A general and stereoselective route to α- or β- galactosphingolipids via a common four-carbon building block

Article abstract of DOI:10.1021/jo070849z

(Chemical Equation Presented) A general synthetic strategy toward α- or β-galactosylceramides and their analogues from 3-azido-2-O-benzyl-1-O- (4-methoxybenzyl)butane-1,2,4-triol is described. The key steps for the installation of the main lipid chain are either a diasteroselective alkynylation reaction yielding the 4R stereocenter of phytosphingosine or a Wittig olefination generating the trans double bond of sphingosine. The methodology allows the preparation of different glycolipids with variations in the structure of the sphingoid base. In particular, three α-GalCer-related compounds have been synthesized and evaluated for their ability to activate CD1d-restricted T-cells.

Full text of DOI:10.1021/jo070849z

restricted antigen presentation to T cells are galactosylceramides,
potent stimulators of the mammalian immune system. Among
these, KRN7000 (1, Figure 1), the synthetic analogue of
agelasphin (isolated from a marine sponge), is an R-galacto-
sylphytosphingosine derivative (R-GalCer) that binds to CD1d
molecules on antigen presenting cells and is a powerful
immunostimulant of type I natural killer T (iNKT) cells.2,3 iNKT
cells release proinflammatory (Th1) and immunomodulatory
(Th2) cytokines upon activation, which can differently influence
the immune response to several diseases including tumors,
atherosclerosis, infections, and autoimmunity.4 Structure-
activity relationship studies of KRN7000 analogues revealed
that it is possible to bias the NKT cells response to R-GalCer
to either a Th1 or a Th2 response with potential medical
application.5
A General and Stereoselective Route to r- or
â-Galactosphingolipids via a Common
Four-Carbon Building Block
Pamela Matto,† Emilia Modica,† Laura Franchini,†
Federica Facciotti,‡ Lucia Mori,‡ Gennaro De Libero,‡
Grazia Lombardi,§ Silvia Fallarini,§ Luigi Panza,§
Federica Compostella,† and Fiamma Ronchetti*,†
Dipartimento di Chimica, Biochimica e Biotecnologie per la
Medicina, UniVersita` di Milano, Via Saldini 50, 20133-Milano,
Italy, Experimental Immunology, Department of Research, Basel
UniVersity Hospital, Hebelstrasse 20, 4031-Basel, Switzerland,
and Dipartimento di Scienze Chimiche, Alimentari,
Farmaceutiche e Farmacologiche, UniVersita` del Piemonte
Orientale, Via BoVio 6, 28100-NoVara, Italy
Another galactosylceramidic CD1 antigen is sulfatide (2,
Figure 1), a mixture of 3-sulfated â-D-galactosylceramides with
a D-erythro-sphingosine sphingoid base and different fatty acids
at the ceramide moiety. Sulfatide is a self-antigen, found in
myelin, and presented by all human CD1 family members to
specific T cells.6 Recent studies have demonstrated that the
immunogenicity of sulfatide depends both on the length of the
ceramide acyl chain and the position of the sulfate group or the
nature of the glycosidic linkage.7
fiamma.ronchetti@unimi.it
ReceiVed May 4, 2007
The studies on KRN7000 and sulfatide outlined above
demonstrate the importance of the antigen structure for the
immune responses of these molecules. Differences in biological
activities have been postulated to be associated with alteration
of CD1-lipid complex stability. Thus, the availability of
KRN7000 or sulfatide structural analogues provides a useful
tool for further expanding our understanding on biological
issues, investigating the mechanism involved in CD1-mediated
antigen presentation, or developing methods for more selective
activations of T cells.
A general synthetic strategy toward R- or â-galactosylcera-
mides and their analogues from 3-azido-2-O-benzyl-1-O-(4-
methoxybenzyl)butane-1,2,4-triol is described. The key steps
for the installation of the main lipid chain are either a
diasteroselective alkynylation reaction yielding the 4R ste-
reocenter of phytosphingosine or a Wittig olefination gen-
erating the trans double bond of sphingosine. The method-
ology allows the preparation of different glycolipids with
variations in the structure of the sphingoid base. In particular,
three R-GalCer-related compounds have been synthesized
and evaluated for their ability to activate CD1d-restricted
T-cells.
In this study, we report a flexible approach to glycosphin-
golipid analogues, synthesized in a modular way which allows
(2) (a) Morita, M.; Motoki, K.; Akimoto, K.; Natori, T.; Sakai, T.; Sawa,
E.; Yamaji, K.; Koezuka, Y.; Kobayashi, E.; Fukushima, H. J. Med. Chem.
1995, 38, 2176-2187. (b) Kawano, T.; Cui, J. Q.; Koezuka, Y.; Toura, I.;
Kaneko, Y.; Motoki, K.; Ueno, H.; Nakagawa, R.; Sato, H.; Kondo, E.;
Koseki, H.; Taniguchi, M. Science 1997, 278, 1626-1629.
(3) (a) Savage, P. B.; Teyton, L.; Bendelac, A. Chem. Soc. ReV. 2006,
35, 771-779. (b) Brutkiewicz, R. R. J. Immunol. 2006, 177, 769-775.
(4) (a) Van Kaer, L. Nature ReV. Immunol. 2005, 5, 31-42. (b) Bendelac,
A.; Savage, P. B.; Teyton, L. Annu. ReV. Immunol. 2007, 25, 297-336.
(5) (a) Porcelli, S. A. Ceramide derivatives as modulators of immunity
and autoimmunity. U.S. Patent 2006/0052316, Mar 9, 2006. (b) Goff, R.
D.; Gao, Y.; Mattner, J.; Zhou, D.; Yin, N.; Cantu, C.; Teyton, L.; Bendelac,
A.; Savage, P. B. J. Am. Chem. Soc. 2004, 126, 13602-13603. (c) Schmieg,
J.; Yang, G.; Franck, R. W.; Tsuji, M. J. Exp. Med. 2003, 198, 1631-
1641. (d) Yang, G.; Schmeig, J.; Tsuji, M.; Franck, R. W. Angew. Chem.,
Int. Ed. 2004, 43, 3818-3822.
CD1 proteins are a family of highly conserved molecules that
bind and display a variety of lipids, glycolipids, and lipopeptides
to T lymphocytes.1 In humans, there are five known isoforms,
CD1a, CD1b, CD1c, CD1d, and CD1e, while the mouse has
only CD1d. The best characterized lipids involved in CD1-
(6) (a) Shamshiev, A.; Donda, A.; Carena, I.; Mori, L.; Kappos, L.; De
Libero, G. Eur. J. Immunol. 1999, 29, 1667-1675. (b) Shamshiev, A.;
Gober, H. J.; Donda, A.; Mazorra, Z.; Mori, L.; De Libero, G. J. Exp. Med.
2002, 195, 1013-1021.
(7) (a) Compostella, F.; Franchini, L.; De Libero, G.; Palmisano, G.;
Ronchetti, F.; Panza, L. Tetrahedron 2002, 58, 8703-8708. (b) Compostella,
F.; Ronchi, S.; Panza, L.; Mariotti, S.; Mori, L.; De Libero, G.; Ronchetti,
F. Chem.sEur. J. 2006, 12, 5587-5595. (c) Modica, E.; Compostella, F.;
Colombo, D.; Franchini, L.; Cavallari, M.; Mori, L.; De Libero, G.; Panza,
L.; Ronchetti, F. Org. Lett. 2006, 8, 3255-3258.
* To whom correspondence should be addressed. Phone: +39-02-50316037.
Fax: +39-02-50316036.
† Universita` di Milano.
‡ Basel University Hospital.
§ Universita` del Piemonte Orientale.
(1) (a) De Libero, G.; Mori, L. Nature ReV. Immunol. 2005, 5, 485-
496. (b) Moody, D. B.; Zajonc, D. M.; Wilson, I. A. Nature ReV. Immunol.
2005, 5, 387-399. (c) Lawton, A. P.; Kronenberg, M. Immunol. Cell Biol.
2004, 82, 295-306. (d) De Libero, G.; Mori, L. Trends Immunol. 2006,
27, 485-492.
10.1021/jo070849z CCC: $37.00 © 2007 American Chemical Society
Published on Web 09/05/2007
J. Org. Chem. 2007, 72, 7757-7760
7757

SCHEME 1. Synthesis of the Common Intermediate 3
FIGURE 1. Structure of KRN7000 and sulfatide.
us to independently vary the structure of the lipid moiety and
the configuration of the glycosidic bond.8
In both cases, a variety of lipid moieties could be easily attached,
thus allowing for the synthesis of a wide variety of analogues,
differing in the sphingoid chain, that have not been prepared
previously.
We focused our attention on the synthesis of the R-GalCer
15a and two structurally related compounds 15b and 15c,
bearing a shorter branched and an aromatic chain, respectively.
To verify whether the modification of the linear alkyl chain of
the sphingoid tail affects biological activities, the newly
synthesized compounds have been evaluated for their ability to
activate CD1d-restricted T-cell (a mouse iNKT cell hybridoma).
Moreover, the approach toward â-glycolipids with a sphin-
gosine-like backbone was successfully explored obtaining the
allylic alcohol 22, a key precursor for oxa-sulfatide analogues.
Our strategy is based on the common precursor 3 that could
be easily converted into different structurally related compounds.
The great scenario of glycolipid structures accessible from
compound 3 is because, once glycosylated, it opens the
possibility to obtain the motif of the main natural sphingoid
bases (phytosphingosine, sphingosine, and sphinganine). So, by
changing the configuration of the glycosidic bond or the
character of the sphingoid motif, different classes of natural or
modified glycolipid structures are accessible. Here, our general
approach is applied to the conversion of compound 3 into
derivatives structurally related to KRN7000 and sulfatide. The
retrosynthetic plan (see the scheme in the Supporting Informa-
tion), shows that protected azido triol 3 possesses a primary
OH group which could be glycosylated to obtain either R- or
â-galactosyl derivatives. The R-glycosylated adduct is the proper
substrate for the obtainment of phytosphingosine glycolipids
through the Carreira enantioselective addition of terminal
alkynes to aldehydes, which was previously successfully
exploited by us in the synthesis of the sphingoid skeleton.9 On
the other hand, the â-glycosylated adduct could be easily
transformed, after the introduction of the trans double bond via
Wittig olefination, in a precursor of a series of sulfated â-D-
galactosyl-oxa-ceramides, i.e., analogues bearing an oxygen
atom in place of a methylene group in the sphingosine backbone.
The centerpiece of our synthetic route is the common
precursor 3 which was prepared using commercially available
(2R,3R)-2,3-O-benzylidene-D-threitol 4 as the starting material
(Scheme 1). Compound 4 was treated with 1 equiv of p-
methoxybenzyl chloride in the presence of sodium hydride to
give the monobenzylated derivative 5, which was subjected to
a regioselective reductive cleavage with borane tetrahydrofuran
complex yielding 1,2-diprotected tetrol 6. Selective silylation
of the primary alcohol followed by activation of the remaining
hydroxyl of 7 with chloromesyl chloride and azide displacement
afforded compound 8 in 80% yield. The desired intermediate 3
was finally obtained after selective deprotection of the silyl ether
with tetrabutylammonium fluoride.
With building block 3 in hand, the strategy (Scheme 2) toward
R-glycolipids was first developed by taking into consideration
the one-pot R-glycosylation protocol of Kobayashi.10 The
reaction, based on a halide ion-catalytic mechanism, consisted
in the in situ generation of the galactosyl bromide by reaction
of tetrabenzylgalactose 9 with carbon tetrabromide (CBr4) and
triphenylphosphine (Ph3P), known as Appel agents, followed
by coupling with acceptor 3 in the presence of N,N-tetramethy-
lurea. Purification by flash chromatography allowed recovery
of the R-glycosylated product 10 in high yield (85%). The
stereochemistry of the anomeric linkage was unambiguously
assigned by 1H NMR analysis. The p-methoxybenzyl group of
compound 10 was then deprotected, and the primary alcohol
of 11 was oxidized under Swern conditions to give aldehyde
12 which was the substrate for the Carreira alkynylation.11
We first examined the asymmetric alkynylation of compound
12 with tetradecyne to produce the “natural” C-18 sphingoid
chain. We expected high stereoselectivity by the prominent
stereodifferentiating ability of the Carreira protocol and also
convenient stereocontrol by changing only the chiral ligand. In
fact, by carrying out the addition reaction in the presence of
zinc trifluoromethanesulfonate and (-)-N-methylephedrine as
chiral additive, we were able to obtain the propargylic alcohol
13a in 65% yield.12 The R configuration for the new stereocenter
was expected because of the use of (-)-N-methylephedrine, and
(8) For related flexible strategies, see, for example: (a) Rai, A. N.; Basu,
A. J. Org. Chem. 2005, 70, 8228-8230. (b) Barrett, A. G. M.; Beall, J. C.;
Braddock, D. C.; Flack, K.; Gibson, V. C.; Salter, M. M. J. Org. Chem.
2000, 65, 6508-6514. (c) Reference 5a. (d) Howell, A. R.; So, R. C.;
Richardson, S. K. Tetrahedron 2004, 60, 11327-11347. (d) Bundle, D.
R.; Ling, C. C.; Zhang, P. Synthetic methods for the large scale production
from glucose of analogs of sphingosine, azidosphingosine, ceramides,
lactosyl ceramides, and glycosyl phytosphingosine. WO 03/101937 A1, Dec
11, 2003. (e) Du, W.; Kulkarni, S. S.; Gervay-Hague, J. Chem. Commun.
2007, 2336-2338.
(10) (a) Shingu, Y.; Nishida, Y.; Dohi, H.; Kobayashi, K. Org. Biomol.
Chem. 2003, 1, 2518-2521. (b) Nishida, Y.; Shingu, Y.; Dohi, H.;
Kobayashi, K. Org. Lett. 2003, 5, 2377-2380.
(11) Frantz, D. E.; Fa¨ssler, R.; Tomooka, C. S.; Carreira, E. M. Acc.
Chem. Res. 2000, 33, 373-381.
(9) Franchini, L.; Compostella, F.; Donda, A.; Mori, L.; Colombo, D.;
De Libero, G.; Matto, P.; Ronchetti, F.; Panza, L. Eur. J. Org. Chem. 2004,
4755-4761.
7758 J. Org. Chem., Vol. 72, No. 20, 2007

SCHEME 2. Synthesis of r-Galactosyl Glycolipids 15a-c from Common Precursor 3
SCHEME 3. Synthesis of â-Galactosyl Glycolipids from
Common Precursor 3
this was confirmed by preparation of the (R)- and (S)-MTPA
1
esters of 13a and analysis of their H NMR spectra (see the
Supporting Information).13
The azido group of compound 13a was then reduced with
hydrogen sulfide in pyridine-water, followed by introduction
of the fatty acid chain to give 14a.7a Finally, simultaneous
reduction of the triple bond and hydrogenolysis of the benzyl
groups in the presence of palladium over charcoal gave product
15a.
The same synthetic steps were followed for the preparation
of analogues 15b and 15c from aldehyde 12, the only difference
being the alkyne used in the alkynylation reaction. Compounds
15b and 15c were obtained in more than satisfactory yield and
were fully characterized before biological testing.
The strategy toward â-glycolipids was then examined (Scheme
3). Glycosylation of compound 3 with known pivaloylated
trichloroacetimidate 1614 at -50 °C in the presence of trieth-
ylsilyl trifluoromethanesulfonate as a catalyst afforded â-ga-
lactoside 17 in 70% yield. The â-configuration of compound
17 was easily assigned on the basis of the typical 8.0 Hz value
for the trans-diaxial J1′,2′ coupling constant of the anomeric
hydrogen. Before proceeding with the chain elongation, it was
necessary to exchange the ester protecting groups of galactose
for benzyl ethers in order to avoid any problem during the
planned reduction of ester 21. So, compound 17 was subjected
to Ze`mplen transesterification followed by benzylation to
produce galactoside 18. The p-methoxybenzyl ether of com-
pound 18 was selectively removed by treatment with DDQ to
obtain 19 which was oxidized under Swern conditions. A Wittig
olefination using (carbethoxymethylene)triphenyl-phosphorane
led to the E-unsaturated ester 21, which produced the corre-
sponding allyl alcohol 22 upon reduction with DIBALH at -78
°C. Compound 22 is an useful intermediate for development of
new analogues. In fact, through simple alkylation it is a
significant precursor of oxa-analogues of â-GalCers, e.g., the
precursor of oxa-sulfatides. By varying the alkylating agent, it
is possible to easily modify the length of the sphingoid skeleton,
generating glycolipid libraries. For our own purposes, we
terminated the process at this stage even if it is possible to easily
continue with standard procedures (alkylation, azide reduction-
amide bond formation, debenzylation with sodium in ammonia,
and selective sulfation of position 3 of the sugar).7a,c
The biological activities of compounds 15a-c were deter-
mined by using a T-cell antigen presentation assay. KRN7000
was used as positive control for validation of the biological
assay. Briefly, bone-marrow-derived mouse dendritic cells (DC,
5 × 104/well) were preincubated (2 h) with increasing concen-
trations (0.003-30 µg/mL) of each compound and used as
antigen presenting cells (APC). Mouse FF13 iNKT hybridoma
cells (105/well), previously generated and characterized,15 were
used as responder cells, and their activation was evaluated by
(12) For our synthetic purposes we only isolated the major product,
having the proper R-configuration. Therefore, the diasteroselectivity of the
reaction was not investigated.
(13) (a) Dale, J. A.; Mosher, H. S. J. Am. Chem. Soc. 1973, 95, 512-
519. (b) Devijver, C.; Salmoun, M.; Daloze, D.; Braekman, J. C.; De Weerdt,
W. H.; De Kluijver M. J.; Gomez, R. J. Nat. Prod. 2000, 63, 978-980. (c)
Chun, J.; Byun, H.-S.; Arthur, G.; Bittman, R. J. Org. Chem. 2003, 68,
355-39.
(14) Zimmermann, P.; Bommer, R.; Ba¨r, T.; Schmidt, R. R. J. Carbohydr.
Chem. 1988, 7, 435-452.
(15) Schu¨mann, J.; Facciotti, F.; Panza, L.; Michieletti, M.; Compostella,
F.; Collmann, A.; Mori, L.; De Libero, G. Eur. J. Immunol. 2007, 37, 1431-
1441.
J. Org. Chem, Vol. 72, No. 20, 2007 7759

68.4, 70.1, 70.7, 71.4, 72.2, 72.8, 76.5, 101.3, 173.0; ESI-MS m/z
) 824.7 (100) [M + Na]+, 1626.7 (95) [2M + Na]+. Anal. Calcd
for C46H91NO9 (801.67): C, 68.87; H, 11.43; N, 1.75. Found: C,
68.83; H, 11.40; N, 1.76.
measuring the release of IL-2 by ELISA 24 h later. Figure 2
(see the Supporting Information) shows that all compounds were
active in inducing IL-2 release in a concentration-dependent
manner and possess different potencies as compared to KRN7000.
This might be ascribed to the fact that NKT cells may very
efficiently discriminate lipids with different acyl chain length.
Thus, the carbon truncation of the amide chain is sufficient to
dramatically reduce cytokine release. The lower immunogenicity
of the 15a-c compounds than KRN7000 might be related to a
lower TCR binding affinity to CD1d-lipid complexes and to
the formation of less stable immunological synapse, as recently
demonstrated.16
In conclusion, azido triol 3 is a versatile building block for
glycosphingolipid synthesis. In fact, after glycosylation it allows
the access to a diverse array of sphingoid bases. Here we have
reported a new scheme for synthesizing biologically active
R-GalCer related compounds. The in vitro characterization of
their activities shows that despite main differences in the
sphingoid chain, compounds 15a-c possess similar potencies
and efficacies.
In addition, we have shown that an alternative functional-
ization of compound 3 provides access to â-GalCer related
glycolipids. Moreover, the direct alkylation of compounds 11
or 19 would allow for the preparation of families of R- or
â-glycosyl-oxa-sphinganines. From this picture, we see that the
lipid chains can be easily modified and the glycoconjugate
structures altered by use of different starting sugars or glyco-
sylation conditions. Thus, the flexibility of our approach permits
the synthesis of different glycolipid derivatives and provides a
powerful tool for analogues development and elucidation of their
biological functions.
(2S,3S,4R)-2-Docosanoylamino-8-methyl-1-(R-D-galactopyra-
nosyloxy)-3,4-nonanediol (15b). Prepared from 0.15 g (0.13 mmol)
of 14b according to the general procedure (see the Supporting
Information). 15b (0.064 g, 70%): [R]D ) + 58.0 (c 0.5, pyridine);
1H NMR (C5D5N) δ 0.78 (d, 6 H, J ) 6.5 Hz), 0.85 (t, 3 H, J )
7.0 Hz), 1.15-1.92 (m, 44 H), 2.16-2.26 (m, 1 H), 2.37-2.47
(m, 2 H), 4.26-4.32 (m, 2 H), 4.35-4.45 (m, 4 H), 4.50 (dd, 1 H,
J ) 6.0, 6.0 Hz), 4.54 (d, 1 H, J ) 3.5 Hz), 4.62-4.70 (m, 2 H),
5.23-5.29 (m, 1 H), 5.57 (d, 1 H, J ) 3.5 Hz), 5-60-5.90 (br s,
6H), 8.44 (d, 1 H, J ) 8.0 Hz); 13C NMR (C5D5N) δ: 14.0, 22.4,
22.5, 22.6, 23.9, 26.1, 28.0, 29.3-29.8 (15 C), 30.2, 31.9, 34.3,
36.5, 39.3, 51.2, 62.4, 68.4, 70.1, 70.7, 71.4, 72.2, 72.8, 76.5, 101.3,
173.0; ESI-MS m/z ) 712.6 [M + Na]+. Anal. Calcd for C38H75-
NO9 (689.54): C, 66.15; H, 10.96; N, 2.03. Found: C, 66.19; H,
10.97; N, 2.06.
(2S,3S,4R)-2-Docosanoylamino-1-(R-D-galactopyranosyloxy)-
7-phenyl-3,4-heptanediol (15c). Prepared from 0.15 g (0.13 mmol)
of 14c according to the general procedure (see the Supporting
Information). 15c (0.065 g, 70%): [R]D ) +48.0 (c 0.5, pyridine);
1H NMR (C5D5N) δ 0.84 (t, 3 H, J ) 6.5 Hz), 1.10-1.35 (m, 36
H), 1.74-1.98 (m, 4 H), 2.15-2.33 (m, 2 H), 2.35-2.47 (m, 2 H),
2.58-2.74 (m, 2 H), 4.23 (dd, 1 H, J ) 3.5, 8.0 Hz), 4.27-4.32
(m, 1 H), 4.34 (dd, 1 H, J ) 11.0, 5.0 Hz), 4.36-4.43 (m, 3 H),
4.48 (dd, 1 H, J ) 6.0, 6.0 Hz), 4.53 (d, 1 H, J ) 3.0 Hz), 4.60-
4.67 (m, 2 H), 5.23-5.29 (m, 1 H), 5.30-5.80 (br s, 6H), 5.57 (d,
1 H, J ) 3.5 Hz), 7.14-7.26 (m, 5 H), 8.40 (d, 1 H, J) 9.0 Hz);
13C NMR (C5D5N) δ 14.0, 22.7, 26.1, 28.3, 29.4-29.8 (16 C), 31.9,
34.1, 36.3, 36.5, 51.0, 62.4, 68.1, 70.0, 70.8, 71.3, 72.0, 72.8, 76.6,
101.2, 125.7, 128.4 (2 C), 128.6 (2 C), 143.1, 173.0; ESI-MS m/z
) 746.6 [M + Na]+. Anal. Calcd for C41H73NO9 (723.53): C,
68.01; H, 10.16; N, 1.93. Found: C, 68.00; H, 10.17; N, 1.96.
Experimental Section
(2S,3S,4R)-2-Docosanoylamino-1-(R-D-galactopyranosyloxy)-
3,4-octadecanediol (15a). Prepared from 0.15 g (0.12 mmol) of
compound 14a according to the general procedure (see the
Supporting Information). 15a (0.063 g, 65%): [R]D ) +40.0 (c
0.5, pyridine); 1H NMR (C5D5N) δ 0.85 (t, 6 H, J ) 7.0 Hz), 1.16-
1.44 (m, 58 H), 1.63-1.95 (m, 5 H), 2.23-2.31 (m, 1 H), 2.38-
2.48 (m, 2 H), 4.28-4.34 (m, 2 H), 4.36-4.45 (m, 4 H), 4.50 (dd,
1 H, J ) 6.0, 6.0 Hz), 4.54 (d, 1 H, J ) 3.0 Hz), 4.62-4.69 (m,
2 H), 4.80-5.15 (br s, 6H), 5.22-5.28 (m, 1 H), 5.56 (d, 1 H, J )
3.5 Hz), 8.45 (d, 1 H, J ) 8.0 Hz); 13C NMR (C5D5N) δ 14.0,
22.7, 26.1, 26.2, 29.3-30.1 (28 C), 31.9, 34.1, 36.5, 51.2, 62.4,
Acknowledgment. We acknowledge Magdalena Kistowska
for invaluable help and Kirin Brewery for providing KRN7000.
This work was supported by the Italian Ministry of University
and Research Grant FIRB-RBNE01PPTF, IRCAD-Novara, and
the European Union MOLSTROKE (Molecular basis of vascular
events leading to thrombotic stroke) project, LSHM-CT-2004-
005206 (to GDL).
Supporting Information Available: Experimental procedures
and/or characterization data for the synthesis of compounds 3, 5-8,
10-12, 13a-c, 14a-c, and 17-22, retrosynthetic scheme, Figure
1
2, H NMR spectra of all compounds, and 13C NMR spectra for
(16) McCarthy, C.; Shepherd, D.; Fleire, S.; Stronge, V. S.; Koch, M.;
Illarionov, P. A.; Bossi, G.; Salio, M.; Denkberg, G.; Reddington, F.; Tarlton,
A.; Reddy, B. G.; Schmidt, R. R.; Reiter, Y.; Griffiths, G. M.; van der
Merwe, P. A.; Besra, G. S.; Jones, E. Y.; Batista, F. D.; Cerundolo, V. J.
Exp. Med. 2007, 204, 1131-1144.
selected compounds. This material is available free of charge via
the Internet at http://pubs.acs.org.
JO070849Z
7760 J. Org. Chem., Vol. 72, No. 20, 2007