2–CH3), 3.49–3.54 (m, 2H, H3 and H4),
4.04–4.10 (m, 2H, –O–CH2–CH3), 4.21–4.25 (m, 1H, H5),
0
0
J6,6 ¼11.5 Hz, H6 ), 4.56–4.58 (m, 2H, H2 and H7), 4.76
0
(d, 1H, J¼14.6 Hz, H7 ), 4.95–4.97 (m, 1H, H5), 5.86 (d,
1H, J1,2¼2.8 Hz, H1), 7.31 (d, 2H, J¼7.5 Hz, 2£Ar-H), 7.75
(d, 2H, J¼7.5 Hz, 2£Ar-H). dC (75.3 MHz, CDCl3): 14.11
(q, –CH3), 21.67 (q, –CH3), 26.41 (q, –CH3), 26.99 (q,
–CH3), 65.01 (t, –CH2–), 68.00 (t, –CH2–), 71.66 (d,
–CH–), 75.78 (t, –CH2–), 77.70 (d, –CH–), 79.53 (s, –C–),
85.19 (d, –CH–), 104.65 (d, –CH–), 113.42 (s, –C–),
128.07 (d, –CH–), 129.86 (d, –CH–), 132.57 (s, –C–),
144.95 (s, –C–), 153.81 (s, CvO). m/z (%, FAB): 490
[(MþþH), 25], 334 (12), 185 (100). HRMS (FAB):
C20H28NO12S calcd 506.1332; found 506.1336.
1.1.4. 1,2-O-Isopropylidene-6-O-methyl-3-nitromethyl-
a-D-allofuranose (9). A solution of compound 8 (0.037 g,
0.07 mmol) and potassium carbonate (0.03 g) in methanol
(3 ml) was stirred at room temperature for 16 h. The
reaction mixture was neutralized with DOWEX 50W acidic
resin, filtered and the solvents removed. The residue was
submitted to flash column chromatography (ethyl acetate/
hexane, 1:7) to give the title compound (0.009 g, 43% yield)
as an oil. {[a]2D0¼þ32.208 (c, 0.9 in CHCl3)}. nmax (NaCl):
0
4.40–4.43 (d, 1H, J6,6 ¼13.3 Hz, H6). 4.49–4.61 (m, 1H,
0
H6 ), 4.60–4.68 (m, 3H, H2 and –O–CH2–Ph), 4.83 (d, 1H,
J1,2¼11.24 Hz, H1), 7.25–7.32 (m, 5H, 5£Ar-H). dC
(75.3 MHz, CDCl3): 25.11 (q, –SiCH3), 24.25 (q,
–SiCH3), 24.12 (q, –SiCH3), 23.78 (q, –SiCH3), 14.01
(q, –O–CH2–CH3), 17.96 [s, –SiC(CH3)3], 18.05 [s,
–SiC(CH3)3], 25.85 [q, –SiC(CH3)3], 25.95 [q,

R. G. Soengas et al. / Tetrahedron 59 (2003) 6285–6289
6289
SiC(CH3)3], 64.91 (t, –CH2–), 70.74 (d, –CH–), 75.23 (d,
–CH–), 75.78 (t, –CH2–), 75.99 (d, –CH–), 76.03 (t,
–CH2–), 82.94 (d, –CH–), 98.28 (d, –CH–), 127.47 (d,
–CH–), 127.48 (d, 2£–CH–), 128.19 (d, 2£–CH–), 138.06
(s, –C–), 154.44 (s, CvO). m/z (%): 542 [(Mþ257), 0.1],
434 (1), 360 (1), 259 (3), 147 (7), 91 (100), 73 (20). Anal:
C28H49NO9Si2 requires: C, 56.06; H, 8.23; N, 2.33; found:
C, 56.42; H, 8.32; N, 2.32.
91 (100), 73 (23). Anal: C25H45NO7Si2 requires: C, 56.89;
H, 8.59; N, 2.65; found: C, 56.62; H, 8.70; N, 2.69.
Acknowledgements
We gratefully acknowledge Professor G. W. J. Fleet for
helpful discussions on this chemistry. Thanks are also due to
´
the Spanish ‘Ministerio de Ciencia y Tecnologıa’ and to the
1.1.7. 3-O-Benzyl-1,2-di-O-tert-butyldimethylsilyl-6-
deoxy-6-nitro-b-D-glucopyranose (18). A solution of
compound 17 (0.08 g, 0.13 mmol) and potassium carbonate
(0.04 g) in methanol (9 ml) was stirred at room temperature
for 16 h. The reaction mixture was neutralized with
DOWEX 50W acidic resin, filtered and the solvents
removed. The residue was submitted to flash column
chromatography (ethyl acetate/hexane, 1:7) to give the
title compound (0.042 g, 61% yield) as a solid. Mp: 101–
1038C (hexane). {[a]2D0¼21.338 (c, 1.0 in CHCl3)}. nmax
(NaCl): 3505 (–OH), 1560 (–NO2), 1362 (–NO2). dH
(500 MHz, CDCl3): 0.05 (s, 3H, –SiCH3), 0.07 (s, 3H,
–SiCH3), 0.14 (s, 3H, –SiCH3), 0.15 (s, 3H, –SiCH3), 0.87
[s, 9H, –SiC(CH3)3], 0.95 [s, 9H, –SiC(CH3)3], 3.26–3.32
(m, 2H, H4 and H5), 3.42 (dd, 1H, J3,4¼J3,2¼7.30 Hz, H3),
‘Xunta de Galicia’ for financial support and the former for a
grant to Raquel G. Soengas.
References
1. Acheson, R. M. Acc. Chem. Res. 1971, 4, 177.
2. (a) Ranson, J. H. Chem. Ber. 1900, 33, 199. (b) Trimnell, D.;
Doane, W. M.; Russell, C. R.; Rist, C. E. Carbohydr. Res.
1970, 13, 301. (c) Smith, J. G.; Sheepy, J. M. J. Chem. Soc.,
Chem. Commun. 1976, 339. (d) Vercek, B.; Cucek, K. Synlett
1999, 1, 120.
3. Lichtenthaler, F. W.; Bambach, G. J. Org. Chem. 1972, 37,
1621.
4. Milenkov, B.; Hesse, M. Helv. Chim. Acta 1986, 69, 1323.
5. Austin, G. N.; Baird, P. D.; Fleet, G. W. J.; Peach, J. M.;
Smith, P. W.; Watkin, D. J. Tetrahedron 1987, 43, 3095.
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1063.
0
3.99–4.02 (m, 1H, H6), 4.40 (dd, 1H, J6,6 ¼13.0 Hz,
0
0
J6 ,5¼9.8 Hz, H6 ), 4.55–4.58 (m, 2H, H2 and –O–CH2–
Ph), 4.66 (d, 1H, J¼11.5 Hz, –O–CH2–Ph), 4.99 (d, 1H,
J1,2¼12.2 Hz, H1), 7.34–7.40 (m, 5H, 5£Ar-H). dC
(75.3 MHz, CDCl3): 25.04 (q, –SiCH3), 24.21 (q,
–SiCH3), 24.05 (q, –SiCH3), 23.61 (q, –SiCH3), 17.99
[s, –SiC(CH3)3], 18.10 [s, –SiC(CH3)3], 25.91 [q,
–SiC(CH3)3], 26.03 [q, –SiC(CH3)3], 70.46 (d, –CH–),
72.24 (d, –CH), 75.82 (t, –CH2–), 76.09 (d, –CH–), 76.46
(t, –CH2–), 85.35 (d, –CH–), 98.27 (d, –CH–), 127.97 (d,
2£–CH–), 128.37 (d, –CH–), 129.02 (d, 2£–CH–), 138.45
(s, –C–). m/z (%): 542 [(Mþ257), 0.1], 378 (0.3), 187 (3),
7. Fleet, G. W. J.; Witty, D. W. Tetrahedron: Asymmetry 1990, 1,
119.
8. Paulsen, H.; Brieden, M.; Sinnwell, V. Liebigs Ann. Chem.
1985, 113.
´ ´
9. Soengas, R. G.; Estevez, J. C.; Estevez, R. J.; Maestro, M. A.
Tetrahedron: Asymmetry 2003, 14, 1653.
10. Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon: New York, 1988.