Synthesis and structural analyses of 3-acetamido-1,4-di-O-acetyl-2,3,5-trideoxy-5-C-(isopropylphosphinyl)-D- erythro-pentopyranoses

Article abstract of DOI:10.1016/S0008-6215(02)00397-X

¹H NMR spectroscopy of phosphorus containing hetero sugars (phospha sugars), revealed the α and β configurations and chair conformations for 3-acetamido-1,4-di-O-acetyl-2,3,5-trideoxy-5-C-(isopropylphosphinyl)-α- and β-D-erythro-pentopyranoses. The conformation of the title compounds was determined by ¹H NMR as ¹C₄ in CDCl₃ and the conformation was in accord with that in solid state determined by X-ray crystallographic analysis.

Full text of DOI:10.1016/S0008-6215(02)00397-X

Carbohydrate Research 338 (2003) 283–291
www.elsevier.com/locate/carres
Note
Synthesis and structural analyses of
3-acetamido-1,4-di-O-acetyl-2,3,5-trideoxy-5-C-
(isopropylphosphinyl)- -erythro-pentopyranoses
D
Tatsuo Oshikawa,a,* Kuniaki Seo,a,* Mitsuji Yamashita,b Tadashi Hanaya,c
Yoshihiro Hamauzu,a Hiroshi Yamamotoc
aDepartment of Material Sciences and Biochemistry, Numazu College of Technology, Numazu 410-8501, Japan
bDepartment of Materials Chemistry, Faculty of Engineering, Shizuoka Uni6ersity, Hamamatsu 432-8561, Japan
cDepartment of Chemistry, Faculty of Science, Okayama Uni6ersity, Tsushima-naka 700-8530, Japan
Received 19 March 2002; received in revised form 1 July 2002; accepted 4 October 2002
Abstract
1H NMR spectroscopy of phosphorus containing hetero sugars (phospha sugars), revealed the a and b configurations and chair
conformations for 3-acetamido-1,4-di-O-acetyl-2,3,5-trideoxy-5-C-(isopropylphosphinyl)-a- and b-D-erythro-pentopyranoses. The
1
1
conformation of the title compounds was determined by H NMR as C4 in CDCl3 and the conformation was in accord with that
in solid state determined by X-ray crystallographic analysis. © 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Phospha sugar; 1C4 conformation; NMR; X-ray
In order to prepare potentially bioactive hetero sug-
ars, the present phospha sugar synthesis was performed
and the conformations of 3-acetamido-1,4-di-O-acetyl-
2,3,5-trideoxy-phospha sugar derivatives elucidated.
Yamamoto et al. reported the syntheses of phospha
sugars1 and their NMR analysis which established the
configuration at the phosphorus in the pyranoid rings
and the conformation of the six membered heterocycles.
The X-ray analyses of phospha sugar analogs had been
reported by Luger et al. and ourselves.2,3 In the present
3. 5-O-Triphenylmethylation of 3 with 1 equiv. of
triphenylmethyl chloride in pyridine afforded 4. 3-O-
Mesylation of 4 with methanesulfonyl chloride in pyri-
dine afforded 5 in good yield. 2-O-Deoxygenation of
compound
5
in accordance with the reported
procedure5,6 gave compound 6 in quantitative yield.
Conversion of 6 into 8 was readily achieved by heating
with sodium azide and successive treatment with acidic
methanol. Compounds 8a and 8b were separated by
column chromatography on silica gel. 5-O-Tosylation
of the separated 8b with 1 equiv. of tosyl chloride in
paper the phospha sugar 16 was synthesized from
lose as a starting material via the process shown in
Scheme 1. Methyl 3,5-O-isopropylidene- -xylofura-
D-xy-
pyridine afforded
9 in quantitative yield. 3-Ace-
D
toamido-2-deoxy derivative 11 was prepared by reduc-
tion of 9 with n-Bu3SnH, followed by acetylation with
acetic anhydride. On heating compound 11 with
sodium iodide in acetone in a sealed tube methyl 3-ace-
noside (1) was prepared according to the reported
procedure,4 2-O-methylthiocarbonylation of methyl-
compound (1) with an excess amount of carbon
disulfide and methyl iodide in DMSO under alkaline
solution was carried out to afford 2a and 2b, easily
separated by column chromatography on silica gel.
Treatment of 2b with acidic methanol gave compound
toamido-2,3,5-trideoxy-5-iodo-b-D-erythro-pentofura-
noside 12 was obtained in quantitative yield.
Conversion of 12 into the phosphinate 13 was readily
performed by heating with an excess amount of diethyl
isopropylphosphonite at 150 °C. Treatment of com-
pound 13 with sodium dihydrobis(2-methoxy-
ethoxy)aluminate (SDMA) gave compound 14 which
was subsequently followed by ring-enlargement
* Corresponding author. Fax: +81-55-9265804
E-mail address: oshix@numazu-ct.ac.jp (T. Oshikawa).
0008-6215/03/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(02)00397-X

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T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291
caused by the opening of the furanoid ring (15) and the
successive closing to prepare a pyranoid ring under
acidic conditions. The known two step procedure3,7
gave trideoxy-ribopyranose type phospha sugars 16a–d.
Diastereomers 16a, 16b, 16c, and 16d were separated,
respectively, by using flash chromatography on silica
gel (eluent; ethyl acetate/methanol=4/1, v/v) from the
mixture of products. The overall chemical yields of
diastereomers 16a, 16b, 16c, and 16d were 7, 5, 5 and
11%, respectively, from compound 13.
16a vs. 20.5–21.7 Hz for 16b–d), and J4,P (9.2 Hz for
16a vs. 21.4–22.0 Hz for 16b–d) with respect to the
corresponding vicinal dihedral angles. As a result, com-
pounds 16a and 16b–d were shown to exist predomi-
4
1
nantly in the C1 and C4 conformations, respectively.
The orientation of the PꢀO group could be established
by the l values of H-4 for 16a, and HR-2 and HS-2 for
16b–d. An appreciable downfield shift (0.05–0.31 ppm)
is observed for 16a compared with 16b–d, the observa-
tion shows the axial orientation of the ring PꢀO group
for compound 16a. The equatorial PꢀO orientation was
assigned to the result of upfield shift for products
16a–d. The small magnitudes of J5R,P support the anti
orientation of HR-5ꢁC5ꢁPꢀO for 16c and 16d. The
equatorial PꢀO group orientation was assigned to the
rest of the compounds, products 16c and 16d. The
appreciable downfield shift observed for HR-2 of 16c
and 16d could be explained by its axial orientation. The
anomeric orientation at C-1 was derived from the mag-
nitudes of J1,2 and J1,P. The moderate magnitudes of
The precise structures of these compounds 16a, 16b,
16c, and 16d were determined on the basis of the 500
1
MHz H NMR spectra and by X-ray crystallography
(Fig. 1). The assignments of all signals were readily
made by employing first-order analysis with the aid of
a decoupling technique. The analyzed results are sum-
marized in Table 1. The conformations of these phos-
pha sugar derivatives (in CDCl3 solution) was derived
by the careful analysis of the magnitudes of J2R,P (20.5
Hz for 16a vs. 2.0–9.8 Hz for 16b–d), J2S,P (7.3 Hz for
Scheme 1. Reagents: (i) CS2/MeI; (ii) MeOH/H2SO4; (iii) TrCl/py; (iv) MsCl/py; (v) n-Bu3SnH; (vi) NaN3; (viii) TsCl/py; (ix)
n-Bu3SnH; (x) Ac2O/py; (xi) NaI; (xii) P(OEt)2i-Pr; (xiii) SDMA; (xiv) HCl; (xv) Ac2O/py.

T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291
285

286
T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291

T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291
287
Scheme 2.
Table 2
13C NMR (67.80 MHz) chemical shifts for 16a, 16b, 16c, and 16d
Chemical shift l ppm, (JP–C, Hz)
Compd. C-1
C-2
C-3
C-4
C-5
PꢁCH(CH3)2 PꢁCH(CH3)2 CꢀO
CH3ꢁCꢀO
16a
16b
16c
16d
65.81 (73.1) 46.32 (2.4) 29.62 68.61 (0.0) 24.87 (68.3) 25.10 (54.8)
64.33 (70.8) 45.44 (6.1) 30.32 69.99 (4.8) 26.45 (71.1) 25.63 (56.3)
65.07 (70.7) 47.78 (0.0) 29.27 69.32 (6.1) 27.18 (67.1) 24.77 (57.3)
65.09 (75.7) 44.86 (6.1) 28.56 69.78 (7.3) 24.57 (70.8) 25.36 (58.6)
14.57 (4.2)
14.77 (7.3)
15.15 (0.0)
14.32 (0.0)
167.92, 20.86 20.96
169.27, 23.45
169.60
169.99, 23.11 20.95
169.78, 20.85
169.52
169.24, 20.79 21.15
169.61, 23.17
170.71
170.78, 23.29 21.28
169.25, 20.99
168.98
J1,P of 16a and 16d suggest the syn connection of
HꢁC-1ꢁPꢀO for these compounds. The large magnitude
of J1,2R (11.6 Hz) indicated axial H-1 orientation for
16c, whereas the smaller J1,2R values (2.2–2.8 Hz) sug-
gested the equatorial H-1 orientation for 16b and 16d.
Small coupling constants J1,5S and J2S,4=1.1–2.4 Hz
were shown in the compounds 16b–d. Obviously com-
program,8 giving a good fit with the measured spec-
trum. The chemical shift values of 13C NMR are shown
in Table 2.
Rod-shaped crystals of 16c and 16d were grown from
ethyl acetate–hexane. Precise lattice constants and
three dimensional intensity data were obtained by a
RIGAKU AFC7R four-circle diffractometer with Ni-
filtered CuKa radiation. Phase determination was made
by a direct method (SIR92).9 the molecular structures for
compounds 16c and 16d are shown in Fig. 2. A water
molecule is present in crystal 16c (16c/H2O=1/1) but is
not shown in Fig. 2. A summary of crystal data for
compounds 16c and 16d is shown in Table 3. In 16c,
the substituent groups at C-1, C-3, and P are orientated
equatorially, while those are at C-4 and PꢀO are axial.
However, in molecular structure of 16d, the substituents
at C-3 and P are equatorial, while those at C-1, C-4,
and PꢀO are axial. The acetoxy groups on C-1, C-3,
and C-4 have usual syn arrangement between the CꢀO
bond and the adjacent CꢁH bond. The Cremer–Pople
1
pounds 16b–d retain the conformation of C4 from the
above conformation analyses, and the long range cou-
plings (J1,5S=1.8 Hz for 16b, J1,5S=2.4 Hz for 16d,
and J2S,4=1.1–1.2 Hz for 16b–d) of compounds 16a–d
support. As for the more precise conformation of 16b–
d, it is noted that the magnitudes of J2R,P and J2S,P tend
to become appreciably closer to intermediate values,
4
1
which suggest an equilibrium mixture of C1 and C4
4
conformers at room temperature (ca. 20% of the C1
conformation was contained in the compounds 16b–d
from the observed coupling constant values). A part of
1
the H NMR spectra of compounds 16a–d were as-
signed with difficulty, because the methylene protons
on C-2 and C-5 overlapped with the acetyl group, and
it was reexamined more precisely by using a simulation
puckering parameters10 are Q=0.600 A, q=168.5°,
,
,
„=252.5° for 16c and Q=0.5602 A, q=167.4°, „=

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T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291
262.2° for 16d, respectively, and the six membered rings
of the compounds 16c and 16d were distorted slightly
from the 1C4 conformation. The X-ray analysis of
crystals 16c and 16d, the structures were first solved at
223 K, but they could not be resolved at 295 K because
carbon and phosphorus atoms of six membered ring are
disordered at 295 K. In the crystals 16c and 16d may
exist in the same way of equilibrium as the obtained
imeter DIP-4 (JASCO Ltd.). Mass spectra were
recorded on Shimadzu GCMS-AP5050 gas-chro-
matograph-mass spectrometer using electron impact 70
eV. X-Ray single crystallographic measurements were
conducted on a RIGAKU AFC7R using cut crystals of
size (0.2×0.2×0.6 mm). Phase determination was
made by a direct method (SIR 92) and expanded using
Fourier techniques. After convergence of all parame-
ters, final R values were 5.6% for 16c and 6.4% for 16d,
respectively.
1
results by H NMR, where the compounds exist in an
1
4
equilibrium mixture of C4 and C1 in CDCl3 solution.
1
This is the first observed C4 conformation of phospha
sugar by X-ray crystal structure analysis.
1.2. Methyl 2-deoxy-3-O-methanesulfonyl-5-O-
triphenylmethyl-b- -threo-pentofuranoside (6)
D
1. Experimental
To a dried toluene (80 mL) solution of compound 5
(4.17 g) were added n-Bu3SnH (2.83 g) and a catalytic
amount of AIBN. The reaction mixture was heated for
2 h under a nitrogen atmosphere. Toluene was removed
under reduced pressure. The residue was dissolved in
acetonitrile, and washed several times with n-hexane to
remove organic tin compound. The hexane layer was
further extracted with acetonitrile. The acetonitrile ex-
tract was collected and concentrated under reduced
pressure. The crude product was purified by column
chromatography on silica gel to afford syrupy product
1.1. General procedures
Synthetic procedures for compound 5 from 1 as starting
material were in with a previous paper.1 1H NMR
spectra were measured in CDCl3 (TMS as the internal
standard) on a Brucker 500 (500 MHz) and 13C NMR
were measured in CDCl3 (CDCl3 as the internal stan-
dard) on a JASCO EX270 (67.80 MHz). Melting points
were measured with a micro melting point apparatus
(Yanagimoto Co., Ltd., Japan) and are uncorrected.
Column chromatography was performed by Merck Lo-
bar silica gel. The reaction were monitored by TLC on
Kieselgel 60 F254 (Merck) with detection by H2SO4.
Optical rotations were determined with a digital polar-
1
6 in quantitative yield. H NMR (CDCl3): l, 2.3–2.4
(m, 2H, H-2 and 2%), 2.78 (s, 3H, OSO2CH3), 3.2–3.6
(m, 2H, H-5 and 5%), 3.40 (s, 3H, OCH3), 4.2–4.3 (m,
1H, H-4), 5.08 (dd, J=4.3 and 2.5 Hz, 1H, H-1),
5.2–5.3 (m, 1H, H-3), 7.2–7.5 (m, 15H, aroma).
Fig. 2. Molecular structure for compounds 16c (left) and 16d (right).

T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291
289
Table 3
Crystal and structure refinements for 16c and 16d
16c
16d
Molecular formula
Molecular weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions (A)
a
b
c
C14H24NPO6·H2O
351.34
223
orthorhombic
P212121 (c19)
C14H24NPO6
333.32
223
monoclinic
P21 (c4)
,
14.877(3)
23.416(3)
5.253(2)
90.296(5)
1830.1(6)
4
9.7660(8)
8.588(1)
10.1716(5)
i (°)
Volume (A )
3
,
853.1(1)
2
1.235
Z (molecules/cell)
Dcalcd (g cm−3
)
1.275
Absorption coefficient (mm−1
F(000)
)
712.00
340.00
Crystal size (mm)
Reflections collected
Independent reflections
Refinement method
Goodness-of-fit indicator
Final R indices [I\2|(I)]
R1
0.20×0.20×0.30
1359
1346 (Rint=0.302)
Full-matrix least-squares on F2
3.44
0.2×0.2×0.6
1457
1633 (Rint=0.059)
Full-matrix least-squares on F2
2.77
0.056
0.059
0.064
0.180
wR
1.3. Methyl 3-azido-2,3-dideoxy-5-O-(triphenylmethyl)-
a- and - -erythro-pentofuranoside (7)
filtered and the filtrate was concentrated under reduced
pressure. The residue was purified by column chro-
matography on silica gel (eluent; ethyl acetate/hexan=
1/2, v/v) to obtain syrupy product 8a (0.44 g) in 51%
D
To a solution of compound 6 (3.39 g) in DMF (40 mL)
was added sodium azide (7.5 g), and the mixture heated
for 2 h at 110 °C. The reaction mixture was filtered, and
the filtrate was concentrated under reduced pressure.
The syrupy residue was dissolved in chloroform and
washed with water several times. The water layer was
further extracted with chloroform several times. The
organic layer were collected, dried with anhydrous
sodium sulfate, and evaporated. The residue was
purified by column chromatography on silica gel (elu-
ent; ethyl acetate/hexane=1/2, v/v) to obtain syrupy
1
yield and 8b (0.26 g) in 30% yield. H NMR (CDCl3)
for 8a: l, 1.90–2.60 (m, 3H, H-2, 2% and OH), 3.38 (s,
3H, OCH3), 3.5–4.0 (m, 4H, H-3, 4, 5 and 5%), 5.07 (d,
J=5.3 Hz, 1H, H-1). 1H NMR (CDCl3) for 8b: l,
2.0–2.5 (m, 2H, H-2 and 2%), 2.9–3.1 (br s, 1H, OH),
3.38 (s, 3H, OCH3), 3.6–3.8 (br m, 2H, H-5 and 5%),
4.0–4.3 (m, 2H, H-3 and 4), 5.09 (dd, J=2.1 and 5.0
Hz, 1H, H-1). Anal. Calcd for C6H11N3O3: C, 41.61; H,
6.40; N, 24.27. Found: C, 41.65; H, 6.32; N, 24.25.
1
product 7 (2.74 g) in 93% yield. H NMR (CDCl3): l,
1.5. Methyl 3-azido-2,3-dideoxy-5-O-p-toluenesulfonyl-
b-D-erythro-pentofuranoside (9)
1.9–2.2 (m, 2H, H-2 and 2%), 2.86 and 2.91 (2s, 2H, H-5
and 5%), 3.28 (s, 3H, OCH3), 3.9–4.3 (m, 2H, H-3 and
4), 5.03 (dd, J=4.8 and 2.0 Hz, 1H, H-1), 7.2–7.6 (m,
15H, aroma).
To a solution of 8b (1.10 g) in pyridine (15 mL) was
added p-toluenesulfonyl chloride (1.2 g), and the reac-
tion and wash-up were the same as that for compound
8. Compound 9 was purified by column chromatogra-
phy on silica gel (ethyl acetate/hexane=1/2, v/v) (1.85
1.4. Methyl 3-azido-2,3-dideoxy-a- and b- -erythro-
D
pentofuranoside (8)
1
g, 98%). H NMR (CDCl3): l, 1.9–2.4 (m, 2H, H-2,2%),
To a solution of 7 (2.0 g) in dried methanol (10 mL)
was added HCl in methanol solution (0.5 wt%, 0.4 mL),
and the mixture was stirred for 1 h at 40–50 °C. The
reaction mixture was neutralized with lead carbonate
and left overnight in a refrigerator. The precipitate was
2.45 (s, 3H, CH3 of tosyl), 3.27 (s, 3H, OCH3), 3.9–4.2
(m, 4H, H-3,4,5, and 5%), 5.01 (dd, J=1.9 and 4.7 Hz,
1H, H-1), 7.31 and 7.84 (2H each, 2 br d, J=8.3 Hz,
C6H4ꢁS).

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T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291
1.6. Methyl 3-acetamido-2,3-dideoxy-5-O-p-toluene-
sulfonyl-b- -erythro-pentofuranoside (11)
(br d, J=4.6 Hz, 1H, H-1), 7.9 (br d, J=7.1 Hz, 1H,
NH). Anal. Calcd for C13H26NO5P: C, 50.81; H, 8.53;
N, 4.56. Found: C, 50.83; H, 8.50; N, 4.55.
D
To a solution of 9 (1.85 g) in dried toluene (100 mL)
was added n-Bu3SnH (2.17 g) under a nitrogen atmo-
sphere at 120 °C for 15 min. Concentration of the
reaction mixture afforded compound 10, which was
dissolved in pyridine (10 mL). Acetic anhydride (0.75
mL) was added, the reaction mixture stirred for
overnight at room temperature, and then the solvents
were removed under reduced pressure. The crude prod-
ucts was dissolved in acetonitrile, and excess organo tin
was removed by hexane extraction (several times). The
syrupy crude product was dissolved in CHCl3, and the
organic layer was washed with water, dried over anhy-
drous sodium sulfate, and evaporated. The product was
purified by column chromatography on silica gel (ethyl
acetate/methanol=10/1, v/v) and gave pure 11 in 89%
1.9. Preparation of phospha sugar derivatives (16)
To a solution 13 (776 mg) in dry THF (25 mL) SDMA
(70% in toluene, 1.2 g) was added at 0 °C, and the
mixture was stirred for 1 h. A small amount of water
containing concd HCl was added. The precipitate was
filtered off, the filtrate was evaporated in vacuo. The
residue was purified by column chromatography on
silica gel (ethylacetate/methanol=3/1, v/v) to give
syrupy compound 14 (305 mg). This syrup was immedi-
ately dissolved in water containing a small amount of
THF and hydrochloric acid (0.2 mL) was added. The
mixture was heated under nitrogen for 3.5 h at 110 °C
(bath temp.). The mixture was cooled, diluted with
water, and the acid neutralized with Amberlite IR-45A
ion-exchenge resin, and filtered. The resin was washed
with water and ethanol and filtered. The filtrates were
combined, and evaporated in vacuo to give syrupy 15
(223 mg). This syrup was treated with acetic anhydride
(1.0 mL) in dry pyridine (15 mL). Pyridine was evapo-
rated in vacuo to give syrupy 16. This syrup was
immediately purified by column chromatography on
silica gel (ethylacetate/methanol=2/1, v/v), and sepa-
rated by column chromatography on silica gel (ethylac-
etate/methanol=4/1–2/1, v/v) to give 16a–d. Chemical
yields of 16a, 16b, 16c and 16d were 59 mg (7% from
13), 46 mg (5%), 44 mg (5%), and 90 mg (11%),
respectively. and optical rotations were [h]D −21.7° (c
1.15) for 16a, −34.5° (c 1.45) for 16b, −28.1° (c 1.78)
for 16c, and −66.4° (c 1.28) for 16d in CHCl3, respec-
tively. Anal. Calcd for C14H24NO6P (16a): C, 50.45; H,
7.26; N, 4.20. Found: C, 50.40; H, 7.29; N, 4.22. Anal.
Calcd for C14H24NO6P (16b): C, 50.45; H, 7.26; N,
4.20. Found: C, 50.44; H, 7.24; N, 4.25. Anal. Calcd for
C14H24NO6P (16c): C, 50.45; H, 7.26; N, 4.20. Found:
C, 50.44; H, 7.26; N, 4.22. Anal. Calcd for C14H24NO6P
(16d): C, 50.45; H, 7.26; N, 4.20. Found: C, 50.48; H,
7.20; N, 4.21.
1
yield. H NMR (CDCl3): l, 1.9–2.3 (m, 2H, H-2,2%),
1.92 (s, 3H, NꢁAc), 2.44 (s, 3H, CH3 of tosyl), 3.16 (s,
3H, OCH3), 3.9–4.6 (m, 4H, H-3, 4. 5, and 5%), 4.98 (d,
J=3.7 Hz, 1H, H-1), 3.89 (br d, J=7.5 Hz, 1H, NH),
7.31 and 7.84 (2H each, 2br d, J=8.3 Hz, C6H4ꢁS).
Anal. Calcd for C15H21NO6S: C, 52.46; H, 6.16; N,
4.08. Found: C, 52.44; H, 6.19; N, 4.10.
1.7. Methyl 3-acetamido-2,3,5-trideoxy-5-iodo-b-D-ribo-
furanoside (12)
A mixture of compound 11 (1.97 g) and sodium iodide
(1.8 g) in acetone (30 mL) in a sealed tube was heated
for 4 h in a boiling water bath, and precipitate was
filtered, the filtrate was concentrated. The residue was
dissolved in chloroform and washed with water. The
water layer was further extracted with chloroform. The
organic layer was collected, dried over anhydrous
sodium sulfate, and evaporated to afford crystalline 12
1
(1.43 g) in 96% yield. H NMR (CDCl3): l, 1.9–2.6 (m,
2H, H-2 and 2%), 1.98 (s, 3H, NꢁAc), 3.2–3.5 (m, 2H,
H-5,5%), 3.39 (s, 3H, OMe), 3.9–4.7 (m, 2H, H-3,4),
5.08 (dd, J=1.3 and 5.3 Hz, 1H, H-1), 6.10 (br s, 1H,
NH).
1.8. Methyl 3-acetamido-2,3,5-trideoxy-5-C-(ethoxyiso-
propylphosphinyl)-b- -erythro-pentofuranoside (13)
D
The mixture of 12 (1.09 g) and diethyl isopropylphos-
phonite (10 mL) was heated at 150 °C for 8 h. Excess
amount of phosphonite was remove under reduced
pressure, and crude product 13 was purified by column
chromatography on silica gel (ethyl acetate/methanol=
2. Supplementary material
Full crystallographic details excluding structure features
have been deposited with the Cambridge Crystallo-
graphic Data Centre (CCDC). These data may be
obtained, on request, from The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
1
10/1, v/v) to afford in quant. yield. H NMR (CDCl3):
l, 1.0–1.4 (m, 10H, PꢁCH(CH3)2 and PꢁOCCH3), 1.6–
2.4 (m, 4H, H-2,2%,5, and 5%). 1.97 (s, 3H, NꢁAc), 3.33
(s, 3H, OCH3), 3.8–4.6 (m, 4H, H-3,4,PꢁOCH2), 4.97

T. Oshikawa et al. / Carbohydrate Research 338 (2003) 283–291
Nakashima, T. J. Org. Chem. 1985, 50, 3516–3521;
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