Versatile synthesis of rare nucleotide furanoses

Article abstract of DOI:10.1021/ol702392x

(Chemical Equation Presented) Direct activation of unprotected thioimidoyl furanosides yielded in only one step and few minutes a panel of rare uridine 5′-diphosphofuranoses. Diastereoselectivity of the reaction was tightly connected with reaction time, t

Full text of DOI:10.1021/ol702392x

ORGANIC
LETTERS
2007
Vol. 9, No. 25
5227-5230
Versatile Synthesis of Rare Nucleotide
Furanoses
Pauline Peltier, Richard Daniellou, Caroline Nugier-Chauvin,* and
Vincent Ferrie`res*
Ecole Nationale Supe´rieure de Chimie de Rennes, Organic and Supramolecular
Chemistry, CNRS, AVenue du Ge´ne´ral Leclerc, F-35700 Rennes
Vincent.ferrieres@ensc-rennes.fr
Received October 3, 2007
ABSTRACT
Direct activation of unprotected thioimidoyl furanosides yielded in only one step and few minutes a panel of rare uridine 5′-diphospho-
furanoses. Diastereoselectivity of the reaction was tightly connected with reaction time, temperature, and nature of the furanosyl donor. This
approach was totally selective since no ring expansion from the initial five-membered ring to the more stable pyranose form was observed.
Glycoconjugates are mainly built up with hexoses present
in a pyranose configuration. Nevertheless, their presence in
microorganisms, but not in mammals, in a furanose form
adds supplementary variability to the complexity of such
biomolecules. Therefore, because of the millions of deaths
caused each year, Mycobacterium, Trypanosoma, Leishma-
nia, or Aspergillus species are widely studied in order to
precise their biological involvements and to find alternative
treatments to the drugs currently used.1 Surprinsingly,
hexofuranose residues occurring in various polysaccharides
and glycoconjugates produced by infectious bacteria, pro-
tozoa, and fungi belong mainly to either D-galactose (D-Galf)
or D-fucose (D-Fucf) series.
(UDP)-pyranose to the corresponding furanosyl donor, is
required. Up to now, UDP-R-D-galactofuranose 1R (UDP-
R-D-Galf) is the only activated intermediate identified as a
key substrate for transferases. However, the existence of
D-fucofuranose (D-Fucf) as well as L-arabinofuranose (L-Araf)
in natural oligosaccharides probably involves similar bio-
synthetic mechanisms and the requisite for their correspond-
ing nucleotide sugars.7 Moreover, owing to structural ho-
mology, the targeted natural and non-natural UDP-furanoses
(2) Miletti, L. C.; Marino, C.; Marino, K.; de Lederkremer, R. M.; Colli,
W.; Alves, M. J. M. Carbohydr. Res. 1999, 320, 176-182.
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Lowary, T. L. J. Am. Chem. Soc. 2006, 128, 6721-6729.
(4) Wing, C.; Errey, J. C.; Mukhopadhyay, B.; Blanchard, J. S.; Field,
R. A. Org. Biomol. Chem. 2006, 4, 3945-3950.
(5) Chad, J. M.; Sarathy, K. P.; Gruber, T. D.; Addala, E.; Kiessling, L.
L.; Sanders, D. A. R. Biochemistry 2007, 46, 6723-6732.
(6) Kleczka, B.; Lamerz, A.-C.; van Zandbergen, G.; Wenzel, A.;
Gerardy-Schahn, R.; Wiese, M.; Routier, F. H. J. Biol. Chem. 2007, 282,
10498-10505.
(7) Konishi, T.; Takeda, T.; Miyazaki, Y.; Ohnishi-Kameyama, M.;
Hayashi, T.; O’Neill, M. A.; Ishii, T. Glycobiology 2007, 17, 345-354.
The biosynthesis of such hexofuranosides requires three
families of enzymes, as opposed to pyranosides. In addition
to classical hydrolases2 and transferases,3,4 the involvement
of pyranose mutases,5,6 which isomerize uridine 5′-diphospho
(1) Lowary, T. L. Curr. Opin. Chem. Biol. 2003, 7, 749-756.
10.1021/ol702392x CCC: $37.00
© 2007 American Chemical Society
Published on Web 11/13/2007

1-4 are potentially suitable substrates for both pyranose
mutases and furanosyl transferases.
dation promoted by the boron trifluoride etherate complex
followed by methanolysis (Scheme 2). On another side,
These elaborate and relatively unstable derivatives gener-
ally involve time-consuming reactions, activated intermedi-
ates, and additives.8,9 Herein we present a short and versatile
chemical synthesis of eight UDP-furanoses directly from
unprotected thioimidoyl donors (Scheme 1).
Scheme 2. Synthesis of Thioimidates
Scheme 1. Retrosynthetic Analysis of Uridine
5′-Diphospho-furanoses
fluorinated thiogalactofuranoside 7 and thiofucofuranoside
8 were synthesized from a common intermediate 10.19
Nucleophilic opening of the cyclic sulfate with fluoride and
hydride anions, respectively, was followed by acidic des-
ulphation to afford intermediates 1120 and 12 in 86% and
88% yield, respectively. Further hydrogenolysis in the
presence of palladium(II) acetate, acetylation, and acetolysis
under controlled conditions yielded the peracetylated blocks
13 and 14, respectively. The target thiofuranosides 7 and 8
were finally obtained according to Ferrier procedure and final
Zemplen transesterification.
With the unprotected thioimidoyl donors in hand, the direct
synthesis of nucleotide furanoses was first attempted in the
galacto series from thioimidate 5, using a freshly prepared
acidic form of UDP in dry dimethylformamide. A series of
assays with the donor 5 was perfromed to determine the
optimum reaction time toward the ratio UDP-Galf/UDP and
the diastereoselectivity (Table 1). The 31P NMR of the crude
self-promoted reaction revealed that UDP-R-D-Galf 1R was
kinetically obtained after only few minutes and reached a
maximum after 10 min (entries 1-3). Subsequently, maxi-
mum of overall conversion was observed after 20 min (entry
4). Nevertheless, longer reaction times resulted in substantial
degradation of the desired UDP-Galf with the amount of 1R
decreasing faster than its anomer (entries 4-6). Finally, it
is noteworthy that these data show the complete absence of
UDP-pyranoses.
Thioimidates have recently gained interest thanks to their
use as efficient donors in glycosylation reactions.10-12 On
this basis, we expected that the acidic form of UDP could
behave like phosphoric acid13 and react as an acceptor
without previous chemical activation.14-17 Moreover, from
a structural point of view, D-Galf, D-Fucf, and L-Araf share
the same skeleton but are subtly modified on the C-5 side
arm of L-Araf by adding hydrophobic methyl group (D-Fucf)
or hydroxymethyl function (D-Galf), able to act as both donor
and/or acceptor of hydrogen bonding. To complete this
collection, we also prepared the C-5 fluoromethyl derivative
3, the fluorine atom being nearly isosteric to oxygen but
acting only as hydrogen-bond acceptor.
Benzimidazolyl thiofuranosides 5-8 were prepared from
the corresponding peracylated furanoses. While the synthesis
of 5 was already described,13 the arabinosyl derivative 6 was
obtained from the known compound 918 by first thioglycosi-
(8) Wittmann, V.; Wong, C. H. J. Org. Chem. 1997, 62, 2144-2147.
(9) Errey, J. C.; Mukhopadhyay, B.; Kartha, K. P. R.; Field, R. A. Chem.
Commun. 2004, 2706-2707.
(10) Euzen, R.; Gue´gan, J. P.; Ferrie`res, V.; Plusquellec, D. J. Org. Chem.
2007, 72, 5743-5747.
(11) Euzen, R.; Ferrie`res, V.; Plusquellec, D. Carbohydr. Res. 2006, 341,
2759-2768.
(12) Smoot, J. T.; Pornsuriyasak, P.; Demchenko, A. V. Angew. Chem.,
Int. Ed. 2005, 44, 7123-7126.
(13) Euzen, R.; Ferrie`res, V.; Plusquellec, D. J. Org. Chem. 2005, 70,
847-855.
(14) Marlow, A. L.; Kiessling, L. L. Org. Lett. 2001, 3, 2517-2519.
(15) Zhang, Q.; Liu, H.-w. J. Am. Chem. Soc. 2000, 122, 9065-9070.
(16) Marin˜o, K.; Marino, C.; Lima, C.; Baldoni, L.; de Lederkremer, R.
M. Eur. J. Org. Chem. 2005, 2005, 2958-2964.
(17) Tsvetkov, Y. E.; Nikolaev, A. V. J. Chem. Soc., Perkin Trans. 1
2000, 889-891.
(19) Pathak, A. K.; Pathak, V.; Seitz, L.; Maddry, J. A.; Gurcha, S. S.;
Besra, G. S.; Suling, W. J.; Reynolds, R. C. Bioorg. Med. Chem. 2001, 9,
3129-3143.
(20) Euzen, R.; Lopez, G.; Nugier-Chauvin, C.; Ferrie`res, V.; Plusquellec,
D.; Re´mond, C.; O’Donohue, M. Eur. J. Org. Chem. 2005, 4860-4869.
(18) Wang, Z.; Prudhomme, D. R.; Buck, J. R.; Park, M.; Rizzo, C. J.
J. Org. Chem. 2000, 65, 5969-5985.
5228
Org. Lett., Vol. 9, No. 25, 2007

Table 1. Monitoring of the Phosphorylation Reaction by 31P
Table 2. Synthesis of Target UDP Furanoses 1-4
NMR
donor
(R)
time (min)
(temp, °C)
overall yield
(%) (R/â)
entry
time (min)
1R/UDP (%)
1â/UDP (%)
1R/1â
entry
1
product
1
2
3
4
5
6
2
5
10
20
45
180
5
13
27
22
4
2
7
23
40
16
20
1:0.4
1:0.5
1:0.9
1:1.8
1:4
5
10
(0)
8
(-10)
60
(0)
10
1R
1â
32 (1:2)
21 (1:0)
37 (1.3:1)
27 (2:1)
(CH2OH)
2
3
4
6
2R
(H)
2â
7
3R
5
1:4
(CH2F)
8
3â
4R
(CH3)
(0)
4â
Despite the really short reaction time, inescapable partial
degradation of UDP further occurred to produce uridine 5′-
monophosphate (UMP). However, no UMP-Galf was ob-
served. This was corroborated by reverse phase HPLC which
also showed high resolution between 1R and 1â. Unfortu-
nately, the 1,2-cis anomer 1R was collected with UDP. This
problem was overcome using an alkaline phosphatase which
transformed UDP into uridine and monophosphate (Figure
1).21 Consequently, after only 10 min at 0 °C, followed by
reactive under the conditions used than UMP released in
small amounts in the reaction media.
This approach was subsequently extended to the L-arabino,
D-fuco and D-fluorogalacto series starting from the corre-
sponding benzimidazolyl furanosides 6-8.22 As expected,
conditions had to be optimized according to the nature of
the carbohydrate. All reactions were carried out between -10
and 0 °C and the interconversion of functional groups at
anomeric positions of 6 and 8 was efficient in less than 10
min as already observed from donor 5. While chromato-
graphic analysis indeed showed the formation of both 1,2-
cis and 1,2-trans anomers from the arabinosyl precursor 6,
purification finally gave pure 2R in 21% yield since 2â was
too labile to be isolated. Nevertheless, the 2R/2â ratio was
estimated to 1:1.8 according to analytical HPLC. As far as
the fucosyl derivative is concerned, efforts to separate both
anomers of UDP-Fucf 4 were unsuccessful. Therefore, 4R
and 4â were isolated in a 27% yield with a 1,2-cis/1,2-trans
ratio close to 2:1.
Finally, the 6-deoxy-6-fluoro-thioimidate 7 set him apart
from the other donors since its transformation required longer
reaction time (Table 2, entry 3). This phenomenon could
probably be related to the remote but strong electronic effect
of the fluorine atom in primary position. Interestingly,
preparative chromatography, without previous degradation
of UDP by alkaline phosphatase, directly afforded pure 3R
and 3â in a 37% overall yield with a 1.3:1 ratio (Figure 1,
Table 2).
Figure 1. Chromatographic profiles for UDP-furanoses 1-4.
simple workup, the desired UDP-Galf 1 was synthesized and
isolated in a 32% overall yield. Preparative chromatography
allowed us to separate and isolate both anomers 1R and 1â
in a 1:2 ratio (Table 2). Structures of 1R and 1â were
unambiguously established on the basis of NMR data. First,
the five-membered ring of the unknown 1,2-trans compound
1â was notably deduced from the high chemical shift
obtained for C-1 of the galactofuranosyl residue (δC-1 104.7
ppm). Second, this entity is also characterized by a coupling
constant lower than 1 Hz between H-1 and H-2, that is
relevant to a 1,2-trans relationship, and a JH-1,P value of 5.8
Hz. Moreover, on the basis of the two upfield doublets in
the 31P NMR spectrum, the presence of UMP-Galf is
completely dismissed. This demonstrated that (i) no isomer-
ization into the more stable pyranosyl derivatives of both
donor 5 and product 1 occurred under the present acidic
conditions and (ii) the acidic form of UDP is much more
Once again, neither pyranose forms nor UMP-furanoses
were ever observed and all the desired nucleotide furanoses
1
were fully characterized on the assumption of H, 13C, and
31P NMR data.23
Despite their biological importance, the synthesis of
nucleotide sugars still remains a challenge for chemists. The
(22) Typical procedure for the synthesis of UDP-furanoses: To UDP
disodium salt dihydrate (2 equiv) in DMF (3 mL) at 0 °C was added
Amberlite IR-120 (H+-form) until the UDP was completely dissolved. The
resin was filtered off and washed with DMF. The filtrate and washing were
freeze-dried, redissolved in anhydrous DMF (1 mL) and cooled (Table 1).
A solution of the desired donor (1 equiv) in DMF (1 mL) was added
dropwise. The mixture was stirred for an appropriate period, diluted with
cold water (1 mL) and 0.5 M NH4HCO3 (0.5 mL), and finally freeze-dried.
In the case of donors 5, 6, and 8, the residue was treated with alkaline
phosphatase (20 µL, 1 unit/µL, 2 mL of deionized water), and the mixture
was kept at room temperature until UDP was no longer detected by NMR
31P. The residue was centrifugated, and the resulting filtrate was purified
by HPLC.
(21) Hanessian, S.; Lu, P. P.; Ishida, H. J. Am. Chem. Soc. 1998, 120,
13296-13300.
Org. Lett., Vol. 9, No. 25, 2007
5229

versatility of our approach was underlined by synthesizing
six unknown UDP-furanoses, These likely glycosyl donors
are essentially required to investigate the processes involved
in the hexofuranose incorporation within cell wall glyco-
conjugates. They could be of great interest to identify putative
glycosyltransferases, to study the action of the correlate
mutases as well to develop antimicrobial agents. This
efficient one-step procedure complements well the chemical
approaches proposed in the literature.24 The absence of any
protecting groups, on both donor and UDP, and of any
additives not only results in a direct access to the desired
UDP-furanoses but also in an increase reactivity of thioimi-
doyl donors. Moreover, neither ring expansion nor UMP-
furanoses were observed. All these facts let us consider that
the proposed chemical method comes closer to the chemo-
enzymatic ways recently published.9
(23) Selected data for UDP-furanoses 1-4 in D2O. 1â: 1H NMR (D2O)
d ) 5.55 (d, 1 H, J1,P ) 5.8 Hz, H-1 Gal); 13C NMR (D2O) d ) 104.7 (d,
JC-1,P ) 5.1 Hz, C-1 Gal); 31P NMR (D2O) d ) -10.3 (d, JP,P ) 21.7 Hz,
Pa), -12.5 (d, Pb). HRMS (ESI-): [C15H22N2O17P2]- calcd, 565.0472;
found, 565.0470. 2R: 1H NMR (D2O) d ) 5.58 (d, 1 H, J1,P ) 6.0 Hz, H-1
Ara); 13C NMR (D2O) d ) 104.9 (d, JC-1,P ) 5.4 Hz, C-1 Ara); 31P NMR
(D2O) d ) -10.2 (d, JP,P ) 19.6 Hz, Pa), -12.6 (d, Pb). HRMS (ESI-):
[C14H21N2O16P2]- calcd, 535.0366; found, 535.0359. 3R: 1H NMR (D2O)
d ) 5.58 (dd, 1 H, J1,P ) 5.7 Hz, J1,2 ) 4.2 Hz, H-1 6F-Gal); 13C NMR
(D2O) d ) 97.6 (C-1 6F-Gal); 31P NMR (D2O) d ) -10.1 (d, JP,P ) 19.6
Hz, Pa), -11.5 (d, Pb). HRMS (ESI-): [C15H22FN2O16P2]- calcd, 567.0429;
found, 565.0419. 3â: 1H NMR (D2O) d ) 5.53 (d, 1 H, J1,P ) 5.8 Hz, H-1
6 F-Gal); 13C NMR (D2O) d ) 103.9 (C-1 6F-Gal); 31P NMR (D2O) d )
-10.3 (d, JP,P ) 19.6 Hz, Pa), -12.6 (d, Pb). HRMS (ESI-): [C15H22-
FN2O16P2]- calcd, 567.0429; found, 565.0446. 4R: 1H NMR (D2O) d )
5.62 (d, 1 H, J1,P ) 5.9 Hz, J1,2 ) 4.2 Hz, H-1 Fuc); 13C NMR (D2O) d )
97.8 (C-1 Fuc); 31P NMR (D2O) d ) -11.4 (d, JP,P ) 19.6 Hz, Pa), -12,7
(d, Pb). HRMS (ESI-): [C15H23N2O16P2]- calcd, 549.0523; found, 549.0514.
4â: 1H NMR (D2O) d ) 5.59 (d, 1 H, J1,P ) 5.9 Hz, H-1 Fuc); 13C NMR
(D2O) d ) 103.8 (C-1 Fuc); 31P NMR (D2O) d ) -11.5 (d, JP,P ) 21.8
Hz, Pa), -13.8 (d, Pb). HRMS (ESI-): [C15H23N2O16P2]- calcd, 549.0523;
found, 549.0514.
Acknowledgment. The authors would like to thank J. P.
Gue´gan (ENSCR) and Dr. S. Pilard (University of Picardie)
for their technical assistance. P.P. is grateful to the Re´gion
Bretagne for a grant.
Supporting Information Available: Experimental prepa-
rations and NMR data for all new compounds. This material
is available free of charge via the Internet at http://pubs.acs.org.
OL702392X
(24) Hanessian, S.; Lou, B. Chem. ReV. 2000, 100, 4443-4463.
5230
Org. Lett., Vol. 9, No. 25, 2007