Development of carbohydrate-based scaffolds for restricted presentation of recognition groups. Extension to divalent ligands and implications for the structure of dimerized receptors

Article abstract of DOI:10.1021/jo034336d

The solution structure of glycosyl amides has been studied by using NMR. A strong preference is displayed by tertiary aromatic glycosyl amides for E-anti structures in contrast with secondary aromatic glycosyl amides where Z-anti structures predominate. The structural diversity displayed by these classes of molecules would seem to be important as the directional properties of the aromatic ring, or groups attached to the aromatic ring, would be determined by choosing to have either a secondary or tertiary amide at the anomeric center and could be considered when designing bioactive molecules with carbohydrate scaffolds. The structural analysis was also carried out for related divalent secondary and tertiary glycosyl amides and these compounds display preferences similar to that of the monovalent compounds. The constrained divalent compounds have potential for promoting formation of clusters that will have restricted structure and thus have potential for novel studies of mechanisms of action of multivalent ligands. Possible applications of such compounds would be as scaffolds for the design and synthesis of ligands that will facilitate protein - protein or other receptor - receptor interactions. The affinity of restricted divalent (or higher order) ligands, designed to bind to proteins that recognize carbohydrates which would facilitate clustering and concomitantly promote protein - protein interactions, may be significantly higher than monovalent counterparts or multivalent ligands without these properties. This may be useful as a new approach in the development of therapeutics based on carbohydrates.

Full text of DOI:10.1021/jo034336d

Develop m en t of Ca r boh yd r a te-Ba sed Sca ffold s for Restr icted
P r esen ta tion of Recogn ition Gr ou p s. Exten sion to Diva len t
Liga n d s a n d Im p lica tion s for th e Str u ctu r e of Dim er ized
Recep tor s
Paul V. Murphy,* Helena Bradley, Manuela Tosin, Nigel Pitt, Geraldine M. Fitzpatrick, and
W. Kenneth Glass
Chemistry Department, Centre for Synthesis and Chemical Biology, Conway Institute of Biomolecular and
Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
paul.v.murphy@ucd.ie
Received March 13, 2003
The solution structure of glycosyl amides has been studied by using NMR. A strong preference is
displayed by tertiary aromatic glycosyl amides for E-anti structures in contrast with secondary
aromatic glycosyl amides where Z-anti structures predominate. The structural diversity displayed
by these classes of molecules would seem to be important as the directional properties of the aromatic
ring, or groups attached to the aromatic ring, would be determined by choosing to have either a
secondary or tertiary amide at the anomeric center and could be considered when designing bioactive
molecules with carbohydrate scaffolds. The structural analysis was also carried out for related
divalent secondary and tertiary glycosyl amides and these compounds display preferences similar
to that of the monovalent compounds. The constrained divalent compounds have potential for
promoting formation of clusters that will have restricted structure and thus have potential for
novel studies of mechanisms of action of multivalent ligands. Possible applications of such
compounds would be as scaffolds for the design and synthesis of ligands that will facilitate protein-
protein or other receptor-receptor interactions. The affinity of restricted divalent (or higher order)
ligands, designed to bind to proteins that recognize carbohydrates which would facilitate clustering
and concomitantly promote protein-protein interactions, may be significantly higher than
monovalent counterparts or multivalent ligands without these properties. This may be useful as a
new approach in the development of therapeutics based on carbohydrates.
1. In tr od u ction
modulation of signal transduction pathways. Multivalent
carbohydrate ligands have advantages over their mono-
valent counterparts, which generally bind their receptors
weakly (mM). The development of low molecular weight
compounds that bind strongly to carbohydrate receptors
has therefore been difficult and this has greatly hindered
the development of therapeutics based on carbohydrates.4
There has been interest in the development of multi-
valent ligands as high affinity antagonists of receptors
of interest for the development of agents for the treat-
ment of inflammation5 and infection6 and for xenotrans-
plantation7 and anti-cancer vaccines.8 Synthetic multi-
Pharmacophore group presentation is important in
medicinal chemistry. Researchers working in this area
often introduce conformational restriction to obtain a
precise presentation of groups important for recognition
at the receptor. The benefits of synthesizing compounds
with restricted structures are that they can be more
potent, display higher selectivity, and have increased
metabolic stability and better bioavailability.1 They can
also provide information regarding the desired bioactive
conformation and exclude presentations of the binding
groups that have different and perhaps unwanted activi-
ties.
(4) Wong, C. H. Acc. Chem. Res. 1999, 32, 376.
Multivalency2,3 has attracted attention from research-
ers in diverse fields including those interested in drug
development. For example, the recognition of carbohy-
drate clusters by receptors is believed to be important
for generating high affinity interactions between two
cells, thus mediating cell-cell recognition, adhesion, and
(5) (a) Simanek, E. E.; McGarvey, G. J .; J ablonski J . A.; Wong, C.-
H. Chem. Rev. 1998, 98, 833 and references cited therein. (b) Hanes-
sian, S.; Mascitti, V.; Rogel, O. J . Org. Chem. 2002, 67, 3346 and
references cited therein. (c) Murphy, P. V.; Hubbard, R. E.; Manallack,
D. T.; Wills, R. E.; Montana, J . G.; Taylor, R. J . K. Bioorg. Med. Chem.
1998, 6, 2421.
(6) (a) von Itzstein, M.; Wu, W.-Y.; Kok, G. B.; Pegg, M. S.; Dyason,
J . C.; J in, B.; Phan, T. V.; Smythe, M. L.; White, H. F.; Oliver, S. W.;
Colman, P. M.; Varghese, J . N.; Ryan, D. M.; Woods, J . M.; Bethell, R.
C.; Hotham, V. J .; Cameron, J . M. Nature 1993, 363, 418. (b)
Kamitakahara, H.; Suzuki, T.; Nishigori, N.; Suzuki, Y.; Kanie, O.;
Wong, C.-H. Angew. Chem., Int. Ed. 1998, 37, 1524. (c) Kitov, P. I.;
Sadowska, J . M.; Mulvey, G.; Armstrong, G. D.; Ling, H.; Pannu, N.
S.; Read, R. J .; Bundle, D. R. Nature 2000, 403, 669.
(1) For examples relating to peptides and peptidomimetics see:
Hruby, V. J . Acc. Chem. Res. 2001, 34, 389.
(2) Lee, Y. V.; Townsend, R. R.; Hardy, M. R.; Lo¨nngren, J .; Arnarp,
J .; Haraldsson, M.; Lo¨nn, H. J . Biol. Chem. 1983, 258, 199.
(3) Mammen, M.; Choi, S.-K.; Whitesides, G. M. Angew. Chem. Int.
Ed. 1998, 37, 2754.
(7) Liu, B.; Roy, R. J . Chem. Soc., Perkin Trans. 1 2001, 773.
10.1021/jo034336d CCC: $25.00 © 2003 American Chemical Society
Published on Web 06/18/2003
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J . Org. Chem. 2003, 68, 5692-5704

Development of Carbohydrate-Based Scaffolds
SCHEME 1
F IGURE 1. (a) The divalent ligand that promotes clustering
of receptors and receptor-receptor interactions. (b) The diva-
lent ligand that promotes clustering of receptors but not
receptor-receptor interactions.
valent ligands can also effect or promote biological
processes.9 The cross-linking of multivalent carbohy-
drates with lectins can lead to formation of supra-
molecular assemblies that have roles in signal transduc-
tion.10
The mechanisms by which cells exploit multivalent
interactions to bind with increased affinity and specificity
and how cell-surface receptor organization influences
signaling and the cellular responses that result have been
reviewed11 and can be influenced by the ligand architec-
ture.12 An explanation often offered is that increases in
binding affinity are due to the chelate effect. Toone and
co-workers have provided evidence that observed en-
hancements in the apparent binding affinity of multi-
valent ligands appear, in some cases at least, to be the
result of entropically driven aggregation and precipita-
tion.13 On the other hand Burke, Kiessling, and co-
workers have described a trivalent ligand that promotes
synergistic formation of soluble lectin clusters; in this
case the chelate effect cannot operate and precipitation
of the ligand does not occur at concentrations where the
clusters are soluble.14 Other thermodynamic analyses of
multivalent ligand binding have been carried out by
Brewer and co-workers.15
Enhancements in binding affinity and perhaps speci-
ficity, observed for multivalent ligands, could also be
explained if receptor-receptor interactions were pro-
moted as a result of clustering (Figure 1). Synthetic
ligands, which would promote such interactions, may
show higher affinities. The determination of whether
such mechanisms for generating high-affinity interac-
tions operate could be investigated by synthesizing
multivalent ligands that are structurally restricted; the
presentation of the groups required for recognition could
be organized in a manner such that a particular ligand
would promote clustering and receptor-receptor interac-
tions whereas another ligand would promote clustering
but not receptor-receptor interactions; there should be
significant differences in binding affinities, perhaps also
in specificity, and there may be consequences for biologi-
cal function. To investigate these issues it is necessary
to develop scaffolds that facilitate the presentation of
multiple binding groups into precise and well-defined
orientations. The study of these processes with use of
these tools will aid in understanding the mechanism of
action of multivalent ligands in greater detail and
perhaps provide new strategies that can be considered
in drug development.
Our initial interest is in the generation of a diverse
range of structurally restricted divalent ligands so that
they can be used for homo- and heterodimerization of
receptors and that diverse clustering mechanisms and
functional consequences can be investigated in detail.
Dimerization is the simplest form of receptor clustering
and its role as a regulatory mechanism in signal trans-
duction has been reviewed; it can be promoted by small
molecules that have been referred to as “chemical induc-
ers of dimerization”.16 Dimeric compounds often show
improved activity; it has been shown for example that
dimerization of an inactive fragment of a natural product
can produce a compound with twice the potency of the
natural product.17 In this paper we describe monovalent
aromatic glycosyl amides that have potential as scaffolds
for restricted presentation of binding groups for targeting
receptors. This work has been extended to the synthesis
of structurally related divalent glycosyl amides18 that
have well-defined structures with potential for use in
structurally restricted receptor clustering.
(8) (a) Liebe B.; Kunz, H. Angew. Chem., Int. Ed. Engl. 1997, 36,
618. (b) Keil, S.; Claus, C.; Dippold, W.; Kunz, H. Angew. Chem., Int.
Ed. 2001, 40, 366 and references cited therein. (c) Deshpande, P.;
Danishefsky, S. J . Nature 1997, 387, 167. (d) Hummel, G.; Schmidt,
R. R. Tetrahedron Lett. 1997, 38, 1173. (e) For a multivalent vaccine
see: Ragupathi, G.; Coltart, D. M.; Williams, L. J .; Koide, F.; Kagan,
E.; Allen, J .; Harris, C.; Glunz, P. W.; Livingston P. O.; Danishefsky,
S. J . Proc. Natl. Acad. Sci. (U.S.A.) 2002, 99, 13699.
(9) Gestwicki, J . E.; Strong, L. E.; Kiessling, L. L. Chem. Biol. 2000,
7, 583.
(10) Sacchettini, J . C.; Baum, L. G.; Brewer, C. F. Biochemistry 2001,
40, 3009.
(11) Kiessling, L. L.; Gestwicki, J . E.; Strong, L. E. Curr. Opin.
Chem. Biol. 2000, 4, 696.
(12) Comparisons were made between low molecular weight com-
pounds, dendrimers, globular proteins, linear polymers, and polydis-
perse polymers. Gestwicki, J . E.; Cairo, C. W.; Strong, L. E.; Oetjen,
K. A.; Kiessling, L. L. J . Am. Chem. Soc. 2002, 124, 14922.
(13) Corbell, J . B.; Lundquist, J . L.; Toone, E. J . Tetrahedron:
Asymmetry 2000, 11, 95.
(14) Burke S. D.; Zhao, Q.; Schuster, M. C.; Kiessling, L. L. J . Am.
Chem. Soc. 2000, 122, 4518.
(15) Dam, T. K.; Roy, R.; Das, S. K.; Oscarson, S.; Brewer, C. F. J .
Biol. Chem. 2000, 275, 14223.
2. Resu lts a n d Discu ssion
2.1. Syn th eses of Mon ova len t Glycosyla m id es. A
series of secondary and tertiary amides (Table 1, Scheme
1) were first prepared for structural evaluation. The
(16) Klemm, J . D.; Schreiber, S. L.; Crabtree, G. R. Annu. Rev.
Immunol. 1998, 21, 418-422.
(17) Carlier, P. R.; Du, D.-M.; Han, Y.-F.; Liu, J .; Perola, E.;
Williams, I. D.; Pang, Y.-P. Angew. Chem., Int. Ed. 2000, 39, 1775.
(18) A preliminary account of the work described herein has been
published previously. Bradley, H.; Fitzpatrick, G.; Glass, W. K.; Kunz,
H.; Murphy, P. V. Org. Lett. 2001, 3, 2629.
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Murphy et al.
TABLE 1. Str u ctu r e of Mon ova len t Glycosyl Am id es
a
Spectra were recorded in D2O at 10-40 °C with HOD (δ 4.80) as the internal reference.
reaction of D-glucose or D-galactose with an amine gives
a glycosylamine, which is acylated selectively at nitrogen
by treatment with an acid chloride in methanol in the
presence of sodium carbonate; this protocol was used to
prepare compounds 5-12.19 The four-component Ugi
condensation of the 2,3,4,6-tetra-O-acetylated-â-D-glyco-
pyranosylamine with formaldehyde, isocyanide, and car-
boxylic acid and subsequent removal of the acetate
protecting groups was also used to synthesize tertiary
amides; this conveniently provided the neoglycopeptides
1-4. A variation of the Staudinger reaction was used for
synthesis of secondary amides; activation of the appropri-
ate 2,3,4,6-tetra-O-acetylated-â-D-glycopyranosyl azide by
triphenylphosphine in the presence of benzoyl chloride
gives a protected glycosylamide from which the protecting
groups were removed to give 13 and 14.
2.2. Str u ctu r e of Mon ova len t Glycosyla m id es.
Structural analyses of some â-glycosyl amide derivatives
(Figure 2) have been reported previously.20,21 Previous
research has indicated that an antiperiplanar (anti)
rather than synperiplanar (syn) conformation is often
(20) Avalos, M.; Babiano, R.; Carretero, M. J .; Cintas, P.; Higes, F.
J .; J ime´nez, J . L.; Palacios, J . C. Tetrahedron 1998, 54, 615.
(21) The R-glycosides have not been reported. Conventions for
describing the configurations and conformations of the â-derivatives
have been described previously, see: Avalos, M.; Babiano, R.; Dura´n,
C. J .; J ime´nez, J . L.; Palacios, J . C. J . Chem. Soc., Perkin Trans. 2
1992, 2205 and references cited therein.
(19) Tertiary amides have been prepared previously. See: (a)
Lockhoff, O.; Sadler, P. Carbohydr. Res., 1998, 314, 13. (b) Retailleau,
L.; Laplace, A.; Fensterbank, H.; Larpent, C. J . Org. Chem., 1998, 63,
608.
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Development of Carbohydrate-Based Scaffolds
F IGURE 2. Nomenclature of glycosyl amides.
1
preferred for such amides. The H and 13C NMR spectra
for most of the known tertiary amide derivatives (R1 *
H) show two signal sets and this has been attributed to
the presence of Z-anti and E-anti isomers of the â-glycosyl
amide. The previous workers have found correlation of
the major preferred solution structure with that observed
in the solid state.22 A set of rules was established, based
on 1H and 13C chemical shifts, that are used to assign
the Z or E configuration. For example, for glycosyl amides
the chemical shift for the anomeric proton of the Z-anti
isomer will be greater than that of the E-anti isomer due
to deshielding caused by the carbonyl group; the chemical
shift of the signal observed for the anomeric carbon of
the Z-isomer is usually less than that of the E-isomer. A
range of novel unprotected galactose and glucose deriva-
tives 1-14, synthesized as outlined in Scheme 1, have
been studied and the results are summarized in Table
1. In general E-anti structures predominate for the
tertiary aromatic amides (1, 2, 5-8, 11, 12) whereas for
secondary aromatic amides (13, 14) Z-anti structures are
favored. In the NMR spectra the tertiary amides 1-12
showed two clear signal sets whereas the secondary
amides 13 and 14 showed only one signal set. The
resonances for the anomeric protons for all the glycosyl
amides were generally doublets and had coupling con-
stants consistent with the â-configuration; the NMR data
and NOE enhancements observed for the remaining
F IGURE 3. Summary of NOE data for tertiary amides. There
were strong NOE enhancements between the aromatic protons
and H-1 and also between H-2 and the methylene group (or
methyl group) bonded to the nitrogen atom. Strong NOEs were
not observed between the methylene group (or methyl group)
and H-1 as would have been expected for syn conformations.
4
pyranose ring protons confirmed that the C1 conforma-
F IGURE 4. Summary of NOE data for aromatic secondary
amides. There were strong NOE enhancements between NH
and H-2 and between NH and aromatic protons. Strong NOEs
were not observed between the NH and H-1 as would have
been expected for syn conformations (spectra were recorded
in D2O:H2O 10:90 so that NH could be observed). Strong NOEs
were not observed between aromatic protons and H-1 as would
be expected for E-anti.
tions are always favored, as expected. The NOE data also
supported the structures proposed for the secondary and
tertiary amide derivatives (Figures 3 and 4). For example,
strong enhancements of the signal for the anomeric
proton and a significantly weaker enhancement for the
methyl signal were observed in the 1D NOE spectrum of
5 obtained by irradiating the aromatic signal; this is
consistent with a predominant E-anti structure. Tertiary
aromatic amides, in contrast with secondary aromatic
amides, are generally not planar and the observed
dihedral angle depends on the extent of steric interac-
tions; angles of up to 90 ° between the carbonyl and
aromatic group have been observed.23 Interestingly a
weak enhancement of the signal for H-5 but not for H-3
was observed after irradiating the aromatic signal of 5,
suggesting that the aromatic ring may be rotated toward
the H-5 proton in the E-anti structure. The 1D and 2D
NOE spectra in general showed evidence for exchange
between the Z and E isomers, providing further support
for the proposed structures for the tertiary amides. The
1D NOE spectrum for galactose derivative 13 obtained
in D2O after the irradiation of signal for the anomeric
proton showed only a very weak enhancement of the
signal for the aromatic protons when compared to the
enhancement observed for H-3 and H-5; a strong en-
hancement would have been expected for significant
population of the E-anti structure. The spectrum of 13
was also recorded in 10:90 D2O:H2O; the coupling con-
stant that was observed between H-1 and the NH was
9.0 Hz; the 1D-NOE spectrum of 13 in this solvent
mixture showed a strong enhancement of the signals for
aromatic protons and H-2 on irradiation of the signal for
the NH; these data further support the Z-anti structural
assignment for the secondary amides, which is consistent
with that found by other workers. Some other trends are
evident. The tendency to adopt the E-anti structure for
the tertiary amides was greater for aromatic derivatives
(1, 2, 5-8, 11, 12) than for aliphatic derivatives (3, 4, 9,
(22) Avalos, M.; Babiano, R.; Carretero, M. J .; Cintas, P.; Higes, F.
J .; J ime´nez, J . L.; Palacios, J . C. Tetrahedron 1998, 54, 615.
(23) Bragg, R. A.; Clayden J .; Morris, G. A.; Pink, J . H. Chem. Eur.
J . 2002, 8, 1279 and references cited therein.
J . Org. Chem, Vol. 68, No. 14, 2003 5695

Murphy et al.
SCHEME 2
10), and increasing the substitution on the carbon
adjacent to the nitrogen (R1 substituent) showed an
increase in the E/ Z ratio (compare 2, 5-8, 11, 12). For
the benzyl derivatives (8, 11, 12) no major changes in
the E/ Z ratio were observed on variation of the substitu-
ent on the aromatic ring. The structural preference
displayed by tertiary aromatic amides may be due to a
simple steric effect between the ortho aromatic protons
and the R1 substituent; as the size of the R1 substituent
increases the greater the steric interaction and thus there
is an increase in preference for the E-anti structure. This
effect is not as pronounced when the R2 substituent is
methyl. We anticipate on the basis of the above results
that the E/ Z ratio might be higher (>93:7) for N-glycosyl-
N-isopropyl aromatic amides. These predictions have
been supported by molecular mechanics calculations of
such derivatives but we have not been able to prepare
these derivatives as yet using the synthetic routes
described herein; work is currently in progress to inves-
tigate the synthesis of these compounds.
SCHEME 3
2.3. P oten tia l of Mon ova len t Ar om a tic Glycosyl
Am id es a s Sca ffold s. The use of carbohydrates as
scaffolds in peptidomimetic and other research related
to drug development has recently been explored by
Hirschmann, Nicolaou, Smith, and co-workers24 and
other researchers.25 The low bioavailability of peptide
drugs has led to investigations of placing pharmacophoric
groups on a nonpeptide scaffold; the scaffold can orient
these groups in the direction of their respective binding
subsites. The results obtained indicate that evaluation
of compounds based on monosaccharide and even disac-
charide26 scaffolds holds great promise for being univer-
sally useful as a drug discovery platform. Also some
workers have been exploring the synthesis and evalua-
tion of carbohydrate mimetics and “carbohybrids”27 with
a view to developing compounds that will bind with high
affinities to carbohydrate receptors. In these contexts the
structural diversity (i.e. E-anti for tertiary amides, Z-anti
for secondary amides) displayed by amides 1-14, in
particular for the aromatic amides, would seem to be
important. The directional properties of the aromatic ring
or groups attached to the aromatic ring would be deter-
mined by choosing to have either a secondary or tertiary
amide at the anomeric center and this could be taken
into consideration in the design of bioactive molecules
based on carbohydrate templates.
2.4. Syn th esis of Diva len t Glycosyl Am id es. Hav-
ing observed the strong preferences for E-anti structure
for tertiary aromatic glycosyl amides, it seemed appropri-
ate to prepare structurally related divalent compounds
and thus the synthesis of 17-20 was carried out. Reac-
tion of the amine 15 with succinic acid in the presence
of diisopropylethylamine gives 16. The Ugi reaction of
16 with 15, formaldehyde, and methyl isocyanoacetate
and subsequent removal of the protecting groups gave
17 (Scheme 2). A double Ugi reaction of terephthalic acid
with 15, formaldehyde, and methyl isocyanoacetate fol-
lowed by deacetylation was used to synthesize 18. The
secondary amide 19 was prepared via the EDC-promoted
coupling of 15 with terephthalic acid (Scheme 3) followed
by deprotection. The synthesis of 20 (Scheme 4) was
carried out by coupling of an amine derived from glucu-
ronic acid with terephthalic acid, using a mixture of DCC,
HOBT, and DMAP in THF and subsequent deprotection.
(24) (a) Hirschmann, R.; Nicolaou, K. C.; Pietranico, S.; Salvino, J .;
Leahy, E. M.; Sprengeler, P. A.; Furst, G.; Smith, A. B., III; Strader,
C. D.; Cascieri, M. A.; Candelore, M. R.; Donaldson, C.; Vale, W.;
Maechler, L. J . Am. Chem. Soc. 1992, 114, 9217. (b) Nicolaou, K. C.;
Salvino, J . M.; Raynor, K.; Pietranico, S.; Reisine, T.; Freidinger, R.
M.; Hirschmann, R. In Peptides-Chemistry, Structure, and Biology:
Proceedings of the 11th American Peptide Symposium; Rivier, J . E.,
Marshall, G. R., Eds.; ESCOM: Leiden, The Netherlands, 1990; pp
881-884. (c) Hirschmann, R.; Nicolaou, K. C.; Pietranico, S.; Leahy,
E. M.; Salvino, J .; Arison, B. H.; Cichy, M. A.; Spoors, P. G.;
Shakespeare, W. C.; Sprengeler, P. A.; Hamley, P.; Smith, A. B., III;
Reisine, T.; Raynor, K.; Maechler, L.; Donaldson, C.; Vale, W.;
Freidinger, R. M.; Cascieri, M. A.; Strader, C. D. J . Am. Chem. Soc.
1993, 115, 12550. (d) Hirschmann, R.; Hynes, J ., J r.; Cichy-Knight,
M. A.; van Rijn, R. D.; Sprengeler, P. A.; Spoors, P. G.; Shakespeare,
W. C.; Pietranico-Cole, S.; Barbosa, J .; Liu, J .; Yao, W.; Rohrer, S.;
Smith, A. B., III J . Med. Chem. 1998, 41, 1382-1391.
(25) (a) Ghosh, M.; Dulina, R. G.; Kakarla, R.; Sofia, M. J . J . Org.
Chem. 2000, 65, 8387. (b) Wunberg, T.; Kallus, C.; Opatz, T.; Henke,
S.; Schmidt, W.; Kunz, H. Angew. Chem., Int. Ed. 1998, 37, 2503. (c)
Boer, J .; Gottschling; Schuster; Holzmann, B.; Kessler, H. Angew.
Chem., Int. Ed. Engl. 2001, 40, 3870. (d) Wessel, H. P.; Banner, D.;
Gubernator, K.; Hilpert, K.; Myller, K.; Tschopp, T. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 751. (e) Moitessier, N.; Dufour, S.; Chre´tien,
F.; Thiery, J . P.; Maigret, B.; Chapleur, Y. Bioorg. Med. Chem. 2001,
9, 511. (f) Zuccarello, G.; Bouzide, A.; Kvarnstrom, I.; Niklasson, G.;
Svensson, S. C. T.; Brisander, M.; Danielsson, H.; Nillroth, U.; Karlen,
A.; Hallberg, A.; Classon, B.; Samuelsson, B. J . Org. Chem. 1998, 63,
4898. (g) Hanessian, S.; Huynh, H. K. Synlett 1999, 1, 102. (h) Xuereb,
H.; Maletic, M.; Gildersleeve, J .; Pelczer, I.; Kahne, D. J . Am. Chem.
Soc. 2000, 122, 1883. (i) Kawato, H. C.; Nakayama, K.; Inagaki, H.;
Ohta, T. Org. Lett. 2001, 3, 3451. (j) Liao, Y.; Li, Z. M.; Wong, H. N. C.
Chin. J . Chem. 2001, 19, 1119. (k) Murphy, P. V.; O’Brien, J . L.; Gorey-
Feret, L.; Smith, A. B., III Bioorg. Med. Chem. Lett. 2002, 12, 1763-
66. (l) The Versatile Assembly on Sugar Templates (VAST) program
initiated by Alchemia Corporation, see: Schliebs, D. Mod. Drug Discov.
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(26) For an example of a disaccharide scaffold see: Baizman, E. R.;
Branstrom, A. A.; Longley, C. B.; Allanson, N.; Sofia, M. J .; Gange,
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Chem. Biol. 1999, 3, 291-298;
5696 J . Org. Chem., Vol. 68, No. 14, 2003

Development of Carbohydrate-Based Scaffolds
SCHEME 4
2.5. Str u ctu r e of Diva len t Glycosyl Am id es. The
structural preferences displayed by the divalent glycosyl
amides 17-20 were consistent with that observed for the
related monovalent compounds. The Z-anti:E-anti ratio
was 27:73 for the divalent galactose derivative 17; this
is a more flexible compound than the other divalent
compounds prepared due to the presence of succinic acid
linker. This contrasts with the remainder of divalent
structures 18-20, which are more rigid. A series of 1D
NOE, 2D NOESY, and 2D ROESY experiments for 18
showed strong NOE enhancements for the major isomer
(87%) consistent with the amides adopting E-anti con-
formations; there were strong enhancements observed
between the methylene protons adjacent to the nitrogen
atom at C-1 with H-2 and between H-1 and the aromatic
protons. Also the chemical shift for the anomeric proton
of the major isomer at δ 4.98 is consistent with that
observed for E-anti structures in the monovalent series.
The presence of a minor isomer (13%, 18c and 18d ),
where one amide is E-anti and the other Z-anti (Figure
5), can be detected from the NMR data as there are two
anomeric signals (1H NMR, δ 5.90 and δ 4.90, 40 °C)28
that show clear cross-peaks with the anomeric signal at
δ 4.98 in the 2D NOESY and ROESY spectra; these cross-
peaks had opposite sign to the NOE enhancements,
indicating that exchange between the isomers occurs
further supporting the structural assignment.29 The NMR
spectra for this compound were also obtained in CD3OD
and the E-anti isomer also predominated in this solvent.
Interpretation of the data obtained suggests that the
major structural isomer adopted by 18 is either 18a or
18b (Figure 5). Both of these isomers contain a C-2
symmetry axis; for 18a the carbohydrates are in a cis
arrangement, for 18b they are trans. The aromatic signal
for 18 in D2O or CD3OD appears as a singlet; however,
at -85 °C in CD3OD the aromatic signal appeared as two
broad signals (∼1:2 ratio) supporting the most likely
possibility that there is dynamic equilibrium between the
cis and trans isomers. Computational methods (Monte
Carlo conformational searches)30 would indicate that 18a
and 18b are both low-energy structures although a
significantly higher number of structures with trans
geometries (Figure 6) were found within 3 kcal mol-1 of
the global minimum. The NMR spectra for the secondary
amide derivatives 19 and 20 were similar to those
observed for the related monovalent compounds 13 and
F IGURE 5. Structure of 18.
F IGURE 6. Lowest energy structures for 18b.
1
14. A single set of signals was evident in the H and 13C
was irradiated and strong NOE enhancements were
observed for H-2, H-3, and H-5 but only a very minor
enhancement was observed for the aromatic protons; this
is again consistent with the Z-anti structure being
preferred for these amides. This suggests that the major
isomers adopted by 19 are 19a and 19b (Figure 7, 8) and
that those of 20 are 20a and 20b. For 19a and 20a the
carbohydrates can again be considered to be cis, whereas
for 19b and 20b they are trans. Calculations with Monte
NMR spectra. The signal for the anomeric proton of 19
appeared at δ 5.24 (J 1,2 ) 8.9 Hz) and for that of 20 at δ
5.33 (J 1,2 ) 8.7 Hz) in the 1H spectrum. The 1D NOE
spectrum for 20 was obtained where the anomeric signal
(28) At 10 °C the signals are doublets at δ 5.58 and δ 4.60.
(29) Exchange between Z- and E-anti conformations has been
observed also for other tertiary amides described herein by NOE. See
the Supporting Information for selected spectra.
(30) Calculations were carried out with Macromodel 6.0.
J . Org. Chem, Vol. 68, No. 14, 2003 5697

Murphy et al.
F IGURE 7. Structure of 19 and 20.
F IGURE 9. Atoms (the ring O, C-1, C-2, C-3, C-4, C-5) of one
of the galactose residues (shown top left) of the lowest energy
structures of the divalent ligands 18a , 18b (green), 19a , and
19b (red) were superimposed. The peptide chains of 18 have
been removed for clarity.
F IGURE 8. Lowest energy structures for 19a (top) and 19b
(bottom) obtained by a Monte Carlo conformational search.
their own structural space. This structural diversity
would be increased by using a range of monosaccharides
(D and L) or by using higher order saccharides (oligosac-
charides).
Carlo conformational searching techniques indicate that
both 19a and 19b are low-energy structures (Figure 8).
2.6. P oten tia l Ap p lica tion s of Restr icted Diva len t
Liga n d s. It is clear that the structural space occupied
by cis and trans isomers of 18 and 19 (Figure 9) differs
considerably and as a consequence the structural space
occupied by receptors that would be clustered by binding
to the two saccharide units, or to any bioactive group
attached to the saccharide unit, will also differ consider-
ably. This provides a basis for generating structural
diversity combined with an ability to present the struc-
ture of the binding groups in well-defined orientations.
Furthermore, the various hydroxyl groups on the sac-
charide units can be used for attachment of bioactive
groups or molecular recognition components, in a fashion
similar to that adopted by those interested in using
carbohydrate-based scaffolds in medicinal chemistry; this
approach would facilitate the generation of a library of
divalent compounds where the recognition components
belonging to each member of the library would occupy
3. Su m m a r y a n d Con clu sion s
The structure of unprotected glycosyl amides in water
has been investigated. The structural preferences for the
secondary amides are clearly different from those ob-
served for the tertiary glycosyl amides and there are
strong preferences for E-anti structures for the aromatic
tertiary amides. Monovalent and divalent compounds
based on aromatic glycosyl amides have potential as
scaffolds to present binding groups in well-defined ori-
entation. The results have implications for the structures
of clusters that will form on binding of divalent ligands
to receptors. Preliminary molecular modeling studies31
we have carried out indicate that 18-20 and related
scaffolds can, at least in principle, be used as a basis for
(31) These studies will be discussed in a subsequent publication.
5698 J . Org. Chem., Vol. 68, No. 14, 2003

Development of Carbohydrate-Based Scaffolds
H-2), 3.37-3.52 (overlapping signals, 3H, H-3, H-4, H-5); 13C
NMR (D2O, E-isomer) δ 175.7 (s, CO2Me), 172.4, 172.2 (each
s, each CdO), 133.7 (s, aromatic C), 131.4, 129.3, 127.2 (each
d, aromatic C), 87.8 (d, C-1), 78.2, 75.8, 70.4, 69.4 (each d),
61.0 (t, C-6), 53.1 (q, OCH3), 45.2 (t, CH2), 41.6 (t, CH2); νmax
(KBr) 3445, 2954, 2881, 1910, 1745, 1648, 1556, 1448, 1371,
1222, 1080 cm-1. HRMS-FAB: found 435.1378 [M + Na]+,
required 435.1380. Analytical HPLC (C-4; 5:95; CH3CN:H2O)
indicated >95% purity.
[2-(Ben zoyl-(â-D-ga la ctop yr a n osyl)-a m in o)-a cetyla m i-
n o]-a cetic Acid , Meth yl Ester (2). 2,3,4,6-Tetra-O-acetyl-
â-D-galactopyranosylamine32 (15; 0.5 g, 1.44 mmol), benzoic
acid (0.18 g, 1.44 mmol), and formaldehyde (0.11 mL, 1.44
mmol) were suspended in methanol (5 mL) and stirred at room
temperature for 1 h. Methyl isocyanoacetate (0.13 mL, 1.44
mmol) was then added and the reaction mixture was allowed
to stir at room temperature. TLC analysis (EtOAc) showed that
the reaction was complete after 48 h. The solvent was removed
and the residue purified by chromatography (EtOAc:petroleum
ether, 1:1) to give [2-(benzoyl-(2,3,4,6-tetra-O-acetyl-â-D-ga-
lactopyranosyl)-amino)-acetylamino]-acetic acid, methyl ester
as a white foam (0.6 g, 73%); Rf 0.32 (EtOAc); [R]D +33.3 (c
0.02, MeOH); mp 25-29 °C; 1H NMR (270 MHz, DMSO-d6) δ
8.17 (br s, 1H, NH), 7.25-7.51 (overlapping signals, 5H,
aromatic H), 5.10-5.24 (overlapping signals, 4H, H-1-4),
3.63-4.19 (overlapping signals, 7H, H-5, H-6a, H-6b, 2 × CH2),
3.64 (s, 3H, OMe), 1.95-2.05 (overlapping signals, 12H, OAc);
13C NMR (CDCl3) δ 170.4, 170.1, 169.9 (each s, each CdO),
135.2, 134.5 (each s, aromatic C), 130.9 (s, aromatic C), 128.9,
128.8, 127.1, 126.8, 126.5 (each d, aromatic C), 90.1 (br signal,
d, C-1), 73.3, 68.6, 67.0, 66.0 (each d), 61.4 (t, C-6), 52.3 (q,
OCH3), 41.3, 41.2 (each t, each CH2), 20.7 (2 signals), 20.6,
20.5 (each q, each OAc); νmax (KBr) 3400, 2977, 2544, 1763,
1671, 1541, 1439, 1370, 1220, 1051 cm-1. HRMS-CI: found
581.1983 [M + H]+, required 581.1987. This intermediate (0.37
g, 0.65 mmol) was suspended in methanol (10 mL) and NaOMe
(0.2 mL of a 0.25 M solution) was added. The reaction mixture
was allowed to stir at room temperature. TLC analysis (MeOH:
EtOAc, 1:4) showed that the reaction was complete after 2.5
h. Amberlite (H+) was added and after 5 min the reaction
mixture was filtered and the solvent removed. The residue was
purified by chromatography (MeOH) to yield 2 as an off-white
foam (0.16 g, 59%); Rf 0.5 (MeOH:EtOAc, 1:4); [R]D +40.0 (c
0.04, MeOH); mp 58-60 °C; 1H NMR (300 MHz, D2O; Z:E,
10:90) δ 7.65 (s, 5H, aromatic H), 5.77 (br s, H-1, Z-isomer),
4.86 (d, 1H, J 1,2 ) 9.0 Hz, H-1, E-isomer), 4.46 (s, 2H, CH2),
4.21 (s, 2H, CH2), 3.97 (d, 1H, J 4,3 ) 3.0 Hz, H-4), 3.81-3.92
(overlapping signals, 6H, H-2, H-6a, H-6b, OCH3), 3.64 (dd,
1H, J 5,6a ) 4.0 Hz, J 5,6b ) 7.6 Hz, H-5), 3.59 (dd, 2H, J 3,4 ) 3.0
Hz, J 3,2 ) 9.5Hz, H-3); 13C NMR (D2O) δ 175.9 (s, CO2Me,
Z-isomer), 175.7 (s, CO2Me, E-isomer), 172.4, 172.2 (each s,
each CdO, E-isomer), 171.5 (s, CdO, Z-isomer), 133.7 (s,
aromatic C, E-isomer), 131.4, 129.2, 127.1, 126.5 (each d,
aromatic C, E-isomer), 131.0, 129.9 (2 signals), 129.0 (each d,
each aromatic C, Z-isomer), 88.4 (d, C-1, E-isomer), 77.6, 72.9,
68.8, 68.0 (each d, E-isomer), 75.4, 73.1, 73.0, 69.0 (each d,
Z-isomer), 61.4 (t, Z-isomer), 61.3 (t, C-6, E-isomer), 53.1 (q,
OCH3), 45.3, 43.7 (each t, each CH2, Z-isomer), 45.1, 41.6 (each
t, each CH2, E-isomer); νmax (KBr) 3413, 2938, 1744, 1654,
1555, 1449, 1369, 1225, 1096 cm-1. HRMS-FAB: found
435.1374 [M + Na]+, required 435.1380. Analytical HPLC (C-
4; 5:95 CH3CN:H2O) indicated >90% purity.
F IGURE 10. Structures of 21-23.
the design of ligands suitable for clustering proteins and
the modeling indicates it might be possible to present
recognition groups in such a way that a restricted
divalent ligand could promote receptor-receptor interac-
tions. For example, divalent compound 22 (Figure 10)
bearing the trimannoside 21, a ligand for Concanavalin
A, can bring the two monomeric proteins within a
distance where protein-protein interactions may occur;
this is unlikely for the related tertiary amides 23.
Synthesis and biological evaluation of these ligands is
underway and the results will be reported in due course.
Irrespective of the results that these studies will generate
it seems worthwhile to further explore the synthesis of
restricted divalent ligands for applications in biological
and medicinal chemistry.
4. Exp er im en ta l Section
[2-(Ben zoyl-(â-D-glu copyr an osyl)-am in o)-acetylam in o]-
a cet ic Acid , Met h yl E st er (1). 2,3,4,6-Tetra-O-acetyl-â-D-
glucopyranosylamine (0.3 g, 0.86 mmol), benzoic acid (0.11 g,
0.86 mmol), formaldehyde (0.06 mL, 0.86 mmol), and methyl
isocyanoacetate (0.08 mL, 0.86 mmol) were suspended in
methanol (5 mL). The reaction mixture was allowed to stir at
room temperature. Analysis by TLC (EtOAc) showed that the
reaction was complete after 24 h. Excess solvent was removed
and the residue was purified by chromatography (EtOAc:
petroleum ether, 2:1) to yield [2-(benzoyl-(2,3,4,6-tetra-O-
acetyl-â-D-glucopyranosyl)-amino)-acetylamino]-acetic acid,
methyl ester as a yellow syrup (0.24 g, 49%); Rf 0.27 (EtOAc);
1H NMR (300 MHz, CDCl3) δ 7.48 (br s, 5H, aromatic H), 6.91
(br s, 1H, NH), 5.04-5.17 (broad overlapping signals, H-1-
4), 4.01-4.21 (br signals, 6H, H-6a, H-6b, 2 × CH2), 3.75 (s,
3H, OCH3), 3.60-3.75 (br signal, 1H, H-5), 2.10, 2.04, 2.01,
1.99 (each s, each 3H, each OAc); 13C NMR (CDCl3) δ 170.7,
170.5, 170.3, 169.4, 168.6 (each s, each CdO), 134.5 (s,
aromatic C), 131.1, 129.1, 127.0 (each d, aromatic C), 74.6, 73.4,
68.6, 68.1 (each d), 61.9 (t, C-6), 52.5 (q, OCH3), 41.5 (t, CH2),
20.9, 20.7 (each q, each OAc); νmax (KBr) 3400, 2977, 2544,
1763, 1671, 1541, 1439, 1370, 1220, 1051 cm-1. HRMS-CI:
found 581.1987 [M + H]+, required 581.1983. This intermedi-
ate (0.13 g, 0.22 mmol) was suspended in MeOH (20 mL),
sodium methoxide (0.1 mL of a 0.25 M solution) was added,
and the reaction mixture was allowed to stir at room temper-
ature. TLC analysis (MeOH:EtOAc, 1:4) showed that the
reaction was complete after 3 h. Amberlite (H+) was added
and after 5 min the reaction mixture was filtered and the
solvent removed to yield 1 as a yellow solid (0.08 g, 98%); Rf
0.5 (MeOH:EtOAc, 1:4); [R]D +25.0 (c 0.04, H2O); mp 70-74
°C; 1H NMR (300 MHz, D2O; Z:E, 8:92) δ 7.65 (s, 5H, aromatic
H), 5.94 (br s, 1H, H-1, Z-isomer), 4.92 (d, 1H, J 1,2 ) 8.9 Hz,
H-1, E- isomer), 4.42 (AB d, 2H, J ) 17.0 Hz, CH2), 4.19 (AB
[2-(Acetyl-(â-D-galactopyr an osyl)-am in o)-acetylam in o]-
a cetic Acid , Meth yl Ester (3). The amine 15 (0.5 g, 1.44
mmol) was suspended in dry THF (30 mL). To this solution
was added formaldehyde (0.11 mL, 1.44 mmol), acetic acid
(0.15 mL, 2.0 mmol), methyl isocyanoacetate (0.15 mL, 1.73
mmol), and zinc chloride (0.5 M solution in THF, 0.2 mL, 1.44
mmol), and the mixture was allowed to stir at -25 to -40 °C.
d, 2H, J ) 17.0 Hz, CH2), 3.86 (dd, 1H, J 6a,5 ) 1.9 Hz, J 6a,6b
12.4 Hz, H-6a), 3.85 (s, 3H, OCH3), 3.80 (dd, 1H, J 6b,5 ) 5.5
Hz, J 6b,6a ) 12.4 Hz, H-6b), 3.67 (apt t, J 2,1 ) J 2,3 ) 8.9 Hz,
)
(32) Bertho, A.; Maier, J . J ustus Liebigs Ann. Chem. 1932, 498, 50,
55.
J . Org. Chem, Vol. 68, No. 14, 2003 5699

Murphy et al.
TLC analysis (EtOAc) showed that the reaction was complete
after 24 h. The solvent was removed and the residue purified
by chromatography (EtOAc) to give [2-(acetyl-(tetra-O-acetyl-
â-D-galactopyranosyl)-amino)-acetylamino]-acetic acid, methyl
ester33 as a white foam (0.08 g, 11%); Rf 0.27 (EtOAc); [R]D
+43.75 (c 0.02, MeOH); 1H NMR (270 MHz, CDCl3) δ 7.27 (br
s, 1H, NH), 6.00 (d, 1H, H-1), 5.17-5.47 (overlapping signals,
H-2-4), 3.99-4.22 (overlapping signals, H-5, H-6a, H-6b, 2 ×
CH2), 3.74 (s, 3H, OCH3), 2.00-2.20 (overlapping signals, 4 ×
OAc, CH3); 13C NMR (CDCl3) δ 172.7, 170.5, 170.4, 170.2,
170.0, 169.8, 169.2 (each s, each CdO), 80.5 (d, C-1), 74.0, 71.1,
67.4, 66.5 (each d), 61.9 (t, C-6), 52.5 (q, OCH3), 48.6 (t, CH2),
41.3 (t, CH2), 22.2 (q, CH3), 20.8, 20.7 (2 signals) (each q, each
4.21 (overlapping signals, 4H, H-2, H-4, CH2), 3.70-3.92
(overlapping signals, CHPh, H-3, H-5, H-6a, H-6b, OCH3), 2.25
(s, 3H, NAc); 13C NMR (D2O) δ 174.8, 173.1, 172.2 (each s, each
CdO), 134.9 (s, aromatic C), 130.2, 128.9, 128.8, 128.5 (each
d, aromatic C), 88.2 (d, C-1), 77.9, 73.1, 69.0, 68.5 (each d),
61.2 (t, C-6), 53.1 (q, OCH3), 41.9 (t, CH2), 22.3 (q, CH3); νmax
(KBr) 3428, 2925, 2839, 1743, 1646, 1539, 1442, 1374, 1223,
1083 cm-1. HRMS-FAB: found 449.1537 [M + Na]+, required
449.1536. Analytical HPLC (C-4; 2:98 CH3CN:H2O) indicated
>85% purity.
N-Meth yl-D-ga la ctop yr a n osyla m in e. To a solution of
methylamine in methanol (5.4 mL, 11.2 mmol) was added
D-galactose (2.0 g, 11.2 mmol). The reaction mixture was
heated to 60-65 °C for 30 min. The reaction mixture was then
allowed stir at room temperature. After 9 h of reaction the
solvent was removed and the residue recrystallized from
ethanol to give the title compound as an off-white solid (1.76
g, 82%); [R]D -11.67 (c 0.02, MeOH); mp 118-120 °C; 1H NMR
(300 MHz, D2O; 1:2 mixture of R:â anomers) δ 5.32 (d, 1H,
J 1,2 ) 3.2 Hz, H-1, R-anomer), 4.65 (d, 1H, J 1,2 ) 7.8 Hz, H-1,
â-anomer), 3.48-4.05 (overlapping signals, 12H, H-2-6), 2.38,
2.32 (each s, each 3H, each CH3); 13C NMR (D2O, â-anomer) δ
98.5 (d, C-1, R-anomer), 91.4 (d, C-1, â-anomer), 76.2, 74.0,
70.6, 69.3 (each d, â-anomer), 75.3, 73.1, 72.4, 69.1 (each d,
R-anomer), 61.5 (t), 61.3 (t), 31.1 (q, CH3); νmax (KBr) 3312,
2966, 2860, 1654, 1503, 1452, 1357, 1240, 1142, 1058, 987
cm-1. HRMS-FAB: found 194.1030 [M + H]+, required
194.1028.
OAc); νmax (film) 2884, 2086, 1741, 1447, 1374, 1241 cm-1
.
HRMS-CI: found 519.1828 [M + H]+, required 519.1826. This
intermediate (0.02 g, 0.04 mmol) was suspended in MeOH (5
mL), sodium methoxide (0.1 mL of a 0.25 M solution) was
added, and the reaction mixture was allowed to stir at room
temperature. After 40 min another 0.1 mL of NaOMe was
added to the reaction mixture. After a further 2 h of reaction
an additional 0.1 mL of NaOMe was added. TLC analysis
(MeOH:EtOAc, 1:4) showed that the reaction was complete
after a total of 3.5 h. Amberlite (H+) was added and after 5
min the reaction mixture was filtered and the solvent removed
to give the title compound as a clear oil (0.01 g, 71%); Rf 0.17
(MeOH:EtOAc, 1:4); 1H NMR (300 MHz, D2O; Z:E, 1:3) δ 5.65
(d, 1H, J 1,2 ) 9.1 Hz, H-1, Z-isomer), 5.12 (d, 1H, J 1,2 ) 8.2
Hz, H-1, E-isomer), 3.80-4.25 (overlapping signals, 13H, H-2-
6, 2 × CH2, OCH3), 2.37 (s, 3H, NAc).
N-Meth yl-N-(â-D-ga la ctop yr a n osyl)-ben za m id e (5). So-
dium carbonate (0.17 g, 1.6 mmol) was added to a solution of
N-(methyl)-D-galactopyranosylamine (0.12 g, 0.6 mmol) in
methanol (15 mL). The resulting solution was cooled to 0 °C
and benzoyl chloride (0.14 mL, 1.2 mmol) was added dropwise
over 5 min. The ice bath was then removed and the reaction
mixture was allowed to stir at room temperature. TLC analysis
(MeOH:EtOAc, 1:3) showed the reaction was complete after
20 min. The solvent was removed and the residue purified by
chromatography (2×, MeOH:EtOAc, 1:30 to 1:10) to yield the
title compound as a clear oil (0.05 g, 27%); Rf 0.34 (MeOH:
EtOAc, 1:3); [R]D +40.0 (c 0.02, H2O); mp 78-80 °C; 1H NMR
(300 MHz, D2O; Z:E, 15:85) δ 7.58-7.66 (m, 5H, aromatic H),
[2-(Acetyl-(â-D-galactopyr an osyl)-am in o)-2-ph en ylacet-
yla m in o]-a cetic Acid , Meth yl Ester (4). The amine 15 (0.3
g, 0.86 mmol) was suspended in dry THF (20 mL). To this
solution was added benzaldehyde (0.10 mL, 0.95 mmol), acetic
acid (0.07 mL, 1.2 mmol), and methyl isocyanoacetate (0.10
mL, 0.32 mmol). The reaction mixture was cooled to -25 °C,
zinc chloride (0.5 M solution in THF, 0.12 mL, 0.86 mmol) was
added, and the mixture was allowed to stir at -25 to -40 °C.
After 3 h at this temperature the reaction was complete and
the reaction mixture was allowed to stir at room temperature.
TLC analysis showed that the reaction was complete after 48
h. The solvent was removed and the product purified by
chromatography (EtOAc) to give [2-(acetyl-(tetra-O-acetyl-â-
D-galactopyranosyl)-amino)-2-phenylacetylamino]-acetic acid,
methyl ester (0.18 g, 35%); Rf 0.18 (EtOAc); [R]D -58.75 (c 0.04,
CHCl3); 1H NMR (300 MHz, CDCl3) δ 7.29-7.48 (m, 5H,
aromatic H), 4.85-5.59 (overlapping signals, 4H, H-1-4),
3.73-4.03 (br signals, 9H, H-5, H-6a, H-6b, CHPh, CH2,
OCH3), 2.16 (s, 3H, NAc), 2.04, 2.03, 2.01, 1.97 (each s, each
OAc); 13C NMR (CDCl3) δ 171.3, 170.4 (2 signals), 170.2, 169.7,
169.4 (each s, each CdO), 129.0, 128.9, 128.7, 128.4 (each d,
aromatic C), 73.0, 72.2, 67.4, 63.0, 60.6 (each d), 61.3 (t, C-6),
52.4 (q, OCH3), 41.7 (t, CH2), 31.0 (d, CHPh), 20.9, 20.8 (2
signals), 20.7 (each q, each OAc); νmax (KBr) 3432, 2973, 2858,
1754, 1672, 1540, 1439, 1370, 1228, 1052 cm-1. HRMS-FAB:
found 617.1960 [M + Na]+, required 617.1959. This intermedi-
ate (0.09 g, 0.15 mmol) was suspended in MeOH (10 mL),
sodium methoxide (0.1 mL of a 0.25 M solution) was added,
and the reaction mixture was allowed to stir at room temper-
ature. After 6 and 15 h additional portions of NaOMe solution
(each 0.1 mL) were added to the reaction mixture. After a n
additional 15 h of reaction another 0.1 mL of NaOMe was
added. TLC analysis (MeOH:EtOAc, 1:4) showed that the
reaction was complete after a total of 24 h. Amberlite (H+) was
added and after 5 min the reaction mixture was filtered and
the solvent removed. The residue was purified by chromatog-
raphy (MeOH:EtOAc, 1:40) to yield the title compound 4 as
an off-white foam (0.03 g, 45%); Rf 0.17 (MeOH:EtOAc, 1:4);
[R]D +45.0 (c 0.04, H2O); 1H NMR (300 MHz, D2O; Z:E, 1:1) δ
7.64 (br s, 2H, aromatic H), 7.50 (br s, 3H, aromatic H), 5.60
(br s, 1H, H-1, Z-isomer), 5.11 (br s, 1H, H-1, E-isomer), 4.03-
5.63 (d, 1H, J 1,2 ) 9.4 Hz, H-1, Z-isomer), 4.69 (d, 1H, J 1,2
)
9.2 Hz, H-1, E-isomer), 4.01 (apt t, 1H, J 2,3 ) J 2,1 ) 9.2 Hz,
H-2), 3.94 (d, 1H, J 3,4 ) 3.0 Hz, H-3), 3.86 (dd, 2H, J 6a,5 ) 7.8
Hz, J 6a,6b ) 12.0 Hz, H-6a), 3.79 (dd, 1H, J 6b,5 ) 4.5 Hz, J 6b,6a
) 12.0 Hz, H-6b), 3.54 (br signal, 1H, H-5), 3.39 (dd, 1H, J 4,3
) 3.4 Hz, J 4,5 ) 9.5 Hz, H-4), 3.09 (s, 3H, OCH3); 13C NMR δ
(D2O) 176.0 (s, CdO), 134.5 (s, aromatic C), 131.1, 129.2, 127.1
(each d, aromatic C), 88.5 (d, C-1, E-isomer), 82.7 (d, C-1,
Z-isomer), 77.3, 73.5, 68.9, 67.4 (each d), 61.2 (t), 28.0 (q, CH3);
νmax (KBr) 3409, 2909, 1502, 1447, 1367, 1279, 1055 cm-1
.
HRMS-FAB: found 320.1118 [M + Na]+, required 320.1110.
N-Eth yl-D-ga la ctop yr a n osyla m in e. The reaction of D-
galactose (2.5 g, 13.46 mmol) and ethylamine (13.5 mL, 2.0 M
solution in MeOH, 27 mmol) in MeOH (35 mL) as described
above gave N-methyl-D-galactopyranosylamine as a white solid
1
(1.06 g, 68%); H NMR (300 MHz, D2O) δ 5.16 (br d, 1H, H-1
for R-anomer), 4.50-4.47 (br d, 1H, H-1 for â-anomer), 4.00-
3.25 (m, 7H, H-2-H-6 for both anomers), 2.90-2.75 (m, 2H,
CH2CH3 for R-anomer), 2.70-2.50 (m, 2H, CH2CH3 for â-ano-
mer), 0.99 (t, 3H, CH2CH3 for both anomers); 13C NMR (300
MHz, D2O) for â-anomer δ 90.0 (d, C-1), 76.1, 74.0, 70.8, 69.3
(each d), 61.4 (t, C-6), 39.5 (t, CH2CH3), 14.1 (q, CH2CH3), for
R-anomer 97.2 (d, C-1), 75.3, 73.1, 72.4, 69.1 (C-2-C-5, each
d), 61.2 (t, C-6), 35.4 (t, CH2CH3), 16.3 (q, CH2CH3).
N-Eth yl-N-(â-D-ga la ctop yr a n osyl)-ben za m id e (6). The
reaction of N-ethyl-D-galactopyranosylamine (0.99 g, 4.78
mmol) with benzoyl chloride (1.1 mL, 9.6 mmol) as described
for 5 gave a mixture (1.32 g, 89%) that contained the title
compound. An analytical sample of the title compound (0.210
g, 14%) was obtained after two chromatographic separations
1
(33) Kunz, H.; Pfrengle, W. J . Am. Chem. Soc. 1988, 110, 651.
5700 J . Org. Chem., Vol. 68, No. 14, 2003
(MeOH:EtOAc gradient elution). H NMR (300 MHz, D2O) δ

Development of Carbohydrate-Based Scaffolds
7.50-7.40 (m, 5H, aromatic H), 5.42 (br s, H-1 for Z-isomer),
4.57 (d, 1H, J 1,2 ) 9.0 Hz, H-1 for E-isomer), 4.00-3.28 (m,
9H, H-2-H-7 and CH2CH3), 1.25 (t, 3H, CH2CH3 for E-isomer),
1.12-0.96 (br t, 3H, CH2CH3 for Z-isomer); 13C NMR (300
MHz, D2O) δ 175.7 (s, CdO), 135.1 (s, aromatic C), 130.8 (d,
aromatic CH), 129.1 (d, aromatic CH), 126.8 (d, aromatic CH),
88.9 (d, C-1), 77.3, 73.8, 68.9, 67.7 (C-2-C-5, each d), 61.3 (t,
C-6), 37.4 (t, CH2CH3), 13.8 (q, CH2CH3); νmax (KBr) 3393, 2976,
(MeOH:EtOAc, 1:4); 1H NMR (300 MHz, D2O; Z:E, 33:67) δ
7.39-7.55 (m’s, 5H, aromatic H), 5.66 (d, 1H, J 1,2 ) 8.3 Hz,
H-1, Z-isomer), 4.72 (d, 1H, J 1,2 ) 8.5 Hz, H-1, E-isomer), 3.42-
4.07 (overlapping signals, 8H, H-2-6, CH2Ph), 2.39, 2.31, 2.30,
2.11 (each s, each CH3, Z- and E-isomers); 13C NMR (D2O) δ
177.3, 175.7 (each s, each CdO, E- and Z-isomers), 138.2, 138.0
(each s, aromatic C), 129.0, 128.9, 128.7, 127.6, 127.3 (2
signals), 126.9 (each d, aromatic C), 88.1 (d, C-1, E-isomer),
83.6 (d, C-1, Z-isomer), 77.4, 74.1, 73.9, 69.0, 68.9, 68.4, 67.9
(each d), 61.3, 61.2 (each t, each C-6), 47.7, 45.4 (each t, CH2-
Ph), 22.3, 21.6 (q, CH3). HRMS-FAB: found 334.1270 [M +
Na]+, required 334.1267.
2937, 1623, 1577, 1497, 1446, 1395, 1330, 1234, 1076 cm-1
.
CI-HRMS: found 312.1447, required 312.1451 [M + H]+.
N-Isobu tyl-â-D-ga la ctop yr a n osyla m in e. The reaction of
D-galactose (2.0 g, 10.77 mmol) and isobutylamine (2.1 mL,
21.54 mmol) in methanol as described for N-isobutyl-â-D-
galactopyranosylamine gave the title compound as a white
solid (2.45 g, 97%); Rf 0.24 (in 1:4 MeOH/EtOAc); 1H NMR (300
MHz, D2O) δ 3.90-3.30 (7H, H-1-H-7), 3.90-3.80 (m, 2H),
3.70-3.60 (m, 2H), 3.60-3.50 (m, 2H), 3.45-3.30 (apt t, 1H),
2.65-2.58 (m, 1H, CH(H)CH(CH3)2), 2.46-2.41 (m, 1H, CHaHb-
CH(CH3)2), 1.75-1.55 (m, 1H, CHaHbCH(CH3)2), 0.83 (d, 6H,
CHaHbCH(CH3)2). CI-HRMS: found 236.1502, required 236.1498
[M + H]+.
N-Isobu tyl-N-(â-D-galactopyr an osyl)-ben zam ide (7). The
reaction of N-isobutyl-â-D-galactopyranosylamine (1.11 g, 4.62
mmol) with benzoyl chloride as described for 5 gave a white
solid (1.30 g, 83%) containing the title compound; an extra
chromatographic separation was necessary to obtain an ana-
lytical sample (0.200 g, 13%, Rf 0.59 in 1:4 MeOH/EtOAc); 1H
NMR (300 MHz, D2O) δ 7.92 (m, ArH for Z-isomer), 7.60-
7.40 (m, 5H, ArH for both conformers), 5.21 (br d, 1H, H-1 for
Z-isomer), 4.54 (d, 1H, J 1,2 ) 9.0 Hz, H-1 for E-isomer), 4.00-
3.10 (m, 9H, H-2-H-7 and CH2CH(CH3)2), 2.20-2.10 (m, 1H,
CH2CH(CH3)2), 0.93 (d, 6H, CH2CH(CH3)2 for E-isomer), 0.65
(br t, 6H, CH2CH(CH3)2 for Z-isomer); 13C NMR (300 MHz,
D2O) δ 175.8 (s, CdO), 135.1 (s, aromatic C), 131.0 (d), 129.1
(d), 127.1 (each d, each aromatic C), 89.0 (d, C-1), 77.3, 73.9,
69.0, 67.6 (C-2-C-5, each d), 61.5 (t, C-6), 49.1 (t, CH2CH-
(CH3)2), 27.8 (d, CH2CH(CH3)2), 20.0, 19.9 (each q, each CH2-
CH(CH3)2); νmax (KBr) 3381, 2958, 2871, 1625, 1448, 1384,
1231, 1075 cm-1. CI-HRMS: found 340.1759, required 340.1760
[M + H]+.
N-Meth yl-N-(â-D-galactopyr an osyl)-acetam ide (10). The
reaction of N-(methyl)-D-galactopyranosylamine (0.12 g, 0.6
mmol) and acetyl chloride (0.1 mL, 1.2 mmol) as described for
1
5 gave the title compound as a white solid (0.12 g, 80%); H
NMR (300 MHz, D2O; Z:E, 47:53) δ 5.51 (d, 1H, J 1,2 ) 9.0 Hz,
H-1, Z-isomer), 4.98 (d, 1H, J 1,2 ) 8.8 Hz, H-1, E-isomer), 3.77-
4.05 (overlapping signals, 12H, H-2-6, E- and Z- isomers), 3.11
(s, 3H,COCH3, Z-isomer), 2.97 (s, 3H, COCH3, E-isomer), 2.29
(s, 3H, CH3, Z-isomer), 2.25 (s, 3H, CH3, E-isomer); 13C NMR
(D2O) δ 176.6 (s, CdO, E-isomer), 175.7 (s, CdO, Z-isomer),
87.5 (d, C-1, E-isomer), 82.5 (d, C-1, Z-isomer), 77.4 (2 signals),
73.8, 73.5, 69.0, 68.9, 67.6, 67.1 (each d, Z- and E-isomers),
61.1 (2 signals) (each t, Z- and E-isomers), 30.2, 27.4 (q,
COCH3, Z- and E-isomers), 21.9, 21.1 (q, CH3, Z- and E-
isomers); νmax (film) 3437, 2115, 1640, 1414, 1261, 1077 cm-1
LRMS-ES: found 258.0 [M + Na]+, required 258.1.
.
N-(4-Meth oxyben zyl)-â-D-galactopyr an osylam in e.34 The
reaction of 4-methoxybenzylamine (1.45 mL, 11 mmol) and
D-galactose (2.0 g, 11 mmol) as described for N-(4-methyl)-â-
D-galactopyranosylamine gave the title compound as a white
solid (0.92 g, 28%); Rf 0.52 (MeOH:EtOAc, 2:1); [R]D -18.33 (c
0.02, MeOH); mp 96-102 °C; 1H NMR δ (300 MHz, D2O) 7.42
(d, 2H, J ) 8.2 Hz, aromatic H), 7.06 (d, 2H, J ) 8.4 Hz,
aromatic H), 3.50-4.09 (overlapping signals, 12H, H-1-6,
OCH3, CH2Ar); 13C NMR (D2O) δ 160.8 (s, aromatic C), 134.7
(s, aromatic C), 133.0, 132.0 (each d, each aromatic C), 117.1,
116.9 (each d, each aromatic C), 91.7 (d, C-1), 78.7, 76.5, 74.7,
73.5 (each d), 64.0 (t, C-6), 58.3 (q, OCH3), 46.5 (t, CH2); νmax
(KBr) 3356, 2921, 2836, 1636, 1508, 1432, 1300, 1248, 1100,
N-(Ben zyl)-â-D-ga la ctop yr a n osyla m in e. The reaction of
benzylamine (1.22 mL, 11.2 mmol) and D-galactose (2.0 g, 11.2
mmol) as described for N-methyl-â-D-galactopyranosylamine
gave the title compound as an off-white solid (0.28 g, 10%); Rf
0.31 (MeOH:EtOAc, 1:3); [R]D -18.33 (c 0.02, MeOH); mp 72-
1042 cm-1
.
N-(4-Meth oxyben zyl)-N-(â-D-ga la ctop yr a n osyl)-ben za -
m id e (11). The reaction of N-(4-methoxybenzyl)-â-D-galacto-
pyranosylamine (0.5 g, 1.67 mmol) and benzoyl chloride (0.39
mL, 3.34 mmol) as described for 5 gave the title compound as
a yellow foam (0.13 g, 19%); Rf 0.27 (MeOH:EtOAc, 1:8); [R]D
-5.0 (c 0.02, MeOH); 1H NMR (500 MHz, D2O, 10 °C; Z:E,
6:94) δ 7.24-7.42 (overlapping signals, aromatic H), 5.45 (br
s, H-1, Z-isomer), 4.68 (d, 1H, J 1,2 ) 8.8 Hz, H-1, E-isomer),
4.62 (AB d, 2H, J ) 15.5 Hz, CH2Ar), 3.62-3.73 (overlapping
signals, 6H, H-2, H-4, H-6a, OCH3), 3.59 (dd, 1H, J 6b,6a ) 12.0
1
75 °C; H NMR (300 MHz, D2O, 2:3 mixture of R:â anomers)
δ 7.49 (s, 5H, aromatic H), 5.34 (br s, 1H, H-1, R-isomer), 4.65
(d, 1H, J 1,2 ) 7.6 Hz, H-1, â-isomer), 3.51-4.15 (overlapping
signals, 8H, H-2-6, CH2Ph); 13C NMR (D2O) δ 139.5 (s,
aromatic C), 129.0, 128.9, 127.8 (each d, aromatic C), 89.3 (d,
C-1), 76.1, 73.9, 70.9, 69.2 (each d), 61.4 (t, C-6), 48.7 (t, CH2-
Ph); νmax (KBr) 3276, 2894, 1645, 1452, 1356, 1055 cm-1
.
HRMS-FAB: found 270.1341 [M + H]+, required 270.1341.
Hz, J 6b,5 ) 4.3 Hz, H-6b), 3.40 (dd, 1H, J 5,6a ) 8.0 Hz, J 5,6b
)
4.2 Hz, H-5), 3.28 (dd, 1H, J 3,4 ) 3.5 Hz, J 3,2 ) 9.5 Hz, H-3);
13C NMR (D2O) δ 176.0 (s, CdO), 172.0 (s, aromatic C), 158.0
(s, aromatic C), 133.2, 131.1, 130.6, 129.6, 129.3, 129.1, 128.8,
127.0, 114.2 (each d, aromatic C), 89.0 (d, C-1), 77.3, 73.7, 68.9,
68.0 (each d), 61.3 (t, C-6), 55.7 (q, OCH3), 45.0 (t, CH2Ph);
νmax (film) 3457, 3055, 2930, 1697, 1629, 1513, 1451, 1265,
1177, 1036 cm-1. HRMS-FAB: found 426.1527 [M + Na]+,
required 426.1529.
N-(Ben zyl)-N-(â-D-galactopyr an osyl)-ben zam ide (8). The
reaction of N-(benzyl)-â-D-galactopyranosylamine (0.5 g, 1.96
mmol) with benzoyl chloride (0.5 mL, 3.92 mmol) as described
for 5 gave the title compound as a white foam (0.5 g, 71%);
[R]D +30.0 (c 0.02, H2O); 1H NMR δ (500 MHz, D2O, 40 °C;
Z:E >10:90) 7.52-7.77 (overlapping signals, 10H, aromatic H),
5.70 (br s, 1H, H-1, Z-isomer), 5.01 (br s, 1H, H-1, E-isomer),
4.07-4.10 (br signals, 5H, H-2-4, CH2Ph), 3.99 (dd, 1H, J 6a,5
) 7.4 Hz, J 6a,6b ) 11.8 Hz, H-6a), 3.92 (dd, 1H, J 6b,5 ) 4.2 Hz,
J 6b,6a ) 11.8 Hz, H-6b), 3.61-3.90 (br signal, 1H, H-5); 13C
NMR (D2O) δ 176.0 (s, CdO), 138.2 (s, aromatic C), 135.0 (s,
aromatic C), 129.5, 128.9, 126.5, 126.3, 126.1 (each d, each
aromatic C), 89.0 (d, C-1), 77.0, 74.3, 69.5, 68.0 (each d), 61.0
N-(4-Ch lor oben zyl)-â-D-ga la ctop yr a n osyla m in e. Reac-
tion of 4-chlorobenzylamine (1.33 mL, 11 mmol) and D-
galactose (2.0 g, 11 mmol) as described for N-(methyl)-â-D-
galactopyranosylamine gave the title compound as white
crystals (1.84 g, 55%); Rf 0.3 (EtOAc:petroleum ether, 1:4); [R]D
1
-23.3 (c 0.02, MeOH); mp 144-146 °C; H NMR (300 MHz,
(t, C-6), 45.2 (t, CH2Ph); νmax (film) 3412, 2930, 2866, 2102,
-1
DMSO-d6) δ 7.43-7.31 (m, 4H, aromatic H), 4.61 (d, 1H, J
1888, 1622, 1428, 1281, 1070 cm
.
N-(Ben zyl)-N-(â-D-galactopyr an osyl)-acetam ide (9). The
reaction of N-(benzyl)-â-D-galactopyranosylamine (0.5 g, 1.96
mmol) and acetyl chloride (0.28 mL) as described for 5 gave
the title compound as a white foam (0.03 g, 5%); Rf 0.22
(34) (a) Retailleau, L.; Laplace, A.; Fensterbank, H.; Larpent, C. J .
Org. Chem. 1998, 63, 608. (b) Pigman, W.; Cleaveland, E. A.; Couch,
D. H.; Cleaveland, J . H. J . Am. Chem. Soc. 1951, 73, 1967.
J . Org. Chem, Vol. 68, No. 14, 2003 5701

Murphy et al.
4.2, OH), 4.52 (t, 2H, J 6,5 ) 5.6 Hz, H-6a, H-6b), 4.46 (d, 1H,
J 4,3 ) 3.1 Hz, H-4), 4.23 (d, 1H, J ) 4.5 Hz, H-1), 3.26-3.65
(overlapping signals, 3H, H-2, H-3, H-5), 3.86 (AB d, 2H, J )
14.2 Hz, CH2Ar); 13C NMR (DMSO-d6) δ 140.8, 131.6 (each s,
each aromatic C), 130.4, 128.6 (each d, each aromatic C), 90.5
(d, C-1), 76.6, 74.8, 71.6, 69.2 (each d), 61.3 (t, C-6), 48.5 (t,
CH2); νmax (KBr) 3435, 2963, 2895, 2845, 1762, 1491, 1426,
1196, 1078, 928 cm-1. HRMS-FAB: found 326.0771 [M + Na]+,
required 326.0771.
8.5 Hz, aromatic H), 7.69-7.74 (apt t, 1H, J ) 8.5 Hz, aromatic
H), 7.58-7.63 (apt t, 2H, J ) 8.5 Hz, aromatic H), 5.22 (d,
1H, J 1,2 ) 8.3 Hz, H-1), 4.09 (d, 1H, J ) 3.0 Hz, H-3), 3.80-
3.95 (overlapping signals, 5H, H-2, H-4-6); 13C NMR (D2O) δ
172.3 (s, CdO), 133.1 (s, aromatic C), 133.0, 129.1, 127.8 (each
d, each aromatic C), 80.7 (d, C-1), 77.1, 73.8, 69.6, 69.0 (each
d), 61.2 (t); νmax (KBr) 3400, 1665, 1558, 1109, 1098 cm-1
.
HRMS-FAB: found 306.0954 [M + Na]+, required 306.0954.
Analytical HPLC (C-4 column; 5:95 CH3CN:H2O) indicated
>90% purity.
N -(4-C h lo r o b e n zy l)-N -â-D -g a la c t o p y r a n o s y lb e n z-
a m id e (12). Reaction of N-(4-chlorobenzyl)-â-D-galactopyra-
nosylamine (0.5 g, 1.65 mmol) and benzoyl chloride (0.38 mL,
3.3 mmol) as described for 5 gave the title compound as an
off-white solid (0.12 g, 17%); Rf 0.44 (MeOH:EtOAc, 1:20 × 2);
N-(â-D-Glu cop yr a n osyl)-ben za m id e (14). Benzoyl chlo-
ride (0.19 mL, 1.6 mmol) and 2,3,4,6-tetra-O-acetyl-â-D-glu-
copyranosyl azide (0.3 g, 0.8 mmol) were suspended in dry
CH3CN (10 mL). Triphenylphosphine (0.43 g, 1.04 mmol) was
dissolved in dry dichloromethane (1 mL) and this solution was
then added to the reaction mixture, which was allowed to stir
at room temperature. TLC analysis (EtOAc) showed the
reaction was complete after an additional 24 h. The solvent
was removed and the residue washed with sodium bicarbonate
(3 × 50 mL) and water (3 × 50 mL), extracted with dichlo-
romethane (3 × 50 mL), and dried (MgSO4) and excess solvent
was removed. The residue was purified by chromatography
(EtOAc:petroleum ether 1:1) to give N-(2,3,4,6-tetra-O-acetyl-
â-D-glucopyranosyl)benzamide as a white foam (0.17 g, 47%);
1
[R]D +10.0 (c 0.04, MeOH); H NMR (500 MHz, D2O, 10 °C;
Z:E, 7:93) δ 7.42 (d, 2H, J ) 7.3 Hz, aromatic H), 7.38 (d, 2H,
J ) 6.8 Hz, aromatic H), 7.35 (d, 2H, J ) 8.3 Hz, aromatic H),
7.25 (d, 2H, J ) 8.3 Hz, aromatic H), 5.44 (br s, 1H, H-1,
Z-isomer), 4.68 (d, 1H, J 1,2 ) 9.0 Hz, H-1, E-isomer), 4.61 (AB
d, 2H, J ) 15.5 Hz, CH2Ar), 3.64-3.73 (overlapping signals,
3H, H-2, H-4, H-6a), 3.57 (dd, 1H, J 6b,5 ) 4.0 Hz, J 6b,6a ) 11.8
Hz, H-6b), 3.40 (dd, 1H, J 5,6a ) 7.3 Hz, J 5,6b ) 3.9 Hz, H-5),
3.28 (dd, 1H, J 3,2 ) 9.5 Hz, J 3,4 ) 2.9 Hz, H-3); 13C NMR (D2O)
δ 175.8 (s, CdO), 136.6 (s, aromatic C-CO), 134.7 (s, aromatic
CCl), 132.4 (s, aromatic C), 131.2, 129.3 (2 signals), 129.2,
129.0, 128.6, 128.5, 127.1 (each d, each aromatic C), 88.9 (d,
C-1), 77.4, 73.7, 68.9, 68.0 (each d), 61.4 (t, C-6), 45.2 (t, CH2-
Ar); νmax (KBr) 3409, 2929, 2869, 1653, 1493, 1410, 1340, 1086
cm-1. HRMS-FAB: found 430.1035 [M + Na]+, required
430.1033.
1
Rf 0.54 (EtOAc). H NMR38 (300 MHz, CDCl3) δ 7.76 (dd, 2H,
J ) 1.6, 7.0 Hz, aromatic H), 7.42-7.54 (m, 3H, aromatic H),
7.06 (d, 1H, J NH,H-1 ) 9.1 Hz, NH), 5.50 (apt t, 1H, J 1,2
)
J NH,H-1 ) 9.1 Hz, H-1), 5.39 (apt t, 1H, J 3,2 ) J 3,4 ) 9.4 Hz,
H-3), 5.13 (2 × overlapping apt t, 2H, J ) 9.5 Hz, H-2, H-4),
4.32 (dd, 1H, J 6a,6b ) 12.4 Hz, J 6a,5 ) 4.4 Hz, H-6a), 4.11 (dd,
1H, J 6b,6a ) 12.4 Hz, J 6b,5 ) 2.0 Hz, H-6b), 3.91 (ddd, 1H, J 5,6b
) 2.0 Hz, J 5,6a ) 4.4 Hz, J 5,4 ) 10.1 Hz, H-5), 2.01, 2.04 (2
signals), 2.03 (each s, each 3H, each OAc); 13C NMR (CDCl3)
δ 171.5, 170.8, 170.1, 169.8, 167.5 (each s, each CdO), 133.1
(s, aromatic C), 132.4, 132.3, 128.9, 128.7 (each d, aromatic
C), 79.1, 73.9, 73.0, 71.1, 68.2 (each d), 62.0 (t), 20.9 (2 signals),
20.8 (2 signals) (each q, each OAc); νmax (KBr) 3057, 2928, 1760,
1577, 1537, 1439, 1369, 1223, 1043 cm-1. HRMS-CI: found
452.1559 [M + H]+, required 452.1557. This intermediate (0.07
g, 0.14 mmol) was suspended in MeOH (10 mL). NaOMe (0.1
mL of a 0.25 M solution) was added. The reaction was not
complete after 2 h so another 0.1 mL of NaOMe was added to
the reaction mixture and TLC analysis (MeOH:EtOAc, 1:4)
after a total of 3.5 h showed that the reaction was complete.
Amberlite (H+) was then added and after 5 min the reaction
mixture was filtered and the solvent removed to give the title
compound as a white solid (0.04 g, 100%); Rf 0.18 (MeOH:
EtOAc, 1:4); [R]D -45.0 (c 0.04, H2O) (lit. [R]D -11.6 (c 0.6,
H2O)); mp 218-220 °C (lit. mp 230-232 °C);39 1H NMR40 (300
MHz, D2O) δ 7.91 (d, 2H, J ) 7.2 Hz, aromatic H), 7.73 (apt t,
1H, J ) 7.2 Hz, aromatic H), 7.62 (apt t, 2H, J ) 7.2 Hz,
aromatic H), 5.27 (d, 1H, J 1,2 ) 9.3 Hz, H-1), 3.98 (dd, 1H,
J 6a,5 ) 2.2 Hz, J 6a,6b ) 12.4 Hz, H-6a), 3.84 (dd, 1H, J 6b,5 ) 5.1
Hz, J 6b,6a ) 12.3 Hz, H-6b), 3.65-3.73 (overlapping signals,
3H, H-3-5), 3.57 (apt t, 1H, J 2,1 ) J 2,3 ) 9.3 Hz, H-2); 13C NMR
(D2O) δ 172.2 (s, CdO), 133.1 (s, aromatic C), 133.0, 129.1,
127.7 (each d, aromatic C), 80.2 (d, C-1), 77.9, 76.8, 72.0, 69.5
(each d), 60.8 (t); νmax (KBr) 3400, 2856, 1663, 1526, 1291, 1090
cm-1. HRMS-FAB: found 306.0952 [M + Na]+, required
306.0955. Analytical HPLC (C-4; 5:95 CH3CN:H2O) indicated
>95% purity.
N-(â-D-Ga la ctop yr a n osyl)ben za m id e (13). Benzoyl chlo-
ride (0.19 mL, 1.6 mmol) and 2,3,4,6-tetra-O-acetyl-â-D-galac-
topyranosyl azide35 (0.3 g, 0.8 mmol) were suspended in dry
CH3CN (10 mL). Triphenylphosphine (0.43 g, 1.04 mmol) was
dissolved in dry dichloromethane (1 mL), which was then
added to the reaction mixture,36 and the solution was left
stirring at room temperature. TLC analysis (EtOAc:petroleum
ether, 1:1) showed the reaction was complete after 24 h at room
temperature. The reaction mixture was washed with sodium
bicarbonate (3 × 50 mL) and water (3 × 50 mL), extracted
with dichloromethane (3 × 50 mL), dried (MgSO4), and filtered
and excess solvent was removed. The residue was purified by
chromatography (EtOAc:petroleum ether, 1:6) to yield N-(2,3,4,6-
tetra-O-acetyl-â-D-galactopyranosyl)benzamide as an off-white
foam (0.01 g, 28%); Rf 0.57 (EtOAc:petroleum ether, 1:1); [R]D
-12.5 (c 0.04, CHCl3); mp 40-44 °C; 1H NMR (300 MHz,
CDCl3) δ 7.78 (dd, 2H, J ) 5.0, 1.3 Hz, aromatic H), 7.41-
7.59 (m, 3H, aromatic H), 7.13 (d, 1H, J NH,H-1 ) 9.1 Hz, NH),
5.49 (d, 1H, J ) 2.6 Hz, H-4), 5.46 (apt t, 1H, J 1,2 ) J NH, H-1
)
9.1 Hz, H-1), 5.21-5.30 (overlapping signals, 2H, H-2, H-3),
4.10-4.18 (overlapping signals, 3H, H-5, H-6a, H-6b), 2.16,
2.05, 2.04, 2.02 (each s, each 3H, each OAc); 13C NMR (CDCl3)
δ 171.9, 170.6, 170.3, 170.0, 167.3 (each s, each CdO), 133.5
(s, aromatic C), 132.6, 128.9, 127.5 (each d, aromatic C), 84.0
(d, C-1), 72.6, 71.1, 68.9, 67.5 (each d), 61.4 (t), 20.9, 20.8 (2
signals), 20.7 (each q, each OAc); νmax (film) 3410, 2357, 1745,
1669, 1528, 1371, 1243, 1082, 910 cm-1. HRMS-CI: found
452.1557 [M + H]+, required 452.1556. This intermediate (0.13
g, 0.29 mmol) was suspended in MeOH (20 mL) and NaOMe
(0.1 mL of a 0.25 M solution in MeOH) was added. TLC
analysis (MeOH) showed that the reaction was complete after
1 h. Amberlite (H+) was added and after 5 min the reaction
mixture was filtered and the solvent removed to give the title
compound as an off-white solid (0.08 g, 99%); Rf 0.55 (MeOH);
[R]D +95.0 (c 0.04, H2O) (lit.37 [R]D +25.0 (c 0.02, H2O)); mp
114-118 °C; 1H NMR (300 MHz, D2O) δ 7.91 (dd. 2H, J ) 1.5,
N-(2,3,4,6-Tetr a -O-a cetyl-â-D-ga la ctop yr a n osyl)-su cci-
n a m ic Acid (16). The amine 15 (2.0 g, 5.76 mmol) and
succinic anhydride (5.76 g, 57.6 mmol) were suspended in CH2-
Cl2 (50 mL), DIPEA (1.0 mL, 5.76 mmol) was added, and the
reaction was allowed to stir at room temperature under an
(35) Tropper, F. D.; Andersson, F. O.; Braun, S.; Roy, R. Synthesis
1992, 618.
(36) Boullanger, P.; Maunier, V.; Lafont, D. Carbohydr. Res. 2000,
324, 97.
(38) Kovacs, L.; Osz, E.; Domokos, V.; Holzer, W.; Gyo¨rgydea´k, Z.
Tetrahedron 2001, 57, 4609.
(39) Cerezo, A. S.; Sproviero, J . F.; Deulofeu, V.; Delpy, S. Carbo-
hydr. Res. 1968, 7, 395.
(37) Savel’ev, A. N.; Ibatyllin, T. M.; Eneyskaya, E. V.; Kachurin,
A. M.; Neustroev, K. N. Carbohydr. Res. 1996, 296, 261.
(40) Sriram, D.; Stinivasan, S.; Priya, K.; Aruna, V.; Loganathan,
D. Acta Crystallogr. 1998, C54, 1670.
5702 J . Org. Chem., Vol. 68, No. 14, 2003

Development of Carbohydrate-Based Scaffolds
inert atmosphere. More DIPEA (2.0 mL, 11.52 mmol) was
added after 48 h and analysis by TLC (MeOH:EtOAc, 1:4)
indicated that the reaction was complete after stirring for a
further 24 h. The reaction mixture was diluted with CH2Cl2
(50 mL), washed with HCl (1.0 M solution, 2 × 100 mL), and
dried (MgSO4), excess solvent was removed, and the residue
was purified by chromatography (EtOAc:petroleum ether, 2:1)
to give the title compound as an off-white solid (1.45 g, 56%);
CO); νmax(film) 3512, 2661, 1633, 1426, 1270, 1185 cm-1
HRMS-ES: found 592.1966 [M + Na]+, required 592.1966.
.
N,N′-Di-(â-D-ga la ctop yr a n osyl)-ter ep h th a la m id e (19).
Terephthalic acid (0.17 g, 1.0 mmol), EDC (0.38 g, 2.0 mmol),
and DMAP (catalytic) were suspended in dry dichloromethane
(10 mL). The reaction mixture was stirred at room temperature
for 30 min, and then the amine 15 (0.7 g, 2.0 mmol) was added.
The reaction was allowed to stir at room temperature. TLC
analysis (EtOAc) showed the reaction was complete after 72
h. Excess solvent was removed and the residue purified by
chromatography (EtOAc:petroleum ether, 3:1) to yield N,N′-
di(tetra-O-acetyl-â-D-galactopyranosyl)terephthalamide as a
white foam (0.31 g, 19%); Rf 0.54 (EtOAc:petroleum ether, 3:1);
[R]D +50.0 (c 0.02, CHCl3); 1H NMR (300 MHz, CDCl3) δ 7.85
(s, 4H, aromatic H), 7.23 (d, 1H, J NH,H1 ) 9.0 Hz, NH), 5.20-
5.54 (overlapping signals, H-1-4), 4.09-4.17 (overlapping
signals, H-5, H-6a, H-6b), 2.04-2.20 (overlapping signals,
OAc); 13C NMR (CDCl3) δ 172.1, 170.6, 170.2, 170.0 (each s,
each CdO), 166.3 (s, aromatic CdO), 136.5 (s, aromatic C),
127.9, (d, aromatic C), 79.5, 72.7, 70.9, 68.9, 67.5 (each d), 61.4
(t), 21.0, 20.9, 20.8 (each q, each OAc); νmax (KBr) 2972, 2933,
2356, 2336, 1752, 1673, 1547, 1501, 1368, 1229 cm-1. HRMS-
FAB: found 847.2385 [M + Na]+, required 847.2398. This
intermediate (0.1 g, 0.12 mmol) was suspended in MeOH (10
mL). Sodium methoxide (0.1 mL of a 0.25 M solution) was
added and the reaction mixture was allowed to stir at room
temperature. TLC analysis (MeOH) after 3 h showed that the
reaction was complete. Amberlite (H+) was added and after 5
min the reaction mixture was filtered and the solvent removed.
The residue was purified by chromatography (MeOH:EtOAc,
1:1) to give the title compound 17 as a white solid (0.04 g, 67%,
mixture of anomers); Rf 0.21 (MeOH); [R]D +65.0 (c 0.04, H2O);
mp 60-64 °C; 1H NMR (300 MHz, D2O) δ 8.02 (s, 4H, aromatic
H), 5.24 (d, 1H, J 1,2 ) 8.9 Hz, H-1), 3.76-4.11 (overlapping
signals, 6H, H-2-6); 13C NMR (D2O) δ 173.9 (s, CdO), 139.4
(s, aromatic C), 130.7 (d, aromatic CH), 83.2 (d, C-1), 79.8, 76.3,
72.2, 71.6 (each d), 63.8 (t); νmax (KBr) 3410, 2931, 1660, 1550,
1424, 1299, 1086 cm-1. LRMS-FAB: found 511.0 [M + Na]+,
required 511.2. The compound was further purified by pre-
parative HPLC (C-4 column; 5:95 CH3CN:H2O) indicating 99%
purity.
1
Rf 0.37 (EtOAc); [R]D +28.0 (c 0.5, CHCl3); mp 57-60 °C; H
NMR (300 MHz, CDCl3) δ 6.90 (br s, 1H, CO2H), 6.71 (d, 1H,
J NH,H-1 ) 9.0 Hz, NH), 5.44 (d, 1H, J 4,3 ) 3.0 Hz, H-4), 5.28
(apt t, 1H, J H-1,NH ) J 1,2 ) 9.0 Hz, H-1), 5.16 (dd, 1H, J 3,4
)
3.0 Hz, J 3,2 ) 9.0 Hz, H-3), 5.11 (apt t, 1H, J 2,1 ) J 2,3 ) 9.0
Hz, H-2), 4.04-4.16 (overlapping signals, 3H, H-5, H-6a, H-6b),
2.36-2.80 (m, 4H, CH2CH2), 2.06, 2.05, 2.04, 2.00 (each s, each
3H, each CH3); 13C NMR (CDCl3) δ 176.6 (s, COOH), 172.3,
171.5, 170.7, 170.2, 170.0 (each s, each CdO), 78.4 (d, C-1),
72.3, 70.9, 68.3, 67.2 (each d), 61.2 (t, C-6), 30.6, 28.6 (each t,
CH2CH2), 20.7, 20.6 (each q, each 2 signals, each CH3); νmax
(KBr) 3051, 2981, 1787, 1666, 1599, 1538, 1371, 1227 cm-1
.
HRMS-ESI: found 470.1274 [M + Na]+, required 470.1274.
{2-[â-D-Ga la ctop yr a n osyl-(3-â-D-ga la ctop yr a n osylca r -
b a m oylp r op ion yl)-a m in o]-a cet yla m in o}-a cet ic
Acid ,
Meth yl Ester (17). The amine 15 (0.78 g, 2.2 mmol), the acid
16 (0.5 g, 1.12 mmol), and formaldehyde (0.15 mL, 2.2 mmol)
were suspended in methanol (25 mL) and the reaction mixture
was stirred at room temperature for 1 h. Methyl isocyanoac-
etate (0.2 mL, 2.2 mmol) was then added and the reaction
mixture was allowed to stir at room temperature. Analysis by
TLC (EtOAc) showed the reaction was complete after 24 h.
Excess solvent was removed and the product was purified by
chromatography (EtOAc) to give {2-[tetra-O-acetyl-â-D-galac-
topyranosyl-(3-tetra-O-acetyl-â-D-galactopyranosyl carbamoyl-
propionyl)-amino]-acetylamino}-acetic acid, methyl ester as a
white foam (0.5 g, 50%); Rf 0.075 (EtOAc); [R]D +16.0 (c 0.5,
CHCl3); mp 100-102 °C; 1H NMR (300 MHz, CDCl3) δ 7.19 (t,
1H, J ) 6.0 Hz, NH-CH2), 6.69 (d, 1H, J ) 9.5 Hz, NH-CH),
5.90 (d, 1H, J ) 9.0 Hz, CH-NH), 5.46 (d, 1H, J ) 1.5 Hz,
H-4), 5.42 (d, 1H, J ) 3.0 Hz, H-4′), 5.25 (t, 1H, J 1,2 ) 9.5 Hz,
H-1), 4.95-5.19 (overlapping signals, 4H, H-2, 2′, H-3, 3′),
3.71-4.27 (overlapping signals, 10H, H-5, 5′, H-6a, 6a′, H-6b,
6b′, NHCH2CO, NHCOCH2N), 3.76 (s, 3H, OCH3), 2.49-2.67
(m’s, 4H, CH2CH2CO), 2.18, 2.13, 2.04, 2.03, 2.02, 2.00, 1.99,
1.98 (each s, each 3H, each OAc); 13C NMR (CDCl3) δ 173.0,
171.8, 171.6, 170.5 (2 signals), 170.4, 170.3, 170.0 (2 signals),
169.8, 169.7 (each s, each CdO), 80.4, 78.1 (each d, C-1, C-1′),
73.6, 72.4, 72.3, 70.9, 70.7, 68.1, 67.2, 67.1 (each d), 61.6, 61.3
(each t, C-6, C-6′), 52.6 (q, OCH3), 47.5, 41.0, 31.0, 28.5 (each
t, each CH2), 21.0, 20.7, 20.6, 20.5 (each q, each CH3); νmax
(KBr) 3381, 2951, 2855, 1752, 1676, 1541, 1439, 1371, 1229,
1050 cm-1. HRMS-ESI: found 928.2811 [M + Na]+, required
928.2811. This intermediate (0.15 g, 0.17 mmol) was sus-
pended in methanol (5 mL). NaOMe (0.1 mL of a 0.25 M
solution) was added and the reaction mixture was stirred at
room temperature. Analysis by TLC (MeOH) showed that the
reaction was complete after 40 h. Amberlite (H+) was added
and after 5 min the reaction mixture was filtered and the
solvent removed to give a yellow oil (0.09 g, 97%) that was
further purified by using chromatography (MeOH:EtOAc, 1:1)
and preparative HPLC (C-18, CH3CN:H2O gradient eluant,
1:99 to 100:0 over 40 min) to give 17 as an off-white solid; Rf
0.31 (MeOH); [R]D -25.0 (c 0.02, MeOH); 1H NMR (600 MHz,
D2O, 20 °C; Z:E, 27:73) δ 5.45 (d, 1H, J 1,2 ) 9.0 Hz, H-1,
Z-isomer), 5.19 (d, 1H, J 1,2 ) 8.0 Hz, H-1, E-isomer), 4.97 (d,
1H, J 1′,2′ ) 9.0 Hz, H-1′, E- and Z-isomer), 3.70 (s, 3H, OCH3),
3.50-4.40 (m’s, 16H, H-2-6, H-2′-6′, CH2CONH, CH2NHCO),
2.89 (m’s, 2H, CH2CH2CONH), 2.60 (m’s, 2H, CH2CH2CONH);
13C NMR (D2O) δ 174.7, 175.3, 178.2, 178.9 (each s, each
CdO), 89.0 (d, C-1, E-isomer), 85.3 (d, C-1, Z-isomer), 82.5 (d,
C-1′), 80.2, 79.4, 76.1, 75.4, 72.1, 71.4, 70.7 (each d), 63.8, 63.7
(each t, C-6, C-6′), 55.6 (q, OCH3), 47.4, 43.9, 32.9, 30.8 (t, CH2-
N,N′-Di(â-D-ga la ct op yr a n osyl)-N,N′-d i[m et h oxyca r b -
on ylm eth ylcar bam oylm eth yl]-ter eph th alam ide (18). Tere-
phthalic acid (0.2 g, 1.2 mmol), amine 15 (0.84 g, 2.4 mmol),
and formaldehyde (0.17 mL, 2.4 mmol) were suspended in
methanol (20 mL) and stirred at room temperature for 1 h.
Methyl isocyanoacetate (0.22 mL, 2.4 mmol) was then added
and the reaction mixture was allowed to stir at room temper-
ature. TLC analysis (EtOAc) showed that the reaction was
complete after 48 h. The solvent was removed and the residue
purified by chromatography (EtOAc) to give N,N′-di(2,3,4,6-
tetra-O-acetyl-â-D-galactopyranosyl)-N,N′-di[methoxycarbon-
ylmethylcarbamoylmethyl]terephthalamide as an off-white
foam (0.45 g, 34%); Rf 0.21 (EtOAc); mp 115-118 °C; [R]D
1
+15.0 (c 0.02, CHCl3); H NMR (270 MHz, C5D5N, 100 °C) δ
8.16 (t, 2H, J ) 3.0 Hz, NHCH2), 7.96 (s, 4H, aromatic H),
5.80-5.87 (overlapping signals, 6H, H-1, H-2, H-4), 6.05 (dd,
2H, J ) 3.5, 9.0 Hz, H-3), 3.90-4.60 (m’s, 14H, H-5, H-6a,
H-6b, methylenes), 3.72 (s, 6H, OMe), 2.16, 2.14, 2.09, 2.05
(each s, each 6H, OAc); 13C NMR (C5D5N, 100 °C) δ 171.8,
170.3, 169.9, 169.6, 169.4, 168.5 (each s, each CdO), 137.6 (s,
aromatic C), 127.6 (d, aromatic C), 73.6, 71.9, 68.1, 67.4 (each
d), 61.8 (t, C-6), 51.5 (q, OCH3), 41.5 (t, CH2), 20.1, 20.0, 19.9,
19.6 (each q, each OAc); νmax (film) 3058, 1749, 1667, 1536,
1439, 1371, 1224, 1055 cm-1. LRMS-ES: found 1105.4 [M +
Na]+, required 1105.3. This intermediate (0.07 g, 0.067 mmol)
was suspended in MeOH (5 mL) and NaOMe (0.1 mL of a 0.25
M solution) was then added. TLC analysis (MeOH) showed
that the reaction was complete after 1 h. Amberlite (H+) was
added and after 5 min, the reaction mixture was filtered and
excess solvent removed to give and the residue, which was
purified by preparative HPLC (C-18, CH3CN:H2O, 1:99 to 5:95
J . Org. Chem, Vol. 68, No. 14, 2003 5703

Murphy et al.
gradient elution over 1 h) and gave the title compound as a
white solid; Rf 0.48 (MeOH); [R]D +262.5 (c 0.008, MeOH); 1H
NMR (500 MHz, D2O, 10 °C; EE:EZ, 83:17) δ 7.40-7.60 (m’s,
4H, aromatic H), 5.58 (d, 1H, J 1,2 ) 9.0 Hz, H-1 (EZ isomer)),
4.61 (d, 2H, J 1,2 ) 9.0 Hz, H-1 (EE isomer)), 4.60 (d, 1H, J 1,2
) 9.0 Hz, H-1 (EZ isomer)), 4.22 (AB d, 4H, J ) 16.5 Hz, NCH2-
CONHCH2), 3.92 (AB d, 4H, J ) 17.5 Hz, NCH2CONHCH2),
showed that the reaction was complete after 2 h. The mixture
was diluted with water (10 mL), neutralized with Amberlite
(H+), and filtered and the solvent was removed to give the title
compound as an off-white solid (0.05 g, quantitative); this
residue was further purified by preparative HPLC (C-4; 5:95
CH3CN:H2O); Rf 0.69 (MeOH); [R]D +15.0 (c 0.04, H2O); mp
130-132 °C; 1H NMR (300 MHz, D2O) δ 7.99 (s, 2H, aromatic
H), 5.33 (d, 1H, J 1,2 ) 8.7 Hz, H-1), 4.10 (d, 1H, J ) 9.2 Hz,
H-5), 3.59-3.77 (m, 3H, H-2-4); 13C NMR (D2O) δ 174.2 (s,
COOH), 171.0 (s, CdO, amide), 136.7 (s, aromatic C), 128.2
(d, aromatic C), 80.1, 77.4, 76.5, 71.8, 71.7 (each d); νmax (KBr)
3437, 2929, 1792, 1645, 1550, 1442, 1234, 1063 cm-1. LRMS-
ES (negative): found 515.0 [M - H]-, required 515.1.
Molecu la r Mod elin g P r oced u r es. Monte Carlo confor-
mational searching techniques and minimization of structures
with Macromodel 6.0 were used to generate low-energy
structures for 18 and 19. The SUMM method, GB/SA solvation
model for water, and AMBER (all atom) force field were
employed. Each structure generated was minimized with the
PRCG method. Structures with energy values 3 kcal/mol above
the global minimum structure were rejected for both 18 and
19. For calculations of 18 the distance between the ortho
aromatic protons and anomeric proton were constrained to
within 4 Å; 5000 structures were generated for minimization;
the amide torsion angle was allowed to have values ranging
from 0 to 180 deg. Distance constraints were not used for
calculations of 19; 1000 structures were generated for mini-
mization. The Macromodel command files and coordinate input
and output files are provided in the Supporting Information.
3.92 (d, 2H, J 4,3 ) 3.0 Hz, H-4), 3.69 (apt t, 2H, J 2,3 ) J 2,1
)
9.0 Hz, H-2), 3.51-3.71 (overlapping signals, 10H, H-6a, 6b,
OCH3), 3.42 (dd, 2H, J 5,4 ) 8.0 Hz, J 5,6 ) 3.5 Hz, H-5), 3.39
(dd, 2H, J 3,4 ) 3.0 Hz, J 3,2 ) 9.0 Hz, H-3); 13C NMR (D2O, 40
°C)
δ
174.6, 172.3 (each
s,
2
signals, each
CdO), 136.4 (s, aromatic C), 128.0 (d, aromatic C), 88.5 (d,
C-1, EE-isomer), 83.5 (d, C-1, ZE-isomer), 77.8, 73.0, 69.0, 68.1
(each d), 61.5 (t, C-6), 53.2 (q, OCH3), 45.3, 41.8 (t, each CH2);
νmax (film) 3383, 3045, 1620, 1421, 1255, 1109, 725 cm-1
.
HRMS-ES: found 769.2392 [M + Na]+, required 769.2392.
N,N′-Di(â-D-glu copyr an u r on osyl)-ter eph th alam ide (20).
2,3,4-Tri-O-acetyl-â-D-glucopyranosylamine uronic acid methyl
ester41 (0.8 g, 2.4 mmol), HOBt (0.72 g, 3.0 mmol), and
terephthalic acid (0.44 g, 2.67 mmol) were suspended in dry
THF (15 mL) at 0 °C. DCC (5.3 mL of a 1.0 M solution in CH2-
Cl2, 5.3 mmol) and DMAP (catalytic) were then added and the
reaction mixture was allowed to stir at room temperature. TLC
analysis (EtOAc) showed the reaction was complete after 26
h. The solvent was removed, the residue was dissolved in CH2-
Cl2 (20 mL), washed with water (2 × 20 mL) and sodium
bicarbonate (2 × 20 mL), dried (MgSO4), filtered, and the
solvent was removed. The residue was purified by chroma-
tography (EtOAc:petroleum ether, 2:1) to give a white solid
that was further purified by recrystallization (petroleum ether/
EtOAc mixture) (0.13 g, 12%); Rf 0.49 (EtOAc); [R]D -15.0 (c
0.04, CHCl3); 1H NMR (300 MHz, CDCl3) δ 7.82 (s, 2H,
aromatic H), 7.38 (d, 1H, J NH,H-1 ) 9.5 Hz, NH), 5.49 (apt t,
Ack n ow led gm en t. The authors thank Enterprise
Ireland and Pfizer Pharmaceuticals Inc., Ringaskiddy,
Co. Cork for an Irish American Partnership award to
H.B.; Enterprise Ireland for a Basic Research Award
(SC2002/225) and DAAD for a travel grant for H.B.; the
Health Research Board (Ireland) and the Wellcome
Trust for an equipment grant; Dublin Coorporation and
IRCSET for scholarships to M.T.; Professor Horst Kunz
for discussions and for hosting a research visit from
H.B.; and the referees for their useful comments regard-
ing the structural preferences exhibited by the tertiary
amides.
1H, J 1,2 ) J NH,H1 ) 9.5 Hz, H-1), 5.46 (apt t, 1H, J 3,2 ) J 3,4
)
9.5 Hz, H-3), 5.15 (apt t, 1H, J 4,3 ) J 4,5 ) 9.5 Hz, H-4), 5.09
(apt t, 1H, J 2,3 ) J 2,1 ) 9.5 Hz, H-2), 4.25 (d, 1H, J 5,4 ) 9.5 Hz,
H-5), 3.73 (s, 3H, OCH3), 2.06, 2.05 (2 signals) (each s, each
3H, each OAc); 13C NMR (CDCl3) δ 171.6, 170.0, 169.8, 167.3,
166.6 (each s, each CdO), 136.4 (s, aromatic C), 128.0 (d,
aromatic C), 78.9, 74.2, 72.0, 70.8, 70.0 (each d), 53.2 (q, OCH3),
20.9, 20.8, 20.7 (each q, each OAc); νmax (KBr) 3485, 3339, 3059,
3026, 2956, 2853, 1751, 1667, 1538, 1502, 1376, 1089 cm-1
.
HRMS-FAB: found 819.2072 [M + Na]+, required 819.2073.
This intermediate (0.08 g, 0.10 mmol) was suspended in LiOH
solution (2.5 mL of 0.5 M, 1.24 mmol) and the reaction mixture
was allowed to stir at room temperature. TLC analysis (MeOH)
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
and selected 1D- and 2D-NOE spectra, synthetic procedures
and analytical data for known compounds, and molecular
modeling procedures and coordinate files. This material is
available free of charge via the Internet at http://pubs.acs.org.
(41) (a) Gyo¨rgydea´k, Z.; Thiem, J . Carbohydr. Res. 1995, 268, 85.
(b) Graf von Roedern, E.; Lohof, E.; Hessler, G.; Hoffmann, M.; Kessler,
H. J . Am. Chem. Soc. 1996, 118, 10156.
J O034336D
5704 J . Org. Chem., Vol. 68, No. 14, 2003