Diastereoselective synthesis of novel iminosugar-containing UDP-Galf mimics: Potential inhibitors of UDP-Gal mutase and UDP-Galf transferases

Article abstract of DOI:10.1021/jo061130e

Tetra-O-benzyl-D-glucofuranose was converted into uridine diphosphono-β-Galf mimics based on an iminosugar skeleton linked to UMP by a 2-hydroxypropyl tether. The synthesis is based on the highly regio- and stereoselective cycloaddition of an original uri

Full text of DOI:10.1021/jo061130e

Diastereoselective Synthesis of Novel Iminosugar-Containing
UDP-Galf Mimics: Potential Inhibitors of UDP-Gal Mutase and
UDP-Galf Transferases
Virginie Liautard, Alphert E. Christina, Vale´rie Desvergnes, and Olivier R. Martin*
Institut de Chimie Organique et Analytique, CNRS & UniVersite´ d’Orle´ans, BP 6759,
45067 Orle´ans, France
oliVier.martin@uniV-orleans.fr
ReceiVed June 2, 2006
Tetra-O-benzyl-D-glucofuranose was converted into uridine diphosphono-â-Galf mimics based on an
iminosugar skeleton linked to UMP by a 2-hydroxypropyl tether. The synthesis is based on the highly
regio- and stereoselective cycloaddition of an original uridin-5′-yl allylphosphonate with a 1,4-dideoxy-
1,4-iminogalactitol-derived cyclic nitrone, followed by the reductive elaboration of the cycloaddition
product. The resulting iminogalactose-UMP conjugates are novel sugar nucleotide mimics which could
be useful as inhibitors of UDP-Gal mutase and UDP-Galf transferases.
Introduction
ization of UDP-Galp into UDP-Galf by UDP-Gal mutase3 and
transfer of Galf into galactans by one or more UDP-Galf
transferases.4 The mechanism of the remarkable ring contraction
promoted by the mutase is not yet fully elucidated, despite the
availability of the X-ray crystal structure of the enzyme3 and
elegant bioorganic studies by the groups of Liu,5 Kiessling,6
and Sinay¨,7 in particular. Investigations on Galf transferases are
still in their infancy, and only one enzyme of this family has
yet been characterized.8 Interestingly, mycobacterial galactans
appear to be assembled by the action of a single enzyme.4b,8
While D-galactose is widely distributed in higher eukaryotes
as a glycoside in the pyranose form (Galp), the furanoid form
(Galf) of this hexose occurs much less frequently and is a
characteristic sugar component of bacterial and fungal cell wall
glycoconjugates.1 Because of its specificity to a number of
pathogenic microorganisms, the biosynthetic pathway of galacto-
furanose-containing glycans is becoming an important target
for the development of new antibiotic agents, especially
antimycobacterial agents.2 The incorporation of D-galactofura-
nose into these complex glycans involves two steps: isomer-
(3) (a) Sanders, D. A. R.; Staines, A. G.; McMahon, S. A.; McNeil, M.
R.; Whitfield, C.; Naismith, J. H. Nat. Struct. Biol. 2001, 8, 858-863. (b)
Beis, K.; Srikannathasan, V.; Liu, H.; Fullerton, S. W.; Bamford, V. A.;
Sanders, D. A.; Whitfield, C.; McNeil, M. R.; Naismith, J. H. J. Mol. Biol.
2005, 348, 971-982.
(4) (a) Mikusova, K.; Yagi, T.; Stern, R.; McNeil, M. R.; Besra, G. S.;
Crick, D. C.; Brennan, P. J. J. Biol. Chem. 2000, 275, 33890-33897. (b)
Kremer, L.; Dover, L. G.; Morehouse, C.; Hitchin, P.; Everett, M.; Morris,
H. R.; Dell, A.; Brennan, P. J.; McNeil, M. R.; Flaherty, C.; Duncan, K.;
Besra, G. S. J. Biol. Chem. 2001, 276, 26430-26440.
(5) Huang, Z.; Zhang, Q.; Liu, H. W. Bioorg. Chem. 2003, 31, 494-
502.
* To whom correspondence should be addressed. Tel: ++ 33 2 38 49 45
81. Fax: ++ 33 2 38 41 72 81. E-mail: Olivier.Martin@univ-orleans.fr.
(1) Trypanosomatids: (a) De Lederkremer, R. M.; Colli, W. Glycobiology
1995, 5, 547-552. S. disenteriae: (b) Dmitriev, B. A.; Lvov, V. L.;
Kochetkov, N. K. Carbohydr. Res. 1977, 56, 207-209. M. tuberculosis:
(c) Besra, G. S.; Khoo, K. H.; McNeil, M. R.; Dell, A.; Morris, H. R.;
Brennan, P. J. Biochemistry 1995, 34, 4257-4266. For other microorganisms
containing Galf, see references cited in ref 2.
(2) (a) Pedersen, L. L.; Turco, S. J. Cell. Mol. Life Sci. 2003, 60, 259-
266. (b) The galactofuran synthesis is essential for the growth of myco-
bacteria: Pan, F.; Jackson, M.; Ma, Y.; McNeil, M. J. Bacteriol. 2001,
183, 3991-3998. (c) Galf has been found recently in lower eukaryotes:
Bakker, H.; Kleczka, B.; Gerardy-Schahn, R.; Routier, F. H. Biol. Chem.
2005, 386, 657-661. (d) Beverley, S. M.; Owens, K. L.; Showalter, M.;
Griffith, C. L.; Doering, T. L.; Jones, V. C.; McNeil, M. R. Eukaryotic
Cell 2005, 4, 1147-1154.
(6) Soltero-Higgin, M.; Carlson, E. E.; Gruber, T. D.; Kiessling, L. L.
Nat. Struct. Mol. Biol. 2004, 11, 539-543.
(7) Caravano, A.; Sinay¨, P.; Vincent, S. P. Bioorg. Med. Chem. Lett.
2006, 16, 1123-1125.
(8) Rose, N. L.; Completo, G. C.; Lin, S.-J.; McNeil, M.; Palcic, M. M.;
Lowary, T. J. Am. Chem. Soc. 2006, 128, 6721-6729.
10.1021/jo061130e CCC: $33.50 © 2006 American Chemical Society
Published on Web 08/23/2006
J. Org. Chem. 2006, 71, 7337-7345
7337

Liautard et al.
SCHEME 1. UDP-Galactofuranose Biosynthesis
SCHEME 2. Synthetic Targets and Retrosynthesis
Nevertheless, it is accepted that both of those two enzymes’
families involve in their reaction an oxocarbenium-type transi-
tion state, and it is well-known that five-membered ring
iminosugars are efficient mimics of putative oxocarbenium
intermediates. In this context and in relation with our studies
on iminosugar-containing glycoside analogues,9 we initiated a
research program on the synthesis of new UDP-Galf mimics
based on a 1,4-dideoxy-1,4-imino-D-galactitol entity. As po-
tential inhibitors of these enzymatic processes,10 such com-
pounds may prove useful as tools for biochemical investigations
and may constitute leads for the development of new families
of antibiotic agents. The first and only examples of iminosugar-
based analogues of UDP-Galf have been reported by Fleet and
co-workers;11 in these structures, uridine is linked to the
iminogalactitol core by a dipeptide-like tether.
Synthetic Design. We have recently reported the stereose-
lective synthesis of R-linked UDP-Galf mimics containing a
carbon tether between 1,4-dideoxy-1,4-iminogalactitol and
UMP.12 In this paper, we wish to report a different, efficient,
and stereoselective methodology leading to mimics of â-linked
UDP-Galf illustrated by structure A. Our retrosynthetic analysis
takes advantage of D-glucose as the chiral starting material and
is based on a galactofuranose-derived cyclic nitrone as the key
intermediate. The key step of our strategy is the cycloaddition
of a uridine derivative carrying an allylphosphono group with
the cyclic nitrone, followed by the elaboration of the resulting
bicyclic system (Scheme 2).
of natural products, such as alexines,13 lentiginosine,14 and
laccarin,15 or to reach glycoside analogues, such as imino-C-
disaccharides16 and other compounds of biological interest.17
To the best of our knowledge, two examples of cycloaddition
of sugar-derived cyclic nitrones with a simple alkenylphospho-
nate have been reported.18
Results and Discussion
Preparation of Nitrone 4. Our synthesis started from tetra-
O-benzyl-D-glucofuranose 1. This versatile substrate was pre-
pared in three steps from D-glucose by glycosylation with
1-octanol in the presence of FeCl3, under conditions adapted
from Ferrie`res et al.,19,20 benzylation of the resulting glucofura-
noside, and hydrolysis of the glycoside. Compound 1 was
converted into the corresponding open chain O-silylated oxime
(with O-tert-butyldiphenylsilylhydroxylamine21) under condi-
tions described by Tamura.15 The oxime 2 was mesylated at
O-4, and the resulting aldehydo-glucose oxime 3 was cyclized
(13) (a) Hall, A.; Meldrum, K. P.; Therond, P. R.; Wightman, R. H.
Synlett 1997, 123-125. (b) Carmona, A. T.; Wightman, R. H.; Robina, I.;
Vogel, P. HelV. Chim. Acta 2003, 86, 3066-3073. (c) Cardona, F.; Faggi,
E.; Liguori, F.; Cacciarini, M.; Goti, A. Tetrahedron Lett. 2003, 44, 2315-
2318. (d) Cordero, F. M.; Gensini, M.; Goti, A.; Brandi, A. Org. Lett. 2000,
2, 2475-2477. (e) Desvergnes, S.; Py, S.; Vallee, Y. J. Org. Chem. 2005,
70, 1459-1462.
(14) Brandi, A.; Cicchi, S.; Cordero, F. M.; Frignoli, R.; Goti, A.; Picasso,
S.; Vogel, P. J. Org. Chem. 1995, 60, 6806-6812.
(15) Tamura, O.; Toyao, A.; Ishibashi, H. Synlett 2002, 1344-1346.
(16) Duff, F. J.; Vivien, V.; Wightman, R. H. Chem. Commun. 2000,
2127-2128.
Related iminosugar-derived cyclic nitrones are convenient
precursors that have been recently exploited for the preparation
(17) (a) Van den Broek, L. A. G. M. Tetrahedron 1996, 52, 4467-4478.
(b) Peer, A.; Vasella, A. HelV. Chim. Acta 1999, 82, 1044-1065. (c) Cicchi,
S.; Marradi, M.; Vogel, P.; Goti, A. J. Org. Chem. 2006, 71, 1614-1619.
(18) (a) Chevrier, C.; LeNouen, D.; Neuburger, M.; Defoin, A.; Tarnus,
C. Tetrahedron Lett. 2004, 45, 5363-5366. (b) Chevrier, C.; LeNouen,
D.; Defoin, A.; Tarnus, C. Eur. J. Org. Chem. 2006, 2384-2392.
(19) Ferrie`res, V.; Bertho, J. N.; Plusquellec, D. Carbohydr. Res. 1998,
311, 25-35.
(9) See for example: Boucheron, C.; Desvergnes, V.; Compain, P.;
Martin, O. R.; Lavi, A.; Mackeen, M.; Wormald, M. R.; Dwek, R. A.;
Butters, T. D. Tetrahedron: Asymmetry 2005, 16, 1747-1756.
(10) For a review of iminosugar-based glycosyl transferase inhibitors,
see: Compain, P.; Martin, O. R. Curr. Top. Med. Chem. 2003, 3, 541-
560.
(11) Lee, R. E.; Smith, M. D.; Pickering, L.; Fleet, G. W. J. Tetrahedron
Lett. 1999, 40, 8689-8692.
(12) Liautard, V.; Desvergnes, V.; Martin, O. R. Org. Lett. 2006, 8,
1299-1302.
(20) For improvement of the procedure, see ref 12.
(21) Denmark, S. E.; Dappen, M. S.; Sear, N. L.; Jacobs, R. T. J. Am.
Chem. Soc. 1990, 112, 3466-3474.
7338 J. Org. Chem., Vol. 71, No. 19, 2006

Synthesis of Iminosugar-Containing UDP-Galf Mimics
SCHEME 3
3
FIGURE 1. Observed NOE’s in 6 and JH,H (Hz) data for 7.
alkenes,13a,b,23 but with a higher degree of stereoselectivity. By
this process, in one step, one C-C and one C-O bond were
efficiently created with a very high control of the two stereo-
genic centers that were generated.
The N-O bond in compound 6 could be cleaved selectively
using Zn in the presence of a catalytic amount of copper(II)
acetate,25 thus affording imino-C-glycofuranosyl compound 7.
The NMR data (Figure 1) of 7 confirmed its 1,2-trans
configuration (â-C-glycosidic linkage). Under hydrogenolytic
conditions, compound 6 was converted into the novel Galf
pyrophosphate mimic 8 in 40% yield. A two-step sequence
based on the cleavage of the N-O bond using Zn dust in acetic
by treatment with tetrabutylammonium triphenyldifluorosili-
conate15 to give the galacto-configured cyclic nitrone 4 in 69%
isolated yield. The reaction with TBAF gave 4 in lower yield
due to the partial desilylation of the substrate. Compound 4 is
the first example of a hexofuranose-derived cyclic nitrone and
is a convenient starting material for the synthesis of a diversity
of galactofuranoside mimics based on a 1,4-iminogalactitol
skeleton. To develop a methodology for the coupling of uridine
monophosphate derivatives with the iminogalactitol moiety, we
investigated the [3 + 2] dipolar cycloaddition of nitrone 4 with
various unsaturated phosphonates. In a first model experiment,
the reaction of 4 with commercial diethyl vinylphosphonate was
found to give a mixture of stereoisomers in good yield; however,
the isomers could not be separated. The cycloaddition process
using diethyl allylphosphonate22 5 as the dipolarophile model
proved more interesting. After 16 h at 90 °C in tetrachloro-
ethylene, the reaction gave a cycloadduct with a very high
degree of regio- and stereoselectivity. Only one product as a
single stereoisomer was observed and isolated. Indeed, com-
pound 6 was isolated in 88% yield after chromatography
(Scheme 4). The NMR data confirmed that the C-C bond
formation had taken place at the terminal position of the allyl
group, as predicted from previous studies on the cycloaddition
of cyclic nitrones related to 4 and monosubstituted alkenes, such
as, for example, allyl alcohol.13a,b,17a,23,24
Furthermore, the detected NOE effects in 6 (Figure 1)
provided evidence for a pseudo-â configuration of the newly
created C-C bond (C-3a(S) configuration) and an endo orienta-
tion of the H-C(2) proton (C-2(S)). From the structure of the
final product thus determined, it is inferred that the cycloaddition
took place highly selectively in an exo-anti mode, namely, by
addition to the least hindered Si face of the nitrone (anti with
respect to the substituent at C-2) and with the alkene substituent
in the exo direction. The reaction of nitrone 4 with reagent 5
thus occurred with the same orientation as that of the cycload-
ditions of related cyclic nitrones to simple monosubstituted
26
acid, followed by deprotection of the benzyl ethers using BCl3
in dichloromethane, provided more efficiently compound 8 as
hydrochloride salt27 in 94% overall yield. Interestingly, it was
possible to cleave selectively the benzyl groups without affecting
the N-O bond by performing the deprotection with a large
excess of BCl3; this process provided the original and interesting
pyrrolidino-isoxazolidine 9 in 85% yield. This reaction widened
the scope of our investigation by increasing the structural
diversity of the tether between the iminosugar skeleton and the
UMP moiety.
The corresponding free phosphonic acids 10 and 11 were
efficiently obtained as hydrobromides of the iminosugar by
treatment of 8 and 9, respectively, with an excess of trimeth-
ylsilyl bromide (Scheme 5).28 These two new iminosugar
phosphonates are of interest as potential inhibitors of various
carbohydrate-processing enzymes.
To obtain â-linked UMP-Galf mimics, the required allylphos-
phonate carrying a uridin-5′-yl group as ester substituent was
prepared from reagent 5 by way of a very convenient, direct
conversion of the phosphonate into the corresponding phospho-
nochloridate using oxalyl chloride (Scheme 6).29
The reaction of 5 with this reagent gave chiral chloride 12 in
situ, which was reacted with 2′,3′-O-isopropylideneuridine in
(25) Karanjule, N. S.; Markad, S. D.; Sharma, T.; Sabharwal, S. G.;
Puranik, V. G.; Dhavale, D. D. J. Org. Chem. 2005, 70, 1356-1363.
(26) For debenzylation using BCl3, see for example: (a) Kibuchi, Y.;
Kurata, H.; Nishiyama, S.; Yamumara, S. Tetrahedron Lett. 1997, 38, 4795-
4798. (b) Bouix, C.; Bisseret, P.; Eustache, J. Tetrahedron Lett. 1998, 39,
825-828. (c) Xie, J.; Me´nand, M.; Vale´ry, J.-M. Carbohydr. Res. 2005,
340, 481-487.
(27) The salts were obtained when no filtration on basic resin was
performed in order to avoid degradation.
(28) For phosphonate deprotection using BrSiMe3, see for example: (a)
Vidil, C.; More`re, A.; Garcia, M.; Barragan, V.; Hamdaoui, B.; Rochefort,
H.; Montero, J.-L. Eur. J. Org. Chem. 1999, 447-450. (b) Ladame, S.;
Faure´, R.; Denier, C.; Lakhdar-Ghazal, F.; Wilson, M. Org. Biomol. Chem.
2005, 3, 2070-2072.
(29) Lapeyre, C.; Bedos-Belval, F.; Duran, H.; Baltas, M.; Gorrichon,
L. Tetrahedron Lett. 2003, 44, 2445-2447.
(22) Dappen, M. S.; Pellicciari, R.; Natalini, B.; Monahan, J. B.; Chiorri,
C.; Cordi, A. A. J. Med. Chem. 1991, 34, 161-168.
(23) Goti, A.; Cicchi, S.; Fedi, V.; Nannelli, L.; Brandi, A. J. Org. Chem.
1997, 62, 3119-3125.
(24) Nagazawa, K.; Georgieva, A.; Koshino, H.; Nakata, T.; Kita, T.;
Hashimoto, Y. Org. Lett. 2002, 4, 177-180.
J. Org. Chem, Vol. 71, No. 19, 2006 7339

Liautard et al.
SCHEME 4
SCHEME 5a
same regio- and stereoselectivity as the reaction of model
allylphosphonate 5. Separation of the diastereomers proved
impossible, and compound 14 was characterized as the mixture
of P-epimers. We first investigated the deprotection of 14 by
hydrogenolysis, a reaction that afforded the novel UMP-imino-
1,4-galactitol conjugate 18. This compound was, however,
difficult to isolate because of degradation during the purification
step; further deprotection by cleavage of the isopropylidene
group was not attempted. The conditions developed for the
elaboration of diethylphosphonate 6 proved also successful for
14: the two-step sequence30 (Zn/AcOH then BCl3) provided
efficiently the ethyl uridinyl phosphonate 16 by way of 15.
Treatment of 16 with an excess BrSiMe3 gave, after purification
by reverse-phase flash chromatography, the original â-linked
UDP-Galf mimic 17 in excellent yield. Compounds 16 and 17
are significant in that they contain a uridine moiety at the same
distance with respect to the sugar unit as uridine in UDP-Galf,
one phosphate being replaced by an isosteric 2-hydroxypropyl
group; the presence of the OH function in this group is important
as it provides, with the phosphate present, a bidentate ligand
for possible complexation of the sugar nucleotide analogue with
the divalent metal cation that may be present in the active site
of the UDP-Galf transferases.
a Conditions: BrSiMe3 (10 equiv), CH3CN, 4 h.
SCHEME 6
As described in the diethylphosphonate series, deprotection
of 14 using only BCl3 provided the original bicyclic analogue
19; selective cleavage of the ethyl phosphonate group could
also be performed in this case by reacting 19 with excess
BrSiMe3. This provided the unusual, bicyclic UDP-Galf mimic
20, in which the pyrophosphate-like tether and the uridine
moiety are in a constrained conformation. Biological investiga-
tions of compounds 16, 17, 19, and 20 are in progress, and the
results will be reported in due course.
In conclusion, the 1,3-dipolar cycloaddition of an iminoga-
lactitol-derived nitrone with an original uridin-5′-yl allylphos-
phonate provided an efficient approach to new UDP-Galf
analogues incorporating an iminogalactitol moiety and UMP.
The tactical combination of successive deprotection steps
provided an efficient and practical access to a diversity of novel
functionalized sugar nucleotide mimics. The resulting com-
pounds are potential inhibitors of UDP-Gal mutase and of UDP-
CH2Cl2 in the presence of triethylamine. This provided quickly
and efficiently the ethyl, uridin-5′-yl allylphosphonate 13 as a
mixture of P-diastereomers in 60% yield after purification by
chromatography (two steps).
The cycloaddition of nitrone 4 with 13 was performed under
the same conditions as with 5 and afforded the expected
coupling product 14 in an isolated yield of 80% (Scheme 7).
Although they are complicated by the presence of diastere-
omers at phosphorus (1:1 ratio), the NMR spectra of 14
demonstrated clearly that the cycloaddition took place with the
(30) This two-step sequence could be performed without further purifica-
tion of 15 to provide 16 in 78% yield.
7340 J. Org. Chem., Vol. 71, No. 19, 2006

Synthesis of Iminosugar-Containing UDP-Galf Mimics
SCHEME 7
as a colorless oil. The 1H NMR spectrum indicates the presence of
a E/Z mixture (E/Z ∼ 4:1 ratio). 1H NMR (500 MHz, CDC13) (M
is major isomer, m is minor isomer): δ 7.83 M (d, 0.8 H, J ) 8.3
Galf transferases, and their biological investigation should help
us better understand these two enzyme families.
Hz, H1), 7.67-7.72 (m, 4 H, HAr), 7.12-7.36 (m, 26.2 H, HAr
+
Experimental Section
H1m), 5.38 m (t, 0.2 H, J ) 6.6 Hz, H2), 4.80 and 4.42 m (2 d, 2
× 0.2 H, J ) 11.2 Hz), 4.66 (m, 2 H, OCH2Ph), 4.52 (m, 3 H,
OCH2Ph), 4.29 (m, 3.4 H, OCH2Ph + H2M), 4.09 m (br d, 0.2 H,
J ) 6.5 Hz, H3), 3.96 M (dd, 0.8 H, J ) 6.5, 0.8 Hz, H3), 3.91 M
+ m (m, 1 H, H4), 3.83 (dd, 1 H, J ) 10.3, 2.6 Hz, H6aM +
H6am), 3.71 m (m, 0.2 H, H6b), 3.66 (m, 1 H, H6bM + H5m),
3.61 M (m, 0.8 H, H5), 2.95 m (d, 0.2 H, J ) 6.9 Hz, OH), 2.54
(E,Z)-2,3,5,6-Tetra-O-benzyl-aldehydo-D-glucose O-(t-butyl-
diphenylsilyl)oxime (2). To a solution of 2,3,5,6-tetra-O-benzyl-
D-glucofuranose19,20 (10 g, 20 mmol) in dry toluene (10 mL/g)
(freshly distilled over CaH2) were added MgSO4 (250 mg), O-(tert-
butyldiphenylsilyl)hydroxylamine21 (10 g, 37 mmol, 1.85 equiv),
and a catalytic amount of PPTS (pyridinium p-toluenesulfonate).
The reaction mixture was stirred for 30 min at 110 °C and cooled
to rt. The solids were removed by filtration, and water (50 mL)
was added. The filtrate was extracted with CH2Cl2 (3 × 50 mL),
and the organic layers were dried with Na2SO4 then filtered and
concentrated under reduced pressure. The resulting colorless residue
was submitted to flash chromatography on silica gel (petroleum
ether/AcOEt 95/5 to 85/15) to afford compound 2 (13.65 g, 86%)
t
M (d, 0.8 H, J ) 8.5 Hz, OH), 1.12 M (s, 6.8 H, Bu), 1.11 m (s,
2.2 H, tBu). 13C NMR (125 MHz, CDC13): δ 154.9 m (C1), 153.9
M (C1), 138.1 m + M (2CqAr), 138.0 m (CqAr), 137.9 M (CqAr),
137.8 m (CqAr), 137.6 M (CqAr), 137.2 M (CqAr), 137.1 m (CqAr),
135.2 M (2CHAr), 135.2 m (CHAr), 135.1 m (CHAr), 133.1 M (CqAr),
133.0 M (CqAr), 132.7 m (2CqAr), 129.5 m (CHAr), 129.4 M (CHAr),
127.2-128.2 M + m (CHAr), 77.7 M (C5), 77.5 m (C5), 77.0 m
J. Org. Chem, Vol. 71, No. 19, 2006 7341

Liautard et al.
(C3), 76.6 M (C3), 76.3 M (C2), 74.2 m (OCH2Ph), 73.2 M (OCH2-
Ph), 73.1 M (OCH2Ph), 73.1 m (OCH2Ph), 72.5 m (C2), 72.0 m
(OCH2Ph), 71.6 M (OCH2Ph), 71.4 m (OCH2Ph), 70.6 M (OCH2-
Ph), 70.1 m (C4), 69.9 M (C6), 69.6 m (C6), 69.6 M (C4), 26.9 m
(tBu), 26.8 M (tBu). HRMS (ESI) calcd for [M + Na]+: 816.3696.
Found: 816.3691. Anal. Calcd for C50H55NO6Si: C, 75.63; H, 6.98;
N, 1.76. Found: C, 75.49; H, 7.19; N, 1.77.
ether 40/60 to 65/35) which afforded cycloaddition product 6 (234
mg, 327 µmol, 88%) as a slightly yellow oil. [R]25 +11.4 (c )
D
1
1.0, MeOH). H NMR (500 MHz, CDCl3): δ 7.21-7.33 (m, 20
H, HAr), 4.79 (d, 1 H, J ) 12.0 Hz), 4.51-4.58 (m, 6 H), 4.36 (d,
1 H, J ) 12.0 Hz) (4 OCH2Ph), 4.31 (m, 1 H, H2), 4.06 (m, 5 H,
2 OCH2CH3, H5), 3.89 (t, 1 H, J ) 6.0 Hz, H4), 3.82 (m, 3 H,
CHOBn-CH2OBn), 3.74 (m, 1 H, H3a), 3.31 (dd, 1 H, J ) 1.0,
7.0 Hz, H6), 2.33 (ddd, 1 H, J ) 3.5, 6, 12.5, H3B), 2.18 (m, 2 H,
H3A, CHBP), 1.93 (ddd, 1 H, J ) 9, 15.0, 18.5 Hz, CHAP), 1.30,
1.29 (2 t, 6 H, OCH2CH3). 13C NMR (125 MHz, CDCl3): δ 138.6,
138.4, 138.0, 137.7 (CqAr), 127.3-128.4 (CHAr), 87.5 (C4), 81.9
(C5), 76.3, 73.3, 72.9, 72.5, 71.9 (2C) (4 OCH2Ph, CHOBn, CH2-
OBn), 70.5 (C2), 69.9 (C6), 67.7 (C3a), 61.7 (d, JC,P ) 6.3 Hz),
61.6 (d, JC,P ) 6.3 Hz) (OCH2CH3), 41.1 (d, JC,P ) 4.6 Hz, C3),
30.0 (d, JC,P ) 138.8 Hz, CH2P), 16.3 (d, JC,P ) 5.9 Hz, OCH2CH3).
31P NMR (202 MHz, CDCl3): δ 26.69. IR (neat): 3086, 3061,
3029, 2979, 2907, 2866, 1496, 1453, 1391, 1365, 1251, 1209, 1158,
1098, 1055, 1027, 963, 915, 825, 738, 698 cm-1. HRMS (ESI)
calcd for [M + H]+: 716.3352. Found: 716.3349. Calcd for [M
+ Na]+: 738.3172. Found: 738.3176. Anal. Calcd for C41H50NO8P‚
H2O: C, 67.11; H, 7.14; N, 1.91. Found: C, 67.21; H, 7.12; N,
1.84.
(E,Z)-2,3,5,6-Tetra-O-benzyl-4-O-methanesulfonyl-aldehydo-
D-glucose O-(t-butyldiphenylsilyl)oxime (3). To a solution of
oxime 2 (4 g, 5 mmol) in dry CH2Cl2 (60 mL) was added dropwise
Et3N (906 µL, 0.065 mol, 1.3 equiv) at rt. The mixture was stirred
for 30 min at rt, and then methanesulfonyl chloride (503 µL, 0.065
mol, 1.3 equiv) was added. After having been stirred for 16 h at rt,
the reaction mixture was concentrated under reduced pressure. The
residue was submitted to flash chromatography on silica gel
(petroleum ether/AcOEt 85/15) which afforded mesylate 3 (3.83
1
g, 88%) as a colorless syrup (E/Z mixture). H NMR (500 MHz,
CDC13) (M is major isomer, m is minor isomer): δ 7.70 and 7.2-
7.36 (m, 31 H, H1, HAr), 5.37 m (dd, 0.2 H, J ) 8.3, 2 Hz, H4),
5.26 M (dd, 0.8 H, J ) 7.6, 2.3 Hz, H4), 5.00 m (dd, 0.2 H, J )
5.6, 2.7 Hz, H2), 4.80 M + m (2d, 1 H, OCH2Ph), 4.58 (2d, 0.4 H,
OCH2Ph), 4.38-4.49 (m, 2.8 H, OCH2Ph), 4.23-4.33 (m, 3 H,
OCH2Ph), 4.11 (m, 1.8 H, OCH2Ph, H2M, H3m), 3.85 M (dd, 0.8
H, J ) 7.6, 3.6 Hz, H3), 3.73 m (dt, 0.2 H, J ) 6, 6, 1.9 Hz, H5),
3.59 (m, 1.8 H, H5M + H6b), 3.45 (m, 1 H, H6a), 2.88 m (s, 0.6
(1S)-2,3,5,6-Tetra-O-benzyl-1,4-dideoxy-1-C-[(2S)-3-diethoxy-
phosphoryl-2-hydroxypropyl]-1,4-imino-D-galactitol (7). Zinc
dust (31 mg, 0.48 mmol) was added to a solution of copper(II)
acetate (0.1 mg) in glacial acetic acid (0.5 mL) under argon
atmosphere, and the mixture was stirred at rt for 10 min until the
color disappeared. Compound 6 (30 mg, 0.042 mmol) in glacial
acetic acid (0.7 mL) and water (0.3 mL) were added successively,
and the reaction mixture was heated at 70 °C for 1 h. After cooling
to rt, EDTA (sodium salt, 0.1 g) was added, and the mixture was
stirred for 10 min, then made alkaline to pH 10 by addition of 3 N
aqueous NaOH. The resulting solution was extracted with chloro-
form (3 × 10 mL), and the combined organic phases were
concentrated under reduced pressure. The crude product was
purified by flash chromatography on silica gel (AcOEt/petroleum
ether 70/30 to 100% AcOEt) to afford the desired galactitol 7 (18
mg, 0.025 mmol, 62%) as a colorless liquid. [R]25D -26 (c ) 0.64,
t
H, SO2CH3), 2.86 M (s, 2.4 H, SO2CH3), 1.15 m (s, 1.7 H, Bu),
1.13 M (s, 7.3 H, tBu). 13C NMR (125 MHz, CDC13): δ 155.5 m
(C1), 154.0 M (C1), 137.7 m, 137.6 m, 137.5 M, 137.2 M, 137.1,
136.6, and 136.2 m (CqAr’s), 135.5 M (CHAr), 135.5 M (CHAr),
135.4 m (CHAr), 135.3 m (CHAr), 133.1 M, 133.0 M, 132.8 m, and
132.7 m (CqAr’s), 129.9-127.4 (CHAr), 82.6 m (C4), 82.5 M (C4),
78.3 M (C3), 77.3 m (C3), 76.9 m (C5), 76.4 M (C5), 75.4 m
(OCH2Ph), 75.1 M (C2), 75.0 M (OCH2Ph), 73.0 M (OCH2Ph),
72.9 m (CH2), 72.2 m (CH2), 72.1 M (OCH2Ph), 71.8 m (CH2),
71.0 m (C2), 70.5 M (OCH2Ph), 68.8 m (CH2), 68.1 M (C6), 38.8
M (SO2CH3), 38.7 m (SO2CH3), 25.2 m (tBu), 26.9 M (tBu). HRMS
(ESI) calcd for [M + Na]+: 894.3472. Found: 894.3480. Anal.
Calcd for C51H57NO8SSi‚H2O: C, 68.81; H, 6.68; N, 1.57. Found:
C, 69.27; H, 6.77; N, 1.57.
1
MeOH). H NMR (500 MHz, CDCl3): δ 7.27-7.32 (m, 20 H,
HAr), 4.72 (d, 1 H, J ) 11.5 Hz, CH2Ph), 4.47-4.55 (m, 5 H, CH2-
Ph), 4.40, 4.38 (2d, 2 H, CH2Ph), 4.25 (m, 1 H, H8), 4.09 (m, 4 H,
OCH2CH3), 3.88 (dd, 1 H, J ) 3.0, 6 Hz, H3), 3.81 (t, 1 H, J )
3.5 Hz, H2), 3.74 (m, 1 H, H5), 3.64 (dd, 1 H, H6B), 3.59 (dd, 1
H, H6A), 3.50 (m, 1 H, H1), 3.27 (dd, 1 H, J ) 6, 4 Hz, H4),
1.88-2.11 (m, 3 H, H7B, 2H9), 1.68 (m, 1 H, H7A), 1.30 (t, 3 H,
OCH2CH3), 1.29 (t, 3 H, J ) 7.5 Hz, OCH2CH3). 13C NMR (125
MHz, CDCl3): δ 138.0 (CqAr), 127.6-127.4 (CHAr), 88.8 (C2),
85.5 (C3), 75.8 (C5), 73.5, 73.0, 72.0, 71.8, 71.7 (4 OCH2Ph, C6),
65.6 (C8), 63.0 (C4), 61.5-62.0 (OCH2CH3), 59.4 (C1), 37.3 (d,
JC,P ) 10.4 Hz, C7), 33.5 (d, JC,P ) 135.8 Hz, C9), 16.5
(OCH2CH3), 16.4 (OCH2CH3). 31P NMR (202 MHz, CDCl3): δ
29.16. IR (NaCl): 3395, 2923, 1719, 1599, 1496, 1453, 1209, 1156,
1095, 1027, 965, 737, 698, 669. HRMS (ESI) calcd for [M + H]+:
718.3509. Found: 718.3522. Calcd for [M + Na]+: 740. 3328.
Found: 740.3328. Anal. Calcd for C41H52NO8P‚H2O: C, 66.92;
H, 7.40; N, 1.90. Found: C, 66.64; H, 7.30; N, 1.95.
(1S)-1,4-Dideoxy-1-C-[(2S)-3-diethoxyphosphoryl-2-hydroxy-
propyl]-1,4-imino-D-galactitol (8). To a solution of phosphonate
7 (117 mg, 163 µmol) in acetic acid (1.0 mL) was added a catalytic
amount of palladium on active charcoal (10%), and the mixture
was stirred overnight at rt under hydrogen atmosphere. The solids
were then removed by filtration and rinsed with CH2Cl2. After
evaporation of the solvents, the crude product was purified by flash
chromatography on silica gel (MeOH/CH2Cl2/pyridine 25/74/1).
Internal Nitrone of 2,3,5,6-Tetra-O-benzyl-4-deoxy-4-hy-
droxylamino-aldehydo-D-galactose [(3S,4S,5S)-3,4-dibenzyloxy-
5-[(1S)-1,2-dibenzyloxyethyl]-1-pyrroline N-oxide] (4). Oxime 3
(4.62 g, 5.30 mmol) as a mixture of E,Z-isomers was dissolved in
dry tetrahydrofuran (30 mL); 4 Å molecular sieves and tetra-
butylammonium triphenyldifluorosilicate (3.43 g, 6.36 mmol, 1.2
equiv) were added, and the mixture was stirred for 45 min at reflux
temperature. The solids were then removed by filtration, and the
filtrate was concentrated. Pure nitrone 4 (1.44 g, 2.68 mmol, 51%)
was obtained as a white solid after purification by flash chroma-
tography on silica gel (EtOAc/petroleum ether, 35/65 to 50/50).
1
[R]25 + 42.9 (c ) 1.0, MeOH). H NMR (500 MHz, CDCl3): δ
D
7.22-7.31 (m, 20 H, HAr), 6.85 (narrow m, 1 H, H1), 4.82 (d, 1 H,
J ) 12 Hz), 4.67 (d, 1 H, J ) 11.5 Hz, OCH2Bn), 4.56 (narrow t,
1 H, J ) 1.6 Hz, H2), 4.41-4.52 (m, 6 H, 3 OCH2Ph), 4.30 (br q,
1 H, H5), 4.25 (narrow m, 1 H, H3), 4.21 (m, 1 H, H4), 3.79 (m,
2 H, 2H6). 13C NMR (125 MHz, CDCl3): δ 138.2, 137.8, 137.1
(CqAr), 133.0 (C1), 127.5-128.5 (CHAr), 82.9, 79.9, 78.8, 75.0,
73.3, 73.0, 71.6, 71.5, 70.2. IR (NaCl): 3425, 3031, 2867, 1577,
1273, 1096, 1028, 911, 817, 738, 698, 674 cm-1. HRMS (ESI)
calcd for [M + Na]+: 560.2413. Found: 560.2411. Anal. Calcd
for C34H35NO5: C, 75.95; H, 6.56; N, 2.61. Found: C, 75.62; H,
6.60; N, 2.51.
Diethyl (2S,3aS,4S,5S,6S)-4,5-Dibenzyloxy-6-[(1S)-1,2-diben-
zyloxyethyl]hexahydropyrrolo[1,2-b]isoxazole-2-methylphospho-
nate (6). To a solution of nitrone 4 (200 mg, 372 µmol) in
tetrachloroethylene (1.5 mL) was added diethyl allylphosphonate
5 (133 mg, 745 µmol, 2 equiv). The mixture was stirred overnight
at 50 °C. After evaporation of the solvent, the crude mixture was
submitted to flash chromatography on silica gel (EtOAc/petroleum
This afforded the desired iminogalactitol 8 (23 mg, 64 µmol, 39%)
1
as a yellow oil. [R]25 -21.3 (c ) 1.0, MeOH). H NMR (500
D
MHz, CD3OD): δ 4.08-4.14 (m, 5 H, H8, 2 OCH2CH3), 3.89 (t,
1 H, J ) 7 Hz, H3), 3.70 (br q, 1 H, H5), 3.64 (t, 1 H, H2), 3.61
(dd, 1 H, J ) 4.5, 11 Hz, H6B), 3.55 (dd, 1 H, J ) 6, 11.5 Hz,
7342 J. Org. Chem., Vol. 71, No. 19, 2006

Synthesis of Iminosugar-Containing UDP-Galf Mimics
H6A), 3.14 (dt, 1 H, J ) 4.5, 8.0, 8.0 Hz, H1), 2.97 (dd, 1 H, J )
7.5, 4.5 Hz, H4), 2.05 (higher order signal, 2 H, CH2P), 1.79, (m,
2 H, 2H7), 1.32 (m, 6 H, 2 OCH2CH3). 13C NMR (125 MHz, CD3-
OD): δ 82.5 (C2), 79.4 (C3), 72.4 (C5), 65.6 (d, JC,P ) 3.1 Hz,
C8), 65.5 (C6), 64.0 (C4), 63.4 (d, JC,P ) 6.3 Hz, POCH2CH3),
provided compound 10 (hydrobromide) (70 mg, 92%) as a white
1
foam. [R]25 -9 (c )1.27, MeOH). H NMR (500 MHz, CD3-
D
OD): δ 4.28-4.22 (m, 1 H, H8), 4.09-4.06 (m, 1 H, H3), 3.96
(dd, 1 H, J ) 4.5, 8.5 Hz, H5), 3.92-3.88 (m, 1 H, H2), 3.73 (dd,
1 H, J ) 4, 11.5 Hz, H6B), 3.67 (dd, 1 H, J ) 4, 11.5 Hz, H6A),
3.58-3.56 (m, 1 H, H4), 3.52-3.49 (dd, 1 H, J ) 4, 8 Hz, H1),
2.23-2.17, (m, 1 H, H7B), 2.10-2.04 (m, 3 H, H9 and H7A). 13C
NMR (125 MHz, CD3OD): δ 79.0 (C2), 76.8 (C3), 69.0 (C5), 65.3,
65.2, 64.9 (C6 or C4 or C8), 60.9 (C1), 37.7 (d, JC,P ) 8.8 Hz,
C7), 36.2 (d, JC,P ) 135 Hz, C9). 31P NMR (202 MHz, CD3OD):
δ 25.29. HRMS (ESI) calcd for [M + H]+: 302.1005. Found:
302.0995. Calcd for [M + Na]+: 324.0824. Found: 324.0814.
63.2 (d, JC,P ) 6.5 Hz, POCH2CH3), 59.8 (C1), 42.2 (d, JC,P
)
12.0 Hz, C7), 34.8 (d, JC,P ) 138 Hz, C9), 16.7 (d, JC,P ) 6.1 Hz,
POCH2CH3). 31P NMR (202 MHz, CD3OD): δ 29.91. HRMS (ESI)
calcd for [M + H]+: 358.1631. Found: 358.1625.
BCl3 Debenzylation of 7 (General Procedure A). To a solution
of phosphonate 7 (110 mg, 0.154 mmol) in dry CH2Cl2 (3 mL)
was added at 0 °C a 1 M BCl3 solution in hexane (1.8 mL, 1.8
mmol, 12 equiv). The medium was stirred overnight at 0 °C, and
then the solid formed was dissolved by addition of MeOH (20 mL)
and a few drops of water. The reaction mixture was then
concentrated under reduced pressure. Purification of the crude
product by flash chromatography on C18-reverse phase silica gel
(H2O/MeOH 1/0 to 7/3) provided the colorless oily compound 8
as its hydrochloride salt (52.7 mg, 87%). [R]25D ) -30 (c ) 0.82,
Diethyl (2S,3aS,4S,5S,6S)-4,5-Dihydroxy-6-[(1S)-1,2-dihy-
droxyethyl]hexahydropyrrolo[1,2-b]isoxazole-2-methylphospho-
nate (11). Compound 11 was prepared by general procedure B
starting from compound 9 (70 mg, 0.197 mmol). After 4 h stirring,
the reaction medium was treated and the product purified under
the same conditions as described above (preparation of 10) to
provide 11 (hydrobromide) as a brown oily compound (46 mg,
1
1
MeOH). H NMR (250 MHz, CD3OD): δ 4.31-4.20 (m, 1 H,
61%). H NMR (500 MHz, CD3OD): δ 4.96 (m, 1 H, H2), 4.18
H8), 4.19-4.03 (m, 5 H, H3, CH2CH3), 3.95 (q, 1 H, J ) 4 Hz,
H5), 3.86 (dd, 1 H, J ) 6.7, 8.2 Hz, H2), 3.62-3.76 (m, 2 H, H6),
3.46-3.58 (m, 2 H, H4 and H1), 2.05-2.12, (m, 4 H, H9 and H7),
1.34 (t, 6 H, J ) 7.1 Hz, CH3). 13C NMR (62.5 MHz, CD3OD): δ
79.1 (C2), 76.8 (C3), 69.0 (C5), 65.2 (C6), 65.0 (C4), 64.8 (d, JC,P
) 2.3 Hz, C8), 63.5 (d, JC,P ) 6.4 Hz, POCH2CH3), 63.4 (d, JC,P
) 6.6 Hz, POCH2CH3), 60.7 (C1), 37.9 (d, JC,P ) 10.6 Hz, C7),
34.1 (d, JC,P ) 137 Hz, C9), 16.7 (d, JC,P ) 6 Hz, POCH2CH3).
31P NMR (202 MHz, CD3OD): δ 28.19. HRMS (ESI) calcd for
[M + H]+: 358.1631. Found: 358.1629.
(m, 1 H, H3a), 4.09-4.07 (m, 2 H, H4 and H5), 3.97-3.94 (m, 1
H, H7), 3.80-3.78 (m, 1 H, H6), 3.71 (dd, 1 H, J ) 5.5, 11.5 Hz,
H8B), 3.65 (dd, 1 H, J ) 6, 11.5 Hz, H8A), 2.84 (dd, 1 H, J ) 3.5,
13 Hz, H3B), 2.42 (td, 1 H, J ) 9, 13.5 Hz, H3A), 2.32 (ddd, 1 H,
J ) 5.5, 15, 20 Hz, CH2BP), 2.18-2.10 (m, 1 H, CH2AP). 13C NMR
(62.5 MHz, CD3OD): δ 80.1 (C2), 78.5 (C4 or C5), 76.4 (C6),
76.0 (C4 or C5), 73.5 (C3a), 68.2 (C7), 63.9 (C8), 38.6 (d, JC-P
)
5.7 Hz, C3), 31.2 (d, JC-P ) 135 Hz, CH2P). 31P NMR (202 MHz,
CD3OD): δ 20.99. HRMS (ESI) calcd for [M + Na]+: 322.0668.
Found: 322.0668.
Diethyl (2S,3aS,4S,5S,6S)-4,5-Dihydroxy-6-[(1S)-1,2-dihy-
droxyethyl]hexahydropyrrolo[1,2-b]isoxazole-2-methylphospho-
nate (9). Compound 9 was obtained using the general procedure
A starting from compound 6 (89 mg, 0.124 mmol). After stirring
overnight at 0 °C, the solid crude product was dissolved with MeOH
(5 mL), and three successive evaporations of the solvents (3 × 5
mL) were performed. Then, the residue was dissolved with MeOH
and water (5 mL, 20/1), and the solution was quickly filtered
through ion-exchange resin (Dowex 1X8, OH- form) which was
then washed with MeOH (20 mL × 2) and water (10 mL).
Purification of the crude product by flash chromatography on C18-
reverse phase silica gel (H2O/MeOH 1/0 to 7/3) provided the
Ethyl (2′,3′-O-Isopropylideneuridin-5′-yl)allylphosphonate (13).
Diethyl allylphosphonate 5 (200 mg, 1.12 mmol) was allowed to
react with oxalyl chloride (490 µL, 5.62 mmol, 5 equiv) in
anhydrous CH2Cl2 (5 mL) under argon for 2 days. The conversion
can be monitored by TLC (eluant: EtOAc containing a few drops
of AcOH). For this purpose, the bottom of the TLC plate spotted
with the reaction mixture was dipped into water containing a few
drops of triethylamine and dried before development. When TLC
showed no more starting material, the solvent was removed under
vacuum along with the excess oxalyl chloride. The residue was
dissolved in anhydrous CH2Cl2, and 2,′3′-O-isopropylideneuridine
(684 mg, 2.41 mmol, 2.15 equiv) and triethylamine (344 µL, 2.46
mmol, 2.2 equiv) were added. The reaction mixture was stirred at
40 °C for 8 h and at rt for 2 days. Subsequently, the resulting
emulsion was treated with water, and the aqueous phase was
extracted with CH2Cl2. The organic layer was dried (Na2SO4) and
concentrated to afford the crude phosphonate 13, which was purified
by flash chromatography on silica gel (EtOAc). This provided the
expected product (253 mg, 607 µmol) as a mixture of P*-
diastereomers in 54% yield for the two steps. 1H NMR (250 MHz,
CDCl3): δ 10.00 (br s, 1 H, H3), 7.43 and 7.38 (2 d, 1 H, H6),
5.76 (m, 3 H, H1′, H5, CHdCH2), 5.23 (m, 2 H, CHdCH2), 4.91
(m, 1 H, H2′), 4.86 (m, 1 H, H3′), 4.35 (m, 1 H, H4′), 4.28 (m, 2
H, 2H5′), 4.14 (m, 2 H, OCH2CH3), 2.67 (dd, 2 H, JH,H ) 7.3 Hz,
JH,P ) 22.0 Hz, CH2P), 1.57 and 1.35 (2s, 2 × 3 H, CMe2), 1.32
and 1.31 (2t, 3 H, OCH2CH3). 13C NMR (62.5 MHz, CDCl3): δ
163.5 (C4), 150.1 (C2), 141.7 and 141.8 (C6), 126.7, 126.8, 126.9,
127.00 (δ of each line is given; 2d, CHdCH2), 120.1, 120.2, 120.4,
120.5 (δ of each line is given; 2d, CHdCH2), 114.4 and 114.5
(CMe2), 102.4 and 102.5 (C5), 93.8 and 93.9 (C1′), 85.4-85.6 (2d,
C4′), 84.3 and 84.4 (C2′), 80.6 (C3′), 65.1 and 65.2 (C5′), 62.4,
62.4, 62.5, 62.6 (δ of each line is given; 2d, POCH2CH3), 31.5 (d,
JC,P ) 138.4 Hz) and 31.4 (d, JC,P ) 138.2 Hz) (CH2P), 27.0, 25.2
(CMe2), 16.4 and 16.3 (POCH2CH3). 31P NMR (202 MHz,
CDCl3): δ 27.88 (0.5P), 27.62 (0.5P). IR (neat): 3610, 3170, 2998,
2818, 1690, 1458, 1420, 1376, 1216, 1257, 1166, 1062, 1032, 852,
822, 762 cm-1. HRMS (ESI) calcd for [M + Na]+: 439.1246.
Found: 439.1248.
colorless oily compound 9 (37.6 mg, 85%). [R]25 ) +24 (c )
D
9.3, MeOH). 1H NMR (500 MHz, CD3OD): δ 4.30 (m, 1 H, H2),
4.08 (m, 4 H, CH2CH3), 3.87 (t, 1 H, J ) 8 Hz, H7), 3.76-3.73
(m, 2 H, H4 and H5), 3.66 (m, 2 H, H8), 3.46 (t, 1 H, J ) 8 Hz,
H3a), 3.02 (d, 1 H, J ) 8.5 Hz, H6), 2.40-2.37 (dd, 1 H, J ) 3.5,
12.5 Hz, H3B), 2.27-2.12 (m, 2 H, CH2P), 2.08-2.04 (m, 1 H,
H3A), 1.34 (t, 6 H, J ) 7.5 Hz, CH3CH2). 13C NMR (62.5 MHz,
CD3OD): δ 81.8 (C4 or C5), 75.5 (C7), 71.6 (C6), 72.2 (C2), 71.3
(C4 or C5), 69.5 (C3a), 65.5 (C8), 63.6 (d, JC-P ) 6.4 Hz, CH2-
CH3), 63.4 (d, JC-P ) 6.5 Hz, CH2CH3), 42.0 (d, JC-P ) 8.9 Hz,
C3), 29.3 (d, JC-P ) 140 Hz, CH2P), 16.7 (d, JC-P ) 6.18 Hz,
CH3CH2). 31P NMR (202 MHz, CD3OD): δ 28.17. HRMS (ESI)
calcd for [M + Na]+: 378.1294. Found: 378.1290. Calcd for [M
+ K]+: 394.1033. Found: 394.1004.
Deprotection of 8: General Procedure B for the Preparation
of Free Phosphonic Acids. (1S)-1,4-Dideoxy-1-[(2S)-3-phosphono-
2-hydroxypropyl]-1,4-imino-D-galactitol (10). To a solution of
phosphonate 8 (78 mg, 0.2 mmol) in dry MeCN (3 mL) was added
BrSiMe3 (0.264 mL, 2 mmol, 10 equiv) at rt. The mixture was
stirred for 2 days; the mixture was then diluted with MeOH (15
mL) and concentrated under reduced pressure. The dilution and
evaporation process was repeated twice. The residue was then taken
up with water and the mixture extracted with CH2Cl2 to remove
traces of less polar organic compounds. The aqueous phase was
concentrated under reduced pressure. Chromatography of the crude
product on C18-reverse phase silica gel (H2O/MeOH 1/0 to 8/2)
J. Org. Chem, Vol. 71, No. 19, 2006 7343

Liautard et al.
Ethyl (2′,3′-O-Isopropylideneuridin-5′-yl)(2S,3aS,4S,5S,6S)-
4,5-dibenzyloxy-6-[(1S)-1,2-dibenzyloxyethyl]hexahydropyrrolo-
[1,2-b]isoxazole-2-methylphosphonate (14). Ethyl (2′,3′-O-iso-
propylideneuridin-5′-yl)allylphosphonate (13) (153 mg, 367 µmol,
1.7 equiv) was added to a solution of nitrone 4 (116 mg, 216 µmol)
in tetrachloroethylene (3 mL). The mixture was stirred for 12 h at
60 °C and for 24 h at 70 °C. After concentration, the crude product
was purified by flash chromatography on silica gel (EtOAc/MeOH
100/0 to 95/10) to give cycloadduct 14 (120 mg, 125 µmol, 58%)
OCH2CH3 and CMe2). 13C NMR (125 MHz, CDCl3; d1, d2 )
diastereomer 1 and 2): δ 163.1 and 163.0 (C4, d1 and d2), 150.1-
150.0 (C2), 142.2 and 141.9 (C6, d1 and d2), 138.3, 138.2, 138.1
(CqAr), 128.5-127.7 (CHAr), 114.6 and 114.5 (CMe2, d1 and d2),
102.7 and 102.6 (C5, d1 and d2), 94.4 and 94.0 (C1′, d1 and d2),
88.7 and 88.6 (C2′′, d1 and d2), 85.5-85.7 (m, C4′, C3′′), 84.5
and 84.4 (C2′, d1 and d2), 80.8 and 80.7 (C3′, d1 and d2), 75.9
and 75.8 (C5′′), 73.6, 73.0, 72.1 (3 OCH2Ph), 71.9, 71.8, 71.7 (C6′′
and 2 OCH2Ph), 65.5 (C8), 64.7 (d, JC-P ) 6 Hz) and 64.8 (d,
JC-P ) 6 Hz) (C5′, d1 and d2), 63.0 (C4′′), 62.3 (d, JC-P ) 6.2
Hz) and 62.1 (d, JC-P ) 6.25 Hz) (CH2CH3, d1 and d2), 59.5 and
59.4 (C1′′, d1 and d2), 37.5-37.8 (m, C7), 33.9 (d, JC-P ) 136
Hz, C9), 27.3 and 25.5 (CMe2, d1 and d2), 16.6 and 16.5 (OCH2-
CH3, d1 and d2). 31P NMR (202 MHz, CDCl3): δ 30.11, 31.71.
IR (NaCl): 3474, 3054, 3033, 2986, 2908, 2868, 1695, 1651, 1586,
1497, 1455, 1422, 1383, 1265, 1215, 1158, 1070, 1028, 971, 895,
862, 815, 744, 702 cm-1. HRMS (ESI) calcd for [M + Na]+:
978.3918. Found: 978.3959. Calcd for [M + H]+: 956.4099.
Found: 956.4108. Anal. Calcd for C51H62N3O13P: C, 64.07; H, 6.54.
Found: C, 64.13; H, 6.85.
(1S)-1,4-Dideoxy-1-C-{(2S)-3-[(ethyl)(uridin-5′-yl)phosphoryl]-
2-hydroxypropyl}-1,4-imino-D-galactitol (16). Compound 16
(hydrochloride) was obtained as a white foam (146 mg, 78%) and
as a mixture of nonseparable P*-diastereomers starting from 15
(283 mg, 0.296 mmol) and following the general procedure A. 1H
NMR (500 MHz, CD3OD; all signals belong to both diastereomers,
unless indicated otherwise): δ 7.75 (d, J ) 8 Hz) and 7.73 (d, J )
8.5 Hz) (1 H, H6, d1 and d2), 5.85 (d, J ) 4.5 Hz) and 5.84 (d, 1
H, J ) 4.5 Hz) (1 H, H1′, d1 and d2), 5.75 (d, J ) 8 Hz) and 5.74
(d, J ) 8 Hz) (1 H, H5, d1 and d2), 4.37-4.12 (m, 8 H), 4.07 (t,
1 H, J ) 7.5 Hz, H3′′), 3.95 (q, 1H, J ) 4 Hz, H5′′), 3.89-3.85
(m, 1 H, H2′′), 3.72 (dd, 1 H, J ) 4, 11.5 Hz, H6′′B), 3.67 (dd, 1
H, J ) 4, 11.5 Hz, H6′′A), 3.55 (ddd, 1 H, J ) 8, 5 Hz, H8′′), 3.51
(dd, 1 H, J ) 4, 7.5 Hz, H4′′), 2.05-2.25 (m, 4H, H9′′ and H7′′),
1.36 (t, 3H, CH3, d1 and d2). 13C NMR (62.5 MHz, CD3OD): δ
166.0 (C4), 150.2 (C2), 142.7 (C6), 103.0 (C5), 91.6-91.7 (C1′),
83.6 and 83.7 (C4′, d1 and d2), 79.2 (C2′′), 76.7 (C3′′), 74.8 and
74.9 (C2′ or C3′), 70.9 (C2′ or C3′), 69.0 (C5′′), 66.4-66.2 (m,
C5′), 65.1 (C6′′), 64.9 (C1′′ or C4′′), 64.7 and 64.6 (C1′′ or C4′′),
63.9 (d, JC-P ) 6.5 Hz) and 63.7 (d, JC-P ) 6.8 Hz) (OCH2CH3),
1
as a colorless oil and as a mixture of P*-diastereomers. H NMR
(500 MHz, CDCl3): δ 8.85 and 8.60 (2 br s, 1 H, NH), 7.2-7.35
(m, 20.5 H, 20HAr, 0.5 H6), 7.14 (d, 0.5 H, J ) 8.0 Hz, 0.5 H6),
5.67 (dd, J ) 1.8, 8.0 Hz) and 5.61 (dd, J ) 1.8, 8.0 Hz) (1 H,
H5), 5.605 and 5.52 (2 br s, 1 H, H1′), 4.97 (dd, J ) 6.4, 1.7 Hz)
and 4.95 (dd, J ) 6.5, 2.0 Hz) (1 H, H2′), 4.85 (dd, J ) 3.8, 6.3
Hz) and 4.82 (dd, J ) 3.7, 6.4 Hz) (1 H, H3′), 4.76 (d, 0.5 H),
4.73 (d, 0.5 H), 4.48-4.57 (m, 6 H), 4.44 (d, 0.5 H), 4.39 (d, 0.5
H) (4 OCH2Ph), 4.35 (m, 1 H, H2′′), 4.04-4.27 (several m, 6 H,
H4′, 2H5′, H5′′, OCH2CH3), 3.96 (t, J ) 5.7 Hz) and 3.94 (t, J )
5.7 Hz) (1 H, H4′′), 3.78-3.82 (m, 3 H, CH2OBn + CHOBn),
3.73 (m, 1 H, H3a′′), 3.34 (br d, 1 H, J ) 7.7 Hz, H6′′), 2.33 (m,
1 H, H3′′B), 2.16 (m, 2 H, CHBP, H3′′A), 1.98 (m, 1 H, CHAP),
1.55 and 1.54 (2s, 3 H, CMe2), 1.33 and 1.32 (2s, 3 H, CMe2),
1.30 and 1.27 (2t, 3 H, CH3CH2O). 13C NMR (125 MHz, CDCl3):
δ 162.93 and 163.90 (C4), 149.88 (C2), 142.40 and 142.23 (C6),
138.62, 138.56, 138.45, 138.41, 137.88, 137.81, 137.75 (CqAr),
127.4-128.4 (CHAr), 114.54 and 114.43 (CMe2), 102.6 (C5), 95.22
and 94.44 (C1′), 87.4 (C4′′), 86.08 and 85.54 (2d, JC,P ) 6.6 Hz,
C4′), 84.19 and 84.13 (C2′), 82.08 and 81.80 (C5′′), 80.77 and 80.59
(C3′), 76.41 and 76.33 (CHOBn), 73.3, 73.27, 73.01, 72.95, 72.45,
71.94, 71.73, 71.68 (4 CH2Ph + CH2OBn), 70.48 and 70.27, 69.97
and 69.76 (C6′′, C2′′), 67.78 and 67.71 (C3a′′), 65.06 (d, JC,P
)
5.9 Hz) and 64.80 (d, JC,P ) 6.2 Hz) (C5′), 62.25 (d, JC,P ) 6.4
Hz) and 62.06 (d, JC,P ) 6.2 Hz) (OCH2CH3), 41.40 (d, JC,P ) 6.6
Hz) and 41.24 (d, JC,P ) 6 Hz) (C3′′), 30.13 (d, JC,P ) 139 Hz,
CH2P), 27.12 and 27.08, 25.31 and 25.25 (CMe2), 16.40 and 16.35
(CH3CH2O). 31P NMR (202 MHz, CDCl3): δ 27.81, 27.51. IR
(NaCl): 3463, 3055, 3033, 2986, 2935, 2869, 1695, 1633, 1497,
1455, 1422, 1382, 1266, 1214, 1158, 1093, 1069, 1027, 972, 886,
860, 810, 737, 701 cm-1. HRMS (ESI) calcd for [M + Na]+:
976.3762. Found: 976.3753. Calcd for [M + K]+: 992.3501.
Found: 992.3521. Anal. Calcd for C51H60N3O13P: C, 64.21; H,
6.34; N, 4.40. Found: C, 64.32; H, 6.14; N, 4.60.
60.6 (C8), 38.4 (d, JC-P ) 12 Hz, C7), 34.9 and 33.0 (d, JC-P
)
137 Hz, C9), 16.7 and 16.8 (CH3, d1 and d2). 31P NMR (202 MHz,
CD3OD): δ 29.68, 30.07. HRMS (LSIMS) calcd for [M + H]+:
556.1907. Found: 556.1906. Anal. Calcd for C20H43ClN3O17P: C,
36.18; H, 6.53; N, 6.33; Cl, 5.34; P, 4.66. Found: C, 35.72; H,
6.13; N, 6.00; Cl, 5.39; P, 4.29.
(1S)-2,3,5,6-Tetra-O-benzyl-1,4-dideoxy-1-C-{(2S)-3-[(ethyl)-
(2′,3′-O-isopropylideneuridin-5′-yl)phosphoryl]-2-hydroxypro-
pyl}-1,4-imino-D-galactitol (15). Zinc dust (64.3 mg, 1.05 mmol)
was added to a solution of copper(II) acetate (0.3 mg) in glacial
acetic acid (3 mL) under argon, and the mixture was stirred at rt
for 10 min until the color disappeared. Compound 14 (200 mg,
0.209 mmol) in glacial acetic acid (4.2 mL) and water (1.8 mL)
were added successively, and the reaction mixture was heated at
70 °C for 1 h. After cooling to rt, EDTA (sodium salt, 500 mg)
was added, and the mixture was stirred for 10 min, then made
alkaline to pH 10 by addition of 2 N aqueous NaOH. The resulting
solution was extracted with chloroform (3 × 100 mL), and the
combined organic phases were concentrated under reduced pressure.
The crude product was purified by flash chromatography on silica
gel (100% AcOEt to AcOEt/MeOH 99/1) to afford the desired
galactitol 15 (137.1 mg, 68%) as a colorless foam and as a
(1S)-1,4-Dideoxy-1-C-{(2S)-3-[(uridin-5′-yl)phosphono]-2-hy-
droxypropyl)}-1,4-imino-D-galactitol (17). Using general proce-
dure B, compound 17 (hydrobromide) was obtained as a purple
foam (66.3 mg, 99%) starting from 16 (65 mg, 0.109 mmol). [R]25
D
-15 (c ) 1.62, MeOH). 1H NMR (500 MHz, CD3OD): δ 7.79 (d,
1 H, J ) 8 Hz, H6), 5.87 (d, 1 H, J ) 4.5 Hz, H1′), 5.7 (d, 1 H,
J ) 8 Hz, H5), 4.32-4.11 (m, 6 H), 4.08-4.05 (m, 1 H, H3′′),
3.96-3.94 (m, 1 H, H5′′), 3.88 (dd, 1 H, J ) 6.5, 8.5 Hz, H2′′),
3.72 (dd, 1 H, J ) 4.5, 11.5 Hz, H6′′B), 3.66 (dd, 1 H, J ) 4, 11.5
Hz, H6′′A), 3.58-3.54 (m, 1 H, H8), 3.51-3.48 (m, 1 H, H4′′),
2.04-2.17 (m, 4 H, H7, H9). 13C NMR (62.5 MHz, CD3OD): δ
166.1 (C4), 152.3 (C2), 142.6 (C6), 102.9 (C5), 91.3 (C1′), 83.9
(d, JC-P ) 7 Hz, C4′), 79.1 (C2′′), 76.8 (C3′′), 75.1 (C2′ or C3′),
71.0 (C3′or C2′), 68.9 (C5′′), 65.7 (d, JC-P ) 5.7 Hz, C5′), 65.2
(C6′′), 65.1 (C4′′ or C1′′), 65.0 (C4′′ or C1′′), 60.8 (C8), 38.0 (d,
JC-P ) 11 Hz, C7), 34.9 (d, JC-P ) 138 Hz, C9). 31P NMR (202
MHz, CD3OD): δ 27.64. HRMS (LSIMS) calcd for [M + H]+:
528.1594. Found: 528.1600.
1
nonseparable mixture of P*-diastereomers. H NMR (500 MHz,
CDCl3; all signals belong to both diastereomers): δ 7.33-7.24 (m,
21 H, CHAr and H6), 5.71-5.63 (m, 2 H, H1′ and H5), 4.92-4.88
(m, 1 H, H2′), 4.97-4.85 (m, 1 H, H3′), 4.72 (d, 1 H, J ) 11.5
Hz, OCH2Ph), 4.50-4.37 (m, 7 H, OCH2Ph), 4.32-4.17 (m, 4 H,
H8, H4′ and H5′), 4.05-4.14 (m, 2 H, OCH2CH3), 3.88 (m, 1 H,
H3′′), 3.82-3.80 (m, 1 H, H2′′), 3.75-3.71 (m, 1 H, H5′′), 3.65-
3.57 (m, 2 H, H-6′′), 3.48-3.43 (m, 1 H, H1′′), 3.30-3.26 (m, 1
H, H4′′), 1.92-2.10 (m, 2 H, CH2P), 1.90-1.83 (m, 1 H, H7B),
1.66-1.59 (m, 1 H, H7A), 1.54 (s, 3 H, CMe2), 1.26-1.3 (m, 6 H,
(1S)-1,4-Dideoxy-1-C-{(2S)-3-[(ethyl)(2′,3′-O-isopropylideneu-
ridin-5′-yl)phosphoryl]-2-hydroxypropyl)}-1,4-imino-D-galacti-
tol (18). To a solution of phosphonate 14 (75 mg, 76.8 µmol) in
acetic acid (1.0 mL) was added a catalytic amount of palladium on
active charcoal (10%), and the mixture was allowed to stir overnight
7344 J. Org. Chem., Vol. 71, No. 19, 2006

Synthesis of Iminosugar-Containing UDP-Galf Mimics
under hydrogen. The solids were then removed by filtration and
rinsed with CH2Cl2. After evaporation of the solvent, the crude
product was purified by flash chromatography on silica gel (MeOH/
dichloromethane/pyridine 25/74/1 to remove impurities, and finally
MeOH to elute the desired compound). This afforded the desired
iminogalactitol 18 (22 mg, 37 µmol, 49%) as a pale yellow oil.
MS (ESI): 596.5 [M + H]+.
(2′3′-O-Isopropylideneuridin-5′-yl)-(2S,3aS,4S,5S,6S)-6-[(1S)-
1,2-dihydroxyethyl]hexahydropyrrolo[1,2-b]isoxazole-2-meth-
ylphosphonate (20). Following the general procedure B, compound
20 (hydrobromide) was obtained as white foam (90 mg, 81%)
starting from 19 (108 mg, 0.183 mmol). [R]25 +5 (c ) 1.29,
D
MeOH). 1H NMR (500 MHz, CD3OD): δ 7.79 (d, 1H, J ) 8 Hz,
H6), 5.86 (d, 2 H, J ) 4.5 Hz, H1′), 5.76 (d, 1 H, J ) 8 Hz, H5),
4.12-4.36 (m, 9 H), 4.00 (dd, 1 H, J ) 10, 5.5 Hz, H7′′), 3.88
(dd, 1 H, J )7.5, 4.5 Hz, H6′′), 3.73 (dd, 1 H, J ) 5, 11.5 Hz,
H8′′B), 3.68 (dd, 1 H, J ) 6, 11.5 Hz, H8′′A), 2.91-2.87 (m, 1 H,
H3′′B), 2.36-2.56 (m, 3 H, CH2P, H3′′A). 13C NMR (125 MHz,
CD3OD): δ 166.0 (C4), 152.2 (C2), 142.8 (C6), 103.0 (C1′), 91.4
(C5), 83.7 (d, JC-P ) 6.6 Hz, C4′), 79.9, 78.4, 77.1 (C6′′), 76.3
(C5′′), 74.8 (C2′), 73.8, 70.9, 68.3 (C7′′), 66.1 (d, JC-P ) 5.5 Hz,
Ethyl (2′,3′-O-Isopropylideneuridin-5′-yl)-(2S,3aS,4S,5S,6S)-
6-[(1S)-1,2-dihydroxyethyl]hexahydropyrrolo[1,2-b]isoxazole-2-
methylphosphonate (19). Compound 19 (hydrochloride) was
obtained as a white foam (150 mg, 74%) and as a mixture of P*-
diastereomers, starting from 14 (349 mg, 0.366 mmol) and following
1
the general procedure A. NMR data of free base: H NMR (500
MHz, CD3OD) δ 7.73 (d, J ) 8 Hz) and 7.71 (d, J ) 8 Hz) (1 H,
H6, d1 and d2), 5.84-5.83 (m, 1 H, H1′), 5.74 (d, J ) 8 Hz) and
5.73 (d, J ) 8 Hz) (1 H, H5, d1 and d2), 4.37-4.12 (m, 8 H),
3.88-3.84 (m, 1 H, H5′′), 3.77-3.71 (m, 2 H, H4′′ and H7′′), 3.66-
3.65 (m, 2 H, H8′′), 3.46 (t, 1 H, J ) 7.5 Hz, H3′′a), 3.04 (d, 1 H,
J ) 8.5 Hz, H6′′), 2.40-2.37 (m, 1 H, H3′′B), 2.27 (dd, 2 H, J )
6.5, 18.5 Hz, CH2P), 2.14-2.06 (m, 1 H, H3′′A), 1.34 (t, 3 H, J )
7 Hz, CH3); 13C NMR (125 MHz, CD3OD): δ 166.0 (C4), 152.2
(C2), 142.8 and 142.7 (C6, d1 and d2), 102.9 (C5), 91.9 (C1′),
83.7-83.6 (m, C4′), 81.9 and 81.8 (C4′′, d1 and d2), 75.9 and 75.9
(C5′′, d1 and d2), 74.9 and 74.8 (C2′, d1 and d2), 71.9 and 71.8
(C6′′, d1 and d2), 71.4, 71.3, 71.2 and 71.1 (C2′′, C7′′, d1 and d2),
70.9 (C3′), 69.7 and 69.6 (C3a, d1 and d2), 66.4 (d, 1 H, J ) 6.5
Hz, C5′), 65.5 and 65.4 (C8′′, d1 and d2), 63.8 (d, J ) 6.25 Hz)
and 64.0 (d, J ) 6.5 Hz) (CH2CH3, d1 and d2), 42.1-42.0 (m,
C3′′, d1 and d2), 29.5 (d, JC-P ) 140 Hz) and 29.4 (d, JC-P ) 140
Hz) (CH2P, d1 and d2), 16.7 and 16.6 (CH3, d1 and d2); 31P NMR
(202 MHz, CD3OD) δ 29.53, 29.04. HRMS (LSIMS) calcd for [M
+ H]+: 554.1751. Found: 554.1768.
C5′), 63.9 (C8′′), 38.6 (d, JC-P ) 7.5 Hz, C3′′), 30.0 (d, JC-P
)
139 Hz, CH2P). 31P NMR (202 MHz, CD3OD): δ 23.74. HRMS
(LSIMS) calcd for [M + H]+: 526.1438. Found: 526.1431.
Acknowledgment. Partial funding of this research by CNRS
is gratefully acknowledged. V.L. thanks the “Ministe`re de
l’Education Nationale, de la Recherche et de la Technologie”
for a Ph.D. fellowship. A.E.C. thanks Schuurman Schimmel-
van Outeren Stichting and Dr. Hendrik Muller’s Vaderlandsch
Fonds for a short term fellowship.
Supporting Information Available: General experimental
methods and 1H and 13C NMR spectral data for selected compounds
(2, 3, 4, 6, 7, 8, 9, 11, 15, 16, 17, and 19) are reported. This material
is available free of charge via the Internet at http://pubs.acs.org.
JO061130E
J. Org. Chem, Vol. 71, No. 19, 2006 7345