Stereoselective synthesis of the isosteric phosphono analogues of N-acetyl-α-D-glucosamine 1-phosphate and N-acetyl-α-D-mannosamine 1-phosphate

Article abstract of DOI:10.1021/jo9519468

The isosteric phosphono analogues of N-acetyl-α-D-glucosamine 1-phosphate and N-acetyl-α-D-mannosamine 1-phosphate (1 and 2) are stereoselectively synthesized starting from 2,3,5-tri-O-benzyl-D-arabinose (3b). Reaction of 3b with divinylzinc stereoselectively affords the glucoenitol 4c, the mercuriocyclization and subsequent iododemercuriation of which stereoselectively afford the α-C-glucopyranosyl iodide 6b with a free hydroxyl group at C-2. Temporary protection of the hydroxyl group and treatment with triethyl phosphite converts 6b into the corresponding phosphonate 7b. The free hydroxyl group of 7b is then converted into an acetamido group by oximation, acetylation of the oxime, reduction, and subsequent acetylation. The reduction of the oxime with diborane stereoselectively affords the gluco isomer, whereas catalytic hydrogenation gives the manno isomer. Acetylation and deprotection afford the desired products 1 and 2.

Full text of DOI:10.1021/jo9519468

3428
J . Org. Chem. 1996, 61, 3428-3432
Ster eoselective Syn th esis of th e Isoster ic P h osp h on o An a logu es of
N-Acetyl-r-D-glu cosa m in e 1-P h osp h a te a n d
N-Acetyl-r-D-m a n n osa m in e 1-P h osp h a te
Fiorenzo Casero, Laura Cipolla, Luigi Lay, Francesco Nicotra,* Luigi Panza, and
Giovanni Russo
Universita` degli Studi di Milano, Dipartimento di Chimica Organica e Industriale, Centro di Studio sulle
Sostanze Organiche Naturali del CNR, Via Venezian 21, I-20133 Milano (I), Italy
Received November 1, 1995X
The isosteric phosphono analogues of N-acetyl-R-D-glucosamine 1-phosphate and N-acetyl-R-D-
mannosamine 1-phosphate (1 and 2) are stereoselectively synthesized starting from 2,3,5-tri-O-
benzyl-D-arabinose (3b). Reaction of 3b with divinylzinc stereoselectively affords the glucoenitol
4c, the mercuriocyclization and subsequent iododemercuriation of which stereoselectively afford
the R-C-glucopyranosyl iodide 6b with a free hydroxyl group at C-2. Temporary protection of the
hydroxyl group and treatment with triethyl phosphite converts 6b into the corresponding
phosphonate 7b. The free hydroxyl group of 7b is then converted into an acetamido group by
oximation, acetylation of the oxime, reduction, and subsequent acetylation. The reduction of the
oxime with diborane stereoselectively affords the gluco isomer, whereas catalytic hydrogenation
gives the manno isomer. Acetylation and deprotection afford the desired products 1 and 2.
Glycosyl phosphates play a central role in the metabo-
N-acetyl-R-D-mannosamine 1-phosphate is another gly-
cosyl phosphate of great interest. It is involved in the
biosynthesis of N-acetylneuraminic acid, a component of
many tumor-associated oligosaccharides and in the bio-
synthesis of many bacterial polysaccharides repeating
units.
lism of carbohydrates. They act as glycosyl donors in the
biosynthesis of oligo- and polysaccharides and glycocon-
jugates, and in some cases they also perform the role of
metabolic regulators.1
N-acetyl-R-D-glucosamine 1-phosphate is a glycosyl
phosphate of particular interest, being the key interme-
diate in the biosynthesis of the N-linked glycoproteins,
a class of glycoproteins involved in many important cell-
cell and cell-pathogen recognition phenomena. Phar-
macologically important examples of these phenomena
are HIV-lymphocyte T adhesion or tumor cells-selectin
adhesion. The first step in the biosynthesis of the
N-linked glycoproteins is the conversion of N-acetyl-R-
D-glucosamine 1-phosphate into UDP-GlcNAc which is
then converted into the dolichyl-N-acetyl-R-D-glucosamine
1-diphosphate. Further glycosylations afford a dolichyl
diphosphate oligosaccharide which is then transferred to
an asparagine residue of the protein. Other important
processes involving N-acetyl-R-D-glucosamine 1-phos-
phate are the biosynthesis of mureine and teichoic acids,
the main components of the bacterial cell walls. More-
over, it has been recently shown that N-acetyl-R-D-
glucosamine 1-phosphate is involved in a glycosylation-
deglycosylation of some proteins, an abundant and
dynamic process the role of which is not clear2 and is
presently under investigation. In light of this evidence,
there is a great interest in the synthesis of inhibitors or
regulators of the metabolic processes in which N-acetyl-
R-D-glucosamine 1-phosphate is involved. These mol-
ecules could interfere in the cell-pathogen adhesion
phenomena and in the formation of bacterial cell wall.
Furthermore, they could spread light on the recently
discovered dynamic glycosylation process.
Antimetabolites of natural phosphates have been
obtained by substituting the oxygen of the phosphoesteric
linkage with a carbon atom. The geometry of the so
modified molecules, defined isosteric phosphono ana-
logues, is approximately the same of that of the parent
natural phosphate.3 So, these analogues fit the active
sites or receptors of the parent substrate. However, they
cannot undergo the cleavage of the phosphoesteric bond,
which is the main metabolic transformation, and this
often results in an inhibition of the metabolic process.
The synthesis of isosteric phosphono analogues of
glycosyl phosphates requires the formation of a C-
glycosidic bond with the desired stereochemistry. Many
examples have been described by us4 and others,5 but the
analogue of N-acetyl-R-D-glucosamine 1-phosphate has
never been synthesized, despite its biological importance.
We recently described the synthesis of the phosphono
analogue 2 of N-acetyl-R-D-mannosamine 1-phosphate,6
the first example of a phosphono analogue of an amino-
sugar. Now we describe our efforts in the synthesis of
the phosphono analogues of N-acetyl-R-D-glucosamine
1-phosphate (1) and N-acetyl-R-D-mannosamine 1-phos-
(3) Engel, R. Chem. Rev. 1977, 77, 350.
(4) (a) Nicotra, F.; Ronchetti, F.; Russo, G. J . Org. Chem. 1982, 47,
4459. (b) Nicotra, F.; Perego, R.; Ronchetti, F.; Russo, G.; Toma, L.
Carbohydr. Res. 1984, 131, 180. (c) Nicotra, F.; Panza, L.; Russo, G.;
Senaldi, A.; Burlini, N.; Tortora, P. J . Chem. Soc., Chem. Commun.
1990, 1396.
(5) (a) Chmielewski, M.; BeMiller, J . N.; Cerretti, D. P. Carbohydr.
Res. 1981, 97, C1. (b) McClard, R. W. Tetrahedron Lett. 1983, 24, 2631.
(c) Maryanoff, B. E.; Nortey, S. O.; Inners, R. R.; Campbell, S. A.; Reitz,
A. B. Carbohydr. Res. 1987, 171, 259. (d) Meuwly, R.; Vasella, A. Helv.
Chim. Acta 1986, 69, 751. (e) Maryanoff, B. E.; Nortey, S. O.; Inners,
R. U.; Campbell, S. A.; Reitz, A. B. Carbohydr. Res. 1987, 171, 259. (f)
Frische, K.; Schmidt, R. R. Liebigs Ann. Chem. 1994, 297. (g) Meyer,
R. B., J r.; Stone, T. E.; J esti, P. K. J . Med. Chem. 1984, 27, 1095.
(6) Cipolla, L.; Lay, L.; Nicotra, F.; Russo, G.; Panza, L. J . Chem.
Soc., Chem. Commun. 1995, 1993.
* To whom correspondence should be addressed. Tel.: +39.2.2367613.
Fax: +39.2.2364369. E-mail: panza@icil64.cilea.it.
X Abstract published in Advance ACS Abstracts, April 15, 1996.
(1) Hers, H. G. Biochem. Soc. Trans. 1984, 12, 729.
(2) (a) Hart, G. W. Curr. Op. Cell Biol. 1992, 4, 1017. (b) Hart, G.
W; Kelly, W. G.; Blomberg, M. A.; Roquemore, E. P.; Dong, L.-Y. D.;
Kreppel, L.; Chou, T.-Y.; Snow, D.; Greis, K. 44. Colloquium Mosbach
1993, DNA Replication and the Cell Cycle; Springer-Verlag: Berlin
Heidelberg, 1993.
S0022-3263(95)01946-3 CCC: $12.00 © 1996 American Chemical Society

Phosphono Analogues of N-Acetyl-R-D-glucosamine 1-Phosphate
J . Org. Chem., Vol. 61, No. 10, 1996 3429
Ch a r t 1
Sch em e 2
Sch em e 1
Ch a r t 2
phate (2), affording alternatively each of the two mol-
ecules in a stereoselective manner (Chart 1).
Resu lts a n d Discu ssion
The most straightforward way to prepare the isosteric
phosphono analogue of a glycosyl phosphate is the
reaction of the protected aldose A with the ylide
(diphenylphosphoranylidine)methanephosphonate5b or
with the anion of a tetraalkyl methylenediphosphonate.5c
This reaction affords directly the desired C-glycosyl
methylenephosphonate C by spontaneous Michael cy-
clization of the R,â-phosphonate intermediate B (Scheme
1, path a). Unfortunately, this process lacks stereose-
lection and it is not generally applicable.5c So, after some
preliminary attempts to apply this reaction to glu-
cosamino derivatives, we decided to effect the synthesis
of the phosphono analogue of N-acetyl-R-D-glucosamine
1-phosphate following the more general procedure which
requires the preparation of a C-glycosyl halide E and its
conversion into a phosphonate C by reaction with a
trialkyl phosphite (Scheme 1, path b).
The synthesis of a C-glycosyl halide E can be easily
and stereoselectively effected by reaction of a properly
protected aldose A with methylenetriphenylphosphorane
and subsequent electrophilic cyclization of the obtained
glycoenitol D (Scheme 1).7 In the case of glucosamine
this procedure is troublesome: in fact, the reaction of
methylenetriphenylphosphorane with properly protected
glucosamino derivatives did not afford the desired ami-
noglucoenitol.8 An interesting alternative to obtain an
aminoglucoenitol is the reaction of N-benzyl-N-(2,3,5-tri-
O-benzyl-D-arabinofuranosyl)amine (3a ) with vinylmag-
nesium bromide (Scheme 2).9 The reaction affords ste-
reoselectively the aminoglucoenitol 4a , the cyclization of
which with mercuric trifluoroacetate gives the R-C-
glucopyranoside 5a .10 We made different attempts to
convert the mercurio derivative 5a into the corresponding
halide. Br2 or I2 in CH2Cl2, in THF-NaHCO3, or in
THF-H2O-pH 4 (citric buffer) and NBS and NIS in CH2-
Cl2 gave unsatisfactory results. In addition, the direct
halocyclization of 4a , tested with the reagents reported
above, was unsuccessful. In the hypothesis that the
nucleophilic character of the amino function of 5a ,
adjacent to the electrophilic carbon of the desired halide,
interferes in the reaction,10 we also lowered its nucleo-
philicity by conversion into an acetamide. This required
the selective acetylation of the open chain precursor 4a
and the subsequent mercuriocyclization of the obtained
product 4b, as 5a was inert to acetylation, also under
drastic conditions (Ac2O, Et3N, DMAP, in toluene).
Unfortunately, the N-acetylated mercurio derivative 5b
also gave unsatisfactory results in the halodemercuria-
tion, whereas treatment of 4b with iodine in THF at pH
4 afforded the very labile iodo derivative 6a , which
decomposes when refluxed with P(OEt)3.
To overcome all these difficulties, we decided to follow
a different synthetic strategy, in which the amino func-
tion is introduced in the molecule after the phosphono
function. The strategy requires the synthesis of an R-C-
glucopyranoside with a deprotected hydroxyl group at
C-2, which is converted into an amino function at the end
of the synthesis. This can be done by stereoselective
vinylation of 2,3,5-tri-O-benzyl-D-arabinose (3b) with
divinylzinc and subsequent stereoselective cyclization of
the obtained enitol 4c. We observed that the direct
iodocyclization of a glucoheptenitol such as 4c occurs with
a debenzylation to afford a furanosidic product.11 The
cyclization of 4c was then effected with mercuric acetate,
and the R-C-glucopyranosyl mercurio derivative 5c12 was
easily converted into the corresponding stabile iodide 6b.
The conversion of 6b into the corresponding phosphonate
required the temporary protection of the free hydroxyl
group at C-2; in fact, direct treatment with P(OEt)3 under
reflux afforded 11 (Chart 2). So, the free hydroxyl group
of 6b was protected as tert-butyldimethylsilyl ether 6c,
and the Arbuzov reaction afforded the phosphonate 7a .
Desilylation of 7a by treatment with trifluoroacetic acid
gave the desired R-C-glucopyranosylmethanephospho-
nate 7b, with a free hydroxyl group at C-2 (Scheme 3).
The conversion of a free hydroxyl group at C-2 of a
glucopyranoside into an amino function is a well-
(7) (a) Pougny, G.-R.; Nassr, M. A.; Sinay¨, P. J . Chem. Soc., Chem.
Commun. 1981, 375. (b) Nicotra, F.; Perego, R.; Ronchetti, F.; Russo,
G.; Toma, L. Gazz. Chim. Ital. 1984, 114, 193.
(8) We tested unfruitfully the reaction on 2-acetamido-2-deoxy-3,4,6-
tri-O-benzyl-D-glucopyranose and 2-amino-2-deoxy-3,4,6-tri-O-benzyl-
D-glucopyranose.
(9) (a) Carcano, M.; Nicotra, F.; Panza, L.; Russo, G. J . Chem. Soc.,
Chem. Commun. 1989, 297. (b) Lay, L.; Nicotra, F.; Panza, L.; Verani,
A. Gazz. Chim. Ital. 1992, 122, 345.
(10) The â-anomer of 5a , in which the two functional groups are
trans related, easily affords the corresponding iodo derivative by
treatment with I2 and NaHCO3.
(11) Nicotra, F.; Panza, L.; Ronchetti, F.; Russo, G.; Toma, L.
Carbohydr. Res. 1987, 171, 49.
(12) Boschetti, A.; Nicotra, F.; Panza, L.; Russo, G. J . Org. Chem.
1988, 53, 4181.

3430 J . Org. Chem., Vol. 61, No. 10, 1996
Casero et al.
Sch em e 3
In conclusion, the phosphono analogue of N-acetyl-R-
D-glucosamine 1-phosphate and N-acetyl-R-D-mannosa-
mine 1-phosphate (1 and 2), glycomimetics of great
biological interest, can be obtained following a procedure
in which the amino function is introduced at the end of
the synthesis. The procedure allows us to obtain stereo-
selectively the product with the gluco or the manno
configuration just by changing the reduction agent.
Exp er im en ta l Section
Gen er a l. 1H NMR and 13C NMR spectra were recorded
with TMS as internal reference. The signals of the aromatic
carbons in the 13C NMR spectra are not reported. [R]D values
were measured at 20 °C and are given in units of 10-1 deg
cm2 g-1
. Column chromatography was performed with the
flash procedure using silica gel 60 (230-400 mesh). TLC was
performed on silica gel 60 F254 plates and visualised by
spraying with a solution containing H2SO4 (31 mL), am-
monium molibdate (21 g), and Ce(SO4)2 (1 g) in water (500
mL) and then heating at 110 °C for 5 min.
established process; it can be effected by oxidation,
oximation, and reduction of the oxime to the correspond-
ing amine by catalytic hydrogenation or treatment with
diborane. It is also established that the process affords
stereoselectively a 2-aminosugar with the manno config-
uration if the anomeric center of the starting ketone is
â, whereas starting from the R-anomer, the gluco isomer
is preferentially formed.13 In our case, starting from an
R-C-glucopyranoside 7b, we expected the formation of the
amino derivative with a gluco configuration.
4,5,7-Tr i-O-ben zyl-D-glu co-1-h ep ten itol (4c). To a 1 M
solution in THF of the commercially available (Aldrich) vinyl-
magnesium bromide (36 mL, 36.0 mmol) was added a solution
in dry THF (10 mL) of dried ZnBr2 (4.01 g, 18.0 mmol). The
reaction mixture was stirred under N2 until the complete
formation of divinylzinc (30 min); via a double-ended needle a
solution of 2,3,5-tri-O-benzyl-â-D-arabinofuranose (3b) (3.0 g,
17.8 mmol) in dry THF (10 mL) was added to the organome-
tallic reagent. After 4 h the reaction was quenched with a
saturated NH4Cl solution; the organic phase was diluted with
CH2Cl2 and sequentially washed with 5% HCl, saturated
NaHCO3 solution, and water. The organic layer was then
dried over Na2SO4, filtered, and evaporated, giving 4c (quan-
titative) as a yellow oil that was used in the next step without
further purification.
C-(2-Hyd r oxy-3,4,6-t r i-O-b en zyl-r-D-glu cop yr a n osyl)-
ch lor om er cu r iom eth a n e (5c).15 To a solution of the glu-
coenitol 4c (3.2 g, 7.1 mmol) in dry THF (15 mL), under N2,
was added Hg(OAc)2 (2.3 g, 7.1 mmol) dissolved in 25 mL of
dry THF. The solution was stirred until the complete disap-
pearance of 4c (6 h), and then KCl (797 mg, 10.7 mmol)
dissolved in the minimum amount of water was added. After
30 min, the reaction mixture was diluted with EtOAc and
washed twice with water; the organic phase was then dried
over Na2SO4, filtered, and concentrated under reduced pres-
sure, yielding 4.9 g of crude product. Purification by flash
chromatography, eluting with 7:3 hexane:EtOAc, afforded 5c
(80%) as a pale yellow oil.
C-(2-Hyd r oxy-3,4,6-t r i-O-b en zyl-r-D-glu cop yr a n osyl)-
iod om eth a n e (6b). Under N2, to a solution of 5c (2.9 g, 4.2
mmol) in dry CH2Cl2 (10 mL), was added 65 mL of a solution
prepared dissolving iodine in dry CH2Cl2 (20 g/L). After 3 h
the reaction was recovered by adding 20 mL of water and
Na2S2O3 and stirred until the organic layer became colorless.
The reaction mixture was then washed first with brine and
after with water; the organic phase was dried over Na2SO4
and filtered and the solvent evaporated. The residual mercury
salts were removed by a simple filtration over a short column
of 70-230 mesh silica gel (h ) 5 cm, eluent 7:3 hexane:EtOAc).
After purification, 6b (2.4 g, quantitative) was obtained as a
colorless oil: [R]D +25.4° (c 1, CHCl3 ); 1H NMR (300 MHz,
CDCl3) δ 3.12 (d, 1H, J ) 9.1 Hz), 3.30 (t, 1H, J ) 10.2 Hz),
3.40 (dd, 1H, J ) 10.2, 5.5 Hz), 3.63 (t, 1H, J ) 4.0 Hz), 3.72-
3.79 (m, 2H), 3.80-3.88 (m, 2H), 4.03 (ddd, 1H, J ) 8.2, 5.8,
2.2 Hz), 4.11 (bdt, 1H, J ) 4.5, 3.5, Hz), 4.53-4.63 (m, 6H),
7.20-7.35 (m, 15H); 13C NMR (75.43 MHz, CDCl3) δ 4.42,
68.42, 68.94, 72.35, 73.16, 73.67, 73.98, 74.61, 75.00, 77.02.
Anal. Calcd for C28H31O5I: C, 58.52; H, 5.44. Found: C, 58.36;
H, 5.53.
7b was oxidized with DMSO-Ac2O to afford the ketone
8a 14 which was converted into the oxime 8b by treatment
with hydroxylamine at pH 4.5. The reduction of the
oxime was first effected by catalytic hydrogenation and
surprisingly afforded the product with the manno con-
figuration. When Pd(OH)2 was used as catalyst the
debenzylated manno derivative 9a was recovered quan-
titatively, whereas when Ni-Raney was used the benzy-
lated manno derivative 9b was obtained in 60% diaster-
eomeric excess. Yields and stereoselection did not change
when the corresponding methyloxime was reduced. These
results suggest a coordination of the R-oriented phospho-
nic group with the metal catalyst, which favors the attack
of the hydrogen from the R-face. The reduction of the
acetyloxime 8c with diborane in THF afforded on the
contrary the expected 2-amino-2-deoxy-R-C-glucopyra-
noside 10a in 64% diastereomeric excess. The diaster-
eomeric excesses were determined by 13C-NMR analysis
of the crude reaction mixture, and the pure isomers were
isolated after acetylation. The configuration of the new
stereocenter was easily attributed in view of the 1H-
coupling constants obtained by decoupling experiments
effected on the final deprotected products (see below).
The acetates 9c and 10b were deprotected by treat-
ment with Me3SiI to afford the phosphono analogues of
N-acetyl-R-D-glucosamine 1-phosphate and N-acetyl-R-
D-mannosamine 1-phosphate (1 and 2). The gluco isomer
1 shows a 10.5 Hz coupling constant between H-2 and
H-3, which indicates the axial orientation of these
hydrogen atoms, as required for a glucopyranosidic
structure in a 4C1 conformation. The manno isomer 2
shows on the contrary a 3.2 Hz coupling constant between
H-2 and H-3 and a 8.1 Hz coupling constant between H-3
and H-4. This indicates the axial orientation of H-3 and
the equatorial orientation of H-2, as required for a
4
mannopyranosidic structure in a C1 conformation.
(13) Lichtentaler, F. W.; Kaji, E. Liebigs Ann. Chem. 1985, 1659
and references cited therein.
(14) No epimerization occurred during the oxidation, as the reduc-
tion of 8a with NaBH4 gave back the starting compound 7b.
(15) We named C-glycoside by semisystematic names generally
accepted for this class of compounds; this allows an easier comparison
with the parent sugar.

Phosphono Analogues of N-Acetyl-R-D-glucosamine 1-Phosphate
J . Org. Chem., Vol. 61, No. 10, 1996 3431
C-(2-O-(ter t-Bu tyld im eth ylsilyl)-3,4,6-tr i-O-ben zyl-r-D-
glu cop yr a n osyl)iod om eth a n e (6c). 6b (2.4 g, 4.2 mmol)
was dissolved in dry DMF (20 mL) under N2, and then
imidazole (850 mg, 12.5 mmol) and TBDMSCl (940 mg, 6.2
mmol) were added; the mixture was stirred overnight. Solvent
was removed and the residue diluted with CH2Cl2. The
remaining solids were removed by filtration and the filtrate
concentrated, yielding 2.86 g of 6c (quantitative) as a yellow
oil that was used in the next step without further purification.
For the characterization an analytical sample was purified by
flash chromatography (eluent 8:2 hexane:EtOAc): [R]D +61.4°
1H, J ) 12.0 Hz), 4.49 (d, 1H, J ) 12.0 Hz), 4.55-4.74 (m,
3H), 4.83 (d, 1H, J ) 11.5 Hz), 5.01 (d, 1H, J ) 11.5 Hz), 7.17-
7.46 (m, 15H); 13C NMR (75.43 MHz, CDCl3) δ 17.00 (2C), 28.45
(J C-P ) 143.6 Hz), 62.51, 62.67, 70.39, 76.13, 76.45, 76.74,
77.31, 77.72, 78.14, 84.71, 207.70; 31P NMR (80.96 MHz,
CDCl3) δ 27.05. Anal. Calcd for C32H39O8P: C, 65.97; H, 6.75.
Found: C, 65.32; H, 6.48.
Dieth yl C-(3,4,6-tr i-O-ben zyl-r-D-a r a bin o-h exosu lop y-
r a n osyl)m eth a n ep h osp h on a te Oxim e (8b). A solution of
the ketone 8a (125 mg, 0.21 mmol) in THF/MeOH 1:1 (4 mL)
was treated with a buffer solution (1.7 mL) prepared with 1 g
of AcONa‚3H2O and 0.5 g of NH2OH‚HCl (the pH is eventually
adjusted to 4.5 by adding AcOH dropwise). After 1 h the
mixture was extracted with CH2Cl2, and the organic layer
washed sequentially with water, saturated NaHCO3, and
water to neutrality. The organic phase was dried over Na2-
SO4, filtered, and concentrated. The crude product (116 mg)
was purified by flash chromatography eluting with 2:8 hexane:
EtOAc, affording 106 mg of oxime 8b (82%), in a mixture of E
and Z isomers as white solid. NMR data refer to the more
abundant isomer: 1H NMR (300MHz, CDCl3) δ 1.28 (t, 3H, J
) 7.4 Hz), 1.30 (t, 3H, J ) 7.4 Hz), 2.36 (ddd, 1H, J ) 19.4,
10.0, 3.9 Hz), 2.49 (dt, 1H, J ) 15.5, 10.5 Hz), 3.57 (dd, 1H, J
) 10.1, 5.1 Hz), 3.66 (dd, 1H, J ) 10.1, 5.0 Hz), 3.83 (t, 1H, J
) 6.0 Hz), 4.01-4.15 (m, 5H), 4.29 (d, 1H, J ) 6.0 Hz), 4.51-
4.54 (m, 4H), 4.67 (d, 1H, J ) 11.5 Hz), 4.80 (d, 1H, J ) 11.9
Hz), 5.45 (dt, 1H, J ) 10.5, 3.9 Hz), 7.10-7.32 (m, 15H), 9.92
1
(c 1, CHCl3); H NMR (300 MHz, CDCl3) δ 0.09 (s, 3H), 0.11
(s, 3H), 0.88 (s, 9H), 3.38 (t, 1H, J ) 11.8 Hz), 3.49 (dt, 1H, J
) 9.6, 3.2 Hz), 3.58 (dd, 1H, J ) 11.8, 4.3 Hz), 3.61-3.68 (m,
2H), 3.75 (dd, 1H, J ) 21.4, 10.7 Hz), 3.76 (dd, 1H, J ) 21.4,
10.7 Hz), 3.88 (dd, 1H, J ) 9.6, 6.4 Hz), 4.02-4.12 (m, 1H),
4.44 (d, 1H, J ) 10.7 Hz), 4.55 (d, 1H, J ) 12.3 Hz), 4.64-
4.84 (m, 4H), 7.00-7.35 (m, 15H); 13C NMR (75.43 MHz,
CDCl3) δ -4.06 (2C), 2.73, 18.50, 26.46 (3C), 69.42, 72.05,
73.54, 74.26, 75.55, 75.94, 77.76, 78.53, 83.37. Anal. Calcd
for C34H45O5ISi: C, 59.29; H, 6.59. Found: C, 58.98; H, 6.55.
Diet h yl C-(2-O-(ter t-Bu t yld im et h ylsilyl)-3,4,6-t r i-O-
ben zyl-r-D-glu cop yr a n osyl)m eth a n ep h osp h on a te (7a ). A
solution of 6c (3.3 g, 4.8 mmol) in triethyl phosphite (30 mL)
was refluxed for 5 h. The solvent was removed under reduced
pressure, and the crude product (3.5 g) was purified by flash
chromatography eluting with a gradient of hexane:EtOAc 7:3
to 6:4 affording 2.6 g of 7a (77%) as a white solid: [R]D +28.4°
(c 1, CHCl3); mp 75-77 °C; 1H NMR (300 MHz, CDCl3) δ 0.08
(s, 3H), 0.10 (s, 3H), 0.85 (s, 9H), 1.20-1.30 (m, 6H), 2.12-
2.25 (m, 2H), 3.49 (t, 1H, J ) 8.6 Hz), 3.61-3.68 (m, 3H), 3.75
(dd, 1H, J ) 10.5, 2.5 Hz), 3.89 (ddd, 1H, J ) 8.7, 6.0, 2.7 Hz),
4.07 (q, 2H, J ) 7.1 Hz), 4.09 (q, 2H, J ) 7.1 Hz), 4.35-4.40
(m, 1H), 4.45 (d, 1H, J ) 10.4 Hz), 4.46 (d, 1H, J ) 12.1 Hz),
4.62 (d, 1H, J ) 12.1), 4.74 (d, 1H, J ) 10.4 Hz), 4.80 (d, 1H,
J ) 12.1 Hz), 4.84 (d, 1H, J ) 12.1 Hz), 7.15-7.38 (m, 15H);
13C NMR (50.29 MHz, CDCl3) δ -4.00, -3.93, 17.05, 17.08,
18.57, 22.45 (J C-P ) 146.0 Hz), 26.56, 62.04, 62.16, 62.33,
62.45, 69.57, 72.65, 73.20 (J C-P ) 6.0 Hz), 73.51, 74.33, 75.59,
76.03, 78.79, 83.54; 31P NMR (80.96 MHz, CDCl3) δ 29.94.
Anal. Calcd for C38H55O8PSi: C, 65.30; H, 7.93. Found: C,
65.53; H, 7.89.
Dieth yl C-(3,4,6-Tr i-O-ben zyl-r-D-glu copyr an osyl)m eth -
a n ep h osp h on a te (7b). A solution in CH2Cl2 (40 mL) of 7a
(2.6 g, 3.7 mmol) was cooled to 0 °C, and a mixture of 9:1 CF3-
COOH/H2O (1.5 mL) was added. The reaction was stirred
overnight; the mixture was then sequentially washed with
saturated NaHCO3 and water. The organic layer was dried
over Na2SO4 and filtered and the solvent evaporated. The
crude product was purified by flash chromatography (eluent
hexane:EtOAc 2:8), and 7b was obtained (2.0 g, 93%) as a
white solid: [R]D +38.3° (c 0.76, CHCl3); mp 79-81 °C; 1H
NMR (300 MHz, C6D6) δ 1.02-1.08 (m, 6H), 2.26 (ddd, 1H, J
) 18.0, 15.5, 7.7 Hz), 2.41 (ddd, 1H, J ) 18.0, 15.6, 5.9 Hz),
3.71 (t, 1H, J ) 5.5 Hz), 3.77 (t, 1H, J ) 5.5 Hz), 3.81-3.91
(m, 4H), 3.94-4.05 (m, 4H), 4.14 (dd, 1H, J ) 4.9, 9.8 Hz),
4.38-4.59 (m, 6H), 4.61-4.66 (m, 1H), 7.01-7.30 (m, 15H);
13C NMR (75.43 MHz, CDCl3) δ 16.96, 27.00 (J C-P ) 142.6 Hz),
62.47 (2C), 62.75, 67.91, 68.88, 69.90 (J C-P ) 9.0 Hz), 73.40,
73.76, 73.97, 74.71, 74.96, 77.63; 31P NMR (80.96 MHz, CDCl3)
δ 30.08. Anal. Calcd for C32H41O8P: C, 65.74; H, 7.07.
Found: C, 65.71; H, 6.99.
Dieth yl C-(3,4,6-tr i-O-ben zyl-r-D-a r a bin o-h exosu lop y-
r a n osyl)m eth a n ep h osp h on a te (8a ). A mixture of 7b (2.0
g, 3.4 mmol) and 3:2 DMSO:Ac2O (15 mL) was stirred
overnight. The reaction was quenched by adding ice-cold
water and extracted with CH2Cl2. The organic phase was then
washed with saturated NaHCO3 and water to neutrality, dried
over Na2SO4, and filtered and the solvent evaporated. The
crude product (2.0 g) was purified by flash chromatography
eluting with 2:8 hexane:EtOAc affording ketone 8a (1.6 g, 81%)
as oil: [R]578 +32.7° (c 1.4, CHCl3); 1H NMR (200 MHz, CDCl3)
δ 1.28 (t, 3H, J ) 7.1 Hz), 1.30 (t, 3H, J ) 7.1 Hz), 2.20 (ddd,
1H, J ) 17.0, 15.0, 6.3 Hz), 2.29 (ddd, 1H, J ) 17.0, 15.0, 5.5
Hz), 3.59 (dd, 1H, J ) 10.8, 3.6 Hz), 3.68 (dd, 1H, J ) 10.8,
2.5 Hz), 3.98 (t, 1H, J ) 7.5 Hz), 4.02-4.18 (m, 6H), 4.37 (d,
(bs, 1H); 13
C NMR (75.43 MHz, CDCl3) δ 16.97 (2C), 26.42 (J C-P
) 140.9 Hz), 62.56 (2C), 66.59, 70.85, 72.18, 72.54, 73.51, 74.31,
76.80, 77.80, 155.34;
31P NMR (80.96 MHz, CDCl3) δ 28.13,
30.97 for the E and Z isomers. Anal. Calcd for C32H40NO8P:
C, 64.31; H, 6.75; N, 2.34. Found: C, 64.01; H, 6.83; N, 2.45.
Dieth yl C-(3,4,6-Tr i-O-ben zyl-r-D-a r a bin o-h exosu lop y-
r a n osyl)m eth a n ep h osp h on a te Acetyloxim e (8c). To a
solution of 8b (300 mg, 0.50 mmol) in dry CH2Cl2 (5 mL) were
added catalytic DMAP, pyridine (324 µL, 4.0 mmol), and Ac2O
(190 µL, 2.0 mmol). After 1 h the solvent was evaporated and
the crude product purified by flash chromatography (eluent
hexane:EtOAc 3:7), affording 320 mg of 8c (quantitative).
NMR data refer to the more abundant isomer. 1H NMR (300
MHz, CDCl3) δ 1.14-1.32 (m, 6H), 2.20 (s, 3H), 2.41-2.57 (m,
2H), 3.58 (dd, 1H, J ) 10.4, 5.2 Hz), 3.64 (dd, 1H, J ) 10.4,
5.2 Hz), 3.89 (dd, 1H, J ) 6.5, 5.2 Hz), 4.01-4.15 (m, 4H), 4.44
(d, 1H, J ) 6.5 Hz), 4.49-4.54 (m, 4H), 4.57 (d, 1H, J ) 11.7
Hz), 4.70 (d, 1H, J ) 11.6 Hz), 4.88 (d, 1H, J ) 11.7 Hz), 5.41
(dt, 1H, J ) 10.4, 4.3 Hz), 7.12-7.40 (m, 15H); 13C NMR (54.29
MHz, CDCl3) δ 16.71 (2C), 19.65, 23.80 (J C-P ) 126.9 Hz),
62.30 (2C), 67.11, 70.73, 72.96, 73.88 (2C), 74.62, 77.00, 77.70,
158.00, 167.98. Anal. Calcd for C34H42NO9P: C, 63.84; H,
6.62; N, 2.19. Found: C, 63.57; H, 6.79; N, 2.34.
Dieth yl C-(2-Am in o-2-deoxy-r-D-m an n opyr an osyl)m eth -
a n ep h osp h on a te (9a ). Product 8b (76 mg, 0.13 mmol)
dissolved in MeOH (5 mL) was hydrogenated, in the presence
of HCl 2N (0.13 mmol, 65 µL), using Pd(OH)2
as catalyst (10%
in weight, 8 mg). The reaction was monitored by TLC using
as eluent 2:8 hexane:EtOAc to detect the starting material and
7:3:1 EtOAc:n-PrOH:H2O to detect the formation of the
product. The suspension was then filtered over a Celite pad,
and the solvent evaporated affording 46 mg of 9a ‚HCl (quan-
titative) as a hygroscopic white solid: [R]578
+18.3° (c 0.6, H2O);
1H NMR (300 MHz, Py-d5) δ 1.28 (t, 6H, J ) 7.0 Hz), 2.84 (dt,
1H, J ) 15.5, 7.4 Hz), 2.93 (dt, 1H, J ) 15.5, 5.2 Hz), 4.05-
4.47 (m, 9H), 4.49 (bd, 1H, J ) 3.9 Hz), 4.61 (t, 1H, J ) 8.1
Hz), 4.91 (dd, 1H, J ) 8.1, 3.9 Hz), 5.47 (m, 1H), 6.65 (bs, 3H);
13C NMR (75.43 MHz, D2O) δ 16.41 (2C), 25.86 (J C-P ) 141.0
Hz), 55.69 (J C-P ) 14.6 Hz), 61.01 (2C), 64.61, 66.89, 67.61,
70.11, 74.50; 31P NMR (80.96 MHz, D2O) δ 29.85. Anal. Calcd
for C11H25ClNO7P: C, 37.78; H, 7.20; N, 4.00. Found: C, 37.54;
H, 7.12; N, 3.87.
Dieth yl C-(2-Am in o-2-deoxy-3,4,6-tr i-O-ben zyl-r-D-m an -
n op yr a n osyl)m eth a n ep h osp h on a te (9b). To a solution of
8b (112 mg, 0.18 mmol) in MeOH (10 mL) was added a Ni-
Raney suspension (20 mg) in water. The solution was stirred
under hydrogen atmosphere overnight. The TLC of the
reaction mixture (eluent EtOAc:CH2Cl2:MeOH 7:5:1) revealed
the presence of two products, the manno and the gluco isomers,

3432 J . Org. Chem., Vol. 61, No. 10, 1996
Casero et al.
1
in a 4:1 ratio, determined by H NMR spectra of the mixture.
solvent evaporated, and the residue washed with Et2O. The
product was purified by crystallization (EtOH/EtOAc) (24 mg,
quantitative) and then dissolved in water and lyophilized,
affording a white hygroscopic solid: [R]D +51.0° (c 1, H2O);
1H NMR (300 MHz, D2O) δ 2.08 (ddd, 1H, H-1a′, J ) 21.2,
17.5, 2.5 Hz), 2.12 (s, 3H, CH3CO), 2.40 (dt, 1H, H-1b′, J )
17.5, 11.3 Hz), 3.57 (t, 1H, H-4, J ) 9.1 Hz), 3.71 (dt, 1H, H-5,
J ) 9.1, 3.4 Hz), 3.78 (dd, 1H, H-3, J ) 10.5, 9.1 Hz), 3.83-
3.92 (m, 2H, H-6a, H-6b), 4.04 (dd, 1H, H-2, J ) 10.5, 5.0 Hz),
4.52-4.57 (m, 1H, H-1); 13C NMR (75.43 MHz, D2O) δ 22.76,
24.60 (J C-P ) 139.1 Hz), 54.19, (J C-P ) 12.1 Hz), 61.37, 70.36,
71.06 (2C), 73.81, 175.36; 31P NMR (80.96 MHz, D2O) δ 27.83.
Anal. Calcd for C9H18NO8P: C, 36.13; H, 6.06; N, 4.68.
Found: C, 36.43; H, 6.25; N, 4.54.
C-(2-Acet a m id o-2-d eoxy-r-D-m a n n op yr a n osyl)m et h -
a n ep h osp h on ic Acid (2). The same procedure described for
the preparation of 1 was used for the hydrolysis of 10b
(quantitative yield from 55 mg, 0.09 mmol of 9c): [R]D +9.0°
(c 0.5, H2O); 1H NMR (300 MHz, D2O) δ 2.20 (s, 3H, CH3CO),
2.24-2.45 (m, 2H, H-1a′, H-1b′), 3.77-3.79 (m, 2H, H-4, H-5),
3.94 (dd, 1H, H-6a, J ) 9.7, 2.6 Hz), 4.00 (dd, 1H, H-6b, J )
9.7, 3.9 Hz), 4.15 (dd, 1H, H-3, J ) 8.1, 3.2 Hz), 4.33-4.41 (m,
1H, H-1), 4.50 (t, 1H, H-2, J ) 3.2 Hz); 13C NMR (75.43 MHz,
D2O) δ 22.85, 28.44 (J C-P ) 135.9 Hz), 53.55 (J C-P ) 12.8 Hz),
61.10, 67.98, 69.84, 72.51, 75.05, 175.29; 31P NMR (80.96 MHz,
D2O) δ 26.68. Anal. Calcd for C9H18NO8P: C, 36.13; H, 6.06;
N, 4.68. Found: C, 36.28; H, 6.12; N, 4.76.
The suspension was filtered over a Celite pad and the crude
product (120 mg) used in the next step. The two C-2 epimers
were separated after acetylation of the amino group.
Dieth yl C-(2-Aceta m id o-2-d eoxy-3,4,6-tr i-O-ben zyl-r-D-
m a n n op yr a n osyl)m eth a n ep h osp h on a te (9c). The crude
product 9b (120 mg) was dissolved in dry CH2Cl2, and pyridine
(48 µL, 0.60 mmol), Ac2O (26 µL, 0.30 mmol), and a catalytic
amount of DMAP were added. After 1 h the reaction was
recovered by evaporating the solvent; the residue (110 mg) was
purified by flash chromatography (eluent EtOAc:CH2Cl2:
MeOH 5:5:0.5), affording 59 mg of the acetylated mannosamine
9c and 14 mg of the acetylated glucosamine 10b as byproduct,
in a 65% overall yield from 8b. Both products are white
solids: [R]D +19.9° (c 0.85, CHCl3); 1H NMR (300 MHz, C6D6)
δ 1.04 (t, 3H, J ) 7.3 Hz), 1.09 (t, 3H, J ) 7.3 Hz), 1.53 (s,
3H), 2.12-2.20 (m, 2H), 3.70-4.09 (m, 9H), 4.31-4.70 (m, 7H),
4.83 (m, 1H), 5.94 (d, 1H, J ) 10.5 Hz), 7.00-7.30 (m, 15H);
13C NMR (54.29 MHz, CDCl3) δ 16.90, 17.01 23.93, 29.16 (J C-P
) 141.0 Hz), 49.67 (J C-P ) 13.7 Hz), 62.62, 62.74, 69.07, 69.27,
72.53, 73.01, 73.64, 74.03, 74.27, 76.90, 170.41; 31P NMR (80.96
MHz, CDCl3) δ 29.03. Anal. Calcd for C34H44NO8P: C, 65.27;
H, 7.09; N, 2.24. Found: C, 65.42; H, 7.04; N, 2.43.
Dieth yl C-(2-Am in o-2-d eoxy-3,4,6-tr i-O-ben zyl-r-D-glu -
cop yr a n osyl)m eth a n ep h osp h on a te (10a ). A solution of 8c
(320 mg, 0.50 mmol) in dry THF (5 mL) was cooled to -5 °C,
and under N2, a 1 M solution of diborane in THF (2 mL) was
added. The reaction was allowed to warm to room tempera-
ture and after complete disappearance of the starting material
MeOH was added dropwise until the borane in excess was
destroyed. The solution was concentrated and the residue
diluted with CH2Cl2; the organic phase was washed with
water, dried over Na2SO4, filtered, and evaporated. The crude
product (290 mg), a mixture of the gluco and manno isomers
in a 4.5:1 ratio (de 64%), determined by 1H NMR, was used
for the acetylation.
11. A solution of 6b (979 mg, 1.7 mmol) in triethyl
phosphite (10 mL) was refluxed for 5 h. The solvent was
removed under reduced pressure, and the crude product,
purified by flash chromatography eluting with CHCl3-EtOAc
10:3, afforded two products, corresponding to the diastereo-
isomers of 11 at the chiral phosphorus (267 of 11a Rf 0.34 and
252 mg of 11b Rf 0.24; 56% overall yield). 11a : white solid;
[R]D +54.6° (c 1.4, CHCl3); mp 57.1 °C; 1H NMR (300 MHz,
CDCl3) δ 1.36 (t, 3H), 2.07 (ddd, 1H, J 1′a,P ) 13.3, J 1′a,1 ) 8.5,
J 1′a,1′b ) 15 Hz, H-1′a), 2.18 (dt, 1H, J 1′b,P ) 15, J 1′b,1 ) 8.5,
Dieth yl C-(2-Aceta m id o-2-d eoxy-3,4,6-tr i-O-ben zyl-r-D-
glu cop yr a n osyl)m eth a n ep h osp h on a te (10b). The proce-
dure was the same used for the acetylation of product 9c.
Crude product 10a (290 mg) afforded 95 mg of 10b and 21 mg
of 9c as byproduct in 37% overall yield from 8c: [R]D -0.9° (c
J 1′a,1′b ) 15 Hz, H-1′b), 3.59-3.73 (m, 4H), 3.94 (dt, 1H, J 3,2
)
6.5, J 3,4 ) 6.5, J 3,P ) 2.5 Hz, H-3), 4.17 (dd, 2H), 4.22 (dd, 2H),
4.35 (ddd, 1H, J 1,2 ) 6.5, J 2,P ) 13.0, J 2,3 ) 6.5 Hz, H-2), 4.80
(dq, 1H, J 1,P ) 8.5 Hz, H-1), 4.80-5.00 (m, 6H, OCHPh); 13C
NMR (75.43 MHz,CDCl3) δ 17.00, 24.2 (J C,P ) 121 Hz), 63.24,
70.07, 72.90, 74.60, 75.59, 82.35, 83.77, 74.1, 74.94, 75.4; 31P
NMR (80.96 MHz, CDCl3) δ 42.55. Anal. Calcd for C30H35O7-
P: C, 66.90; H, 6.55. Found: C, 66.77; H, 6.87. 11b: white
hygroscopic solid; [R]D ) +62.6° (c 1.3, CHCl3); (300 MHz,
CDCl3) δ 1.30 (q, 3H), 2.08 (dt, 1H, J ) 15.5, 6.7 Hz), 2.18
(ddt, 1H, J ) 15.5, 7.3, 2.18 Hz), 3.64-3.69 (m, 4H), 3.94 (dt,
1
1.2, CHCl3); H NMR (300 MHz, C6D6) δ 1.06 (t, 3H, J ) 6.9
Hz), 1.11 (t, 3H, J ) 6.9 Hz), 1.49 (s, 3H), 2.15 (ddd, 1H, J )
15.0, 15.6 4.6 Hz), 2.27 (dt, 1H, J ) 15.6, 8.4 Hz), 3.57 (d, 1H,
J ) 2.3 Hz), 3.75 (bt, 1H, J ) 2.3 Hz), 3.91-4.01 (m, 3H), 4.07-
4.14 (m, 3H), 4.17-4.50 (m, 7H), 4.58 (dd, 1H, J ) 9.6, 2.3
Hz), 4.82 (dddd, 1H, J ) 8.4, 7.0, 4.6, 1.7 Hz), 6.45 (d, 1H, J )
9.6 Hz) 7.03-7.32 (m, 15H); 13C NMR (50.29 MHz, CDCl3), δ
16.90, 17.00, 23.81, 29.60 (J C-P ) 142.8 Hz), 49.06 (J C-P ) 13.8
Hz), 61.95, 62.51, 65.04, 68.92, 72.56, 72.76, 73.70, 74.05,
75.06, 76.05, 170.52; 31P NMR (80.96 MHz, CDCl3) δ 29.89.
Anal. Calcd for C34H44NO8P: C, 65.27; H, 7.09; N, 2.24.
Found: C, 65.18; H, 7.52; N, 2.05.
1H, J ) 7 Hz), 4.20 (m, 4H,), 4.49 (dt, 1H, J 2,1 ) 6.5, J 2,3
)
6.5, J 2,P ) 13 Hz, H-2), 4.81 (m, 1H, J 1,1′a ) 7.3, J 1,1′b ) 6.7,
J 1,2 ) 6.5, J 1,P ) 14Hz, H-1), 4.40-4.58 (m, 3H), 4.73-4.95
(m, 3H); 13C NMR (75.43 MHz,CDCl3) δ 17.06, 24.95 (J C,P
)
122 Hz), 63.7, 69.94, 72.52, 75.18 (2C), 82.75, 82.63, 74.15,
74.32, 75.43. 31P NMR (80.96 MHz, CDCl3) δ 44.30. Found:
C, 66.69; H, 6.40.
C-(2-Aceta m id o-2-d eoxy-r-D-glu cop yr a n osyl)m eth a n e-
p h osp h on ic Acid (1). Fifty mg (0.08 mmol) of 10b was
dissolved in dry CCl4 (2 mL), and TMSI (163 µL, 1.20 mmol)
was added. After 15 min the reaction was complete, the
J O9519468