One-pot carbanionic synthesis of P1,P2-diglycosyl, P1,P1,P2-triglycosyl, and P1,P 1,P2,P2-tetraribosyl methylenediphosphonates

Article abstract of DOI:10.1021/jo061087v

Novel lithiated carbanions derived from ethyl glycosyl- and diglycosyl methylphosphonates were used in a direct and convenient synthesis of P ¹,P²-diglycosyl, P¹,P¹,P ²-triglycosyl and P¹,P

Full text of DOI:10.1021/jo061087v

One-Pot Carbanionic Synthesis of P1 P2-Diglycosyl,
,
P1,P1,P2-Triglycosyl, and P1,P1,P2,P2-Tetraribosyl
Methylenediphosphonates
Claude Grison,*,† Hicham Chibli,† Nicolas Barthe`s,† and Philippe Coutrot‡
UMR 5032 CNRS-UniVersite´ de Montpellier II-ERT 5, 8 rue de l’Ecole Normale, 34296 Montpellier
Cedex 5, France, and UMR 7565 CNRS-UniVersite´ Henri Poincare´, Nancy 1, BP 239, 54506
VandoeuVre-le`s-Nancy, France
cgrison@uniV-montp2.fr
ReceiVed May 26, 2006
Novel lithiated carbanions derived from ethyl glycosyl- and diglycosyl methylphosphonates were used
in a direct and convenient synthesis of P1,P2-diglycosyl, P1,P1,P2-triglycosyl, and P1,P1,P2,P2-tetraribosyl
methylenediphosphonates involving a one-pot methylidenediphosphonylation of sugars.
Introduction
thermore, the methylenediphosphonate moiety should allow
decreased hydrophilicity of the substrates and facilitate cell
penetration while pyrophosphatases attack. These modified
nucleoside diphosphate sugars open different prospects in
chemotherapy.2
For instance, uridine 5′-[(R-D-galactopyranosylhydroxyphos-
phinyl)methyl]phosphonate inhibited competively a specific
glycoprotein galactosyltransferase.3 The synthesis, structural
features, and biological activity of nucleoside methylenediphos-
phonate analogues of ADP or GDP have been studied.4 The
synthesis of NAD+ analogue incorporating a methylenediphos-
The chemical combination of two sugars and the pyrophos-
phoric acid is a fundamental part of the molecular backbone of
reactive biological intermediates. The importance of nucleoside
diphosphate sugars is well-known as soluble precursors involved
in cell-wall polysaccharide biosynthesis.
Considerable efforts have been made in the structural
modifications of nucleoside diphosphate sugars, particularly in
the replacement of the phosphodiester linkage. Thus, methyl-
enediphosphonate linkage has been developed as an interesting
replacement of the pyrophosphate moiety. Indeed, the isosteric
replacement of phosphate with methylenephosphonate or other
phosphonates is now well-known and includes resistance to
hydrolysis and heightened biochemical stability overall.1 Fur-
(2) (a) Klein, E.; Ngheim, H.-O.; Valleix, C.; Mioskowski, C.; Lebeau,
L. Chem Eur. J. 2002, 8, 4649-4655 and references therein. (b) For reviews
see Zolotukhina, M. M.; Krutikov, V. I.; Lavrent’ev, A. N. Russ. Chem.
ReV. 1993, 62, 647-659. (c) Francis, M. D.; Martodam, R. R. Chemical,
Biochemical and Medicinal Properties of the Diphosphonates. In The Role
of Phosphorus in LiVing Systems; Hildebrand, R. L., Ed.; CRC Press: Boca
Raton, FL, 1982; p 55. (d) Engel, R. Chem. ReV. 1977, 77, 349-367.
(3) Vaghefi, M. M.; Bernacki, R. J.; Hennen, W. J.; Robins, R. K. J.
Med. Chem. 1987, 30, 1391-1399.
* Corresponding author.
† UMR 5032 CNRS-Universite´ de Montpellier 2.
‡ UMR 7565, Universite´ Henri Poincare´, Nancy 1.
(1) For latest work in the area, see Zhang, H.; Xu, Y.; Zhang, Z.; Liman,
E. R.; Prestwich, G. D. J. Am. Chem. Soc. 2006, 128, 5642-5643 and
references therein.
(4) Vincent, S.; Grenier, A.; Valleix, C.; Salesse, L.; Lebeau, L.;
Mioskowski, C. J. Org. Chem. 1998, 63, 7244-7257.
10.1021/jo061087v CCC: $33.50 © 2006 American Chemical Society
Published on Web 09/19/2006
7978
J. Org. Chem. 2006, 71, 7978-7988

Carbanionic Synthesis of Methylenediphosphonates
phonate linkage in place of the natural pyrophosphate has been
reported to act as an inhibitor of ADP ribosyl cyclase and to
resist phosphatase degradation.5 Recently, methylenediphos-
phonate analogues of MAD (mycophenolic acid adenine di-
nucleotide),6 TAD (thiazole-4-carboxamide adeninedinucle-
otide),7 and BAD (benzamide adenine dinucleotide)7a,8 were
synthesized as potential inhibitors of IMPDH (inosine mono-
phosphate deshydrogenase). Synthesis of a possible mechanism-
based bisubstrate inhibitor of the elongating R-D-mannosyl
phosphate transferase in Leishmania, comprising a guanosine
subunit bound to the synthetic acceptor substrate through the
methylenediphosphonate linker, has been accomplished.9
However, rational design of transition-state mimics including
trisubstrate analogues (sugar donor, sugar acceptor, and nucle-
otide) seems unknown.
To the best of our knowledge, only the synthesis of nucleoside
methylenediphosphonate sugars or dinucleoside methylene-
diphosphonates is documented.2,10 As part of our program in
the synthesis of analogues of natural glycosyl-disubstituted
pyrophosphates, we have recently described preliminary results
on the one-pot alkylidene diphosphorylation of 2,3-O-isopro-
pylidene uridine or 2,3:5,6-di-O-isopropylidene-D-mannofura-
nose to synthesize the methylenediphosphonate analogues of
natural P1,P2-glycosyl-disubstituted pyrophosphates.11
We report here the full paper concerning the direct and
general procedure for obtaining P1,P2-diglycosyl, P1-glycosyl,
P2-nucleoside methylenediphosphonates, and P1,P1,P2-trigly-
cosyl- and P1,P1,P2,P2-tetraglycosyl methylenediphosphonates
that exploits our carbanionic method based on the alkylidene-
diphosphorylation of nucleophiles.12
analogues of dinucleoside pyrophosphates have been proposed.
A current synthetic approach to these analogues exploits
dicyclohexylcarbodiimide- (DCC-) catalyzed direct coupling of
nucleosides and methylenediphosphonate analogues of nucle-
otides.
For instance, Marquez et al.13 report the preparation of TAD
analogues in 36% yield according to the method. Pankiewicz
et al.8 suggest an interesting process with nucleoside bicyclic
trisanhydrides found in the reaction between nucleoside 5′-
methylenediphosphonates and DCC. Thus, the reaction of the
trisanhydride derivative of 2′,3′-O-isopropylideneadenosin-5′-
yl with 2′,3′-O-isopropylidenetiazofurin leads to the â-methyl-
ene-TAD in 92% overall yield.10a The method has been recently
used in the synthesis of MAD.6a However, these preparations
are limited to small-scale syntheses, the purification of key
intermediates by reversed-phase HPLC being required.
Nucleoside methylenediphosphonate sugars have been pre-
pared by condensation of R-D-glycosyl 1-(methylenediphos-
phonate) with 2′,3′-di-O-acetyladenosine by use of 1-(mesitylene-
2-sulfonyl)-3-nitro-1,2,4-triazole as coupling agent; D-glycosyl
1-(methylenediphosphonate) precursor is obtained in three steps
from glycosylpentaacetate and [(diphenoxyphosphinyl)methyl]-
phosphonic acid at 170 °C under vacuum.3 More recently, a
synthesis of â-methylene-TAD has been proposed, based on
the use of two rounds of Mitsunobu esterification with conve-
niently protected nucleosides14 starting from methylenebispho-
sphonic acid tribenzyl ester according to the method of Saddy
et al.15 However, the success of this strategy is still limited by
the availability of the tetrabenzyl methylenediphosphonate
precursor.15
Our process is exemplified in Scheme 1 in the case of the
preparation of P1,P2-diglycosyl methylenediphosphonate 5-gal-
rib. It involved a five-step sequence based on a selective
phosphonomethylation of ethyl phosphorodichloridate 2 by use
of the lithium anion 1′-gal derived from ethyl glycosyl meth-
ylphosphonate 1-gal followed by a direct substitution of the
chlorine atom of the intermediate 3-gal by the nucleophilic
lithium alcoholate 4′-rib formed in situ after addition of the
second sugar 4-rib.
Results and Discussion
Our first goal was the preparation of a series of P1,P2-
diglycosyl and P1-glycosyl-P2-nucleoside methylenediphospho-
nates to investigate the synthetic potential of the strategy.
Synthesis of P1,P2-Diglycosyl and P1-Glycosyl-P2-Nucleo-
side Methylenediphosphonates 5-sugar-sugar. Different ap-
proaches to the chemical synthesis of such metabolically stable
Critical to the success of this approach was the preparation
of the starting material, ethyl glycosyl methylphosphonate
1-sugar, and the derived lithiated carbanions 1′-sugar, unknown
until now. The model starting compound 1-gal was first
prepared. The 1,2:3,4-di-O-isopropylidene R-D-galactopyrano-
side 4-gal (1 equiv) was slowly added to methylphosphonic
dichloride 6 in the presence of tetrazole as catalyst and
diisopropylethylamine. After 5 h of stirring, ethanol in excess
was added.
The double substitution could not be avoided and a mixture
of the expected product 1-gal accompanied by the disubstituted
product 1-gal-gal was obtained. After silica gel chromatography,
compounds 1-gal and 1-gal-gal were isolated in 39% and 15%
yield, respectively (Scheme 2). We found a more convenient
approach starting from the first addition at -78 °C of the lithium
(5) Hutchinson, E. J.; Taylor, B. F.; Blackburn, G. M. Chem. Commun.
1996, 2765-2766.
(6) (a) Pankiewicz, K. W.; Lesiak-Watanabe, K. B.; Watanabe, K. A.;
Patterson, S. E.; Jayaram, H. N.; Yalowitz, J. A.; Miller, M. D.; Seidman,
M.; Majumdar, A.; Prehna, G.; Goldstein, B. M. J. Med. Chem. 2002, 45,
703-712. (b) Yalowitz, J. A.; Pankiewicz, K. W.; Patterson, S. E.; Jayaram,
H. N. Cancer Lett. 2002, 181, 31-38.
(7) (a) Lesaik, K.; Watanabe, K. A.; Majumdar, A.; Seidman, M.;
Seidman, M.; Vanderveen, K.; Goldstein, B. M.; Pankiewicz, K. W. J. Med.
Chem. 1997, 40, 2533-2538. (b) Zatorski, A.; Goldstein, B. M.; Colby, T.
D.; Jones, J. P.; Pankiewicz, K. W. J. Med. Chem. 1995, 38, 1098-1105.
(c) Zatorski, A.; Lipka, P.; Mollova, N.; Schram, K. H.; Goldstein, B. M.;
Watanabe, K. A.; Pankiewicz, K. W. Carbohydr. Res. 1993, 249, 95-108.
(8) Pankiewicz, K. W.; Lesiak, K.; Zatorski, A.; Goldstein, B. M.; Carr,
S. F.; Sochacki, M.; Majumdar, A.; Seidman, M.; Watanabe, K. A. J. Med.
Chem. 1997, 40, 1287-1291.
(9) Borodkin, V. S.; Ferguson, M. A. J.; Nikolaev, A. V. Tetrahedron
Lett. 2004, 857-862.
(10) (a) Pankiewicz, K. W.; Lesiak, K.; Watanabe, K. A. J. Am. Chem.
Soc. 1997, 119, 3691-3695 and references therein. (b) Morr, M.; Wray,
V. Angew. Chem., Int. Ed. Engl. 1994, 33, 1394-1396. (c) For review see
Scheit, K. H. Nucleotide Analogues; John Wiley and Sons: New York,
1980; pp 96-141.
(13) Marquez, V. E.; Tseng, C. K. H.; Gebeyehu, G.; Cooney, D. A.;
Ahluwalia, G. S.; Kelley, J. A.; Dalal, M.; Fuller, R. W.; Wilson, Y. A.;
Johns, D. G. J. Med. Chem. 1986, 29, 1726-1731.
(14) Ikeda, H.; Abushanab, E.; Marquez, V. Biorg. Med. Chem. Lett.
1999, 9, 3069-3074.
(11) Grison, C.; Letondor, C.; Chibli, H.; Coutrot, P. Tetrahedron Lett.
2005, 6525-6528.
(12) (a) Grison, C.; Comoy, C.; Chatenet, D.; Coutrot, P. J. Organomet.
Chem. 2002, 662, 83-97 (b) Grison, C.; Coutrot, P.; Joliez, S.; Balas, L.
Synthesis 1996, 731-735. (c) Grison, C.; Charbonnier, F.; Coutrot, P.
Tetrahedron Lett. 1994, 35, 5425-5428.
(15) (a) Saddy, M.; Lebeau, L.; Mioskowski, C. J. Org. Chem. 1995,
60, 2946-2947. (b) Saddy, M.; Lebeau, L.; Mioskowski, C. Tetrahedron
Lett. 1995, 36, 2239-2242. (c) Saddy, M.; Lebeau, L.; Mioskowski, C.
Synlett 1995, 643.
J. Org. Chem, Vol. 71, No. 21, 2006 7979

Grison et al.
SCHEME 1. Preparation of 5-gal-rib as an Example of Synthesis of 5-sugar-sugar
SCHEME 2. Preparation of P-Chiral Ethyl Glycosyl Methylphosphonate 1-gal, P-Chiral Galactosyl Ribosyl
Methylphosphonate 1-gal-rib, and Symmetrical Diglycosyl Methylphosphonate 1-gal-gal
alcoholate 4′-gal derived from 1,2:3,4-di-O-isopropylidene R-D-
galactopyranoside 4-gal onto methylphosphonic dichloride 6,
followed after 30 min by addition of lithium ethylate at this
same temperature. Although these conditions could not totally
avoid the double substitution, the phosphonate 1-gal was
obtained in 56% yield with 12% of the digalactosyl methylphos-
phonate byproduct 1-gal-gal isolated after column chromatog-
raphy (Scheme 2, procedure A, and Table 1). This last method
has several advantages in terms of better control of the
monosubstitution leading to the desired product, ease of
purification, and a shorter reaction time. When a stoichiometric
amount of the sugar alcoholate 4′-gal was added onto meth-
ylphosphonic dichloride at -78 °C, the sole symmetrical
diglycosyl methylphosphonate 1-gal-gal was obtained (Scheme
2, procedure B). Interestingly, we noted that the method could
also deliver successfully P-chiral diglycosyl methylphosphonates
when the sequence used two different lithium sugar alcoholates
successively. Only one example was studied with lithium
alcoholate 4′-gal as the first reagent and 4′-rib for the second.
The bulkier sugar alcoholate 4′-gal must be introduced in the
7980 J. Org. Chem., Vol. 71, No. 21, 2006

Carbanionic Synthesis of Methylenediphosphonates
TABLE 1. Preparation of P-Chiral Ethyl Glycosyl Methylphosphonates 1-sugar and Symmetrical Diglycosyl Methylphosphonates
1-sugar-sugar
a Yield of purified products. b Diastereomeric ratios evaluated by 31P NMR on the crude products, specified as â: â′:R: R′anomer order if necessary.
c Major isomer. d It was possible to separate R-epimer and â-epimer and to isolate pure R-epimer. e Thus named as the molecule includes D-manno moiety.
f Unstable product.
first step to ensure the best control of the monosubstitution,
followed by the addition of the most reactive sugar alcoholate
4′-rib in the second step for an efficient second substitution.
As for the phosphonate 1-gal, these conditions could not avoid
the partial double substitution of 6 by 4′-gal in the first addition
step. Consequently, the phosphonate 1-gal-rib was obtained in
50% yield with 10% of the digalactosyl methylphosphonate
byproduct 1-gal-gal isolated after column chromatography
(Scheme 2, procedure C).
Different P-chiral ethyl glycosyl methylphosphonates 1-sugar
and symmetrical diglycosyl methylphosphonate 1-sugar-sugar
were prepared in that way (Table 1).
As clearly indicated from the 31P NMR spectra of the crude
materials, procedure A allows the preparation of glycosyl
methylphosphonates 1-sugar with a wide range of sugars
(protected D-galactose, D-ribose, and D-mannose). It is possible
to introduce the sugar via different hydroxyls (primary alcohol
of protected D-galactose or D-ribose, anomeric hydroxyl of
protected D-mannose, or primary alcohol of 3,6-anhydro-2-
deoxy-4,5:7,8-di-O-isopropylidene-D-manno-octitol). O-benzyl
protection is not easily compatible with the basic medium
and consequently the yields are decreased to a major extent with
tetra-O-benzyl-D-glucopyranose and tri-O-benzyl-D-fucopyra-
nose (Table 1, entries 5 and 6). Moreover, the corresponding
products ethyl glycosyl methylphosphonates 1-glc and 1-fuc
are unstable. It can be also observed that relative amounts of
the byproduct diglycosyl methylphosphonate 1-sugar-sugar
formed in procedure A indicate the following reactivity sequence
J. Org. Chem, Vol. 71, No. 21, 2006 7981

Grison et al.
TABLE 2. Optimization of the Deuteriolysis of 1-man-a
SCHEME 3. Deuteriolysis of 1-gal
reaction time (min)
4-man-aa
1-man-a
1-man-db
5
15
30
41
59
77
38
9
4
21
32
19
a Values were determined in 1H NMR from the integration of H-1 signals
of 4-man-a (R: s, 5.32 ppm; â: d, 4.56 ppm) and H-1 signals of 1-man-a
1
and 1-man-d (m, 5.58-5.52 ppm). b Values were determined in H NMR
from the integration of DCH2P (dt, 1.57 ppm; dt, 1.46 ppm) and Me of an
isopropylidene group (s, 1.39 ppm).
SCHEME 4. Deprotonation and Deuteriolysis of 1-man-a
TABLE 3. 31P NMR of the Different Phosphorus Intermediates in
the Methylene Diphosphonylation of 4-sugar
compound
δ
31P (THF)
1-sugar
1-sugar
3-sugar
s, ∼29 ppm
s, ∼58 ppm
d, ∼50 ppm, 2JP-P ) 76 Hz
d, ∼36 ppm, 2JP-P ) 76 Hz
d, ∼18 ppm, 2JP-P ) 5 Hz
d, ∼16 ppm, 2JP-P ) 5 Hz
5-sugar-sugar
not very important as ethyl phosphonates or phosphates were
not good prodrugs for phosphonates or phosphates. In return,
selective hydrolysis of ethyl ester that removes the chirality at
phosphorus was important, as it can afford bioactive glycosyl
methylphosphonates. Consequently, selective removal of ethyl
protecting group by use of trimethylbromosilane/methanol as
reagent was attempted, and this procedure fully succeeded with
the phosphonate 1-gal. Unfortunately, in other cases, removal
of ethyl group was not selective and was accompanied by a
partial glycosyl O-P bond fragmentation.
Ethyl glycosyl methylphosphonates 1-sugar being so ob-
tained, a preliminary investigation of the formation and proper-
ties of the derived lithiated carbanions 1′-sugar was carried out
with the model phosphonate 1-gal as starting material. The
formation of the lithiated carbanion 1′-gal occurred when the
phosphonate 1-gal was treated with s-BuLi in THF at -78 °C
with stirring for 30 min at this temperature (Scheme 3). The
choice of the base s-BuLi was important and resulted from our
previous works on alkylidene diphosphorylation, where we
showed that s-BuLi limits the formation of side products.12 The
carbanion is characterized in THF by a 31P NMR broad signal
at 58 ppm, typical of this type of lithiated species. After
deuteriolysis of the reaction medium, the 13C NMR of the crude
product showed a complete deuteration (80% in isolated pure
product, dr 1:1). The carbon CH2D-P appeared as coupled both
to phosphorus and deuterium with a doublet of triplets centered
at 11.1 ppm (JC-P ) 144.5 Hz, JC-D ) 21.5 Hz) for one
diastereomer and at 11.2 ppm for the other. The absence of the
CH3-P signal in the crude product of deuteriolysis showed the
complete metalation of 1-gal with s-BuLi. This result was
confirmed by mass spectroscopy with [M + 1] ) 368 found
for the deuterated product 1-gal-d.
for alcoholate 4′-sugar: 4′-rib > 4′-man-b > 4′-gal > 4′-
man-a.
In the case of 1-sugar, the reaction leads to the creation of a
phosphorus stereogenic center and different diastereomers are
observed by NMR analysis. For 1-gal and 1-rib, both epimers
1
are detected by 31P and 13C NMR. In the case of 1-man-a, H
NMR data confirm the formation of R and â anomers, and 31
P
NMR reveals the presence of four diastereomers. The 1H NMR
spectrum of crude 1-man-a allows the characterization of four
stereomers.
In R stereomers, the anomeric hydrogen appears as a doublet
at 5.66 (3J
) 6 Hz) and 5.58 ppm (3J
) 6 Hz),
H-P
H-P
respectively, with a coupling constant JH1-H2 ) 0 Hz, charac-
teristic of the R-anomer. The 13C NMR spectrum shows a
doublet for C-1 at 103.0 and 102.3 ppm.
In 1H NMR, â anomers present a doublet of doublets for H-1
at 5.54 and 5.51 ppm, and in 13C NMR a doublet for C-1 at
96.9 and 96.7 ppm is seen, , characteristic of â-anomer. The
carbon C-2 of the sugar is also coupled with the phosphorus
atom with a coupling constant JC2-P ) 10 Hz for R-anomers
and JC2-P ) 6 Hz for â-anomers.
Similarly, careful examination of 1H NMR spectra of 1-man-b
shows clearly the presence of R- and â-epimers. In R-epimer,
the H-4 signal of resonance is a doublet at 4.48 ppm (3JH4-H5
) 6 Hz) with a typical negligible coupling with H-3, consistent
with R-configuration. In the â-epimer, the H-4 signal is a
multiplet between 4.56 and 4.63 ppm, whereas H-6 and H-3
resonances shift toward a higher field at 3.42 and 3.58-3.64
ppm, respectively. As for 1-man-a, the 31P NMR spectrum of
1-man-b confirms the presence of four stereomers (s, 32.30; s,
32.09; s, 31.95; s, 31.90).
Surprisingly, the thermal stability of the carbanion 1′-gal is
lower than that of the lithium carbanions derived from dialkyl
methylphosphonates, where the stability increases with the steric
hindrance at phosphorus.16 On warming to -50 °C the carbanion
1′-gal is degraded after some minutes, as demonstrated by
quenching of the reaction mixture with water at this temperature.
Only a mixture of complex unidentified degradation products
is obtained without any trace of the starting phosphonate 1-gal.
It appears that there is little to no control of diastereoselec-
tivity in the different cases, but it is difficult to rationalize the
corresponding data as a consequence of the complexity of the
substitution mechanism at P(V). Separation of diastereomers
succeeded only in the case of 1-man-a, where it was possible
to isolate a pure R-anomer and the mixture of both â-anomer
and â′-anomer by silica gel chromatography. In other cases,
diastereomeric mixtures were obtained after chromatographic
purification. However, from a biological point of view, it has
to be noted that the obtention of pure diastereomer 1-sugar was
(16) Teulade, M. P.; Savignac, P. J. Organomet. Chem. 1986, 312, 283-
295.
7982 J. Org. Chem., Vol. 71, No. 21, 2006

Carbanionic Synthesis of Methylenediphosphonates
TABLE 4. Preparation of Diglycosyl Methylenediphosphonates 5-sugar-sugar
a Isolated yields of analytically pure product. b Yields evaluated from 31P NMR analysis of crude product
J. Org. Chem, Vol. 71, No. 21, 2006 7983

Grison et al.
SCHEME 5. Synthetic Route to 5-sugar-sugar-sugar Exemplified with 5-gal-rib-man-b
Similar conditions for the deprotonation of 1-rib and 1-man-b
were investigated. As for 1-gal, metalation was complete after
30 min of stirring with s-BuLi at -78 °C.
Subsequent treatment of the intermediate 3′-sugar with 1 equiv
of a suitable protected sugar 4-sugar from -78 °C to room
temperature involved a novel acid-base exchange that led to
the reprotonation of 3′-sugar into 3-sugar with the concomitant
formation of the lithium alcoolate 4′-sugar derived from 4-sugar.
Finally, 4′-sugar substituted the chlorine of 3-sugar to afford
the desired crude product 5-sugar-sugar.
The chromatographic separation of the recovered 1-sugar and
5-sugar-sugar was easy, except in the case of 1-man-b and
5-man-b-man-b, where a graduated elution was necessary. The
excess of ethyl glycosyl methylphosphonate 1-sugar was
quantitatively recovered after chromatography.
However, in the case of both â-anomers of 1-man-a, depro-
tonation with s-BuLi was incomplete and was accompanied by
2,3:5,6-di-O-isopropylidene R,â-D-mannofuranose 4-man-a as
a side product (Scheme 4). It is more than likely that partial
dephosphorylation results from O-P bond fragmentation.
Indeed, pure starting material 1-man-a itself is fragile and rapidly
degrades, leading to 4-man-a in some hours at room temperature.
A solution of 1-man-a in methanol also degrades, yielding
4-man-a without a trace of methyl diisopropylidene mannoside,
which excludes a substitution of the phosphonate moiety by
MeOH at the anomeric carbon with a C-O bond break.
Obviously the P-O bond appears to be more fragile than the
anomeric C-O bond in 1-man-a. Consequently, the partial
dephosphorylation observed in the deuteriolysis of 1′-man-a can
be simply explained by nucleophilic assistance of the basic
species present in the reaction medium to the natural trend to
the P-O break in the starting compound 1-man-a. It cannot be
excluded either that a “ketene-like” â-elimination mechanism
of the carbanionic species 1′-man-a takes place.
Different nucleophilic sugars 4 were tested with different ethyl
glycosyl methylphosphonates 1-sugar (Table 4). Satisfactory
yields were obtained in all cases where the first sugar was linked
to the phosphonate 1 by the primary alcohol (48-73% yield in
pure product). The reaction was relatively insensitive to changes
in the nature of 4-sugar (gal, rib, man-a, man-b) and the nature
of the nucleophilic hydroxyl group (primary alcohol or anomeric
hydroxyl). The particular example of 2,3-O-isopropylideneuri-
dine 4-uri as nucleophile has to be noted. The reaction sequence
can be used to provide a convenient one-pot synthesis of
nucleoside methylenediphosphonate sugars in reasonable yields
(respectively 30% and 41% yield for isolated products 5-gal-
uri and 5-rib-uri). The phosphonate 1-man-a as starting material
constituted a real difficulty as a result of the great fragility of
the anomeric link between the mannosyl and phosphoryl
moieties in basic medium. In the conditions defined above
(metalation of 1-man-a for 15 min at -78 °C), it was
nevertheless possible to effect in 30% yield the methylene-
diphosphonylation of nucleophilic 1,2:3,4-di-O-isopropylidene-
R-D-galactopyranoside 4-gal into the expected mannosyl ga-
lactosyl methylenediphosphonate 5-gal-man-a. It was noted that
the procedure to prepare the same compound from 1-gal by
use of 4-man-a as nucleophilic sugar was better (67% yield in
pure product) and showed the versatility of the method.
The presence of a spacer arm of two methylene units between
the furanic cycle and the phosphoryl group decreased the
nucleophilicity of 1′-man-b so that the reaction of 1′-man-b with
2 had to be carried out at -50 °C for 1.5 h to optimize the
formation of 3-man-b. In these conditions, diglycosyl diphos-
phonates 5-man-b-man-b and 5-man-b-gal were obtained with-
Consequently, deuteriolysis of lithiated carbanion derived
from 1-man-a and s-BuLi was studied at different reaction times
to examine the variation of the metalation/degradation ratio. The
best conditions of metalation were obtained with stirring of the
reaction medium for 15 min at -78 °C (Table 2).
With the conditions of deprotonation of 1-sugar into 1′-sugar
in hand, the reactivity of the lithiated carbanion 1′-sugar was
then studied in the one-pot methylenediphosphonylation strategy
(Scheme 1). Once formed, the carbanion 1′-sugar reacted with
the readily available ethyl phosphorodichloridate 2. The reaction
was monitored by 31P NMR spectroscopy to ensure the complete
formation of the monochlorinated intermediate 3-sugar (Table
3). As the addition of 2 proceeded, spontaneous metalation of
3-sugar by the carbanion 1′-sugar arose and gave the lithiated
diphosphorylated anion 3′-sugar. It was noted that the latter
intermediate was stable from -78 °C up to room temperature,
which made 31P NMR analyses easier for successive samples
of the reaction medium. Thus, to obtain the complete conversion
of phosphorodichloridate 2 into 3′-sugar, it was necessary to
treat 2 with an excess of carbanion 1′-sugar (2 equiv).
7984 J. Org. Chem., Vol. 71, No. 21, 2006

Carbanionic Synthesis of Methylenediphosphonates
TABLE 5. Preparation of Triglycosyl Methylenediphosphonates 5-sugar-sugar-sugar
a Yield of purified products. b Diastereomeric ratios evaluated by 31P NMR on the crude products, specified as R′: R:â′: â anomer order if necessary.
c Major isomer. d Diastereomeric ratio was determined by integration of H-2 signals of man-b moiety by 1H NMR. e Only two stereomers could be distinguished
1
in H NMR.
out difficulty in satisfactory yields. The particular example of
5-man-b-man-b is interesting as the D-manno configuration is
known to confer a specific chemical character to different
biological systems and to serve as a recognition site.17
In the precedent case of methyl glycosylphosphonates 1-sug-
ar, 31P NMR data allow us to identify all stereomers. In contrast,
31P NMR of P1,P2- diglycosyl diphosphonates 5-sugar-sugar
cannot be used as stereochemical indicators. Although 31P NMR
is generally very sensitive to the stereoelectronic changes at
the phosphorus atom, it appears here that a glycosyl substituent
at P1 and another one different at P2 produce similar environ-
ments around the P1 and P2 atoms. Thus, according to Table 4,
the chemical shifts of 5-gal-gal, 5-gal-rib, 5-rib-rib, and 5-rib-
man-a do not differ notably. In the cases of 5-gal-uri, 5-rib-
uri, and 5-man-b-man-b, the resonances occur at closely related
(17) (a) Ponpipom, M. M.; Shen, T. Y.; Baldeschwieler, J. D.; Wu, P.-
S. Modification of liposome surface properties by synthetic glycolipids. In
Liposome Technology; Gregoriadis, G., Ed.; CRC Press: Boca Raton, FL,
1984; Vol. III, pp 95-115. (b) Slama, J.; Rando, R. R.; Biochemistry 1980,
19, 4595-4600. (c) Ponpipom, M. M.; Bugianesi, R. L.; Robbins, J. C.;
Doebber, T. W.; Shen, T. Y. J. Med. Chem. 1981, 24, 1388-1395. (d)
Doebber, T. W.; Wu, M. S.; Bugianesi, R. L.; Ponpipom, M. M.; Furbisch,
F. S.; Barranger, J. A.; Brady, R. O.; Shen, T. Y. J. Biol. Chem. 1982, 257,
2193-2199.
δ
31P values. Moreover, products 5-sugar-sugar were obtained
as a mixture of inseparable diastereomers after chromatographic
purification.
As mentioned above for the simple ethyl glycosyl meth-
ylphosphonates 1-sugar, an interesting point was to examine
J. Org. Chem, Vol. 71, No. 21, 2006 7985

Grison et al.
SCHEME 6. Preparation of 5-rib-rib-rib-rib
the removal of the ethyl ester (and consequently the removal
of chirality at the phosphorus atom) to obtain potent bioactive
compounds. With Me3SiBr/MeOH or Me3SiBr/Et3N/MeOH as
reagent, we observed, in the cases of 5-man-b-gal and 5-man-
b-man-b, that removal of ethyl group was slowing down and
consequently was not selective and accompanied by mannosyl
O-P fragmentation.
of 5-gal-rib-man-b with two chiral phosphorus atoms confirmed
the synthetic interest of the method (72% in pure product),
whereas 5-man-b-man-b-man-b presents a potent biological
interest in recognition phenomena.17 From a practical point of
view, it was noted that 5-man-b-man-b-man-b and 1-man-b-
man-b in excess were easily separated by chromatography,
contrarily to the precedent case of diethyl dimannosyl methyl-
enediphosphonate 5-man-b-man-b, which was difficult to sepa-
rate from the starting phosphonate 1-man-b. In the case of the
chiral P1,P2-methylenediphosphonate 5-gal-rib-man-b, the com-
plete structural determination by NMR spectroscopy was
difficult and needed heteronuclear single quantum coherence
spectroscopy (HSQC), total correlation spectroscopy (TOCSY),
and HSQC-TOCSY experiments to facilitate the assignment
of individual spin systems (see Supporting Information).
Synthesis of P1,P1,P2,P2-Tetraglycosyl Methylenediphos-
phonates 5-sugar-sugar-sugar-sugar. To complete the study
of the process, we finally described the possible access to
tetraglycosyl methylenediphosphonates exemplified in the case
of the tetraribosyl methylenediphosphonate 5-rib-rib-rib-rib
(Scheme 6). According to the proposed method, the incorpora-
tion of a fourth sugar, 4-rib, succeeded after stirring for 48 h at
room temperature in the last step of the reaction sequence.
Tetraribosyl methylenediphosphonate was so obtained in a
reasonable 30% overall yield and constitute the first example
of this type of compound. The main difficulty was the final
separation of 5-rib-rib-rib-rib from the necessary excess of the
starting phosphonate 1-rib-rib, which needed careful chroma-
tography. The symmetry of 5-rib-rib-rib-rib allowed the ob-
servation of a typical and unique singlet in 31P NMR at 20.0
ppm, whereas 1-rib-rib gave a singlet at 29.2 ppm. Consequently
31P NMR was used as support to easily control the chromato-
graphic purification of 5-rib-rib-rib-rib.
Synthesis of P1,P1,P2-Triglycosyl Methylenediphospho-
nates 5-sugar-sugar-sugar. The complete one-pot carbanionic
synthesis of P1,P2-diglycosyl methylenediphosphonates in hand,
our attention was then turned to the possible preparation of the
first P1,P1,P2-triglycosyl methylenediphosphonates 5-sugar-
sugar-sugar by this way.
Deprotonation of 1-sugar-sugar parallels similarly that
described above with 1-sugar, but the conditions have had to
be adjusted to the particular structures of 5-sugar-sugar-sugar
(Scheme 5, Table 5). Use of n-BuLi or s-BuLi provided lithium
diglycosyl methylphosphonate 1′-sugar-sugar cleanly and quan-
titatively after 30 min in THF at -78 °C. Contrarily to 1-sugar,
the starting phosphonate 1-sugar-sugar was not very sensitive
to the nature of the lithiated base, and no significant difference
on the formation of byproducts was observed. Generated under
these conditions, 1′-sugar-sugar was stable at -78 °C for 30
min, and after addition of 2, it selectively displaced one chlorine
atom of 2 to produce 3-sugar-sugar and then 3′-sugar-sugar
after acid-base exchange. However, complete substitution of
chlorine atom of 2 was difficult as a result of the steric bulk of
the carbanion species 1′-sugar-sugar and was the rate-determin-
ing step of the process.
This disadvantage was overcome upon stirring the reaction
mixture for 90 min at higher temperature (-50 °C) after addition
of 2. From a practical point of view, we noted a decolorizing
of the reaction mixture that indicated the complete substitution
and total disappearance of the carbanion 1′-sugar-sugar. Sub-
sequent addition of the nucleophilic 4-sugar provided the
reactive intermediate 3-sugar-sugar and the transient lithium
alcoholate 4′-sugar. Surprisingly, the displacement of the
chlorine atom of 3-sugar-sugar by 4′-sugar required only 1 h
at 25 °C for completion. This easy substitution parallels exactly
that mentioned above in the preparation of diglycosyl methyl-
enediphosphonates 5-sugar-sugar, where this step was insensi-
tive to the steric effects.
Conclusion
The preparation of new lithiated carbanions derived from
ethyl glycosyl or diglycosyl methylphosphonates and their use
in the one-pot alkylidene diphosphonylation of various nucleo-
philic protected sugars or nucleosides afford a novel and general
method to obtain either the methylenediphosphonate analogues
of natural P1,P2-glycosyl-disubstituted pyrophosphates or a
variety of triglycosyl methylenediphosphonates. Moreover, the
access to tetraglycosyl methylenediphosphonates appears to be
possible. A first structure totally symmetric with the same
protected ribosyl phosphonate ester is described. As lithium
The triglycosyl methylenediphosphonates 5-sugar-sugar-
sugar were isolated in moderate to good yields (30-72%). It
was noteworthy that the incorporation of a third glycosyl residue
did not modify the efficiency of the procedure. The preparation
7986 J. Org. Chem., Vol. 71, No. 21, 2006

Carbanionic Synthesis of Methylenediphosphonates
Hz, 2 H), 4.32 (dd, J ) 5.0, 2.5 Hz, 2 H), 4.35-3.95 (m, 8 H),
1.57 (d, J ) 17.7 Hz, 3 H), 1.54 (s, 6 H), 1.43 (s, 6 H), 1.32 (s, 12
H); 13C NMR (63 MHz, CDCl3) δ 110.2, 109.4, 96.8, 71.09, 71.13,
70.8, 67.6, 64.7 (d, 2JC-P ) 6.3 Hz), 26.08, 26.11, 24.6, 24.5, 11.2
carbanions derived from mixed ethyl glycosyl methylphospho-
nates or from mixed or not mixed diglycosyl methylphospho-
nates are now accessible, it has to be noted that the method can
give the access either to di- or triglycosyl methylenediphos-
phonates with the same or with different glycosyl phosphonate
esters. Combined with the availability of monoglycosyl phos-
phorodichloridate as electrophilic substrate, the method gives
also access to mixed tetraglycosyl methylenediphosphonates.
This versatile four-step reaction that provides such relatively
complex structures takes place in one pot with easily accessible
starting material and in shorter reaction time, in most cases.
This new and direct access to di-, tri-, or tetraglycosyl
methylenediphosphonates should find different applications in
the preparation of compounds of biological interest, if chemose-
lective hydrolysis of the ethyl ester in the final products can be
improved.
1
(d, JC-P ) 144 Hz); 31P NMR (101 MHz, CDCl3) δ 29.33 (s, 1
P); MS (FAB+) m/z calcd for C25H41O13P [M]+ 580.6, found 581.2
[M + 1]+ (100%). Anal. Calcd for C25H41O13P: C, 51.81; H, 6.96;
O, 35.89; P, 5.34. Found: C, 51.42; H, 7.18; P, 5.19.
General Procedure for Preparation of P-Chiral Diglycosyl
Methylphosphonates, 1-sugar-sugar (Protocol C). The lithium
alcoholate 4′-gal (1 equiv, 8.5 mmol) was prepared as described
above in protocol A from 4-gal (1 equiv, 2.21 g, 8.5 mmol) and
was added dropwise to a solution of methyl phosphonic dichloride
6 (1 equiv, 1.12 g, 8.5 mmol) in THF (15 mL) at -78 °C. After
the reaction mixture was stirred for 30 min at -78 °C, the lithium
alcoholate 4′-rib (1 equiv, 8.5 mmol), previously prepared under
the same conditions from 4-rib (1 equiv, 1.73 g, 8.5 mmol), was
added dropwise to the reaction mixture. The mixture was stirred
for 30 min at -50 °C before it was quenched with water (15 mL).
The organic layer was extracted with CH2Cl2 (3 × 30 mL) and
dried over anhydrous sodium sulfate, and solvents were evaporated.
Silica gel column chromatography of the residue provided 2.29 g
(4.2 mmol, 50%) of a 1:1 mixture of 1-gal-rib diastereomers and
0.49 g (0.85 mmol, 10%) of 1-gal-gal.
1-O-Methyl-2,3-O-isopropylidene-â-D-ribofuranosyl 1,2:3,4-
Di-O-isopropylidene-R-D-galactopyranosyl Methylphosphonate,
1-gal-rib. Colorless oil; Rf 0.44 (8:1 ethyl acetate/hexane); 1H NMR
(400 MHz, CDCl3) δ 5.54 (d, J ) 5.0 Hz, 1 H), 4.97 (s, 1 H), 4.72
(d, J ) 4.5 Hz, 1 H), 4.65-4.55 (m, 2 H), 4.35 (dd, J ) 2.3, 5.0
Hz, 1 H), 4.26-4.22 (m, 2 H), 4.20-3.94 (m, 5 H), 3.32 (s, 3 H),
1.55-1.47 (m, 9 H), 1.44 (s, 3 H), 1.32 (s, 9 H); 13C NMR (100
MHz, CDCl3) δ 112.6, 109.6, 109.4, 108.8, 96.3, 85.1, 81.4, 70.7,
70.5, 65.9-64.3, 55.0, 26.4, 26.0, 24.9, 24.5, 11.1 (d, 1JC-P ) 145
Hz); 31P NMR (163 MHz, CDCl3) δ 31.78 (s, 1 P), 31.32 (s, 1 P);
MS (EI+) m/z calcd for C22H37O12P (M + Na)+ 547.5, found 547.5
(100%). Anal. Calcd for C22H37O12P: C, 50.38; H, 7.11; O, 36.61;
P, 5.91. Found: C, 50.15; H, 7.25; P, 6.10.
Experimental Section
General Procedure for Preparation of P-Chiral Ethyl Gly-
cosyl Methylphosphonates, 1-sugar (Protocol A). n-BuLi (1 equiv,
5.3 mL, 1.6 M solution in hexanes, 8.5 mmol) was added dropwise
to a stirred solution of protected sugar, 4-sugar, or ethanol (1 equiv,
8.5 mmol) in anhydrous THF (15 mL) at -50 °C. After being stirred
under nitrogen atmosphere for 30 min, the mixture was allowed to
reach room temperature. The so-obtained lithium alcoholate 4′-
sugar (1 equiv, 8.5 mmol) was added dropwise to a solution of
methyl phosphonic dichloride (1 equiv, 1.13 g, 8.5 mmol) in THF
(15 mL) at -78 °C. After the mixture was stirred for 30 min at
-78 °C, lithium ethanolate (1 equiv, 8.5 mmol) was added
dropwise. The mixture was stirred for 30 min at -50 °C before it
was quenched with water (15 mL). The organic layer was extracted
with CH2Cl2 (3 × 30 mL) and dried over anhydrous sodium sulfate,
and solvents were evaporated. Silica gel column chromatography
of the residue provided pure 1-sugar in 15-70% yield from 4-sugar.
Ethyl (1,2:3,4-Di-O-isopropylidene-R-D-galactopyranosyl) Me-
thylphosphonate, 1-gal. According to protocol A, 2.21 g (8.5
mmol) of 4-gal yielded 1.74 g (4.7 mmol, 56%) of a 1:1 mixture
of 1-gal diastereoisomers and 0.59 g (1.02 mmol, 12%) of 1-gal-
gal. 1-gal: yellow oil; Rf 0.35 (9:1 ethyl acetate/hexane); IR (KBr
plate) 1250, 1065 cm-1; 1H NMR (400 MHz, CDCl3) δ 5.53 (d, J
) 5.0 Hz, 1 H), 4.61 (dd, J ) 7.9, 2.5 Hz, 1 H), 4.33 (dd, J ) 5.0,
2.5 Hz, 1 H), 4.24 (dd, J ) 7.9, 1.6 Hz, 1 H), 4.20-3.95 (m, 5 H),
1.53 (s, 3 H), 1.50 (d, J ) 17.6 Hz, 3 H), 1.43 (s, 3 H), 1.33-1.30
(m, 9 H); 13C NMR (100 MHz, CDCl3) δ 110.2, 109.5, 96.8, 71.5,
Deuteriolysis of 1-gal. n-BuLi (1 equiv, 1.87 mL, 1.6 M solution
in hexanes, 3 mmol) was added dropwise at -78 °C to a stirred
solution of 1-gal (1 equiv, 1.098 g, 3 mmol) in THF (15 mL). The
mixture was maintained for 30 min at -78 °C before it was
quenched with D2O (10 mL). The organic layer was extracted with
CH2Cl2 (3 × 50 mL), dried over Na2SO4, concentrated, and purified
by silica gel chromatography to give a 1:1 mixture of 1-gal-d
diastereomers as a white oil.
Ethyl 1,2:3,4-Di-O-isopropylidene-R-D-galactopyranosyl 1-Deu-
teriomethylphosphonate, 1-gal-d. Rf 0.4 (ethyl acetate); IR (KBr
plate) 1255, 1050 cm-1; 1H NMR (400 MHz, CDCl3) δ 5.54 (d, J
) 5.0 Hz, 1 H), 4.61 (dd, J ) 7.9, 2.5 Hz, 1 H), 4.32 (dd, J ) 5.0,
2.5 Hz, 1 H), 4.24 (dd, J ) 7.9, 1.9 Hz, 1 H), 4.20-3.95 (m, 5 H),
1.54 (s, 3 H), 1.57 (dt, J ) 3.9 Hz, 2 H), 1.43 (s, 3 H), 1.33-1.30
(m, 9 H); 13C NMR (100 MHz, CDCl3) δ 109.5, 108.7, 96.2, 70.7,
2
2
70.4, 67.6, 64.8 (d, JC-P ) 6 Hz), 61.8 (d, JC-P ) 6 Hz), 26.0-
24.5, 16.4 (d, 3JC-P ) 6 Hz), 11.2 (d, JC-P ) 145 Hz); 31P NMR
1
(170 MHz, CDCl3) δ 31.76 (s, 1 P), 31.25(s, 1P). MS (FAB+):
m/z calcd for C15H27O8P [M]+ 366.3, found 367.1 [M + 1]+ (100%).
Anal. Calcd for C15H27O8P: C, 49.18; H, 7.43; O.34,94; P, 8.45.
Found: C, 49.32; H, 7.26; P, 8.64.
2
2
70.4, 67.3, 64.4 (d, JC-P ) 6 Hz), 61.4 (d, JC-P ) 6 Hz), 25.9,
24.9, 16.3 (d, 3JC-P ) 6.3 Hz), 10.9 (dt, 1JC-P ) 144 Hz, 1JC-D
)
General Procedure for Preparation of Diglycosyl Meth-
ylphosphonates, 1-sugar-sugar (Protocol B). The procedure was
exactly the same as described above for 1-sugar except that only
one lithium alcoholate 4′-sugar (2 equiv, 17 mmol) was added
dropwise to a solution of methyl phosphonic dichloride (1 equiv,
1.13 g, 8.5 mmol) in THF (15 mL) at -78 °C. The mixture was
stirred for 30 min at -50 °C before it was quenched with water
(15 mL). The organic layer was extracted with CH2Cl2 (3 × 30
mL) and dried over anhydrous sodium sulfate, and solvents were
evaporated. Silica gel column chromatography of the residue
provided pure 1-sugar-sugar in 85-90% yield from 4-sugar.
Bis(1,2:3,4-di-O-isopropylidene-R-D-galactopyranosyl) Meth-
ylphosphonate, 1-gal-gal. According to protocol B, 4.42 g (17
mmol) of 4-gal yielded 4.19 g (7.2 mmol, 85%) of 1-gal-gal as a
21 Hz); 31P NMR (101 MHz, CDCl3) δ 29.33 (s, 1 P), 28.82 (s, 1
P); MS (FAB+) m/z calcd for C15H26DO8P [M]+ 367.3, found 368.2
[M + 1]+ (100%). Anal. Calcd for C15H26DO8P: C, 49.04; H, 7.68;
O, 34.84; P, 8.43. Found: C, 49.23; H, 7.32; P, 8.16.
General Procedure for Preparation of P1,P2-Diglycosyl Me-
thylenediphosphonates, 5-sugar-sugar. s-BuLi (2 equiv, 1.9 mL,
1.6 M solution in hexanes, 3 mmol) was added dropwise at -78
°C to a stirred solution of 1-sugar (2 equiv, 3 mmol) in THF (15
mL). Stirring was maintained for 30 min at -78 °C. Ethyl
phosphorodichloridate 2 (1 equiv, 0.243 g, 1.5 mmol) was added
dropwise and the mixture was stirred for 30 min at -78 °C. Then
the sugar nucleophile 4 (1 equiv, 1.5 mmol) was added dropwise
and the reaction was stirred for 10 min at -78 °C before it was
warmed slowly to room temperature. The reaction mixture was then
quenched with water (15 mL). The organic layer was extracted with
1
colorless oil: Rf 0.39 (9:1 ethyl acetate/hexane); H NMR (250
MHz, CDCl3) δ 5.54 (d, J ) 5.0 Hz, 2 H), 4.62 (dd, J ) 8.0, 2.5
J. Org. Chem, Vol. 71, No. 21, 2006 7987

Grison et al.
CH2Cl2 (3 × 50 mL) and dried over Na2SO4. Evaporation of
solvents and silica gel column chromatography provided the product
5-sugar-sugar as a mixture of inseparable diastereomers and the
recovered 1-sugar in excess.
the general procedure, starting from 1.52 g (2.9 mmol) of 1-gal-
rib, and after successive addition of 0.234 g (1.45 mmol) of ethyl
phosphorodichloridate 2 and 0.418 g (1.45 mmol) of 4-man-b, 0.942
g (1.04 mmol, 72%) of a 1.8:1 mixture of 5-gal-rib-man-b
diastereomers was obtained and 0.734 g (1.40 mmol) of 1-gal-rib
was recovered. 5-gal-rib-man-b: clear oil; Rf 0.22 (6:4 acetone/
hexane). R anomer: 1H NMR (500 MHz, CDCl3) δ 5.54 (m, 1 H),
4.96 (s, 1 H), 4.75 (m, 2 H), 4.62-4.55 (m, 3 H), 4.38-4.32 (m,
2 H), 4.26-4.03 (m, 14 H), 3.72 (m, 1 H), 3.32 (s, 3 H), 2.54 (m,
2 H), 1.75 (m, 2 H), 1.49-1.43 (m, 15 H), 1.37-1.25 (m, 18 H);
13C NMR (125 MHz, CDCl3) δ 112.5-108.7 (m), 109.3, 96.2,
85,3-84.8 (m), 81.5-80.1 (m), 73.1, 70.6, 70.6-67.3 (m), 66.9-
62.8 (m), 55.0, 31.8, 26.9-23.9 (m), 16.4. 31P NMR (163 MHz):
P1-(Ethyl 1-O-methyl-2,3-O-isopropylidene-â-D-ribofuranosyl)
P2-(Ethyl 1-O-methyl-2,3-O-isopropylidene-â-D-ribofuranosyl)
Methylenediphosphonate, 5-rib-rib. According to the general
procedure, starting from 0.930 g (3 mmol) of 1-rib, and after
successive addition of 0.242 g (1.5 mmol) of ethyl phosphorod-
ichloridate 2 and then 0.306 g (1.5 mmol) of 4-rib, 0.507 g (0.839
mmol, 56%) of 5-rib-rib was obtained and 0.450 g (1.45 mmol) of
1-rib was recovered. 5-rib-rib: yellow oil; Rf 0.2 (ethyl acetate);
1
IR (KBr plate) 1245, 1035 cm-1; H NMR (250 MHz, CDCl3) δ
1
4.96 (s, 2 H), 4.78-4.70 (m, 2 H), 4.61-4.56 (m, 2 H), 4.37-
4.00 (m, 10 H), 3.32 (s, 6 H), 2.54 (t-like, J ) 21.0 Hz, 2 H), 1.46
(s, 6 H), 1.41-1.31 (m, 12 H); 13C NMR (63 MHz, CDCl3) δ 112.2,
109.1, 84.7, 81.2, 66.0, 65.4, 62.8, 54.7, 24.9 (t, 1JC-P ) 136 Hz),
26.1, 22.7, 16.1; 31P NMR (101 MHz) δ 17.36 (s, 2 P); MS (FAB+)
m/z calcd for C23H42O14P2 [M]+ 604.2, found 605.3 [M + 1]+
(35%), 573.3 [M - MeOH]+ (50%), 311.2 [1-rib + 1]+ (35%),
279.2 [1-rib-OMe]+ (60%). Anal. Calcd for C23H42O14P2: C, 45,70;
H, 7,00; O, 37,05; P, 10,25. Found: C, 45.37; H, 6.86; P, 9.98.
P1-(Ethyl 1-O-methyl-2,3-O-isopropylidene-â-D-ribofuranosyl)
P2-(Ethyl 2,3-O-isopropylideneuridine) Methylenediphospho-
nate, 5-rib-uri. According to the general procedure, starting from
0.869 g (2.8 mmol) of 1-rib, and after successive addition of 0.227
g (1.4 mmol) of ethyl phosphorodichloridate 2 and then 0.383 g
(1.35 mmol) of 4-uri, 0.379 g (0.553 mmol, 41%) of 5-rib-uri was
obtained and 0.403 g (1.30 mmol) of 1-rib was recovered. 5-rib-
rib: yellow oil; Rf 0.25 (ethyl acetate); IR (KBr plate) 1720, 1630,
δ 20.90-18.93 (m, 2 P). â anomer: H NMR (500 MHz, CDCl3)
δ 5.54 (m, 1 H), 4.96 (s, 1 H), 4.75 (m, 2 H), 4.67 (m, 1 H), 4.62-
4.55 (m, 3 H), 4.38-4.32 (m, 2 H), 4.26-4.03 (m, 14 H), 3.72 (m,
1 H), 3.50 (m, 1 H), 3.32 (s, 3 H), 2.54 (m, 2 H), 2.07 (m, 2 H),
1.49-1.43 (m, 15 H), 1.37-1.25 (m, 18 H);13C NMR (125 MHz,
CDCl3) δ 112.5-108.7 (m), 109.3, 96.2, 85.3-84.8 (m), 81.5-
80.1 (m), 73.1, 70.6, 70.6-67.3 (m), 66.9-62.8 (m), 55.0, 29.3,
26.9-23.9 (m), 16.4; 31P NMR (163 MHz, CDCl3) δ 20.90-18.93
(m, 2 P). MS (EI+) m/z calcd for C38H64O20P2 [M]+ 902.3, found
925.3 [M + Na]+ (25%). Anal. Calcd for C38H64O20P2: C, 50.55;
H, 7.14; O, 35.44; P, 6.86. Found: C, 50.70; H, 6.96; P, 6.69.
Preparation of P1,P2-tetrakis(1-O-methyl-2,3-O-isopropylidene-
â-D-ribofuranosyl) Methylenediphosphonate, 5-rib-rib-rib-rib.
s-BuLi (2 equiv, 1.9 mL, 1.6 M solution in hexanes, 3 mmol) was
added dropwise at -78 °C to a solution of 1-rib-rib (2 equiv, 1.40
g, 3 mmol) in THF (15 mL). The mixture was stirred for 30 min
at -78 °C. The protected ribosyl phosphorodichloridate 2-rib (1
equiv, 0.482 g, 1.5 mmol) was added dropwise. After being stirred
for 10 min at -78 °C, the mixture was warmed to -50 °C and
stirred for 90 min at this temperature. The reaction mixture was
then cooled to -78 °C and the nucleophilic sugar 4-rib (1 equiv,
0.306 g, 1.5 mmol) was added dropwise. After being stirred for 10
min at -78 °C, the mixture was allowed to warm to room
temperature. Stirring was pursued for 48 h at room temperature
before the mixture was quenched with water (15 mL). The organic
layer was extracted with CH2Cl2 (3 × 50 mL), dried over Na2SO4,
concentrated, and purified by silica gel chromatography and yielded
0.414 g (0.45 mmol, 30%) of 5-rib-rib-rib-rib and 0.65 g (1.30
mmol) of recovered 1-rib-rib. 5-rib-rib-rib-rib: colorless oil; Rf
1
1450, 1250, 1050 cm-1; H NMR (250 MHz, CDCl3) δ 10.07 (br
s, 1 H), 7.46-7.39 (m, 1 H), 5.74-5.64 (m, 2 H), 5.25 (s, 1 H),
4.92-4.77 (m, 2 H), 4.71-4.66 (m, 1 H), 4.57-4.51 (m, 1 H),
4.28-4.00 (m, 10 H), 3.25 (s, 3 H), 2.50 (t-like, J ) 21.0 Hz, 2
H), 1.49 (s, 3 H), 1.40 (s, 3 H), 1.33-1.18 (m, 12 H); 13C NMR
(63 MHz, CDCl3) δ 63.4, 150.1, 141.9, 114.3, 112.3, 109.2, 102.5,
3
93.4 (d, JC-P ) 29 Hz), 85.1-83.8, 81.2, 80.3, 65.9, 65.5, 62.8,
1
54.8, 25.0 (t-like, JC-P ) 135 Hz), 27.2, 26.9, 26.1, 24.7, 16.0;
31P NMR (101 MHz, CDCl3) δ 17.89 (s, 1 P), 17.42 (s, 1 P), 17.17
(s, 2 P); MS (FAB+) m/z calcd for C26H42N2O15P2 [M]+ 684.2,
found 685.3 [M + 1]+ (100%). Anal. Calcd for C26H42N2O15P2:
C, 45.62; H, 6.18; N, 4.09; O, 35.06; P, 9.05. Found: C, 45.74; H,
6.35; N, 3.82; P, 9.22.
1
0.22 (4:6 acetone/hexane); IR (KBr plate) 1245, 1035 cm-1; H
General Procedure for Preparation of P1,P1,P2-Triglycosyl
Methylenediphosphonates, 5-sugar-sugar-sugar. s-BuLi (2 equiv,
1.9 mL, 1.6 M solution in hexanes, 3 mmol) was added dropwise
at -78 °C to a solution of 1-sugar-sugar (2 equiv, 3 mmol) in
THF (15 mL). The mixture was stirred for 30 min at -78 °C before
ethyl phosphorodichloridate 2 (1 equiv, 1.5 mmol) was added
dropwise. After being stirred for 10 min at -78 °C, the mixture
was allowed to warm to -50 °C and stirred for ∼90 min at -50
°C until disappearance of the yellow color of the lithium carbanion
1′-sugar-sugar. The reaction mixture was then cooled to -78 °C
and the nucleophilic 4-sugar was added dropwise. After being
stirred for 10 min at -78 °C, the mixture was allowed to warm to
room temperature before being quenched with water (15 mL) after
1 h at room temperature. The organic layer was extracted with CH2-
Cl2 (3 × 50 mL) and dried over Na2SO4. Evaporation of solvents
and column silica gel chromatography provided the triglycosyl
methylenediphosphonate product 5-sugar-sugar-sugar as a mixture
of inseparable diastereomers and the recovered 1-sugar-sugar in
excess.
NMR (400 MHz, CDCl3) δ 4.97 (s, 4 H), 4.75 (t-like, 4 H), 4.60
(d, J ) 5.9 Hz, 4 H), 4.39-4.35 (m, 4 H), 4.15-4.06 (m, 8 H),
3.32 (s, 12 H), 2.62 (t-like, J ) 21.3 Hz, 2 H), 1.47 (s, 12 H), 1.32
(s, 12 H). 13C NMR (100 MHz, CDCl3): δ 112.5, 109.4, 85.0,
1
81.2, 66.4-66.2 (m), 55.1, 25.4 (t-like, JC-P ) 138 Hz), 26.4,
24.9; 31P NMR (163 MHz, CDCl3) δ 19.98 (s, 1 P); MS (EI+) m/z
calcd for C37H62O22P2 [M]+ 920.8, found 943.5 [M + Na]+ (90%).
Anal. Calcd. for C37H62O22P2: C, 48.26; H, 6.79; O, 38.23; P, 6.73.
Found: C, 48.51; H, 6.93; P, 6.42.
Acknowledgment. We are very grateful to Dr. A. van
Dorsselaer, University Louis Pasteur, Strasbourg, France, for
mass measurements and to Professor C. Roumestand and Dr.
A. Heitz, University Montpellier 1 (Centre de Biochimie
Structurale), for HSQC-TOCSY experiments.
Supporting Information Available: General methods, descrip-
tion of the data, and copies of NMR spectra for new compounds
of Tables 1, 4, and 5, including copies of COSY, HMQC, HSQC,
TOCSY, and HSQC-TOCSY-NMR spectra. This material is
available free of charge via the Internet at http://pubs.acs.org.
P1-(1,2:3,4-Di-O-isopropylidene-R-D-galactopyranosyl) P1-(1-
O-Methyl-2,3-O-isopropylidene-â-D-ribofuranosyl)] P2-[Ethyl
(3,6-anhydro-2-deoxy-4,5:7,8-di-O-isopropylidene)-D-manno-oc-
tosyl)] Methylenediphosphonate, 5-gal-rib-man-b. According to
JO061087V
7988 J. Org. Chem., Vol. 71, No. 21, 2006