Synthesis of the Salmonella type E(1) core trisaccharide as a probe for the generality of 1-(benzenesulfinyl)piperidine/triflic anhydride combination for glycosidic bond formation from thioglycosides.

Article abstract of DOI:10.1021/jo0108818

A synthesis of a chromogenic glycoside of the Salmonella anatum group E(1) core trisaccharide is presented in which all three glycosidic bonds, a 1,2-cis-equatorial, a 1,2-trans-axial, and a 1,2-trans-equatorial linkage representing three of the four main classes of glycosidic bond, are formed with thioglycoside donors activated under a single set of conditions by the combination of 1-(benzenesulfinyl)piperidine and trifluoromethanesulfonic anhydride. 2,3-O-Carbonyl- and 2,3-O-isopropylidene-alpha-L-rhamnopyranosyl thioglycosides are found to be highly alpha-selective rhamnosyl donors under these conditions.

Full text of DOI:10.1021/jo0108818

Syn th esis of th e Sa lm on ella Typ e E1 Cor e Tr isa cch a r id e a s a
P r obe for th e Gen er a lity of 1-(Ben zen esu lfin yl)p ip er id in e/Tr iflic
An h yd r id e Com bin a tion for Glycosid ic Bon d F or m a tion fr om
Th ioglycosid es
David Crich* and Hongmei Li
Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street,
Chicago, Illinois 60607-7061
dcrich@uic.edu
Received August 27, 2001
A synthesis of a chromogenic glycoside of the Salmonella anatum group E1 core trisaccharide is
presented in which all three glycosidic bonds, a 1,2-cis-equatorial, a 1,2-trans-axial, and a 1,2-
trans-equatorial linkage representing three of the four main classes of glycosidic bond, are formed
with thioglycoside donors activated under a single set of conditions by the combination of
1-(benzenesulfinyl)piperidine and trifluoromethanesulfonic anhydride. 2,3-O-Carbonyl- and 2,3-
O-isopropylidene-R-L-rhamnopyranosyl thioglycosides are found to be highly R-selective rhamnosyl
donors under these conditions.
In tr od u ction
groups on thioglycoside reactivity,10,11 but among the
thioglycosides only the highly performant sulfoxide method
has been shown to enable the coupling of a broad range
of donors to an equally broad cross section of acceptors
under a small set of closely related reaction condi-
tions.12,13 The combination of 1-(benzenesulfinyl)piperi-
dine (1, BSP) and triflic anhydride recently developed in
The efficient, stereocontrolled formation of glycosidic
bonds is argueably the most fundamental reaction in
glycoscience, the study of the chemistry and biology of
carbohydrates, their oligomers, and conjugates.1-5 Not
surprisingly, therefore, there is an almost bewildering
diversity of methods available for the synthesis of gly-
cosidic bonds. Some of these can be said to be of purely
historical value while others are in widespread use,6 and
yet more are introduced on an almost daily basis. Despite
the large number of methods available, very few can be
said to be applicable in all circumstances and to have
the type of generality needed in a paradigm-simplifying,
universal method such as will ultimately be required for
a truly automated oligosaccharide synthesizer.7 The
thioglycosides, very widely employed stable glycosyl
donors, provide a good illustration of the problem with a
broad range of mostly unstable activators in common use
depending on the precise linkage required and the array
of protecting groups present.8,9 Tables of reactivity have
been compiled which categorize the effect of protecting
this laboratory for the activation of thioglycosides
evolved,14 via benzenesulfenyl triflate15,16 and then S-aryl
benzenethiosulfinates,17 out of our studies on the ap-
plication of the sulfoxide method to the synthesis of
â-mannosides.16,18,19 In view of the origins of this reagent
combination and the constraints of broad generality and
high reactivity imposed in the developmental stages, it
is not surprising that the BSP/Tf2O/thioglycoside method
(1) Dwek, R. A. Chem. Rev. 1996, 96, 683.
(2) Essentials Of Glycobiology; Varki, A., Cummings, R., Esko, J .,
Freeze, H., Hart, G., Marth, J ., Eds.; Cold Spring Harbor Press: Cold
Spring Harbor, NY, 1999.
(3) Varki, A. Glycobiology 1993, 3, 97.
(4) Bioorganic Chemistry: Carbohydrates; Hecht, S. M., Ed.; OUP:
New York, 1999.
(10) Douglas, N. L.; Ley, S. V.; Lucking, U.; Warriner, S. L. J . Chem.
Soc., Perkin Trans. 1 1998, 51.
(11) Zhang, Z.; Ollmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.;
Wong, C.-H. J . Am. Chem. Soc. 1999, 121, 734.
(12) Kahne, D.; Walker, S.; Cheng, Y.; Engen, D. V. J . Am. Chem.
Soc. 1989, 111, 6881.
(13) Yan, L.; Kahne, D. J . Am. Chem. Soc. 1996, 118, 9239.
(14) Crich, D.; Smith, M. J . Am. Chem. Soc. 2001, 123, 9015.
(15) Crich, D.; Sun, S. J . Am. Chem. Soc. 1998, 120, 435.
(16) Crich, D.; Sun, S. Tetrahedron 1998, 54, 8321.
(17) Crich, D.; Smith, M. Org. Lett. 2000, 4067.
(5) Glycochemistry: Principles, Synthesis, And Applications; Wang,
P., Bertozzi, C. R., Eds.; Dekker: New York, 2001.
(6) Carbohydrates in Chemistry and Biology; Ernst, B., Hart, G. W.,
Sinay¨, P., Eds.; Wiley-VCH: Weinheim, Germany, 2000; Vol. 1.
(7) Plante, O. J .; Palmacci, E. R.; Seeberger, P. H. Science 2001,
291, 1523.
(8) Oscarson, S. In Carbohydrates In Chemistry And Biology; Ernst,
B., Hart, G. W., Sinay, P., Eds.; Wiley-VCH: Weinheim, Germany,
2000; Vol. 1, p 93.
(18) Crich, D.; Sun, S. J . Org. Chem. 1997, 62, 1198.
(19) Crich, D.; Sun, S. J . Am. Chem. Soc. 1997, 119, 11217.
(9) Garegg, P. J . Adv. Carbohydr. Chem. Biochem. 1997, 52, 179.
10.1021/jo0108818 CCC: $22.00 © 2002 American Chemical Society
Published on Web 01/24/2002
4640
J . Org. Chem. 2002, 67, 4640-4646

Salmonella Type E1 Core Trisaccharide
TABLE 1. Glycosid ic Cou p lin g Rea ction s
product
posseses many of the attributes of the sulfoxide method.
Here, we illustrate this versatility through the synthesis
of the trisaccharide core of the salmonella serotype E1
R/â
(% yield) selectivity
20
donor acceptor
base
additive
with its 1,2-cis-equatorial, 1,2-trans-axial, and 1,2-trans-
equatorial linkages, i.e., three of the four main classes,
with only minor variations on a single set of reaction
conditions.
6
6
8
10
12
13
14
14
16
16
19
20
TTBP BF3‚OEt2 15 (75)
16 (80)
â only
â only
R only
R only
1/2
TTBP
TTBP
TTBP
TTBP
17 (63)
18 (64)
21 (90)a
22 (92)a,b
Kochetkov and co-workers previously described two
syntheses of the salmonella type E1 core trisaccharide 2.
In the first of these the difficult â-mannoside linkage was
introduced by anchimerically assisted â-glucoside forma-
tion followed by a three-step protocol for the gluco to
manno inversion of stereochemistry. Both glycosidic
bonds were established through the mercuric cyanide
mediated coupling of glycosyl bromides to the appropriate
alcohols.21,22 The second synthesis was shorter insofar as
the â-mannosidic linkage was introduced directly by
means of Gorin’s 4,6-di-O-acetyl-2,3-O-carbonate-pro-
tected R-mannosyl bromide23 and an insoluble silver
promoter. The R-rhamnosyl linkage was again formed by
the mercuric cyanide mediated coupling of a rhamnosyl
bromide and the galactose alcohol.24 Thus, although
shorter, the second route employed two different heavy
or precious metal mediated coupling reactions. Several
trisaccharide analogues were subsequently synthesized,
in which the reducing end was capped as a phosphate
ester25 or conjugated to polyacrylamide,26 by variations
on the same themes. Trisaccharide 3 was later prepared
by Thorson, who employed a different method for each
of the three glycosidic bonds.27 Thus, the R-rhamnoside
was formed in a Koenigs-Knorr reaction using silver
triflate as mediator, the â-galactoside was introduced by
means of Danishefsky’s glycal assembly method,28 and
finally the â-mannoside was obtained using a mannosyl
transferase and GDP-mannose as the donor with the
usual limitations on scale that this method entails. While
the use of the enzymic coupling is relatively unusual, this
last sequence is not atypical of present oligosaccharide
synthesis with a different method often being required
for each different linkage. In contrast to these previous
syntheses of 2 and 3, the one that we present below is
direct, free of the use of precious or heavy metal promot-
ers, and employs a single standardized glycosylation
method for each of the three disparate linkages.
1/9.6
a
b
Yield for the anomeric mixture. The yield of pure 22â was
71%.
means followed by selective introduction of the 3-O-p-
methoxybenzyl ether, as in 5, by treatment first with
dibutyltin oxide and then PMB chloride as described by
Nicolaou and co-workers.29 The pivalate ester was se-
lected for protection of the remaining hydroxyl group,
giving 6, as it is reputed to minimize ortho ester forma-
tion in the course of neighboring group directed glycosyla-
tions.30-32 S-Phenyl R-L-thiorhamnopyranoside33 was con-
verted to the 2,3-O-carbonate 7 and its 3-O-tert-butyldim-
ethylsilyl ether 8 by standard means. Subsequent events
led us to fall back on the 2,3-O-isopropylidene derivative
10, which was also obtained routinely via 9.34 Finally,
the two thioglycosides 1216 and 13 were obtained from
diol 1135,36 by standard methods.
The formation of the â-galactosidic linkage to alcohol
14 was first attempted by activation of the thioglycoside
6 with BSP and triflic anhydride in the presence of BF3
etherate and 2,4,6-tri-tert-butylpyrimidine (TTBP) as
base when 15 was obtained in 75% yield as a pure
â-anomer (Table 1). The pyrimidine TTBP is a conve-
nient, crystalline alternative to 2,6-di-tert-butyl-4-meth-
ylpyridine (DTBMP) that we recently introduced, whose
nonhygroscopic, much less volatile nature operationally
facilitates the sulfoxide and BSP methods alike.37 The
combination of DTBMP as base to buffer the sulfoxide
glycosylation reaction and BF3‚etherate, with which it
does not form a complex,38 was recommended by Kahne
to minimize ortho ester formation in the course of
neighboring group participation.39 Subsequently, the
PMB group was removed with DDQ to give 16 in 85%
yield. A better overall method, however, simply involved
omitting the base (and the BF3) from the coupling of 6
and 14 when 16 was obtained directly in 80% yield (Table
1). Fortuitously, the acidic conditons of this coupling
affected rearrangement of any kinetic ortho ester and the
removal of the PMB protecting group, thereby revealing
Resu lts a n d Discu ssion
A series of thioglycoside donors were first prepared.
Thus, D-galactose was converted to diol 4 by standard
(29) Nicolaou, K. C.; Mitchell, H. J .; Rodriguez, R. M.; Fylaktakidou,
K. C.; Suzuki, H. Angew. Chem., Int. Ed. Engl. 1999, 38, 3345.
(30) Kunz, H.; Harreus, A. Liebigs Ann. Chem. 1982, 41.
(31) Harreus, A.; Kunz, H. Liebigs Ann. Chem. 1986, 717.
(32) Lemieux, R. U.; Morgan, A. R. Can. J . Chem. 1965, 43, 2199.
(33) Groneberg, R. D.; Miyazaki, T.; Stylianides, N. A.; Schulze, T.
J .; Stahl, W.; Schreiner, E. P.; Suzuki, T.; Iwabuchi, Y.; Smith, A. L.;
Nicolaou, K. C. J . Am. Chem. Soc. 1993, 115, 7593.
(34) Zegelaar-J aarsveld, K.; Van Der Marel, G. A.; Van Boom, J . H.
Tetrahedron 1992, 48, 10133.
(35) Tetsuta, O.; Masahiro, T.; Susuma, K. Tetrahedron Lett. 1994,
35, 6493.
(36) Oshitar, T.; Shibasaki, M.; Yoshizawa, T.; Tomita, M.; Takao,
K.; Kobayashi, S. Tetrahedron 1997, 53, 10993.
(20) Luderitz, O. Angew. Chem., Int. Ed. Engl. 1970, 9, 649.
(21) Kochetkov, N. K.; Dmitriev, B. A.; Chizhov, O. S.; Klimov, E.
M.; Malysheva, N. N.; Chernyak, A. Y.; Bayramova, N. E.; Torgov, V.
I. Carbohydr. Res. 1974, 33, C5.
(22) Kochetkov, N. K.; Dmitriev, B. A.; Malysheva, N. N.; Chernyak,
A. Y.; Klimov, E. M.; Bayramova, N. E.; Torgov, V. I. Carbohydr. Res.
1975, 45, 283.
(23) Gorin, P. A. J .; Perlin, A. S. Can. J . Chem. 1961, 39, 2474.
(24) Betaneli, V. I.; Ovchinnikov, M. V.; Backinowsky, L. V.;
Kochetkov, N. K. Carbohydr. Res. 1980, 84, 211.
(25) Danilov, L. L.; Troitzky, M. F.; Utkina, N. S.; Shibaev, V. N.;
Kochetkov, N. K. Carbohydr. Res. 1980, 87, 141.
(26) Chernyak, A. Y.; Levinsky, A. B.; Dmitriev, B. A.; Kochetkov,
N. K. Carbohydr. Res. 1984, 128, 269.
(27) Zhao, Y.; Thorson, J . S. Carbohydr. Res. 1999, 319, 184.
(28) Seeberger, P. H.; Danishefsky, S. J . Acc. Chem. Res. 1998, 31,
685.
(37) Crich, D.; Smith, M.; Yao, Q.; Picione, J . Synthesis 2001, 323.
(38) Brown, H. C.; Kanner, B. J . Am. Chem. Soc. 1953, 75, 3865.
(39) Thompson, C.; Ge, M.; Kahne, D. J . Am. Chem. Soc. 1999, 121,
1237.
J . Org. Chem, Vol. 67, No. 14, 2002 4641

Crich and Li
the galactose 3-OH for the next coupling and removing
a step from the planned sequence.40
the glycosyl acceptors 19 and 20, respectively. Coupling
of 19 with the mannosyl donor 12 under the standard
BSP/Tf2O conditions gave the trisaccharide 21 in 90%
yield but as a disappointing 2:1 â:R mixture (Table 1).
The poor anomeric selectivity in this coupling is obviously
a function of the acceptor alcohol as we have previously
conducted many couplings with 12 or the corresponding
sulfoxide and found them to be highly â-selective. Much
has rightly been made of the arming and disarming
effects of protecting groups on glycosyl donor reactiv-
ity.11,45,46 It is only recently, however, that their effects
on glycosyl acceptors have begun to be studied in any
systematic manner,47,48 although it has long been recog-
nized that benzylated acceptors are more reactive than
the corresponding acetylated ones.49,50 We presume that
the poor selectivity with acceptor 19 is due to the strongly
electron-withdrawing carbonate protecting group which
reduces the nucleophilicity of the adjacent alcohol. In this
manner the â-selective SN2-like attack on the intermedi-
ate R-mannosyl triflate is retarded, thereby enabling
competing glycosylation by the SN1 pathway. Attention
was therefore focused on the acetonide-protected acceptor
20. In view of the fact that the acetonide group would
eventually need to be removed under acidic conditions,
the donor for this coupling was changed to the 2,3-di-O-
(p-methoxybenzyl) thioglycoside 13 in order that all
protecting groups other than the pivalate ester might be
cleaved in a single step. Application of the BSP/Tf2O
method to the coupling of 13 with 20 in the presence of
TTBP gave the trisaccharide 22 in excellent yield and
selectivity (Table 1).
Previously we discovered that the important â-direct-
ing effect of the 4,6-O-benzylidene group in our thiogly-
coside approaches to â-mannosides is completely over-
ridden by a 2,3-O-carbonate in the donor.14,41 It seemed
logical, therefore, that donors such as 8 would be highly
R-selective in the rhamnosylation of alcohol 16. The
observation of the R-directing nature of the 2,3-O-
carbonate in the benzenesulfenyl triflate and BSP/Tf2O
methods is in complete contrast to the â-directing effect
of the same group in insoluble silver salt mediated
mannosylation and rhamnosylations with glycosyl bro-
mides.23,42 When the BSP/Tf2O conditions were applied
to the coupling of the thioglycoside 8 with 16 in the
presence of TTBP, the desired R-rhamnoside 17 was
obtained in 63% yield as a single anomer (Table 1). We
also investigated the formation of the R-rhamnosidic
linkage by means of the 2,3-O-isopropylidene thioglyco-
side 10. It proved to be very comparable to the carbonate
8 giving the disaccharide 18 in 64% yield as a single
anomer (Table 1). This observation also contrasts with
rhamnosylation using 4-O-benzoyl-2,3-O-cyclohexylidene-
R-L-rhamnopyranosyl bromide and an insoluble silver salt
promoter which is reported to be highly â-selective.43,44
The pivalate ester was removed from 22 by saponifica-
tion with sodium methoxide in hot methanolic THF to
give 23 in 68% yield. Exposure of 23 to a 5% solution of
trifluoroacetic acid in dichloromethane at room temper-
ature, followed by neutralization with commercial tris-
(2-aminoethyl)aminopolystyrene51 and preparative TLC
of the filtrate, afforded the target molecule (3) in 46%
yield as a white crystalline solid whose physical and
spectral parameters matched those reported in the
literature.27
The TBDMS group was removed from disaccharides
17 and 18 with TBAF in the standard manner to give
(40) In the developmental work on the BSP method numerous
neighboring group-directed glycosylations were conducted in the
absence of base without apparent detriment or ortho ester formation.14
(41) Crich, D.; Cai, W.; Dai, Z. J . Org. Chem. 2000, 65, 1291.
(42) Backinowsky, L. V.; Balan, N. F.; Shashkov, A. S.; Kochetkov,
N. K. Carbohydr. Res. 1980, 84, 225.
While the stereochemical assignment of the galacto-
pyranosidic linkage in 15 and 16 is routine and that of
(43) Iversen, T.; Bundle, D. R. Carbohydr. Res. 1980, 84, C13.
(44) Iversen, T.; Bundle, D. R. J . Org. Chem. 1981, 46, 5389.
4642 J . Org. Chem., Vol. 67, No. 14, 2002

Salmonella Type E1 Core Trisaccharide
the mannopyranosidic ones in 21 and 22 almost so, on
the basis of the well-established upfield chemical shift
of the mannose H5 resonance in 4,6-O-benzylidene-
protected â- but not R-mannosides16 and on anomeric 1J CH
coupling constants,52 that of the rhamnosides 17 and 18
is far from obvious. The problem arises because, as is
generally recognized, the 2,3-O-carbonate or the 2,3-O-
isopropylidene group effectively flattens the pyranose
ring into a half-chair conformation thereby excluding the
application of the usual relationships between the ano-
meric 1J CH coupling constant and anomeric configuration
in typical pyranosides with chair conformations.52,53 For
example, we noted earlier41 that a series of 4,6-O-
benzylidene-2,3-O-carbonyl-â-D-mannopyranosides (24)54
and a similarly protected R-D-mannopyranoside (25)41
had very similar anomeric 1J CH couplings of 170.9-172.0
and 171.2 Hz, respectively. Coincidentally, 24 and 25 also
have similar chemical shifts for their mannose H1 and
H5 resonances. The problem is all the more important
because, as in the mannose series,41 we report that both
the 2,3-O-carbonate and 2,3-O-isopropylidene protected
donors 8 and 10 are highly R-selective in our chemistry,
with the probable intermediacy of glycosyl triflates,14,19
whereas earlier workers using similarly protected rham-
nosyl bromides in insoluble silver salt mediated couplings
report high â-selectivity.42-44 The assignment of stereo-
chemistry in these established reports of â-selective
rhamnosylations is based on correlations with known
compounds after removal of the 2,3-O-carbonate or 2,3-
O-alkylidene group, and no meaningful data are provided
for the immediate coupling products with the cyclic
protection in place.42-44 Scrutiny of the physical data for
24 and 25 suggests that the most facile distinction
by Thorson;27 we see no reason to doubt the R-rhamnoside
configuration of 17.
In conclusion we have carried out a direct synthesis of
the salmonella group E1 core trisaccharide 3 in which all
three glycosidic bonds, representing three of the four
main classes, are formed with a single reagent combina-
tion under conditions that differ only by the presence or
absence of a hindered base.
Exp er im en ta l Section
1
Gen er a l P r oced u r es. Unless otherwise stated H and 13C
NMR spectra were recorded in CDCl3 solution at 300 and 75
MHz, respectively. Specific rotations were measured in CHCl3
solution at ambient temperature (21 ( 1 °C) unless stated to
the contrary. All solvents were dried and distilled by the
standard protocols and all experiments conducted under an
atmosphere of dry nitrogen or argon. Organic extracts were
dried over anhydrous MgSO4. HRMS were conducted by the
Research Resources Laboratory of the University of Illinois
at Chicago, IL, or the Mass Spectrometry Laboratory of the
University of Minnesota. Microanalyses were carried out by
Midwest Microlabs, Indianapolis, IN.
Gen er a l P r oced u r e for Glycosyla tion w ith BSP /Tf2O.
To a stirred solution containing thioglycoside (2.0 equiv), TTBP
(4.0 equiv), BSP (2.0 equiv), and activated 4 Å powdered
molecular sieves in CH2Cl2 (0.1 M) was added Tf2O (2.0 equiv)
at -60 °C under Ar. After 5 min, a solution of the glycosyl
acceptor (1.0 equiv) in CH2Cl2 (1.0 M) was added. The reaction
mixture was stirred at -60 °C for 1 hour and then warmed to
0 °C, quenched with saturated aqueous NaHCO3, and diluted
with EtOAc. The reaction mixture was washed with water,
the water phase was extracted with EtOAc three times, and
the combined organic phase was washed with water and brine,
dried, filtered, and concentrated. The crude reaction mixture
was isolated by column chromatography on silica gel.
S-P h en yl 4,6-O-Ben zylid en e-3-O-(p-m eth oxyben zyl)-2-
O-p iva loyl-1-th io-â-D-ga la ctop yr a n osid e (6). Phenyl 4,6-
O-benzylidene-3-O-(p-methoxybenzyl)-1-thio-â-D-galactopyran-
oside (5)29 (1.11 g, 2.32 mmol) and DMAP (0.14 g, 1.16 mmol)
were dissolved in CH2Cl2 (30 mL), and Et3N (0.9 mL, 0.706 g,
6.95 mmol) and pivaloyl chloride (0.58 mL, 4.63 mmol) were
added at room temperature. The reaction mixture was stirred
under reflux for 24 h, cooled to room temperature, and
quenched with CH3OH, diluted with CH2Cl2, and washed with
saturated aqueous NaHCO3 then brine. The organic phase was
dried, filtered, concentrated, and purified by column chroma-
tography on silica gel (eluent: EtOAc/hexane ) 1/3 and then
1/1). The thioglycoside 6 (1.020 g, 1.80 mmol) was obtained in
78% yield as a white solid: mp 176 ( 1 °C; [R]D +4.4° (c, 0.2);
1H NMR δ 7.19-7.62 (m, 12 H), 6.83 (d, J ) 8.7 Hz, 2H), 5.43
(s, 1H), 5.33 (t, J ) 10.0 Hz, 1H), 4.69 (d, J ) 9.6 Hz, 1H),
4.58 (d, J ) 12.0 Hz, 1H), 4.57 (d, J ) 12.0 Hz, 1H), 4.33 (dd,
J ) 1.6, 12.2 Hz, 1H), 4.12 (d, J ) 3.3 Hz, 1H), 3.97 (dd, J )
1.4, 12.2 Hz, 1H), 3.78 (s, 3H), 3.66 (dd, J ) 3.4, 10.0 Hz, 1H),
3.42 (broad s, 1H), 1.21 (s, 9H); 13C NMR δ 176.6, 159.4, 137.9,
133.3, 132.5, 130.1, 129.3, 129.1, 128.9, 128.2, 127.9, 126.7,
113.9, 101.2, 86.0, 78.4, 73.5, 71.1, 70.1, 69.4, 68.1, 55.4, 38.9,
27.4. Anal. Calcd for C32H36O7S‚0.5H2O: C, 66.99; H, 6.50.
Found: C, 66.72; H, 6.45.
3
between the two anomers is to be found in the J H1,H2
coupling constant which is ∼3 Hz in 2454 and <1 Hz in
25.41 If, as is very likely, the 2,3-O-carbonyl and 2,3-O-
alkylidene R- and â-rhamnopyranosides adopt half-chair
conformations similar to those of 24 and 25, then a
similar diagnostic should be available. A literature search
3
revealed the J H1,H2 coupling constants of methyl 2,3-O-
isopropylidene-â- and R-L-rhamnopyranoside (26 and 27)
to be 3 and 0 Hz, respectively, in strong support of this
postulate.55 On this basis we assign the newly formed
linkages in 17 and 18, both with their respective cou-
plings of 0 Hz for the rhamnose moiety, as R-rhamno-
sides. In the case of 18 this assignment is ultimately
borne out by conversion to the target molecule 3, for
1
which we measured anomeric J CH couplings of 155.0,
157.9, and 170.3 MHz consistent with the presence of two
equatorial and one axial glycosidic bonds and whose
physical characteritics were identical with those given
(45) Mootoo, D. R.; Konradsson, P.; Udodong, U.; Fraser-Reid, B. J .
Am. Chem. Soc. 1988, 110, 5583.
(46) Fraser-Reid, B.; Wu, Z. C.; Andrews, W.; Skowronski, E. J . Am.
Chem. Soc. 1991, 113, 1434.
(47) Crich, D.; Dudkin, V. J . Am. Chem. Soc. 2001, 121, 6819.
(48) Boons, G.-J .; Zhu, T. Synlett. 1997, 809.
(49) Sinay¨, P. Pure Appl. Chem. 1978, 50, 1437.
(50) Paulsen, H. Angew. Chem., Int. Ed. Engl. 1982, 21, 155.
(51) Booth, R. J .; Hodges, J . C. J . Am. Chem. Soc. 1997, 119, 4882.
(52) Bock, K.; Pedersen, C. J . Chem. Soc., Perkin Trans. 2 1974,
293.
(53) Bock, K.; Pedersen, C. Acta Chem. Scand. 1975, B29, 258.
(54) Guenther, W.; Kunz, H. Carbohydr. Res. 1992, 228, 217.
(55) Anisuzzaman, A. K. M.; Whistler, R. L. Carbohydr. Res. 1977,
55, 205.
J . Org. Chem, Vol. 67, No. 14, 2002 4643

Crich and Li
S-P h en yl 2,3-O-Ca r b on yl-1-t h io-r-L-r h a m n op yr a n o-
sid e (7). To a stirred solution of phenyl 1-thio-R-L-rhamnopy-
ranoside33 (2.39 g, 9.3 mmol) in pyridine (12 mL) at 0 °C was
added phosgene (7.4 mL of 20% in toluene, 14.0 mmol)
dropwise by syringe pump, after which the reaction mixture
was stirred for 1 h before it was poured slowly into a mixture
of ice-water and saturated aqueous NaHSO3. The water phase
was extracted with EtOAc, and the combined organic phase
was washed with water and brine, dried, filtered, and concen-
trated. The crude reaction mixture was triturated with Et2O
to afford 7 (1.818 g, 6.44 mmol) in 69% yield as white solid:
mp 188 ( 1 °C; [R]D -357.3° (c, 0.1); 1H NMR δ 7.20-7.55 (m,
5H), 5.78 (s, 1H), 4.88 (d, J ) 6.7 Hz, 1H), 4.71 (t, J ) 7.0 Hz,
1H), 4.12-4.26 (m, 1H), 3.56-3.68 (m, 1H), 2.48 (d, J ) 4.7
Hz, 1H), 1.23 (d, J ) 6.1 Hz, 3H); 13C NMR δ 153.5, 132.8,
129.5, 128.7, 82.2, 79.1, 77.8, 74.1, 66.5, 25.9. Anal. Calcd for
min. DMF (10 mL) was then added, the reaction mixture was
stirred for 30 min at room temperature before it was cooled to
0 °C, and p-methoxybenzyl chloride (0.502 g, 3.19 mmol) was
added dropwise. The reaction mixture was first stirred for 15
min at 0 °C and then at room temperature for 5 h. It was
quenched with saturated aqueous NaHCO3, diluted with
EtOAc, and washed with water. The water phase was ex-
tracted with EtOAc three times, and the combined organic
phase was washed with water and brine, dried, filtered, and
evaporated. The crude reaction mixture was purified by
column chromatography on silica gel (eluent: EtOAc/hexane
) 1/3), and 13 (0.491 g, 0.82 mmol) was obtained in 64% yield
as oil: [R]D +44.3° (c, 1.1); 1H NMR δ 7.20-7.60 (m, 14H), 6.89
(d, J ) 8.7 Hz, 2H), 6.86 (d, J ) 8.7 Hz, 2H), 5.66 (s, 1H), 5.46
(s, 1H), 4.75 (d, J ) 1.7 Hz, 1H), 4.66 (s, 2H), 4.59 (d, J ) 11.7
Hz, 1H), 4.20-4.32 (m, 3H), 3.85-4.04 (m, 3H), 3.82 (s, 3H),
3.81 (s, 3H); 13C NMR δ 159.5, 159.4, 137.8, 134.0, 131.8, 130.6,
130.0, 129.9, 129.5, 129.3, 129.0, 128.4, 127.8, 126.3, 114.0,
113.9, 101.6, 87.4, 79.2, 77.7, 75.9, 72.9, 72.8, 68.7, 65.7, 55.4.
Anal. Calcd for C35H36O7S: C, 69.98; H, 6.04. Found: C, 69.60;
H, 5.98.
C
13H14O5S: C, 55.31; H, 5.00. Found: C, 55.37; H, 4.94.
S-P h en yl 2,3-O-Isop r op ylid en e-1-th io-r-L-r h a m n op y-
r a n osid e (9).34 To a stirred solution of phenyl 1-thio-R-L-
rhamnopyranoside33 (1.157 g, 4.51 mmol) and p-TsOH (0.082
g, 0.42 mmol, 10 mol %) in acetone (18 mL) was added 2,2-
dimethoxypropane (5.2 mL, 4.442 g, 41.8 mmol, 10 equiv) at
room temperature, and the reaction mixture was stirred
overnight. After the starting material was consumed, the
reaction mixture was diluted with CH2Cl2 (100 mL) and
washed with saturated aqueous NaHCO3 and water. The
organic phase was dried, filtered, and concentrated. The crude
reaction mixture was purified by column chromatography on
silica gel (eluent: EtOAc/hexane ) 1/5), and compound 9 (1.278
g, 4.31 mmol) was obtained in 95% yield as white solid: mp
78 ( 1 °C; [R]D -220.0° (c, 0.6); 1H NMR δ 7.20-7.54 (m, 5H),
5.75 (s, 1H), 4.35 (d, J ) 5.5 Hz, 1H), 4.02-4.18 (m, 2H), 3.41-
3.53 (m, 1H), 2.75-2.92 (broad s, 1H), 1.54 (s, 3H), 1.37 (s,
3H), 1.18 (d, J ) 6.2 Hz, 3H); 13C NMR δ 133.5, 132.0, 129.2,
129.1, 127.8, 109.9, 83.8, 78.5, 76.7, 75.3, 67.1, 28.3, 26.5, 17.2.
Anal. Calcd for C15H20O4S‚0.25H2O: C, 59.88; H, 6.87. Found:
C, 59.52; H, 6.82.
1-[4-(4-Nitr op h en yl)]bu tyl 4,6-O-Ben zylid en e-3-O-(p-
m eth oxyben zyl)-2-O-p iva loyl-â-D-ga la ctop yr a n osid e (15).
To a stirred solution containing the thiogalactoside 6 (0.300
g, 0.53 mmol), BSP (0.111 g, 0.53 mmol), TTBP (0.264 g, 1.06
mmol), and powdered molecular sieves in CH2Cl2 (0.53 mL)
at -60 °C was added freshly distilled Tf2O (89.3 µL, 0.53
mmol). After 10 min, a mixture of 4-(4-nitrophenyl)-1-butanol
(14) (0.14 mL, 0.80 mmol) and BF3‚Et2O (0.39 mL, 4.25 mmol)
in CH2Cl2 (1.4 mL) was added dropwise. The reaction mixture
was stirred at -60 °C for 1 h and then warmed to 0 °C,
quenched with aqueous NaHCO3, diluted with EtOAc, and
washed with water. The water phase was extracted with
EtOAc, and the combined organic phase was washed with
water and brine, dried, filtered, and concentrated. The crude
reaction mixture was purified by column chromatography on
silica gel (eluent: EtOAc/hexane ) 1/3 then 1/1), and the
saccharide 15 (0.260 g, 0.40 mmol) was obtained in 75% yield
S-P h en yl 2,3-O-Ca r bon a te-4-O-(ter t-bu tyld im eth ylsi-
lyl)-1-th io-r-L-r h a m n op yr a n osid e (8). The thiorhamnoside
7 was converted to the title compound 8, analogously to the
conversion of 9 to 10 described below, in 83% yield as a white
solid: mp 81 ( 1 °C; [R]D -208.8° (c, 0.3); 1H NMR δ 7.32-
7.52 (m, 5H), 5.76 (s, 1H), 4.85 (d, J ) 7.2 Hz, 1H), 4.61 (t, J
) 6.9 Hz, 1H), 4.08-4.20 (m, 1H), 3.50 (dd, J ) 7.2, 9.6 Hz,
1H), 1.22 (d, J ) 6.3 Hz, 3H), 0.92 (s, 9H), 0.20 (s, 3H), 0.12(s,
3H); 13C NMR δ 188.3, 153.5, 132.8, 131.9, 129.5, 128.6, 82.5,
79.9, 78.0, 75.1, 67.2, 25.9, 18.2, 17.6, -4.3, -4.8. Anal. Calcd
for C19H28O5SSi: C, 57.54; H, 7.12. Found: C, 57.22; H, 6.98.
1
as a white solid: mp 153 ( 1 °C; [R]D +4.7° (c, 0.3); H NMR
δ 8.09 (d, J ) 6.8 Hz, 2H), 7.20-7.60 (m, 9H), 6.84 (d, J ) 8.0
Hz, 2H), 5.47 (s, 1H), 5.36 (dd, J ) 8.1, 10.2 Hz, 1H), 4.60 (d,
J ) 12.0 Hz, 1H), 4.57 (d, J ) 12.0 Hz, 1H), 4.41 (d, J ) 8.1
Hz, 1H), 4.26 (d, J ) 12.3 Hz, 1H), 4.10 (d, J ) 3.6 Hz, 1H),
4.02 (d, J ) 12.6 Hz, 1H), 3.82-3.96 (m, 1H), 3.78 (s, 3H),
3.59 (dd, J ) 3.4, 10.0 Hz, 1H), 3.40-3.52 (m, 1H), 3.33 (broad
s, 1H), 2.60-2.74 (m, 2H), 1.50-1.80 (m, 4H), 1.17 (s, 9H);
13C NMR δ 176.9, 159.4, 150.6, 146.3, 137.9, 130.2, 129.4,
129.3, 129.0, 128.2, 126.5, 123.7, 113.9, 101.3, 73.4, 71.0, 69.9,
69.3, 68.4, 66.7, 55.4, 38.9, 35.6, 29.2, 27.6, 27.3. Anal. Calcd
for C36H43O10N: C, 66.55; H, 6.67. Found: C, 66.32; H, 6.81.
S-P h en yl 2,3-O-Isop r op ylid en e-4-O-(ter t-bu tyld im eth -
ylsilyl)-r-L-r h a m n op yr a n osid e (10). To a stirred solution
of 9 (0.846 g, 2.85 mmol) and imidazole (0.490 g, 7.13 mmol)
in DMF (4 mL) was added TBDMSCl (0.526 g, 3.42 mmol) after
which the reaction mixture was stirred at 40 °C overnight until
the starting material was consumed. The reaction mixture was
then diluted with EtOAc and washed with water, and the
water phase was extracted with EtOAc three times. The
combined organic phase was washed with brine, dried, filtered,
and concentrated. The crude reaction mixture was purified by
column chromatography on silica gel (eluent: EtOAc/hexane
) 1/5) to give 10 (0.864 g, 2.10 mmol) in 74% yield as an oil:
[R]D -173.5° (c, 2.0); 1H NMR δ 7.20-7.52 (m, 5H), 5.73 (s,
1H), 4.32 (d, J ) 5.7 Hz, 1H), 3.96-4.04 (m, 2H), 3.41 (dd, J
) 7.2, 9.6 Hz, 1H), 1.52 (s, 3H), 1.35 (s, 3H), 1.18 (d, J ) 6.3
Hz, 3H), 0.90 (s, 9H), 0.16 (s, 3H), 0.09 (s, 3H); 13C NMR δ
133.9, 131.9, 129.1, 127.6, 109.3, 84.1, 79.0, 76.9, 76.4, 67.8,
28.3, 26.7, 26.0, 18.3, 17.8, -3.8, -4.7. Anal. Calcd for
P r ep a r a tion of 1-[4-(4-Nitr op h en yl)]bu tyl 4,6-O-Ben -
zylid en e-2-O-p iva loyl-1-th io-â-D-ga la ctop yr a n osid e (16)
by Rem ova l of th e P MB Gr ou p fr om 15. PMB ether 15
(0.321 g, 0.49 mmol) was dissolved in a mixture of CH2Cl2 (9
mL) and H2O (0.5 mL) at room temperature, and then DDQ
(0.252 g, 1.08 mmol) was added at 0 °C. The reaction mixture
was stirred at 0 °C for 30 min and then at room temperature
until the starting material was consumed. The reaction was
quenched with saturated aqueous NaHCO3, diluted with CH2-
Cl2, and washed with saturated aqueous NaHCO3 and water
until the organic phase was clear. The organic phase was
washed with brine, dried, filtered, and concentrated. The crude
reaction mixture was purified by column chromatography on
silica gel (eluent: EtOAc/hexane ) 1/3 and then 1/1), and the
alcohol 16 (0.222 g, 0.42 mmol) was obtained in 85% yield as
white foam: [R]D -1.6° (c, 3.5); 1H NMR δ 8.10 (d, J ) 8.8 Hz,
2H), 7.20-7.58 (m, 7H), 5.55 (s, 1H), 5.09 (dd, J ) 8.1, 9.9 Hz,
1H), 4.44 (d, J ) 8.1 Hz, 1H), 4.30 (d, J ) 12.9 Hz, 1H), 4.19
(d, J ) 3.6 Hz, 1H), 4.07 (d, J ) 12.9 Hz, 1H), 3.86-3.98 (m,
1H), 3.72 (ddd, J ) 3.9, 10.5, 10.5 Hz, 1H), 3.40-3.54 (m, 2H),
2.62-2.78 (m, 2H), 2.47 (d, J ) 10.8 Hz, 1H), 1.50-1.84 (m,
4H), 1.18 (s, 9H); 13C NMR δ 178.2, 150.5, 146.4, 137.5, 129.4,
C
21H34O4SSi: C, 61.42; H, 8.34. Found: C, 61.45; H, 8.43.
S-P h en yl 4,6-O-Ben zylid en e-2,3-d i-O-(p-m eth oxyben -
zyl)-1-th io-r-D-m a n n op yr a n osid e (13). Phenyl 4,6-O-ben-
zylidene-1-thio-R-D-mannopyranoside (11)35,36 (0.461 g, 1.28
mmol), NaH (0.128 g, 3.19 mmol), and Bu4N+I- (1.204 g, 3.19
mmol) were mixed together and dried under vacuum for 30
4644 J . Org. Chem., Vol. 67, No. 14, 2002

Salmonella Type E1 Core Trisaccharide
128.4, 126.5, 123.7, 101.4, 100.9, 75.7, 72.0, 71.9, 69.2, 68.8,
66.6, 35.6, 29.2, 27.6, 27.2, 27.1. Anal. Calcd for C28H35O9N‚
0.5H2O: C, 62.44, H, 6.74. Found: 62.47; H, 6.60.
chromatography on silica gel (eluent: EtOAc/hexane ) 1/3 and
then 1/1), and compound 19 (0.124 g, 0.18 mol) was obtained
in 82% yield as a white solid: mp 168 ( 1 °C; [R]D -13.9° (c,
1
0.2); H NMR δ 8.11 (d, J ) 7.0 Hz, 2H), 7.24-7.56 (m, 7H),
Dir ect F or m a tion of 1-[4-(4-Nitr op h en yl)]bu tyl 4,6-O-
Ben zylid en e-2-O-p iva loyl-1-t h io-â-D-ga la ct op yr a n osid e
(16) fr om Th ioglycosid e 6. Thioglycoside 6 (0.491 g, 0.87
mmol), BSP (0.182 g, 0.87 mmol), and powdered molecular
sieves were dissolved in distilled CH2Cl2 (8.7 mL) at room
temperature. This solution was cooled to -78 °C, stirred for
30 min, and then warmed to -60 °C, and Tf2O (146 µL, 0.245
g, 0.87 mmol) was added. After 10 min, alcohol 14 (186 µL,
1.04 mmol) was added, and the reaction mixture was stirred
at -60 °C for 1 h before warming to 0 °C. The reaction mixture
was quenched with saturated aqueous NaHCO3, diluted with
EtOAc, and washed with water. The water phase was ex-
tracted with EtOAc, and the combined organic phase was
washed with water and brine, dried, filtered, and concentrated.
The crude reaction mixture was purified by column chroma-
tography on silica gel (eluent: EtOAc/hexane ) 1/3 and then
1/1), which afforded 16 (0.367 g, 0.69 mmol) in 80% yield as
white foam with physical data identical to those of the above
sample.
5.53 (s, 1H), 5.29 (dd, J ) 8.1, 10.4 Hz, 1H), 5.07 (s, 1H), 4.71
(dd, J ) 5.8, 7.6 Hz, 1H), 4.52 (d, J ) 7.2 Hz, 1H), 4.45 (d, J
) 8.4 Hz, 1H), 4.28-4.40 (m, 2H), 4.04-4.16 (m, 1H), 3.99 (t,
J ) 6.6 Hz, 1H), 3.87-3.96 (m, 1H), 3.85 (dd, J ) 3.7, 10.0
Hz, 1H), 3.53 (t, J ) 6.3 Hz, 1H), 3.48 (s, 1H), 3.40-3.58 (m,
1H), 2.66-2.78 (m, 2H), 1.46-1.80 (m, 4H), 1.29 (d, J ) 6.9
Hz, 3H), 1.18 (s, 9H); 13C NMR δ 176.9, 153.4, 150.4, 146.4,
137.2, 129.4, 129.3, 128.4, 126.4, 123.7, 101.4, 101.0, 98.0, 79.4,
77.6, 77.4, 75.2, 75.0, 70.8, 69.8, 69.1, 68.8, 68.5, 66.3, 39.0,
35.6, 29.2, 27.6, 18.8. Anal. Calcd for C35H43O14N‚0.5H2O: C,
59.15; H, 6.24. Found: C, 59.25; H, 6.03.
1-[4-(4-Nitr oph en yl)]bu tyl 4,6-O-Ben zyliden e-2-pivaloyl-
3-O-(2,3-O-isop r op ylid en e-r-L-r h a m n op yr a n osyl)-â-D-ga -
la ctop yr a n osid e (20). Desilylation of 18, by the same protocol
used for the conversion of 17 to 19, gave compound 20 (0.141
g, 0.20 mol) in 80% yield as a white solid: mp 85 ( 1 °C; [R]D
1
+28.3° (c, 0.2, CHCl3); H NMR (500 MHz) δ 8.10 (d, J ) 8.4
Hz, 2H), 7.33-7.56 (m, 7H), 5.52 (s, 1H), 5.31 (dd, J ) 8.1,
10.4 Hz, 1H), 5.02 (s, 1H), 4.46 (d, J ) 8.1 Hz, 1H), 4.32 (d, J
) 12.0 Hz, 1H), 4.28 (d, J ) 4.2 Hz, 1H), 4.02-4.16 (m, 3H),
3.86-3.98 (m, 1H), 3.80-3.86 (m, 1H), 3.77 (dd, J ) 3.4, 10.0
Hz, 1H), 3.40-3.52 (m, 2H), 3.30-3.40 (m, 1H), 2.64-2.78 (m,
2H), 2.20-2.30 (broad s, 1H), 1.50-1.80 (m, 4H), 1.48 (s, 3H),
1.20-1.30 (m, 6H), 1.17 (s, 9H); 13C NMR (125 MHz) δ 177.0,
150.8, 146.7, 137.9, 129.6, 129.5, 128.6, 126.7, 124.0, 109.8,
101.6, 101.4, 100.7, 79.7, 78.0, 76.0, 75.7, 74.2, 70.0, 69.4, 68.9,
67.7, 66.8, 39.5, 35.8, 29.4, 28.1, 27.9, 27.5, 26.2, 18.3. Anal.
Calcd for C37H49O13N: C, 62.09; H, 6.90. Found: C, 61.60; H,
6.77.
1-[4-(4-Nitr oph en yl)]bu tyl 4,6-O-Ben zyliden e-2-pivaloyl-
3-O-(2,3-O-ca r b on yl-4-O-(t er t -b u t yld im e t h ylsilyl)-r-L-
r h a m n op yr a n osyl)-â-D-ga la ctop yr a n osid e (17). Coupling
of donor 8 (0.294 g, 0.74 mmol) with acceptor 16 (0.196 g, 0.37
mmol, 1.0 equiv) by the standard BSP protocol afforded 17
(0.190 g, 0.23 mmol) in 63% yield as a glass: [R]D +6.7° (c,
1
0.2); H NMR δ 8.11 (d, J ) 8.7 Hz, 2H), 7.20-7.56 (m, 7H),
5.51 (s, 1H), 5.25 (dd, J ) 7.4, 10.0 Hz, 1H), 5.10 (s, 1H), 4.61
(t, J ) 7.0 Hz, 1H), 4.47 (d, J ) 11.1 Hz, 1H), 4.45 (d, J ) 12.0
Hz, 1H), 4.34 (d, J ) 12.3 Hz, 1H), 4.30 (d, J ) 3.3 Hz, 1H),
4.08 (d, J ) 12.6 Hz, 1H), 3.84-4.00 (m, 2H), 3.78 (dd, J )
3.6, 9.9 Hz, 1H), 3.40-3.52 (m, 2H), 3.36 (dd, J )6.7, 10.0 Hz,
1H), 2.64-2.80 (m, 2H), 1.50-1.80 (m, 4H), 1.22 (d, J ) 6.6
Hz, 1H), 1.15 (s, 9H), 0.85 (s, 9H), 0.13 (s, 3H), 0.07 (s, 3H);
13C NMR δ 188.5, 176.8, 153.5, 150.4, 146.4, 137.4, 129.3,
128.4, 126.3, 123.8, 101.6, 101.1, 98.2 (1J CH ) 168.6 Hz), 80.3,
80.0, 76.9, 75.6, 74.5, 69.3, 69.2, 68.8, 66.4, 65.8, 38.9, 35.6,
29.2, 27.6, 27.3, 25.8, 21.2, 17.9, -4.3, -5.0. Anal. Calcd for
1-[4-(4-Nitr oph en yl)]bu tyl 4,6-O-Ben zyliden e-2-pivaloyl-
3-O-[4-O-(2,3-O-d iben zyl-4,6-O-ben zylid en e-â-D-m a n n op y-
r a n osyl)-2,3-O-ca r b on yl-r-L-r h a m n op yr a n osyl]-â-D-ga -
la ctop yr a n osid e (21â) a n d 1-[4-(4-Nitr op h en yl)]bu tyl 4,6-
O-Ben zylid en e-2-p iva loyl-3-O-[4-O-(2,3-d i-O-b en zyl-4,6-
O-ben zylid en e-r-D-m a n n op yr a n osyl)-2,3-O-ca r bon yl-r-L-
r h a m n op yr a n osyl]-â-D-ga la ctop yr a n osid e (21r). Coupling
of 12 (0.067 g, 0.124 mmol) with 19 (0.043 g, 0.062 mmol) by
the standard BSP protocol gave 21âR (0.064 g, 0.056 mmol)
C
41H57O14NSi: C, 60.35; H, 7.04. Found: C, 60.21; H, 7.06.
1-[4-(4-Nitr oph en yl)]bu tyl 4,6-O-Ben zyliden e-2-pivaloyl-
1
3-O-(2,3-O-isop r op ylid en e-4-O-(ter t-bu tyld im eth ylsilyl)-
r-L-r h a m n op yr a n osyl)-â-D-ga la ctop yr a n osid e (18). By the
standard BSP protocol, coupling of thioglycoside 10 (0.258 g,
0.63 mmol) with acceptor 16 (0.197 g, 0.37 mmol) gave the
disaccharide 18 (0.198 g, 0.24 mmol) in 64% yield as a white
solid: mp 128 ( 1 °C; [R]D -25.3° (c, 0.1); 1H NMR (500 MHz)
δ 8.10 (d, J ) 8.4 Hz, 2H), 7.20-7.56 (m, 7H), 5.52 (s, 1H,
1J CH ) 166.1 Hz), 5.27 (dd, J ) 8.1, 10.4 Hz, 1H), 5.02 (s, 1H),
4.46 (d, J ) 8.1 Hz, 1H), 4.32-4.38 (m, 2H), 4.07 (dd, J ) 1.4,
12.3 Hz, 1H), 3.98-4.04 (m, 2H), 3.88-3.98 (m, 1H), 3.83 (dd,
J ) 6.4, 10.0 Hz, 1H), 3.73 (dd, J ) 3.6, 10.5 Hz, 1H), 3.42-
3.54 (m, 2H), 3.22-3.32 (m, 1H), 2.64-2.78 (m, 2H), 1.52-
1.82 (m, 4H), 1.48 (s, 3H), 1.25 (s, 3H), 1.20 (d, J ) 3.9 Hz,
3H), 1.18 (s, 9H), 0.8 (s, 9H), 0.11(s, 3H), 0.04 (s, 3H); 13C NMR
(125 MHz) δ 177.0, 150.8, 146.7, 137.9, 129.6, 129.4, 128.6,
126.6, 124.0, 109.2, 101.7, 101.5, 100.8, 80.2, 79.0, 77.7, 76.3,
76.2, 76.1, 69.8, 69.6, 68.8, 67.0, 66.9, 39.1, 35.9, 29.4, 28.4,
27.9, 27.5, 26.6, 26.2, 18.4, 18.3, -3.5, -4.6. Anal. Calcd for
in 90% yield with a â:R ratio of 2:1 as determined from the H
NMR spectrum of the R:â mixture after column chromatog-
raphy. Part of the â:R mixture was further purified by the
preparative TLC on silica gel (eluent: EtOAc/hexane ) 1/2)
to give samples of the two pure isomers. The pure â isomer
was a white solid: mp 108 ( 1 °C; [R]D -16.3° (c, 1.7); 1H NMR
δ 8.10 (d, J ) 8.7 Hz, 2H), 7.18-7.56 (m, 22H), 5.58 (s, 1H),
5.53 (s, 1H), 5.34 (dd, J ) 7.6, 10.0 Hz, 1H), 5.10 (s, 1H), 4.64-
4.76 (m, 4H), 4.58 (d, J ) 12.6 Hz, 1H), 4.47 (d, J ) 8.1 Hz,
1H), 4.42 (d, J ) 7.5 Hz, 1H), 4.24-4.38 (m, 4H), 4.06-4.20
(m, 2H), 3.82-4.00 (m, 5H), 3.78 (dd, J ) 3.4, 10.0 Hz, 1H),
3.48-3.62 (m, 3H), 3.48 (s, 1H), 3.26-3.36 (m, 1H), 2.68-2.78
(m, 2H), 1.56-1.80 (m, 4H), 1.30 (d, J ) 6.3 Hz, 3H), 1.17 (s,
9H); 13C NMR δ 176.9, 153.0, 150.4, 138.0, 137.6, 137.4, 129.5,
129.3, 129.0, 128.9, 128.5, 128.3, 128.2, 127.9, 127.8, 127.7,
126.4, 126.3, 126.2, 123.7, 101.7, 101.6, 101.1, 100.7, 98.2, 80.7,
78.8, 78.6, 78.2, 78.0, 77.6, 76.7, 75.8, 75.5, 74.9, 72.7, 69.4,
69.2, 68.8, 68.4, 67.7, 66.3, 64.2, 39.0, 35.6, 29.2, 27.6, 27.3,
17.7; ESIHRMS calcd for C62H69O19N1Na [M + Na]+ m/e
1154.4361, found m/e 1154.4292. The pure R isomer was a
glass: [R]D +8.3° (c, 0.1); 1H NMR δ 8.10 (d, J ) 8.8 Hz, 2H),
7.20-7.58 (m, 22H), 5.63 (s, 1H), 5.47 (s, 1H), 5.26 (dd, J )
8.0, 10.0 Hz, 1H), 4.90 (s, 1H), 4.80-4.92 (m, 2H), 4.56-4.72
(m, 4H), 4.38-4.48 (m, 3H), 4.33 (d, J ) 11.7 Hz, 1H), 4.20-
4.28 (m, 2H), 4.08 (d, J ) 11.7 Hz, 1H), 3.64-3.98 (m, 8H),
3.40-3.52 (m, 2H), 3.28 (dd, J ) 7.3, 10.4 Hz, 1H), 2.64-2.78
(m, 2H), 1.56-1.80 (m, 4H), 1.15 (s, 9H), 0.86 (d, J ) 6.3 Hz,
3H); 13C NMR δ 176.8, 152.9, 150.3, 137.9, 137.8, 137.4, 129.4,
129.3, 128.9, 128.6, 128.5, 128.4, 128.3, 128.2, 128.1, 127.7,
127.6, 126.3, 126.2, 123.7, 101.5, 101.4, 101.1, 101.0, 97.9, 80.4,
C
43H63O13NSi: C, 62.22; H, 7.65. Found: C, 62.05; H, 7.57.
1-[4-(4-Nitr oph en yl)]bu tyl 4,6-O-Ben zyliden e-2-pivaloyl-
3-O-(2,3-O-ca r b on yl-r-L-r h a m n op yr a n osyl)-â-D-ga la ct o-
p yr a n osid e (19). To a stirred solution of 17 (0.176 g, 0.22
mmol) in THF (20 mL) was added Bu4N+F- (0.43 mL of 1.0 N
in THF, 0.43 mol) at 0 °C, followed by stirring for 1 h at 0 °C
and then 4 h at room temperature until the starting material
was consumed. The reaction mixture was diluted with EtOAc
and washed with aqueous NH4Cl and water. The water phase
was extracted with EtOAc, and the combined organic phase
was washed with water and brine, dried, filtered, and concen-
trated. The crude reaction mixture was purified by column
J . Org. Chem, Vol. 67, No. 14, 2002 4645

Crich and Li
78.9, 78.6, 77.4, 77.3, 76.6, 76.5, 75.5, 75.4, 74.1, 73.7, 69.3,
68.8, 68.4, 66.3, 64.9, 64.5, 38.9, 35.6, 29.2, 27.6, 27.3, 17.0;
ESIHRMS calcd for C62H69O19N1Na [M + Na]+ m/e 1154.4361,
found m/e 1154.4323.
(0.073 g, 0.06 mmol) in a mixture of CH3OH (10 mL) and THF
(1 mL) was added Na (0.023 g, 10 mmol) at room temperature.
After the dissolution of Na, the reaction mixture was warmed
to 60 °C and stirred for 20 h. It was then cooled to room
temperature and neutralized with Amberlyst-15 cation-
exchange resin. Then the mixture was filtered, concentrated,
and purified by column chromatography on silica gel (eluent:
EtOAc/hexane ) 1/1) to give 23 (0.046 g, 0.04 mmol) in 68%
yield as glass together with recovered 22â (0.013 g, 0.01 mmol,
1-[4-(4-Nitr oph en yl)]bu tyl 4,6-O-Ben zyliden e-2-pivaloyl-
3-O-[4-O-(4,6-O-ben zylid en e-2,3-d i-O-(p-m eth oxyben zyl)-
â-D-m an n opyr an osyl)-2,3-O-isopr opyliden e-r-L-r h am n opy-
r a n osyl]-â-D-ga la ctop yr a n osid e (22â) a n d 1-[4-(4-Nitr o-
p h en yl)]bu tyl 4,6-O-Ben zylid en e-2-p iva loyl-3-O-[4-O-(4,6-
O-ben zyliden e-2,3-di-O-(p-m eth oxyben zyl)-r-D-m an n opy-
r a n osyl)-2,3-O-isop r op ylid en e-r-L-r h a m n op yr a n osyl]-â-
D-ga la ctop yr a n osid e (22r). By the standard BSP protocol,
coupling of 13 (0.234 g, 0.39 mmol) with 20 (0.136 g, 0.19
mmol) gave the trisaccharide 22 (0.212 g, 0.18 mmol, R:â )
1:9.6) in 92% yield. The pure â-isomer (0.163 g, 0.14 mmol)
was obtained by column chromatography on silica gel (elu-
ent: EtOAc/hexane ) 1/3) in 71% yield as white foam, and an
R:â mixture (0.049 g, 0.04 mmol, R:â ) 1:1.4) was obtained in
21% yield at the same time. Part of this mixture was purified
by the preparative TLC on silica gel (eluent: EtOAc/hexane
) 1/3) to give the pure R-anomer. â isomer: [R]D -19.0° (c, 0.2);
1H NMR (500 MHz) δ 8.10 (d, J ) 8.7 Hz, 2H), 7.16-7.58 (m,
16H), 6.84 (d, J ) 8.6 Hz, 2H), 6.78 (d, J ) 8.6 Hz, 2H), 5.58
(s, 1H), 5.54 (s, 1H), 5.31 (dd, J ) 8.2, 9.8 Hz, 1H), 5.04 (s,
1
13%): [R]D -35.2° (c, 0.2); H NMR (500 MHz) δ 8.14 (d, J )
8.7 Hz, 2H), 7.18-7.58 (m, 16H), 6.85 (d, J ) 8.6 Hz, 2H), 6.79
(d, J ) 8.6 Hz, 2H), 5.62 (s, 1H), 5.58 (s, 1H), 5.27 (s, 1H),
4.97 (s, 1H), 4.72 (d, J ) 11.7 Hz, 1H), 4.58 (d, J ) 11.7 Hz,
2H), 4.55 (d, J ) 12.0 Hz, 1H), 4.51 (d, J ) 12.0 Hz, 1H), 4.32-
4.40 (m, 3H), 4.26 (dd, J ) 3.0, 6.3 Hz, 1H), 4.22 (d, J ) 3.0
Hz, 1H), 4.09-4.17 (m, 3H), 3.98-4.06 (m, 1H), 3.90-3.96 (m,
3H), 3.88 (d, J ) 3.0 Hz, 1H), 3.82 (s, 3H), 3.80 (s, 3H), 3.54-
3.70 (m, 4H), 3.50 (s, 1H), 3.28-3.38 (m, 1H), 2.66-2.80 (m,
2H), 2.48 (broad s, 1H), 1.61-1.88 (m, 4H), 1.51 (s, 3H), 1.32
(s, 3H), 1.31 (d, J ) 6.3 Hz, 3H); 13C NMR (125 MHz) δ 159.5,
150.7, 146.8, 138.0, 130.5, 129.6, 129.5, 129.4, 128.6, 128.5,
126.6, 126.4, 124.1, 114.1, 113.9, 109.7, 103.2, 101.7, 100.6,
100.3, 81.7, 79.0, 78.5, 77.9, 76.5, 76.0, 75.8, 74.7, 72.1, 70.1,
69.6, 69.5, 69.0, 68.1, 66.9, 65.4, 55.7, 35.8, 29.4, 28.2, 27.8,
26.9, 18.3; ESIHRMS calcd for C61H71O19N1Na [M + Na]+ m/e
1144.4518, found m/e 1144.4558.
1
1H), 4.90 (s, 1H, J CH 160.7 Hz), 4.70 (d, J ) 11.7 Hz, 1H),
4.55(d, J ) 11.7 Hz, 1H), 4.40-4.52 (m, 3H), 4.28-4.38 (m,
2H), 4.20 (dd, J ) 5.7, 10.2 Hz, 1H), 4.02-4.18 (m, 3H), 3.84-
4.02 (m, 5H), 3.79 (s, 3H), 3.77 (s, 3H), 3.72-3.80 (m, 1H),
3.44-3.62 (m, 4H), 3.20-3.30 (m, 1H), 2.68-2.80 (m, 2H),
1.56-1.80 (m, 4H), 1.47 (s, 3H), 1.30 (d, J ) 6.2 Hz, 3H), 1.27
(s, 3H), 1.19 (s, 9H); 13C NMR (125 MHz) δ 177.1, 159.6, 159.5,
150.7, 146.7, 138.0, 137.9, 130.8, 130.7, 130.6, 129.7, 129.6,
129.5, 129.4, 129.2, 128.6, 128.5, 126.7, 126.4, 124.0, 114.2,
114.0, 113.8, 109.6, 101.9, 101.7, 101.5, 100.7, 80.5, 78.9, 78.4,
77.9, 77.8, 77.6, 77.3, 76.5, 76.1, 75.6, 74.7, 72.0, 69.8, 69.5,
69.0, 68.0, 66.8, 65.4, 60.8, 55.7, 55.6, 39.2, 35.8, 29.4, 28.1,
27.9, 27.5, 26.6, 18.2, 14.6; ESIHRMS calcd for C66H79O20N1-
Na [M + Na]+ m/e 1228.5093, found m/e 1228.5032. The
R-anomer was a glass: [R]D +48.4° (c, 1.6); 1H NMR (500 MHz)
δ 8.13 (d, J ) 8.7 Hz, 2H), 7.25-7.55 (m, 16H), 6.87 (d, J )
8.6 Hz, 2H), 6.82 (d, J ) 8.6 Hz, 2H), 5.65 (s, 1H), 5.53 (s,
1H), 5.32 (dd, J ) 8.0, 10.0 Hz, 1H), 5.03 (s, 1H), 4.80 (d, J )
11.0 Hz, 1H), 4.77 (d, J ) 12.5 Hz, 1H), 4.65 (d, J ) 1.0 Hz,
1H), 4.60 (d, J ) 11.5 Hz, 1H), 4.59 (d, J ) 12.5 Hz, 1H), 4.48
(d, J ) 8.0 Hz, 1H), 4.36 (dd, J ) 1.2, 12.2 Hz, 1H), 4.18-4.26
(m, 2H), 4.00-4.14 (m, 3H), 3.92-3.98 (m, 1H), 3.90 (dd, J )
3.5, 10.5 Hz, 1H), 3.82 (s, 3H), 3.78 (s, 3H), 3.75 (dd, J ) 3.5,
10.5 Hz, 1H), 3.71 (dd, J ) 1.0, 3.0 Hz, 1H), 3.46-3.52 (m,
2H), 3.21 (dd, J ) 7.5, 10.0 Hz, 1H), 2.70-2.80 (m, 2H), 1.50-
1.75 (m, 4H), 1.48 (s, 3H), 1.27 (s, 3H), 1.17 (s, 9H), 0.88 (d, J
) 6.3 Hz, 3H); 13C NMR (125 MHz) δ 177.1, 159.8, 150.7, 146.7,
137.9, 131.3, 130.4, 129.6, 129.5, 129.4, 129.2, 128.6, 128.5,
126.6, 124.0, 114.2, 114.1, 109.4, 101.8, 101.5, 100.9, 100.5,
80.5, 80.2, 79.6, 76.7, 76.6, 76.3, 76.1, 73.7, 73.6, 69.8, 69.0,
66.8, 65.9, 64.4, 55.7, 39.2, 35.9, 29.4, 28.4, 27.9, 27.5, 26.6,
17.4; ESIHRMS calcd for C66H79O20N1Na [M + Na]+ m/e
1228.5093, found m/e 1228.5031.
1-[4-(4-Nitr op h en yl)]bu tyl 3-O-(4-O-â-D-m a n n op yr a n o-
syl-r-L-r h a m n op yr a n osyl)-â-D-ga la ctop yr a n osid e (3). To
a stirred solution of trisaccharide 23 (15.8 mg, 0.014 mmol)
in CH2Cl2 (2 mL) was added TFA (0.1 mL) dropwise at room
temperature. After being stirred for 1.5 h, the reaction mixture
was diluted with CH2Cl2 (5 mL), neutralized with 3.03 g of
tris(2-aminoethyl)aminopolystyrene,51 and filtered through a
sintered funnel, washing first with CH2Cl2 to remove the
nonpolar byproducts and then with CH3OH to give a residue
that was purified by the preparative TLC (eluent: CHCl3/CH3-
OH ) 3/1), producing the target molecule 3 (4.3 mg, 0.006
mmol) in 46% yield as a white solid: mp 240 ( 1 °C (lit.27 mp
1
236-237.4 °C); [R]D -52.9° (c, 0.2, H2O); H NMR (500 MHz,
CH3OH-d4) δ 8.17 (d, J ) 8.7 Hz, 2H), 7.48 (d, J ) 8.7 Hz,
2H), 5.05 (s, 1H), 4.87 (s, 1H), 4.26 (d, J ) 7.7 Hz, 1H), 3.92-
4.00 (m, 6H), 3.85-3.92 (m, 2H), 3.72-3.80 (m, 3H), 3.45 (dd,
J ) 3.25, 9.4 HZ, 1H), 3.18-3.24 (m, 1H), 2.80 (t, J ) 7.7 Hz,
2H), 1.75-1.80 (m, 2H), 1.60-1.75 (m, 2H), 1.34 (d, J ) 6.2
Hz, 3H); 13C NMR (125 MHz, CD3OD) δ 152.3, 146.6, 129.6,
123.4, 104.0 9 (1J CH ) 155.0 Hz), 102.8 (1J CH ) 170.3 Hz), 101.2
(1J CH ) 157.9 Hz), 80.7, 79.8, 77.1, 75.5, 74.4, 71.5, 71.4, 71.3,
71.0, 69.3, 69.0, 67.9, 67.5, 61.8, 61.3, 35.5, 29.2, 27.6, 17.3;
ESIHRMS calcd for C28H43O17N1Na [M + Na]+ m/e 688.2429,
found m/e 688.2452.
Ack n ow led gm en t. We thank the NIH for support
of this work (Grant GM 57335) and members of the
Crich group for cover artwork.
Su p p or tin g In for m a tion Ava ila ble: Copies of 1H and 13C
NMR spectra for 3, 21â,R, 22â,R, and 23 (PDF). This material
is available free of charge via the Internet at http://pubs.acs.org.
1-[4-(4-Nitr op h en yl)]bu tyl 4,6-O-Ben zylid en e-3-O-[4-O-
(4,6-O-ben zylid en e-2,3-d i-O-(p-m eth oxyben zyl)-â-D-m a n -
n opyr an osyl)-2,3-O-isopr opyliden e-r-L-r h am n opyr an osyl]-
â-D-ga la ctop yr a n osid e (23). To a stirred solution of 22â
J O0108818
4646 J . Org. Chem., Vol. 67, No. 14, 2002