Glycosamino acids: New building blocks for combinatorial synthesis

Article abstract of DOI:10.1021/ja9525622

In order to produce inexpensive, chemically diverse carbohydrate building blocks more amenable for use in combinatorial organic synthesis, amine and carboxylic acid functional groups were incorporated into several monosaccharides. A series of 12 new glycosamino acids was prepared from commercially available starting materials. Conventional peptide synthesis solution coupling techniques were used to ligate glycosamino acids, producing oligomeric 'glycotides'. Finally, a library of glycotides was produced by coupling of a glycosamino acid mixture to a rigid template.

Full text of DOI:10.1021/ja9525622

3818
J. Am. Chem. Soc. 1996, 118, 3818-3828
Glycosamino Acids: New Building Blocks for Combinatorial
Synthesis
Jason P. McDevitt† and Peter T. Lansbury, Jr.*
Contribution from the Department of Chemistry, Massachusetts Institute of Technology,
Cambridge, Massachusetts 02139
ReceiVed July 31, 1995. ReVised Manuscript ReceiVed January 8, 1996X
Abstract: In order to produce inexpensive, chemically diverse carbohydrate building blocks more amenable for use
in combinatorial organic synthesis, amine and carboxylic acid functional groups were incorporated into several
monosaccharides. A series of 12 new glycosamino acids was prepared from commercially available starting materials.
Conventional peptide synthesis solution coupling techniques were used to ligate glycosamino acids, producing
oligomeric “glycotides”. Finally, a library of glycotides was produced by coupling of a glycosamino acid mixture
to a rigid template.
Introduction
ing blocks by incorporating into them amine and carboxylic
acid functional groups, affording glycosamino acids. These
synthetic monomers can be ligated using the well-developed
chemistry of peptide synthesis.7 The resultant oligomers
(“glycotides”) may be useful drug candidates, since they would
not be susceptible to glycosidases and may not be recognized
by proteases due to the altered backbone relative to natural
peptide substrates. Functional group modifications, in particular
hydroxyl protection, could increase the lipophilicity of the
molecules and render them more likely to permeate cell
membranes. We report herein the synthesis of 12 protected
glycosamino acids and their oligomerization to form two
glycotide oligomers and a small glycotide library.
Combinatorial chemistry has the potential to become an
important tool in the pharmaceutical industry for generating lead
compounds with desirable biological activities and for optimiz-
ing these compounds.1 The ideal monomeric building blocks
for an oligomeric combinatorial library would be structurally
diverse yet conformationally restrained, synthetically accessible,
and easily converted to a series of congeners for the purposes
of lead optimization. Carbohydrates, in addition to possessing
the aforementioned qualities, contain a higher level of functional
group diversity per unit mass than other biopolymeric building
blocks.2 Nature has taken advantage of these properties to
assemble heparin, a polysaccharide library with a wide variety
of distinct biological activities.3
In contrast to the efficient biosynthetic polymerization of
heparin, the assembly of synthetic polysaccharide libraries is
difficult. In spite of significant recent advances using chemical4
and enzymatic5 techniques, solid phase carbohydrate synthesis
has not become routine. Even if all synthetic obstacles could
be overcome, an oligosaccharide library may not produce drug
candidates due to the low bioavailabilities (e.g., susceptibility
to glycosidases, poor cellular uptake) of its components.6
To circumvent the synthetic problems associated with car-
bohydrate libraries, we chose to modify monosaccharide build-
Results and Discussion
Glycosamino acids occur naturally (e.g., sialic acid), and
synthetic congeners have been utilized as peptidomimetics,8
glycosidase inhibitors,9 and starting materials in polymer10 and
natural product syntheses.11 We have synthesized 12 glycos-
amino acid precursors, protected as azido esters, starting from
five different commercially available monosaccharides (Figure
1). In each case, the latent amino group was incorporated by
displacement of a primary or secondary sulfonate ester with an
azide nucleophile. The carboxyl group was introduced using
one of three reactions: (1) Wittig reaction of methyl(triphenyl-
phosphoranylidene) acetate with either a furanose hemiacetal
to form the C-glycosides 1, 2, 3, and 4 or with a 3-ketofuranose
(followed by thiolate Michael addition) to afford 8 and 9; (2)
oxidative cleavage of a C-allyl glycoside (5, 6, 7, 11, 12); and
(3) oxidation of a primary alcohol (10). Monomer syntheses
ranged from 4 to 11 steps, starting with inexpensive com-
mercially available materials and proceeding in unoptimized
overall yields ranging from 5 to 50%.
† Current address: Eastman Chemical Co., Kingsport, TN 37662.
X Abstract published in AdVance ACS Abstracts, April 15, 1996.
(1) (a) Bunin, B. A.; Ellman, J. A. J. Am. Chem. Soc. 1992, 114, 10997-
10998. (b) Hobbs-DeWitt, S.; Kiely, J. S.; Stankovic, C. J.; Schroeder, M.
C.; Reynolds-Cody, D. M.; Pavia, M. R. Proc. Natl. Acad. Sci. U.S.A. 1993,
90, 6909-6913. (c) Moos, W. H.; Green, G. D.; Pavia, M. R. Annu. Rep.
Med. Chem. 1993, 28, 315-324. (d) Gordon, E. M.; Barrett, R. W.; Dower,
W. J.; Fodor, S. P. A.; Gallop, M.A. J. Med. Chem. 1994, 37, 1385-1401.
(2) Musser, J. H.; Fugedi, P.; Anderson, M. B. In Burger’s Medicinal
Chemistry and Drug DiscoVery; Wolff, M. E., Ed.; John Wiley & Sons:
New York, 1995; Vol. 1, pp 902-947.
(3) Jackson, R. L.; Busch, S. J.; Cardin, A. D. Physiol. ReV. 1991, 71,
481-539.
Monomer syntheses were designed to maximize efficiency
by diverging from a common starting material. This principle
(4) (a) Douglas, S. P.; Whitfield, D. M.; Krepinsky, J. J. J. Am. Chem.
Soc. 1991, 113, 5095-5097. (b) Danishefsky, S. J.; McClure, K. F.;
Randolph, J. T.; Ruggeri, R. B. Science 1993, 260, 1307-1309. (c) Yan,
L.; Taylor, C. M.; Goodnow, R., Jr.; Kahne, D. J. Am. Chem. Soc. 1994,
116, 6953-6954. (d) Randolph, J. T.; Danishefsky, S. J. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 1470-1473.)
(7) (a) Bodanszky, A.; Bodanszky, M.; Chandramouli, N.; Kwei, J. Z.;
Marinez, J.; Tolle, J. C. J. Org. Chem. 1980, 45, 72-76. (b) Kent, S. B. H.
Ann. ReV. Biochem. 1988, 57, 957-989.
(8) Graf von Roedern, E.; Kessler, H. Angew. Chem., Int. Ed. Engl. 1994,
33, 687-689.
(5) (a) Kopper, S. Carbohydr. Res. 1994, 265, 161-166. (b) Schuster,
M.; Wang, P.; Paulson, J. C.; Wong, C. H. J. Am. Chem. Soc. 1994, 116,
1135-1136. (c) Halcomb, R. L.; Huang, H.; Wong, C. H. J. Am. Chem.
Soc. 1994, 116, 11315-11322.
(6) Cellular uptake may not be a significant problem, since many natural
carbohydrate ligands, of the type which could be mimicked by glycotides,
have extracellular targets.
(9) Gurjar, M. K.; Mainkar, A. S.; Syamala, M. Tetrahedron: Asymmetry
1993, 4, 2343-2346.
(10) Thiem, J.; Bachmann, F. Trends Polym. Sci. 1994, 2, 425-432.
(11) (a) Casiraghi, G.; Colombo, L.; Rassu, G.; Spanu, P. J. Org. Chem.
1991, 56, 6523-6527. (b) Dondoni, A.; Scherrmann, M. C.; Marra, A.;
Delepine, J. L. J. Org. Chem. 1994, 59, 7517-7520.
0002-7863/96/1518-3818$12.00/0 © 1996 American Chemical Society

Glycosamino Acids
J. Am. Chem. Soc., Vol. 118, No. 16, 1996 3819
(azide hydrogenation and carbamate formation followed by ester
hydrolysis).15 The base-sensitive fluorenyl methyl carbamate
(FMOC)-protected acids, which would be preferred for solid-
phase syntheses involving acid-sensitive monomers, such as the
acetonides 1-6, 8-10, and 12, could be produced by an
analogous procedure.
Glycosamino acids 5 and 6 were prepared from peracetylated
mannose (Scheme 2). The allyl glycoside was generated as an
anomeric mixture 18, which was taken through a series of
transformations to install the azido group at C-6, followed by
oxidative cleavage of the allyl group and separation of anomers
5 and 6 (Scheme 2).
Glycosamino acid 7 was prepared from 1,6-â-D-anhydroglu-
cose in a six step sequence (Scheme 3), the key step being a
stereospecific allylation (22 to 23). The azide was introduced
by displacement of the primary C-6 mesylate (23 to 24), and
the carboxyl group was introduced by oxidative cleavage of
the allyl group (24 to 7).
Glycosamino acids 8 and 9 were prepared by the stereo-
specific Michael addition (directed by the isopropylidene ketal)
of thiolates to the R,â-unsaturated azido ester 27b, which was
produced from 1,2-O-isopropylidene-R-D-xylofuranose (Scheme
4). Compound 10 was produced from the identical starting
material (Scheme 5). In this route, the azide was introduced
by displacement of the C-3 secondary triflate (28 to 29) and
the carboxyl group was introduced by oxidation of a primary
alcohol (29 to 10).
Figure 1. Glycosamino acid precursors discussed herein.9
Scheme 1. Divergent Synthesis of Glycosamino Acid
Precursors 1, 2, 3, and 4a
Glycosamino acid 11 was synthesized from peracetylated
ribose, starting with a nonspecific allylation to generate a
mixture of anomers, 30a and 30b. Compound 30b was
elaborated into 11 by a simple five-step sequence (Scheme 6).
Finally, glycosamino acid 12 was generated from peracetylated
xylose by a similar sequence (Scheme 7).
Assembly of glycosamino acid units into oligoglycotides such
as 16 and 17 (Figure 2) was accomplished using solution-phase
peptide synthesis methods. The amino terminus was deprotected
by hydrogenation (10% Pd on carbon) of the azide, while the
carboxylic acid was liberated by ester hydrolysis. The â-gly-
coside 4 was saponified (providing 4c, c designates free acid),
while the R-glycoside 3 was hydrogenated (3n designates free
amine), and equimolar amounts of the amine and acid compo-
nents were coupled (1-ethyl-3-(3-dimethylaminopropyl)carbo-
diimide hydrochloride and triethylamine in methylene chloride)
to produce a diglycotide 36 (Figure 2) in 28% yield. Hydro-
genation of the diglycotide azide, followed by coupling of the
resultant amine to carboxylic acid 11, afforded triglycotide 16
in 44% yield. Hydrogenation of 12 followed by coupling to
4c provided diglycotide 17 in 67% yield.
In addition to linear glycotide oligomers, a branched,
template-directed glycotide library16 was assembled using 1,3,5-
benzenetricarboxylic acid chloride as the template. A prelimi-
nary, small-scale experiment using ca. 4 molar equiv of the
single monomer 2 produced, after azide hydrogenation followed
by addition of the acid chloride, the desired trifunctional product
37 (Figure 2) with a purity (after extraction, without chroma-
tography) of g90%, as estimated by 1H NMR and HPLC (two
minor impurity peaks were visible).17 A library was produced
a Details are included in the Experimental Section.
is exemplified by the synthesis of compounds 1-4 (Scheme
1). A Wittig reaction on the commercially available 2,3:5,6-
di-O-isopropylidene-R-D-mannofuranose (13), followed by cy-
clization Via intramolecular Michael addition, provided 1412 as
an anomeric mixture. Selective hydrolysis of the 5,6-acetonide
produced the anomeric diols 15, which served as the branching
point in the synthesis. Selective mesylation of the primary
alcohol, followed by treatment with sodium azide, provided the
azido esters 1 and 2 (49% combined overall yield from 13).13
Dimesylation of 15, followed by selective displacement of the
primary mesylate with sodium azide, afforded the base-stable14
monomesylates 3 and 4 (50% combined overall yield).13
Conversion of azido esters 1-4 to the corresponding tert-butyl
carbamate(BOC)-protected acids for use in solid-phase synthesis
(not discussed herein) was achieved using a one-pot procedure
(15) Saito, S.; Nakajima, H.; Inaba, M.; Moriwake, T. Tetrahedron Lett.
1989, 30, 837-838.
(12) Ohrui, H.; Jones, G. H.; Moffatt, J. G.; Maddox, M. L.; Christensen,
A. T.; Byram, S. K. J. Am. Chem. Soc. 1975, 97, 4602-4613.
(13) The pairs of anomeric azido esters 1 and 2 and 3 and 4 were
separated using flash chromatography on silica gel.
(14) The azido ester mesylates 3 and 4 were stable to diazabicyclo-
undecene (1 equiv) in toluene at room temperature or NaOMe (1 equiv) in
methanol at room temperature.
(16) (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, 9217-9218. (b) Carell, T.; Wintner, E.
A.; Bashir-Hashemi, A.; Rebek, J., Jr. Angew. Chem., Int. Ed. Engl. 1994,
33, 2059-2061. (c) Patek, M.; Drake, B.; Lebl, M. Tetrahedron Lett. 1994,
35, 9169-9172.

3820 J. Am. Chem. Soc., Vol. 118, No. 16, 1996
McDeVitt and Lansbury
Scheme 2. Synthetic Route to Glycosamino Acids 5 and 6a
a Details are included in the Experimental Section.
Scheme 3. Synthetic Route to Glycosamino Acid 7a
a Details are included in the Experimental Section.
by hydrogenation of 4 equiv of 4, 4 equiv of 5, and 2 equiv of
8 (at short reaction times, the azide reduction was complete
and the S-benzyl group in 8 was not hydrogenated), followed
by reaction of the amines with the template to produce a
(theoretical) ten component library, nine of which were clearly
observed by fast-atom bombardment mass spectrometry of the
mixture.17 The symmetrical compound containing three groups
derived from 8 ligated to the template was not expected to be
produced in significant amounts due to the experimental
stoichiometry and was not detected.
oped in order to obtain large libraries that will be useful in an
industrial setting. Solid-phase methodology will facilitate
synthesis and characterization of library components by making
glycotide production more amenable to spatially addressable18,19
or encoding20 approaches to combinatorial synthesis. Undoubt-
edly, the requirement for preliminary monomer synthesis reduces
the appeal of glycotide libraries relative to libraries that can be
readily assembled using commercially available monomers.
However, this is a small cost to pay for a combinatorial library
significantly different from any in existence. A library of
glycotides would provide a convenient mechanism to access
the tremendous structural diversity of carbohydrates without the
synthetic difficulties and uncertain bioavailabilities associated
with natural carbohydrates. In addition, carbohydrate pharma-
cophores can be easily incorporated into a directed library using
these monomers. Finally, the general approach of modifying
monosaccharides for convenient oligomerization could be
expanded to include ligation by urea21 or carbamate22 forma-
tion.23
Conclusions
This paper reports 12 new glycosamino acids, a new family
of building blocks for combinatorial synthesis. The compounds
can be accessed by simple synthetic routes starting with
inexpensive starting materials. They can be further function-
alized (acylation of alcohols, etc.) to enlarge the family. These
monomers can be ligated using known chemistry to afford
glycotides. Although solution-phase methods have been used,
solid-phase approaches to glycotide synthesis should be devel-
(18) Geysen, H. M.; Meloen, R. H.; Barteling, S. J. Proc. Natl. Acad.
Sci. U.S.A. 1984, 81, 3998-4002.
(17) The compound library eluted on RP-HPLC (C18, 300 Å) from 20
(19) Fodor, S. P.; Read, J. L.; Pirrung, M. C.; Stryer, L.; Lu, A. T.;
Solas, D. Science 1991, 251, 767-773.
to 55 min in CH3CN/H2O/0.1% TFA using the following gradient:
%
CH3CN at time t ) 20 + 0.9(t-5) through t ) 50 min; % CH3CN ) 60.5
+ 2.5(t-50) after t ) 50 min. Eleven clearly resolved peaks were visible,
two of which constituted less than 2% of the total. These peaks may
correspond to the nine compounds detected by mass spectrometry and trace
impurities.
(20) Ohlmeyer, M. H. J.; Swanson, R. N.; Dillard, L. W.; Reader, J. C.;
Asouline, G.; Kobayashi, R.; Wigler, M.; Still, W. C. Proc. Natl. Acad.
Sci. U.S.A. 1993, 90, 10922-10926.
(21) Hutchins, S. M.; Chapman, K. T. Tetrahedron Lett. 1994, 35, 4055-
4058.

Glycosamino Acids
J. Am. Chem. Soc., Vol. 118, No. 16, 1996 3821
Scheme 4. Synthetic Route to Glycosamino Acids 8 and 9a
a Details are included in the Experimental Section.
Scheme 5. Synthetic Route to Glycosamino Acid 10a
a Details are included in the Experimental Section.
and 4 mL of concentrated sulfuric acid). Improved detection of sugar
amines or sugar amides was achieved by increasing the concentration
of sulfuric acid to 5% and removing the naphthoresorcinol. Errors in
Rf values are (0.1. Chromatographic purifications were performed
with EM Science 230-400 mesh silica gel or Baker silica gel (40 µm
av particle diameter), unless otherwise noted. Reversed phase HPLC
was performed on C18 columns (300 Å). 1H and 13C spectra were
acquired using a Varian XL-300 or Varian UN-300 spectrometer.
Chemical shifts are reported in δ values relative to tetramethylsilane
(δ ) 0) for proton spectra and relative to internal CDCl3 (77.0) for
carbon spectra. 1H NMR are tabulated in the following order:
multiplicity (s, singlet; d, doublet; dd, doublet of doublets; t, triplet; q,
quartet; m, multiplet), number of protons, and coupling constants in
Hertz. Infrared spectra were recorded on a Perkin Elmer 1600 Series
FTIR. All mass spectra were obtained in the FAB mode.
Experimental Section
General Methods. All air-sensitive reactions were performed under
an atmosphere of argon. Unless otherwise noted, materials were
obtained from commercial sources and used without further purification.
Tetrahydrofuran was distilled from sodium benzophenone ketyl.
Dichloromethane, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone
(DMPU), triethylamine, and pyridine were distilled from calcium
hydride. Other solvents were HPLC grade or commercially distilled.
DOWEX 50 × 8-200 was used as a cation exchange resin. Analytical
thin-layer chromatography was performed on EM Science (E. Merck)
silica gel 60 F-254 and Analtech silica gel GF (250 microns). TLC
staining of sugars was normally accomplished by spraying with a
naphthoresorcinol stain (0.2 g of naphthoresorcinol, 100 mL of ethanol,
(22) Cho, C. Y.; Moran, E. J.; Cherry, S. R.; Stephans, J. C.; Fodor, S.
P. A.; Adams, C. L.; Sundaram, A.; Jacobs, J. W.; Schultz, P. G. Science
1993, 261, 1303-1305.
(23) During the review and revision of this manuscript, a communication
appeared which reports an alternative approach to peptide-saccharide
hybrids: Wessel, H. P.; Mitchell, C. M.; Lobato, C. M.; Schmid, G. Angew.
Chem., Int. Ed. Engl. 1995, 34, 2712-13.
Ester 14. Acetonitrile (60 mL) was added to a mixture of
diisopropylidene 13 (1.252 g, 4.81 mmol) and methyl(triphenylphos-
phoranylidene)acetate (3.31 g, 9.90 mmol), and the resulting solution
was heated to reflux under argon. After refluxing 14 h, the solution
was concentrated to a small volume, then taken up in 40 mL EtOAc,

3822 J. Am. Chem. Soc., Vol. 118, No. 16, 1996
Scheme 6. Synthetic Route to Glycosamino Acid 11a
McDeVitt and Lansbury
a Details are included in the Experimental Section.
Scheme 7. Synthetic Route to Glycosamino Acid 12a
a Details are included in the Experimental Section.
Figure 2. Four glycotides, synthesized by solution peptide coupling methods and described herein. Details are included in the Experimental Section.
and washed with water (1 × 30 mL) and brine (1 × 30 mL). The
organic layer was dried over magnesium sulfate, filtered, and concen-
trated. The resultant syrup was purified by flash chromatography
(hexane/ethyl acetate ) 4:1) to give 14 as a mixture of anomers (1.37
g, 4.32 mmol) in 90% yield. Physical data for 14 matched literature
values.12
Diol 15. Water (280 µL) was added to a solution of the diacetonide
14 (176 mg, 0.556 mmol) in glacial acetic acid (2 mL). Stirring was
commenced and proceeded for 16 h at room temperature, at which time
TLC (hexane/EtOAc, 1:1) indicated the absence of 14. The solution
was concentrated under reduced pressure to a syrup, which solidified
upon standing. The white solid was dissolved in CH2Cl2 and filtered
through a plug of silica gel (CH2Cl2/acetone ) 8:1, then 1.5:1). The
solvent was removed in Vacuo to give 15 (131 mg, 0.474 mmol) as a
mixture of anomers in 85% yield. Rf ) 0.2 (dichloromethane/acetone
) 3:1); IR (film) 3441, 2986, 2939, 2878, 1738, 1209, 1088 cm-1; 1H
NMR (300 MHz, CDCl3) δ 4.88 (dd, 0.5H, J ) 6.1, 4.0), 4.84 (dd,
0.5H, J ) 6.2, 3.7), 4.76 (dd, 0.5H, J ) 6.2, 3.7), 4.63 (dd, 0.5H, J )
6.2, 1.0), 4.49 (dd, 0.5H, J ) 7.5, 7.2), 3.76-4.01 (m, 3H), 3.70 (s,
3H), 3.66-3.72 (m, 1H), 3.53 (dd, 0.5H, J ) 7.2, 3.8), 3.13-3.17 (m,
1H), 2.63-2.85 (m, 2H), 2.45-2.57 (m, 1H); 13C NMR (75 MHz,
CDCl3) δ 171.4, 170.7, 113.0, 112.5, 84.6, 84.6, 81.2, 81.2, 80.8, 80.5,
79.8, 77.5, 70.2, 69.9, 64.4, 64.3, 51.9, 51.7, 36.2, 33.2, 26.1, 25.8,
24.8, 24.7; FABMS: 277 (M + H)+.
Azides 1 and 2. A 0 °C solution of the diol 15 (1.29 g, 4.67 mmol)
in pyridine (14 mL) was treated with methanesulfonyl chloride (390
µL, 5.04 mmol). After warming to room temperature and stirring for
18 hours, DMAP (5 mg) was added to the reaction flask. Stirring was
continued for an additional 4 h, at which point only a trace of starting
material remained and a small amount of the dimesylate impurity had

Glycosamino Acids
J. Am. Chem. Soc., Vol. 118, No. 16, 1996 3823
formed. Methanol (3 mL) was added to destroy excess methanesulfonyl
chloride. The resulting solution was concentrated under reduced
pressure to afford an oil, which was partitioned between CH2Cl2 and
water. The aqueous layer was extracted with CH2Cl2 (2 × 15 mL),
and the combined organic layers were washed successively with 1 M
HCl (1 × 25 mL), saturated sodium bicarbonate (1 × 20 mL), and
brine (1 × 25 mL). The organic layer was dried over Na2SO4, filtered,
and concentrated to an oil. Purification by flash chromatography
(hexane/EtOAc ) 1.3:1) provided the monomesylate (1.25 g, 3.54
mmol) as an oil in 76% yield. It is important to remove the dimesylate
impurities before proceeding to the next step. Sodium azide (750 mg,
11.6 mmol) was added to a solution of the monomesylate product (779
mg, 2.20 mmol) in DMF (15 mL). The resulting suspension was stirred
for 8 h in an oil bath heated to 70 °C. The suspension was cooled to
room temperature, and water (30 mL) was added, producing a
homogeneous solution. This solution was extracted with ether (2 ×
30 mL), and the pooled organic extracts were washed with brine (1 ×
30 mL) and dried over sodium sulfate, filtered, and concentrated.
Purification by flash chromatography (ether/petroleum ether ) 1.3:1)
provided the glycosazido esters 1 and 2 (555.9 mg, 1.84 mmol) as a
mixture of anomers in 84% yield. Purification on fine silica gel (EM
Science, silica gel 60) was required to completely resolve the anomers.
(1, R anomer) Rf ) 0.48 (hexane/ethyl acetate ) 1:1); IR (film) 3474
(75 MHz, CDCl3) δ 170.9, 112.9, 80.9, 80.0, 78.7, 77.9, 77.4, 52.3,
51.8, 38.4, 33.2, 25.8, 24.8; HRMS Calcd for C13H21N3O8S (M +
H)+: 380.1128; found: 380.1130.
C-Glycoside 18. A solution of 1,2,3,4,6-penta-O-acetyl-â-D-man-
nopyranose (4.08 g, 10.5 mmol) and allyl TMS (4.93 mL, 31 mmol)
in acetonitrile (40 mL) at 0 °C was treated with TMSOTf (2.24 mL,
11.6 mmol). The ice bath was removed, and the reaction was stirred
48 h and then added to 150 mL cold saturated sodium bicarbonate
solution. The aqueous solution was extracted with CHCl3 (2 × 75
mL). The combined organic extracts were washed with brine (1 ×
100 mL), dried over sodium sulfate, filtered, and concentrated.
Purification by flash chromatography (hexane/ethyl acetate ) 4:1)
afforded 18 (1.51 g, 4.1 mmol) as a mixture of anomers (R/â ≈ 4) in
39% yield. Rf ) 0.35 (hexane/ethyl acetate ) 3:1); IR (film) 1745,
1
1370, 1227, 1050 cm-1; H NMR (R anomer) (300 MHz, CDCl3) δ
5.70-5.83 (m, 1H), 5.08-5.34 (m, 5H), 4.33 (dd, 1H), 4.03-4.15 (m,
2H), 3.88-3.93 (m, 1H), 2.38-2.60 (m, 2H), 2.12 (s, 3H), 2.09 (s,
3H), 2.08 (s, 3H), 2.04 (s, 3H); FABMS: 373 (M + H)+.
Silyl Ether 19. A solution of lithium methoxide (20 mg) in methanol
(10 mL) was added to tetraacetate 18 (654 mg, 1.76 mmol). After
stirring 30 min, cation exchange resin was added to neutralize the
solution. The resin was removed by filtration, and the filtrate was
concentrated to an oil, which was dissolved in anhydrous pyridine (10
mL), cooled to 0 °C, and treated with tert-butyldiphenylsilyl chloride
(1.3 mL, 5.0 mmol). After 16 h, the reaction was quenched with
methanol (150 µL). The reaction flask was cooled to 0 °C, and acetic
anhydride (2 mL) was added. After 20 h, water (30 mL) was added,
and the aqueous solution was extracted with CH2Cl2 (2 × 30 mL).
The combined organic extracts were washed with water (1 × 50 mL),
KHSO4 (1 × 50 mL), sodium bicarbonate (2 × 50 mL), and brine (1
× 50 mL), then dried over sodium sulfate, filtered, and concentrated
to an oil. Purification by flash chromatography (hexane/ethyl acetate
) 4.5:1) afforded 19 (521 mg, 0.91 mmol) as an anomeric mixture in
52% yield. Rf ) 0.5 (hexane/ethyl acetate ) 3:1); IR (film) 2932,
2857, 1748, 1371, 1248, 1224, 1112 cm-1; 1H NMR (R anomer) (300
MHz, CDCl3) δ 7.64-7.76 (m, 4H), 7.35-7.45 (m, 6H), 5.76-5.89
(m, 1H), 5.07-5.32 (m, 5H), 3.97-4.02 (m, 1H), 3.69-3.81 (m, 3H),
2.47-2.58 (m, 1H), 2.35-2.43 (m, 1H), 2.09 (s, 3H), 1.98 (s, 3H),
1.93 (s, 3H), 1.08 (s, 9H); FABMS: 569 (M + H)+.
1
(br), 2990, 2940, 2103, 1737, 1438, 1382, 1085 cm-1; H NMR (300
MHz, CDCl3) δ 4.89 (dd, 1H, J ) 6.0, 4.1), 4.67 (dd, 1H, J ) 6.0,
1.0), 4.47-4.52 (m, 1H), 4.03-4.12 (m, 1H), 3.83 (dd, 1H, J ) 8.3,
4.1), 3.71 (s, 3H), 3.54 (dd, 1H, J ) 12.9, 2.7), 3.42 (dd, J ) 12.9,
6.3), 2.75-2.80 (m, 1H), 2.44-2.58 (m, 2H), 1.51 (s, 3H), 1.32 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 170.5, 113.2, 84.7, 81.0, 80.5, 79.9,
69.7, 54.1, 51.9, 36.2, 26.1, 24.7; HRMS Calcd for C12H19N3O6 (M +
H)+: 302.1352; found: 302.1349. (2, â anomer) Rf ) 0.5 (hexane/
ethyl acetate ) 1:1); IR (film) 3481 (br), 2987, 2934, 2097, 1734, 1438
cm-1; 1H NMR (300 MHz, CDCl3) δ 4.83 (dd, 1H, J ) 6.1, 3.7), 4.77
(dd, 1H, J ) 6.1, 3.3), 4.05-4.13 (m, 1H), 3.93-3.99 (m, 1H), 3.70
(s, 3H), 3.55 (dd, 1H, J ) 12.8, 3.3), 3.50 (dd, J ) 8.2, 3.7), 3.42 (dd,
1H, J )12.8, 6.5), 2.68-2.85 (m, 2H), 2.63-2.68 (m, 1H), 1.48 (s,
3H), 1.34 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 171.2, 112.8, 81.0,
80.9, 80.9, 77.6, 69.4, 54.4, 51.8, 33.3, 25.8, 24.7; HRMS Calcd for
C12H19N3O6 (M + H)+: 302.1352; found: 302.1349.
Azides 3 and 4. Methanesulfonyl chloride (400 µL, 5.17 mmol)
was added to a 0 °C solution of 15 (374 mg, 1.35 mmol) and TEA
(1.4 mL, 10.1 mmol) in CH2Cl2 (10 mL). The resulting suspension
was stirred 48 h at room temperature, at which point methanol (1 mL)
was added to destroy excess methanesulfonyl chloride. The solution
was concentrated to an oil, which was dissolved in EtOAc (20 mL)
and washed with saturated NaHCO3 (2 × 15 mL) and brine (1 × 15
mL). The organic layer was dried over Na2SO4, filtered, and concen-
trated after addition of DMF (1 mL, to prevent bumping). The residual
oil was taken up in DMF (8 mL) and treated with sodium azide (560
mg, 8.6 mmol). The resulting suspension was stirred for 14 h in an
oil bath heated to 70 °C. The suspension was cooled to room
temperature and dissolved in water (25 mL). This solution was
extracted with ether (2 × 25 mL), and the pooled organic extracts were
washed with brine (1 × 30 mL) and subsequently dried over sodium
sulfate, filtered, and concentrated to an oil. Purification by flash
chromatography (hexane/EtOAc ) 3.1:1) gave the glycosazido esters
3 and 4 as an anomeric mixture in 66% yield (338 mg, 0.890 mmol).
The anomers were resolved by repeated purifications on fine silica gel
(EM Science, silica gel 60). (3, R anomer) Rf ) 0.65 (hexane/EtOAc
) 1:1); IR (film) 2988, 2941, 2110, 1738, 1439, 1360, 1178 cm-1; 1H
NMR (300 MHz, CDCl3) δ 4.91-4.96 (m, 1H), 4.82 (dd, 1H, J ) 6.0,
3.7), 4.71 (dd, 1H, J ) 6.0, 0.9) 4.49-4.53 (m, 1H), 4.14 (dd, 1H, J
)7.6, 3.7), 3.89 (dd, 1H, J ) 13.6, 2.6), 3.71 (s, 3H), 3.60 (dd, 1H, J
)13.6, 4.3), 3.13 (s, 3H), 2.47-2.61 (m, 2H), 1.51 (s, 3H), 1.33 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 170.4, 113.3, 84.8, 81.0, 80.2, 77.9,
77.7, 52.2, 52.0, 38.4, 36.0, 26.2, 24.9; HRMS Calcd for C13H21N3O8S
(M + H)+: 380.1128; found: 380.1130. (4, â anomer) Rf ) 0.7
(hexane/ethyl acetate ) 1:1); IR (film) 2988, 2940, 2109, 1736, 1438,
1361, 1178 cm-1; 1H NMR (300 MHz, CDCl3) δ 4.92-4.95 (m, 1H),
4.75-4.83 (m, 2H), 3.96-4.01 (m, 1H), 3.89 (dd, 1H, J ) 13.4, 2.7),
3.82 (dd, 1H, J ) 6.1, 3.5), 3.71 (s, 3H), 3.58 (dd, 1H, J ) 13.4, 4.3),
3.13 (s, 3H), 2.68-2.84 (m, 2H), 1.48 (s, 3H), 1.32 (s, 3H); 13C NMR
Alcohol 20. A solution of the silyl ether 19 (486 mg, 0.85 mmol)
in THF (6 mL) at 0 °C was treated with HF/pyridine complex (1.6
mL). The ice bath was removed, and the reaction proceeded for 16 h
at room temperature, at which time it was again cooled to 0 °C and
sodium bicarbonate (25 mL) was slowly added. The aqueous solution
was extracted with CH2Cl2 (3 × 15 mL). The combined organic
extracts were washed with brine (1 × 40 mL), then dried over sodium
sulfate, filtered, and concentrated to an oil. Purification by flash
chromatography (hexane/ethyl acetate ) 1.8:1) afforded the alcohol
20 (238 mg, 0.72 mmol) as a mixture of anomers in 84% yield. Rf )
0.4 (hexane/ethyl acetate ) 1.1:1); IR (film) 3487 (br), 2943, 1745,
1
1372, 1227, 1048 cm-1; H NMR (R anomer) (300 MHz, CDCl3) δ
5.81-5.94 (m, 1H), 5.10-5.32 (m, 5H), 4.02-4.08 (m, 1H), 3.63-
3.70 (m, 3H), 2.54-2.65 (m, 1H), 2.39-2.48 (m, 1H), 2.26 (dd, 1H,
J ) 6.9, 6.4), 2.14 (s, 3H), 2.08 (s, 3H), 2.02 (s, 3H); FABMS: 331
(M + H)+.
Azide 21. Methanesulfonyl chloride (85 µL, 1.1 mmol) was added
to a 0 °C solution of the alcohol 20 (234 mg, 0.71 mmol) and TEA
(200 µL, 1.5 mmol) in CH2Cl2 (5 mL). The ice bath was removed,
and the reaction proceeded for 18 h at room temperature before water
(10 mL) was added, followed by saturated sodium bicarbonate solution
(2 mL). The aqueous solution was extracted with CH2Cl2 (3 × 7 mL),
and the combined organic extracts were washed with brine (1 × 10
mL), dried over sodium sulfate, filtered, and concentrated to an oil,
which was used directly without further purification. The mesylate
was dissolved in DMF (6 mL) and added to sodium azide (310 mg,
4.8 mmol). The reaction was heated to 80 °C and proceeded for 48 h
before being cooled to room temperature and added to water (12 mL).
The aqueous suspension was extracted with ether (3 × 10 mL), and
the combined organic extracts were washed with brine (1 × 20 mL),
dried over sodium sulfate, filtered, and concentrated. Purification by
flash chromatography (hexane/ethyl acetate ) 3.8:1) afforded the azide
21 (158 mg, 0.44 mmol) as an anomeric mixture in 63% yield. Rf )

3824 J. Am. Chem. Soc., Vol. 118, No. 16, 1996
McDeVitt and Lansbury
0.4 (hexane/ethyl acetate ) 3:1); IR (film) 2101, 1746, 1370, 1247,
7.2, 1.0), 3.68 (dd, 1H, J ) 7.2, 5.9), 3.58-3.60 (m, 1H), 3.34-3.35
(m, 2H); FABMS: 433 (M + H)+.
1
1223, 1045 cm-1; H NMR (R anomer) (300 MHz, CDCl3) δ 5.72-
5.88 (m, 1H), 5.08-5.30 (m, 5H), 4.01-4.07 (m, 1H), 3.81-3.88 (m,
1H), 3.41 (dd, 1H, J ) 12.7, 7.0), 3.24 (dd, 1H, J ) 12.7, 3.0), 2.53-
2.63 (m, 1H), 2.39-2.48 (m, 1H), 2.15 (s, 3H), 2.06 (s, 3H), 2.02 (s,
3H); FABMS: 356 (M + H)+.
C-Glycoside 23. A solution of 22 (1.088 g, 2.52 mmol) and allyl
TMS (1.25 mL, 7.86 mmol) in acetonitrile (11 mL) at 0 °C was treated
with TMSOTf (500 µL, 2.60 mmol). The ice bath was removed, and
the reaction was stirred 16 h and then added to 50 mL cold saturated
sodium bicarbonate solution. The aqueous solution was extracted with
CH2Cl2 (3 × 25 mL). The combined organic extracts were washed
with brine (1 × 50 mL), dried over magnesium sulfate, filtered, and
concentrated. Purification by flash chromatography (hexane/ethyl
acetate, 3.8:1) afforded the R-C-glycoside 23 (459 mg, 0.97 mmol) as
a white solid in 38% yield. A second product, presumably the â
anomer, was isolated but not purified to homogeneity. Rf ) 0.3
(hexane/ethyl acetate ) 3:1); IR (film) 3250, 2899, 1453, 1096, 1067,
1038 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.28-7.37 (m, 15H), 5.70-
5.83 (m, 1H), 5.07-5.14 (m, 2H), 4.61-4.96 (m, 6H), 4.01-4.09 (m,
1H), 3.48-3.84 (m, 6H), 2.46-2.51 (m, 2H), 1.77 (t, 1H, J ) 6.4);
FABMS: 475 (M + H)+.
Esters 5 and 6. A 1:1 solution (1 mL) of acetonitrile/carbon
tetrachloride was added to a mixture of the C-allyl glycoside 21 (153.5
mg, 0.43 mmol) and sodium periodate (540 mg, 2.50 mmol). Water
(0.75 mL) was added to the suspension, followed by catalytic ruthenium
chloride trihydrate (7 mg). The reaction immediately turned brown,
and soon thereafter developed a green color. After 40 min, isopropyl
alcohol (1 mL) was added to the flask, and the contents were filtered
through Celite, rinsing with EtOAc. The filtrate was concentrated to
an oil, dissolved in EtOAc, and dried over sodium sulfate. The drying
agent was removed by filtration, and the filtrate was concentrated to
an oil. The oil was dissolved in DMF (2 mL) and treated with sodium
bicarbonate (120 mg) and methyl iodide (90 µL). After 20 h, water (2
mL) was added to the flask, and the reaction contents were partitioned
between water (additional 4 mL) and EtOAc (5 mL). The aqueous
layer was extracted with EtOAc (2 × 5 mL), and the combined organic
extracts were washed with sodium bicarbonate (1 × 10 mL) and brine
(1 × 8 mL), dried over sodium sulfate, filtered, and concentrated.
Purification by flash chromatography (hexane/ethyl acetate ) 3:1)
afforded the glycosazido esters (138 mg, 0.36 mmol) as an anomeric
mixture in 83% yield. The anomers were resolved by a deacetylation
and subsequent acetonide formation. Lithium methoxide (7 mg, 0.18
mmol) was added to a solution of the azido ester mixture (125 mg,
0.32 mmol) in methanol (4 mL). After 30 min, cation exhange resin
was added. The resin was removed by filtration, and the filtrate was
concentrated. The residual oil was dissolved in dimethoxypropane (3
mL) and treated with catalytic PPTSA (3 mg). The reaction was heated
on an oil bath to 45 °C and proceeded for 1 h. The solution was
concentrated to an oil that was purified by flash chromatography
(hexane/ethyl acetate ) 3:1) to give the R-glycoside 5 (62.1 mg, 0.21
mmol), the â-glycoside 6 (6.6 mg, 0.02 mmol), and a fraction containing
a mixture of the two anomers (13.5 mg, 0.04 mmol) as oils in 85%
yield (70% from 21). (5) Rf ) 0.5 (hexane/ethyl acetate ) 1:1); IR
Azide 24. Methanesulfonyl chloride (100 µL, 1.29 mmol) was added
to a 0 °C solution of the alcohol 23 (388 mg, 0.82 mmol) and TEA
(230 µL, 1.66 mmol) in CH2Cl2 (5 mL). The ice bath was removed,
and stirring was continued for 18 h before methanol (50 µL) was added.
The solution was concentrated to a solid, dissolved in EtOAc (20 mL),
and washed successively with water (1 × 20 mL), sodium bicarbonate
(2 × 20 mL), and brine (1 × 20 mL). The organic solution was dried
over sodium sulfate, filtered, and concentrated to an oil, which was
used directly without further purification. The mesylate was dissolved
in DMF (8 mL) and added to sodium azide (300 mg, 4.6 mmol). The
reaction was heated to 90 °C and proceeded for 20 h before being cooled
to room temperature and added to water (15 mL), causing formation
of a white precipitate. The aqueous suspension was extracted with
ether (3 × 15 mL), and the combined organic extracts were washed
with brine (1 × 25 mL), dried over sodium sulfate, filtered, and
concentrated. Purification by flash chromatography (hexane/ethyl
acetate ) 10:1) afforded the azide 24 (340 mg, 0.68 mmol) as a white
solid in 83% yield. Rf ) 0.4 (hexane/ethyl acetate ) 10:1); IR (film)
1
2919, 2099, 1454, 1285, 1092 cm-1; H NMR (300 MHz, CDCl3) δ
7.21-7.31 (m, 15H), 5.69-5.82 (m, 1H), 5.04-5.11 (m, 2H), 4.51-
4.92 (m, 6H), 4.03-4.11 (m, 1H), 3.53-3.89 (m, 3H), 3.34-3.43 (m,
2H), 3.25 (dd, 1H, J ) 13.7, 5.4), 2.41-2.46 (m, 2H); FABMS: 500
(M + H)+.
(film) 3456 (br), 2989, 2936, 2101, 1783, 1276, 1082, 1053, 865 cm-1
;
1H NMR (300 MHz, CDCl3) δ 4.10-4.22 (m, 3H), 3.84-3.91 (m,
1H), 3.72 (s, 3H), 3.64-3.71 (m, 1H), 3.53 (dd, 1H, J ) 13.2, 6.0),
3.42 (dd, 1H, J ) 13.2, 3.0), 2.71 (dd, 1H, J ) 15.4, 4.0), 2.55 (dd,
1H, J ) 15.4, 8.9), 2.32 (d, 1H, J ) 3.9), 1.50 (s, 3H), 1.36 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 170.7, 110.2, 78.4, 75.6, 74.2, 70.0,
69.8, 52.0, 51.6, 38.1, 27.3, 25.1; HRMS Calcd for C12H19N3O6 (M +
H)+: 302.1352; found: 302.1347. (6) Rf ) 0.45 (hexane/ethyl acetate
) 1:1); IR (film) 3444, 2934, 2100, 1738, 1376, 1220, 1072 cm-1; 1H
NMR (300 MHz, CDCl3) δ 4.19-4.26 (m, 2H), 4.02 (dd, 1H, J ) 7.0,
5.5), 3.71 (s, 3H), 3.54-3.61 (m, 1H), 3.43-3.45 (m, 2H), 3.36 (dd,
1H, J ) 12.2, 7.0), 2.83 (dd, 1H, J ) 16.3, 7.6), 2.71 (dd, 1H, J )
16.3, 5.5), 2.33 (d, 1H, J ) 3.6), 1.52 (s, 3H), 1.35 (s, 3H); 13C NMR
(75 MHz, CDCl3) δ 171.2, 110.0, 79.8, 77.5, 75.0, 72.6, 71.1, 51.9,
51.4, 36.2, 28.2, 26.3; HRMS Calcd for C12H19N3O6 (M + H)+:
302.1352; found: 302.1356.
Ester 7. Water (1.2 mL) and acetic acid (250 µL) were added to a
solution of the C-allyl glycoside 24 (116.3 mg, 0.23 mmol) in CH2Cl2
(1.2 mL). Aliquat 336 (15 mg) was added as a phase transfer catalyst,
and the reaction vessel was cooled to 0 °C before addition of KMnO4
(134 mg, 0.85 mmol) in two portions. The ice bath was removed, and
the reaction proceeded 20 h at room temperature, at which point all
starting material had been consumed. Sodium sulfite (150 mg) was
added to quench the reaction, which was partitioned between CH2Cl2
(3 mL) and water (2.5 mL). The aqueous layer was extracted with
CH2Cl2 (3 mL), and the combined organic extracts were washed with
brine (1 × 5 mL), dried over sodium sulfate, filtered, and concentrated
to an oil that was dissolved in DMF (1 mL). Sodium bicarbonate (20
mg) was added to this solution, followed by methyl iodide (20 µL).
After 40 h, water (1 mL) was added, and the reaction was partitioned
between water (8 mL) and ether (8 mL). The aqueous layer was
extracted with ether (2 × 5 mL), and the combined organic extracts
were washed with brine (1 × 10 mL), dried over sodium sulfate, filtered,
and concentrated to an oil. Purification by flash chromatography
(hexane/EtOAc ) 10:1) gave the glycosazido ester 7 (62.3 mg, 0.12
mmol) as an oil in 50% yield. Rf ) 0.7 (hexane/ethyl acetate ) 3:1);
Benzyl Ether 22. A solution of 1,6-â-D-anhydroglucose (1.00 g,
6.17 mmol) in DMF (20 mL) was added to a 0 °C suspension of NaH
(1.1 g, 27.5 mmol, 60% dispersion in mineral oil, washed with hexanes)
in DMF (10 mL) and stirred for 15 min before being treated with benzyl
bromide (7 mL, 58 mmol). The ice bath was removed, and the reaction
was allowed to proceed at room temperature for 16 h. Methanol (20
mL) was added, and 15 min later the reaction was partitioned between
EtOAc (50 mL) and water (30 mL). The aqueous layer was extracted
with EtOAc (1 × 50 mL), and the combined organic extracts were
washed successively with water (2 × 50 mL), sodium bicarbonate (2
× 50 mL), KHSO4 (1 × 50 mL), and brine (1 × 50 mL). The organic
solution was dried over magnesium sulfate, filtered, concentrated to
an oil that was purified by flash chromatography (hexane/EtOAc )
3:1), and then recrystallized from ethanol to afford 22 (1.88 g, 4.35
mmol) as white crystals in 70% yield. Rf ) 0.6 (hexane/ethyl acetate
1
IR (film) 3030, 2908, 2100, 1738, 1283, 1091 cm-1; H NMR (300
MHz, CDCl3) δ 7.23-7.36 (m, 15H), 4.88 (d, 1H, J ) 10.9), 4.87 (d,
1H, J ) 11.0), 4.78 (d, 1H, J ) 10.9), 4.62-4.69 (m, 3H), 4.57 (d,
1H, J ) 11.0), 3.69-3.80 (m, 3H), 3.65 (s, 3H), 3.38-3.47 (m, 2H),
3.30 (dd, 1H, J ) 13.0, 5.4), 2.78 (dd, 1H, J ) 15.0, 5.4), 2.68 (dd,
1H, J ) 15.0, 9.4); 13C NMR (75 MHz, CDCl3) δ 171.3, 138.3, 137.8,
137.7, 127.7-128.5 (m), 81.7, 79.1, 78.4, 75.3, 75.1, 73.2, 72.0, 71.4,
51.8, 51.5, 32.5; HRMS Calcd for C30H33N3O6 (M + H)+: 532.2448;
found: 532.2446.
1
) 2:1); IR (film) 2918, 1454, 1073, 1028 cm-1; H NMR (300 MHz,
CDCl3) δ 7.21-7.35 (m, 15H), 5.46 (d, 1H, J < 1), 4.51-4.64 (m,
5H), 4.45 (d, 1H, J ) 12.1), 4.40 (d, 1H, J ) 12.1), 3.91 (dd, 1H, J )
Azide 25. Pyridine (50 mL) was added to a 0 °C mixture of 1,2-
O-isopropylidene-R-D-xylofuranose (5.85 g, 30.8 mmol) and tosyl

Glycosamino Acids
J. Am. Chem. Soc., Vol. 118, No. 16, 1996 3825
chloride (6.5 g, 34.0 mmol). The reaction was allowed to warm to
room temperature and stirred 16 h. Methanol (3 mL) was added to
destroy excess tosyl chloride. After 15 min, the solution was
concentrated to a syrup, then taken up in EtOAc (50 mL), and washed
successively with water (1 × 40 mL), sodium bicarbonate (1 × 40
mL), and brine (1 × 40 mL). The organic solution was dried over
sodium sulfate, filtered, and concentrated to a solid. Recrystallization
from absolute ethanol provided the tosylate (5.94 g, 17.3 mmol) in 56%
yield. A portion of the crystals (578 mg, 1.68 mmol) and NaN3 (513
mg, 7.9 mmol) was combined in a flask, to which was added DMF
(12 mL). The suspension was stirred 72 h in an oil bath heated to 70
°C. After cooling to room temperature, the contents of the reaction
flask were added to water (25 mL) and extracted with CH2Cl2 (3 × 15
mL). The combined organic layers were washed with brine (1 × 30
mL) and concentrated to an oil. Purification by flash chromatography
(hexane/EtOAc ) 2:1) gave the azide 25 (338 mg, 1.57 mmol) as white
crystals (cyclohexane was determined to be a suitable solvent for
recrystallization) in 94% yield (53% from 1,2-O-isopropylidene-R-D-
xylofuranose). Rf ) 0.3 (hexane/ethyl acetate ) 3:1); IR (film) 3404
unsaturated ester 27b (3.1 mg, 0.012 mmol) in methanol (0.7 mL).
After stirring 5 min, cation exchange resin was added to neutralize the
solution, which was filtered and concentrated. Purification by flash
chromatography (hexane, then hexane/EtOAc ) 2:1) afforded 8 (4.7
mg, 0.012 mmol) as a colorless oil in quantitative yield. Rf ) 0.6
(hexane/EtOAc ) 3:1); IR (film) 2976, 2965, 2359, 2099, 1738, 1201,
1
1025 cm-1; H NMR (300 MHz, CDCl3) δ 7.26-7.33 (m, 5H), 5.85
(d, 1H, J ) 3.3), 4.83 (d, 1H, J )3.3) 4.32 (dd, 1H, J ) 6.8, 5.0), 3.92
(s, 2H), 3.73 (s, 3H), 3.59-3.62 (m, 2H), 2.98 (d, 1H, J ) 15.6), 2.85
(d, 1H, J ) 15.6), 1.52 (s, 3H), 1.32 (s, 3H); HRMS Calcd for
C18H23N3O5S (M + H)+: 394.1437; found: 394.1428. Upon irradiation
of the benzylic protons (δ 3.92), an NOE was observed at the C-2
hydrogen (δ 4.83).
Thioether 9. Cyclohexyl mercaptan (20 µL, 0.16 mmol) was added
to a solution of lithium methoxide (1.5 mg, 0.04 mmol) and the R,â-
unsaturated ester 27b (5.6 mg, 0.021 mmol) in methanol (0.7 mL).
After stirring 15 min, cation exchange resin was added to neutralize
the solution, which was filtered and concentrated. Purification by flash
chromatography (hexane/EtOAc ) 6:1) afforded the Michael adduct 9
(7.3 mg, 0.019 mmol) as a colorless oil in 91% yield. Michael addition
of cyclohexyl mercaptan to 27a also gave 9 as the only product. Rf )
0.7 (hexane/EtOAc ) 2.5:1); IR (film) 2987, 2932, 2853, 2099, 1740,
1
(br), 2987, 2931, 2098, 1375, 1215, 1070, 1008 cm-1; H NMR (300
MHz, CDCl3) δ 5.96 (d, 1H, J ) 3.7), 4.52 (dd, 1H, J ) 3.7, < 1),
4.24-4.30 (m, 2H), 3.57-3.63 (m, 2H), 2.22 (d, 1H, J ) 5.2), 1.51 (s,
3H), 1.32 (s, 3H); FABMS Calcd for C8H13N3O4 (M + H)+: 216.0984;
found: 216.0986.
1
1437, 1373, 1200, 1166, 1022 cm-1; H NMR (300 MHz, CDCl3) δ
5.89 (d, 1H, J ) 3.4), 4.82 (d, 1H, J ) 3.4), 4.37 (dd, 1H, J ) 6.9,
4.8), 3.72 (s, 3H), 3.54-3.57 (m, 2H), 2.79-2.93 (m, 3H), 1.89-1.99
(m, 2H), 1.71-1.76 (m, 2H), 1.19-1.59 (m, 6H), 1.51 (s, 3H), 1.35
(s, 3H); 13C NMR (75 MHz, CDCl3) δ 170.2, 112.4, 104.4, 86.1, 82.6,
58.3, 51.8, 51.0, 41.6, 37.8, 36.5, 36.1, 26.8, 26.7, 26.3, 26.3, 25.2;
HRMS Calcd for C17H27N3O5S (M + H)+: 386.1750; found: 386.1747.
Upon irradiation at δ 4.37 (H4), NOE’s were observed at δ 2.87
(protons R to ester) and 1.51 (isopropylidene CH3). Upon irradiation
at δ 4.82 (H2), an NOE was observed at 2.90 (methine proton of
cyclohexyl ring).
Silyl Ether 28. Under an argon atmosphere, tert-butyldiphenyl-
chlorosilane (1.23 mL, 4.74 mmol) was added to a 0 °C solution of
1,2-O-isopropylidene-R-D-xylofuranose (601 mg, 3.16 mmol) in pyri-
dine (7 mL). The reaction vessel was warmed to room temperature
and stirring proceeded for 18 h before methanol (100 µL) was added
to destroy residual TBDPSCl. Water (20 mL) was added, and the
aqueous solution was extracted with CH2Cl2 (3 × 15 mL). The
combined organic extracts were concentrated to a volume of 15 mL
and washed with brine (1 × 15 mL), dried over sodium sulfate, and
concentrated under reduced pressure to an oil. Purification by flash
chromatography (hexane/EtOAc ) 7:1) gave the silyl ether 28 (1.326
g, 3.09 mmol) as a colorless oil in 98% yield. Rf ) 0.75 (hexane/
ethyl acetate ) 2:1); IR (film) 3460 (br), 2932, 1428, 1374, 1216, 1113,
1075, 1014 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.66-7.73 (m, 4H),
7.38-7.47 (m, 6H), 6.01 (d, 1H, J ) 3.7), 4.55 (dd, 1H, J ) 3.7, < 1),
4.37 (dd, 1H, J < 1), 4.10-4.14 (m, 3H), 4.06 (d, 1H, J ) 3.1), 1.47
(s, 3H), 1.33 (s, 3H), 1.05 (s, 9H); HRMS Calcd for C24H32SiO5 (M +
H)+: 429.2097; found: 429.2092.
Azide 29. Pyridine (270 µL, 3.0 mmol) was added to a -10 °C
solution of the alcohol 28 (751 mg, 1.75 mmol) in CH2Cl2. After
stirring the solution briefly, trifluoromethanesulfonic anhydride (324
µL, 1.93 mmol) was added, and the reaction was allowed to warm
gradually to room temperature. Monitoring of the reaction by TLC
indicated that it had not gone to completion after 8 h, at which time
additional pyridine (100 µL) and (Tf)2O (50 µL) were added. Within
an hour, all starting material was consumed, and the reaction contents
were added to cold water (25 mL). The aqueous layer was extracted
with CH2Cl2 (2 × 20 mL), and the combined organics were washed
with brine (1 × 40 mL), dried over sodium sulfate, and concentrated.
Traces of pyridine and pyridinium salts were separated from the desired
triflate product by flash chromatography (hexane/EtOAc ) 3:1) through
a short plug of silica gel, yielding the crude triflate, which was used
directly in the next step. The triflate was dissolved in DMF (18 mL),
to which NaN3 (500 mg, 7.7 mmol) was added. After stirring 18 h at
room temperature, all starting material was consumed, leaving the
desired azide product and a significant side-product, presumably
resulting from triflate elimination. Water (60 mL) was added to the
reaction, and the aqueous solution was extracted with ether (3 × 50
mL). The combined ether extracts were washed (1 × 100 mL) with
Ketone 26. A solution of DMSO (185 µL, 2.6 mmol) in CH2Cl2 (1
mL) was added dropwise to a solution of oxalyl chloride (650 µL of
2.0 M solution in CH2Cl2, 1.3 mmol) in CH2Cl2 cooled to below -60
°C. The reaction flask was stirred 15 min at this temperature before a
cooled solution of 25 (217 mg, 1.01 mmol) in CH2Cl2 (2 mL) was
added. Stirring continued for 20 min with gradual warming to -40
°C, at which point DIEA (1.05 mL, 6 mmol) was added. The ice bath
was removed, and the reaction proceeded for 3 h. Water (7 mL) was
added, and the aqueous solution was extracted with CH2Cl2 (2 × 5
mL). The combined organics were washed with 1 M HCl (1 × 7 mL),
saturated NaHCO3 (1 × 7 mL), and brine (1 × 7 mL), then dried over
sodium sulfate, filtered, and concentrated to an oil. Purification by
flash chromatography (hexane/EtOAc ) 4:1) afforded the ketone 26
(122.8 mg, 0.58 mmol) as a colorless oil in 57% yield. Rf ) 0.25
(hexane/ethyl acetate ) 2:1); IR (film) 3400 (small, br), 2992, 2110,
1775, 1377, 1220, 1158, 1081 cm-1; 1H NMR of 26 showed a mixture
of two products, presumably the ketone and the hydrate. HRMS Calcd
for C8H11N3O4 (M + H)+: 214.0828; found: 214.0827.
Esters 27a and 27b. A solution of the ketone 26 (36.6 mg, 0.17
mmol) in DMF (1 mL) was added to a 0 °C solution of trimethyl
phosphonoacetate (100 µL, 0.62 mmol) and potassium tert-butoxide
(20.2 mg, 0.18 mmol) in DMF (0.5 mL). The reaction was warmed to
room temperature and stirred 2 h. Water (3 mL) was added, and the
aqueous solution was extracted with ether (2 × 3 mL). The combined
organic extracts were washed with water (1 × 5 mL), KHSO4
(1 × 5 mL), and brine (1 × 5 mL). After drying over sodium sulfate,
the organic solution was filtered and concentrated. Purification by flash
chromatography (hexane/EtOAc ) 5:1) afforded 27a (4.2 mg, 0.015
mmol) and 27b (23.9 mg, 0.088 mmol) as a mixture of cis-trans isomers
in 61% yield. (27a) Rf ) 0.75 (hexane/ethyl acetate ) 2.5:1); IR (film)
2994, 2953, 2112, 1717, 1371, 1227, 1159 cm-1; 1H NMR (300 MHz,
CDCl3) δ 6.20 (dd, 1H, J ) 2.0, 2.0), 5.98 (d, 1H, J ) 4.7), 5.63-
5.66 (m, 1H), 5.11-5.14 (m, 1H), 3.75 (s, 3H), 3.73 (dd, 1H, J )
12.7, 3.0), 3.64 (dd, 1H, J ) 12.7, 2.9), 1.43 (s, 3H), 1.39 (s, 3H);
HRMS Calcd for C11H15N3O5 (M + H)+: 270.1090; found: 270.1091.
Upon irradiation at δ 5.13 (H2), an NOE was observed at δ 6.20 (vinylic
proton). Upon irradiation at δ 5.64 (H4), an NOE was observed at δ
1.39 (isopropylidene CH3). (27b) Rf ) 0.5 (hexane/ethyl acetate )
2.5:1); IR (film) 2991, 2954, 2107, 1727, 1436, 1374, 1216, 1069, 1018
1
cm-1; H NMR (300 MHz, CDCl3) δ 5.96 (d, 1H, J ) 4.1), 5.87 (dd,
1H, J ) 2.0, 1.5), 5.74-5.76 (m, 1H), 4.97-5.02 (m, 1H), 3.80 (s,
3H), 3.65 (dd, 1H, J ) 13.2, 3.7), 3.40 (dd, 1H, J ) 13.2, 4.3), 1.50
(s, 3H), 1.44 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 165.4, 155.6, 117.2,
113.5, 105.5, 79.2, 78.6, 53.2, 52.4, 27.8, 27.6; HRMS Calcd for
C11H15N3O5 (M + H)+: 270.1090; found: 270.1087. Upon irradiation
at δ 5.00 (H4), an NOE was observed at δ 5.87 (vinylic proton).
Thioether 8. Lithium methoxide (3.0 mg, 0.08 mmol) was added
to a solution of benzyl mercaptan (20 µL, 0.017 mmol) and the R,â-

3826 J. Am. Chem. Soc., Vol. 118, No. 16, 1996
McDeVitt and Lansbury
brine, dried over magnesium sulfate, filtered, and concentrated in Vacuo
to give the crude azide as an oil, which was used directly without further
purification. The crude azide was dissolved in THF (3 mL) and added
to a solution of TBAF (3 mL of 1.0 M solution in THF, 3 mmol) in
THF (5 mL). After 18 h, the solution was concentrated to an oil. Water
(50 mL) was added, and the aqueous solution was extracted with EtOAc
(3 × 50 mL). The combined organic extracts were washed with water
(1 × 100 mL) and brine (1 × 100 mL) before drying over magnesium
sulfate. Filtration, followed by concentration in Vacuo, produced an
oil that was purified by flash chromatography (hexane/EtOAc ) 3:1)
to give the alcohol 29 (260.2 mg, 1.21 mmol) in 69% yield from 28.
Rf ) 0.5 (hexane/ethyl acetate ) 1:1); 1H NMR (300 MHz, CDCl3) δ
6.09 (d, 1H, J ) 5.4), 5.29-5.32 (m, 1H), 5.19-5.20 (m, 1H), 4.17-
4.20 (m, 3H), 1.77 (t, 1H, J ) 6.5), 1.47 (s, 3H), 1.45 (s, 3H).
Ester 10. Water (0.7 mL) and acetic acid (125 µL) were added to
a solution of the primary alcohol 29 (29.8 mg, 0.138 µmol) in CH2Cl2
(1.2 mL). Aliquat 336 (7 mg) was added as a phase transfer catalyst,
and the reaction vessel was cooled to 0 °C before addition of KMnO4
(75 mg, 0.48 mmol). The ice bath was removed, and the reaction
proceeded 24 h at room temperature, at which point all starting material
had been consumed. Sodium sulfite (75 mg) was added to quench the
reaction, which was concentrated to an oil and dissolved in DMF (1
mL). Sodium bicarbonate (10 mg) was added to this solution, followed
by methyl iodide (10 µL). After 40 h, water (1 mL) was added, and
the reaction was partitioned between water (5 mL) and ether (5 mL).
The aqueous layer was extracted with ether (2 × 5 mL), and the
combined organic extracts were washed with brine (1 × 10 mL), dried
over sodium sulfate, filtered, and concentrated to an oil. Purification
by flash chromatography (hexane/EtOAc ) 4:1) afforded the gly-
cosazido ester 10 (3.2 mg, 13.2 µmol) as an oil in 10% yield. Rf )
0.6 (hexane/ethyl acetate ) 2:1); IR (film) 2110, 1748, 1034 cm-1; 1H
NMR (300 MHz, CDCl3) δ 5.92 (d, 1H, J ) 3.4), 4.75 (dd, 1H, J )
4.4, 3.4), 4.57 (d, 1H, J ) 9.6), 3.86 (s, 3H), 3.70 (dd, 1H, J ) 9.6,
4.4), 1.58 (s, 3H), 1.37 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 169.6,
113.8, 104.7, 79.9, 75.9, 63.3, 52.9, 26.5, 26.4; HRMS Calcd for
C9H13N3O5 (M + H)+: 244.0933; found: 244.0934.
δ 7.84-7.88 (m, 2H), 7.37 (d, 2H, J ) 8.0), 5.70-5.84 (m, 1H), 5.07-
5.17 (m, 2H), 4.52 (ddd, 1H, J ) 3.4, 2.5, <1), 4.08 (dd, 1H, J )
12.6, 2.5), 3.91-3.95 (m, 1H), 3.83-3.87 (m, 1H), 3.51 (dd, 1H, J )
12.6, < 1), 3.31 (ddd, 1H, J ) 7.5, 6.9, < 1), 3.12 (d, 1H, J ) 6.9),
2.95 (d, 1H, J ) 7.8), 2.46-2.57 (m, 1H), 2.46 (s, 3H), 2.32-2.41 (m,
1H); FABMS 329 (M + H)+.
Azide 32. The tosylate 31 (415.3 mg, 1.27 mmol) was dissolved in
DMF (10 mL). Sodium azide (530 mg, 8.12 mmol) was added to the
solution, along with a catalytic amount of tetrabutylammonium iodide
(10 mg). The reaction was heated to 110 °C and stirred for 4 days, by
which time conversion of the starting material to product appeared to
be approximately 50%. The suspension was cooled and added to 40
mL of water, which was extracted with ether (2 × 40 mL). The
combined organic extracts were washed with brine (1 × 50 mL), dried
over magnesium sulfate, filtered, and concentrated. The residual oil
was directly acetylated in CH2Cl2 by treatment with acetic anhydride
(1 mL), triethylamine (0.5 mL), and catalytic DMAP (5 mg). After
stirring 24 h at room temperature, sodium bicarbonate (15 mL) was
added. The organic layer was washed with brine (1 × 20 mL), dried
over sodium sulfate, filtered, and concentrated to an oil. Purification
by flash chromatography (hexane/ethyl acetate ) 5:1) afforded 32
(105.5 mg, 0.37 mmol) as an oil in 29% yield from the tosylate (68%
based on unreacted starting material). Rf ) 0.6 (hexane/ethyl acetate
) 3:1); IR (film) 2922, 2852, 2108, 1743, 1375, 1226, 1034 cm-1; 1H
NMR (300 MHz, CDCl3) δ 5.70-5.84 (m, 1H), 5.09-5.15 (m, 2H),
4.70-4.74 (m, 2H), 3.98 (dd, 1H, J ) 3.7, 3.3), 3.87-3.88 (m, 2H),
3.77-3.83 (m, 1H), 2.41-2.51 (m, 1H), 2.19-2.28 (m, 1H), 2.14 (s,
3H), 2.12 (s, 3H); FABMS 284 (M + H)+.
Acid 11. A 1:1 solution (1 mL) of acetonitrile/carbon tetrachloride
was added to a mixture of the C-allyl glycoside 32 (105.5 mg, 0.37
mmol) and sodium periodate (389 mg, 1.80 mmol). Water (0.75 mL)
was added to the suspension, followed by catalytic ruthenium chloride
trihydrate (6 mg). The reaction immediately turned brown, and soon
thereafter the suspension developed a green color. After 15 min,
isopropyl alcohol (1 mL) was added to the flask, and the contents were
filtered through Celite, rinsing with EtOAc. The filtrate was concen-
trated to an oil and purified by flash chromatography (hexane/EtOAc
) 1.1:1, then hexane/EtOAc/AcOH ) 50:50:1) to afford the glycosazido
acid 11 (104.6 mg, 0.35 mmol) as an oil in 93% yield. Rf ) 0.2
(hexane/ethyl acetate/acetic acid ) 50:50:1); IR (film) 3200 (br), 2940,
2112, 1747, 1732, 1714, 1378, 1242, 1092, 1043 cm-1; 1H NMR (300
MHz, CDCl3) δ 4.81 (dd, 1H, J ) 3.9, 2.0), 4.71-4.74 (m, 1H), 4.25-
4.30 (m, 1H), 4.00 (dd, 1H, J ) 3.9, 3.4), 3.90-3.92 (m, 2H), 2.73
(dd, 1H, J ) 16.1, 8.5), 2.54 (dd, 1H, J ) 16.1, 4.7), 2.14 (s, 3H),
2.13 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 175.2, 170.0, 169.9, 70.0,
68.6, 67.4, 65.2, 57.3, 35.4, 21.0, 20.7; HRMS Calcd for C11H15O7N3
(M + H)+: 302.0988; found: 302.0984.
C-Glycosides 33a and 33b. A solution of 1,2,3,4-tetra-O-acetyl-
â-D-xylofuranose (4.34 g, 13.6 mmol) and allyltrimethylsilane (6.5 mL,
4.1 mmol) in acetonitrile (50 mL) at 0 °C was treated with TMSOTf
(2.90 mL, 1.50 mmol). The ice bath was removed, and the solution
was stirred 24 h and then added to cold sodium bicarbonate solution
(150 mL). The aqueous solution was extracted with CH2Cl2 (2 × 100
mL). The combined organic extracts were washed with brine (1 ×
125 mL) and dried over magnesium sulfate. The drying agent was
removed by filtration and the solution was concentrated to an oil.
Purification by flash chromatography (hexane/ethyl acetate ) 5.5:1)
afforded the R anomer 33a (1.36 g, 4.5 mmol), the â anomer 33b (253
mg, 0.8 mmol), and a fraction containing a mixture of the two anomers
(1.988 g, 6.6 mmol) which were separated by additional silica gel
chromatography. The C-glycosylation reaction proceeded in 88%
cumulative yield with a ratio of R to â anomers of approximately 3:1.
(33a) Rf ) 0.5 (hexane/ethyl acetate ) 3:1); IR (film) 2947, 2862,
1754, 1371, 1246, 1223, 1100, 1033 cm-1; 1H NMR (300 MHz, CDCl3)
δ 5.75-5.88 (m, 1H), 4.83-5.20 (m, 5H), 4.11 (dd, 1H, J ) 10.8,
5.5), 3.40-3.46 (m, 1H), 3.25 (dd, 1H, J ) 10.8, 10.4), 2.18-2.27
(m, 2H), 2.03 (s, 3H), 2.03 (s, 3H), 2.02 (s, 3H); HRMS Calcd for
C14H20O7 (M + H)+: 301.1287; found: 301.1292.
C-Glycosides 30a and 30b. A solution of 1,2,3,5-tetra-O-acetyl-
â-D-ribofuranose (2.65 g, 8.3 mmol) and allyltrimethylsilane (4.0 mL,
24.1 mmol) in acetonitrile (25 mL) at 0 °C was treated with TMSOTf
(2.22 g, 10 mmol). The ice bath was removed, and the solution was
stirred for 6 h and then added to cold sodium bicarbonate solution (150
mL). The aqueous solution was extracted with CH2Cl2 (3 × 60 mL).
The combined organic extracts were washed with brine (2 × 100 mL),
dried over magnesium sulfate, filtered, and concentrated. Purification
by flash chromatography (hexane/ethyl acetate ) 3:1) afforded the R
anomer 30a (512 mg, 1.70 mmol) as a colorless oil and the â anomer
30b (1.663 g, 5.54 mmol) as a white solid that was recrystallized from
EtOAc. The reaction proceeded with a cumulative 87% yield and a
ratio of â to R anomers of approximately 3:1. (30b) Rf ) 0.6 (hexane/
ethyl acetate ) 2:1); IR (film) 2978, 1741, 1368, 1260, 1228, 1115
1
cm-1; H NMR (300 MHz, CDCl3) δ 5.70-5.84 (m, 1H), 5.06-5.24
(m, 5H), 4.14 (dd, 1H, J ) 13.3, 1.9), 3.71 (dd, 1H, J )13.3, 1.6),
3.53-3.58 (m, 1H), 2.41-2.51 (m, 1H), 2.18-2.29 (m, 1H), 2.17 (s,
3H), 2.16 (s, 3H), 2.00 (s, 3H); FABMS 301 (M + H)+.
Tosylate 31. A solution of lithium methoxide (50 mg) in methanol
(5 mL) was added to a solution of 30b (979 mg, 3.26 mmol) in methanol
(10 mL). After stirring 3 h, the reaction was neutralized by the addition
of cation exchange resin. Filtration, followed by concentration, afforded
the sugar triol as white crystals (556 mg, 3.19 mmol) in 98% yield. A
portion of the crystals (556 mg, 3.19 mmol) were dissolved in a solution
of tosyl chloride (651 mg, 3.41 mmol) in pyridine (10 mL). After
stirring 48 h at room temperature, the reaction contents were added to
water (20 mL), and the aqueous solution was extracted wtih CH2Cl2
(3 × 10 mL). The combined organic extracts were washed with sodium
bicarbonate (1 × 20 mL), KHSO4 solution (1 × 20 mL), and brine (1
× 20 mL). The organic solution was concentrated and recrystallized
(153 mg) from dichloromethane. The filtrate was concentrated and
purified by flash chromatography (hexane/ethyl acetate ) 2:1) to afford
the tosylate 31 (415.3 mg, 1.27 mmol) as a syrup which crystallized
almost immediately. The combined crystals (568.3 mg, 1.73 mmol)
totaled a 53% yield. Rf ) 0.2 (hexane/ethyl acetate ) 1.5:1); IR (film)
3474, 1359, 1190, 1176, 1096, 855 cm-1; 1H NMR (300 MHz, CDCl3)
Isopropylidene 34. A solution of 33a (171 mg, 0.57 mmol) in
methanol (2 mL) was added to a solution of LiOMe (10 mg, 0.27 mmol)
in methanol (1 mL). The solution was stirred 30 min at room
temperature. Cation exchange resin was added to neutralize the

Glycosamino Acids
J. Am. Chem. Soc., Vol. 118, No. 16, 1996 3827
solution, which was filtered and concentrated. The residual oil was
dissolved in dimethoxypropane (3 mL), to which was added catalytic
PPTSA (3 mg). After stirring 24 h at 50 °C, the solution was
concentrated and then treated with a solution of LiOMe (10 mg) in
methanol (5 mL). After stirring 5 min, the solution was filtered through
cation exchange resin and concentrated to an oil. Purification by flash
chromatography afforded the acetonide 34 (88.7 mg, 0.41 mmol) as
an oil in 73% yield. Rf ) 0.5 (hexane/ethyl acetate ) 1.1:1); IR (film)
General Procedure for Ester Saponification. A 0.5 M solution
of sodium hydroxide (250 µL per 100 mmol of ester) was added to a
solution of the glycosazido ester in methanol (approximately 400 µL
per 100 mmol of ester). The reaction was followed by TLC, and, upon
completion, cation exchange resin was added to neutralize the solution.
After filtration, the filtrate was concentrated and used without further
purification.
Diglycotide 36. The glycosazido ester 3 was hydrogenated accord-
ing to the general procedure to furnish the amine 3n, while the
â-glycoside 4 was saponified according to the general procedure to
give 4c. A solution of the amine 3n (33.8 mg, 0.09 mmol) in
dichloromethane (0.5 mL) was added to a mixture of 4c (36.0 mg,
0.10 mmol), TEA (41 µL, 0.30 mmol), and EDCI (24 mg, 0.12 mmol)
in dichloromethane (1.0 mL). After stirring for 24 h, the solution was
concentrated, taken up in chloroform (5 mL), and extracted with water
(1 × 5 mL) and brine (1 × 3 mL). After drying over sodium sulfate,
the drying agent was removed by filtration, and the solution was
concentrated to an oil. Purification by flash chromatography (EtOAc/
hexane ) 1.8:1) afforded the diglycotide 36 (19.8 mg, 0.03 mmol) as
a clear oil in 28% yield. Rf ) 0.75 (dichloromethane/acetone ) 3:1);
1
3448 (br), 2985, 2877, 1230, 1085, 1046 cm-1; H NMR (300 MHz,
CDCl3) δ 5.80-5.94 (m, 1H), 5.08-5.18 (m, 2H), 3.92-4.07 (m, 2H),
3.41-3.56 (m, 2H), 3.09-3.16 (m, 2H), 2.48-2.56 (m, 1H), 2.32 (d,
1H, J ) 3.9), 2.22-2.32 (m, 1H), 1.42 (s, 3H), 1.41 (s, 3H); HRMS
Calcd for C11H18O4 (M + H)+: 215.1283; found: 215.1285.
Azide 35. Pyridine (74 µL, 0.91 mmol) was added to a solution of
the alcohol 34 (88.7 mg, 0.41 mmol) in CH2Cl2 (2 mL). The solution
was cooled to -30 °C and then treated with (Tf)2O (97.4 µL, 0.58
mmol). The reaction was allowed to proceed at 0 °C for 1 h. Cold
water (3 mL) was added, the layers were separated, and the aqueous
layer was further extracted with CH2Cl2 (1 × 3 mL). The combined
organic extracts were washed with water (1 × 4 mL), cold 3 M HCl
(1 × 4 mL), and brine (1 × 4 mL), then dried over sodium sulfate,
filtered, and concentrated to a yellow oil. Without further purification,
the crude triflate was dissolved in DMF (3 mL) and treated with NaN3
(160 mg, 2.5 mmol). The resulting suspension was stirred 4 h at room
temperature. Water (5 mL) was added, and the aqueous solution was
extracted with ether (2 × 5 mL). The ether extracts were washed with
brine (1 × 10 mL), dried over sodium sulfate, filtered, and concentrated
to a yellow oil. Purification by flash chromatography (hexane, then
hexane/EtOAc ) 8:1) afforded the azide 35 (53.6 mg, 0.22 mmol) as
a pale yellow oil in 54% yield which crystallized upon standing. Rf )
0.8 (hexane/ethyl acetate ) 3:1); IR (film) 2986, 2906, 2103, 1229,
1159, 1103, 1087 cm-1; 1H NMR (300 MHz, CDCl3) δ 5.81-5.96 (m,
1H), 5.09-5.19 (m, 2H), 4.14-4.16 (m, 1H), 3.98 (dd, 1H, J ) 12.9,
1.6), 3.52-3.60 (m, 2H), 3.45-3.53 (m, 2H), 2.49-2.58 (m, 1H),
2.39-2.49 (m, 1H), 1.48 (s, 3H), 1.45 (s, 3H); FABMS Calcd for
C11H17N3O3 (M + H)+: 240.1348; found: 240.1346.
1
IR (film) 3389, 2937, 2109, 1735, 1674, 1538, 1354, 1176 cm-1; H
NMR (300 MHz, CDCl3) δ 6.42 (dd, 1H, J ) 6.3, 5.9), 4.92-4.98 (m,
2H), 4.76-4.81 (m, 3H), 4.66 (dd, 1H, J ) 6.0, 1.0), 4.49 (dd, 1H, J )
7.4, 7.1), 3.87-4.07 (m, 4H), 3.81 (dd, 1H, J ) 7.4, 3.0), 3.71 (s, 3H),
3.62 (dd, 1H, J ) 13.8, 5.0), 3.39-3.48 (m, 1H), 3.12 (s, 3H), 3.12 (s,
3H), 2.67 (d, 2H, J ) 6.7), 2.52 (d, 2H, J ) 7.3), 1.51 (s, 3H), 1.48 (s,
3H), 1.33 (s, 3H), 1.32 (s, 3H); HRMS Calcd for C25H40N4O15S2 (M +
H)+: 701.2010; found: 701.2004.
Triglycotide 16. The diglycotide 36 was hydrogenated according
to the general procedure to afford amine 36n. A solution of 36n (8.0
mg, 12 µmol) in dichloromethane (0.5 mL) was added to a mixture of
the glycosazido acid 11 (9.0 mg, 30 µmol), TEA (10 mg, 100 µmol),
and EDCI (4.5 mg, 23 µmol) in dichloromethane (1 mL). After stirring
for 24 h, the solution was concentrated, taken up in chloroform (3 mL),
and extracted with water (1 × 3 mL) and brine (1 × 3 mL). The
organic extracts were dried over sodium sulfate, then filtered, and
concentrated to an oil. Purification by flash chromatography (dichlo-
romethane/acetone ) 3.8:1) afforded the triglycotide 16 (5.0 mg, 5.2
µmol) as a clear oil in 44% yield. Rf ) 0.2 (dichloromethane/acetone
) 3:1); IR (film) 3378, 2934, 2109, 1738, 1682, 1651, 1538, 1353,
Ester 12. Water (0.5 mL) and acetic acid (100 µL) were added to
a solution of the C-allyl glycoside 35 (18.0 mg, 75 µmol) in CH2Cl2
(0.5 mL). Aliquat 336 (2 mg) was added as a phase transfer catalyst,
and the reaction vessel was cooled to 0 °C before addition of KMnO4
(25 mg). The reaction proceeded 24 h at room temperature. Sodium
sulfite (25 mg) was added to quench the reaction, which was then
partitioned between CH2Cl2 (3 mL) and water (2.5 mL). The aqueous
layer was extracted with CH2Cl2 (3 mL), and the combined organic
extracts were washed with brine (1 × 5 mL) and dried over sodium
sulfate. Filtration, followed by concentration, gave an oil that could
not be purified to homogeneity by flash chromatography and instead
was esterified directly. The oil was dissolved in DMF (1 mL). Sodium
bicarbonate (20 mg) was added to the solution, followed by methyl
iodide (20 µL). The reaction was stirred 24 h at room temperature
and then concentrated to an oil. Water (2 mL) was added, and the
aqueous solution was extracted with ether (2 × 2.5 mL). The ether
extracts were washed with brine (1 × 3 mL), dried over sodium sulfate,
filtered, and concentrated. Purification by flash chromatography
(hexane/EtOAc ) 4:1) gave the glycosazido ester 12 (8.3 mg, 31 µmol)
in 41% yield. Rf ) 0.6 (hexane/ethyl acetate ) 1:1); IR (film) 2986,
1
1227, 1175, 1078 cm-1; H NMR (300 MHz, CDCl3) δ 6.81 (dd, 1H,
J ) 6.4, 5.6), 6.45 (dd, 1H, J ) 6.1, 5.7), 4.93-5.04 (m, 3H), 4.67-
4.79 (m, 6H), 4.49 (dd, 1H, J ) 7.5, 6.6), 4.27-4.32 (m, 1H), 3.86-
4.12 (m, 6H), 3.71 (s, 3H), 3.60-3.70 (m, 2H), 3.33-3.42 (m, 1H),
3.12 (s, 3H), 3.11 (s, 3H), 2.47-2.77 (m, 5H), 2.36 (dd, 1H, J ) 15.4,
4.0), 2.14 (s, 3H), 2.12 (s, 3H), 1.51 (s, 3H), 1.48 (s, 3H), 1.32 (s, 3H),
1.31 (s, 3H); HRMS Calcd for C36H55N5O21S2 (M + H)+: 958.2909;
found: 958.2914.
Diglycotide 17. The glycosazido ester 12 (3.0 mg, 11 µmol) was
hydrogenated according to the general procedure to furnish the
secondary amine 12n. Without further purification, a solution of 12n
in dichloromethane (0.5 mL) was added to a mixture of excess 4c (6.0
mg, 16 µmol), TEA (10 µL, 70 µmol), and EDCI (3.9 mg, 21 µmol)
in dichloromethane (0.5 mL). After stirring for 48 h, the solution was
concentrated, taken up in chloroform (3 mL), and extracted with water
(1 × 3 mL) and brine (1 × 3 mL). The organic extracts were dried
over sodium sulfate, then filtered, and concentrated to an oil. Purifica-
tion by flash chromatography (EtOAc/hexane ) 2.2:1) afforded the
diglycotide 17 (4.4 mg, 7.4 µmol) as a clear oil in 67% yield from the
glycosazido ester. Rf ) 0.75 (dichloromethane/acetone ) 3:1); IR (film)
3388 (br), 2990, 2931, 2109, 1738, 1682, 1651, 1538, 1360, 1231, 1176,
1100 cm-1; 1H NMR (300 MHz, CDCl3) δ 6.11 (d, 1H, J ) 7.8), 4.93-
4.98 (m, 1H), 4.75-4.79 (m, 2H), 4.55-4.60 (m, 1H), 3.87-4.04 (m,
4H), 3.84 (dd, 1H, J ) 7.6, 3.0), 3.72 (s, 3H), 3.54-3.68 (m, 3H),
3.29 (dd, 1H, J ) 9.4, 9.4), 3.13 (s, 3H), 2.78 (dd, 1H, J ) 15.6, 2.8),
2.65 (d, 2H, J ) 6.8), 2.54 (d, 2H, J ) 15.6, 9.4), 1.51 (s, 3H), 1.43
(s, 3H), 1.43 (s, 3H), 1.33 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 170.7,
169.8, 113.0, 110.4, 81.0, 80.0, 78.9, 78.7, 77.9, 77.2, 76.9, 74.1, 69.6,
52.2, 52.0, 48.6, 38.5, 37.9, 36.1, 26.6, 26.5, 25.9, 24.9; HRMS Calcd
for C23H36N4O12S (M + H)+: 593.2129; found: 593.2113.
1
2901, 2105, 1740, 1229, 1102 cm-1; H NMR (300 MHz, CDCl3) δ
4.16-4.18 (m, 1H), 3.91-3.98 (m, 2H), 3.71 (s, 3H), 3.63-3.70 (m,
2H), 3.57 (dd, 1H, J ) 12.8, 1.8), 2.77 (dd, 1H, J ) 16.0, 2.8), 2.58
(dd, 1H, J ) 16.0, 9.4), 1.49 (s, 3H), 1.45 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 170.9, 110.8, 79.4, 76.8, 73.5, 68.2, 58.9, 51.9, 37.7, 26.6,
26.3; HRMS Calcd for C11H17N3O5 (M + H)+: 272.1246; found:
272.1241.
General Procedure for Hydrogenation of Azides. Ethyl acetate
(approximately 0.5 mL + 1 mL per 100 mg azide) was added to a
flask containing 10% palladium on activated carbon. The flask was
evacuated and flushed with hydrogen several times. A solution of the
azide (2-10 mg of azide per milligram of catalyst) was added to the
flask, which was again flushed several times with hydrogen and stirred
4-24 h under a hydrogen atmosphere. The suspension was then filtered
through Celite and rinsed with ethyl acetate, and the filtrate was
concentrated in Vacuo and used without further purification.
Template-Anchored Triglycotide 37. Glycosazido ester 2 (28.1 mg,
0.093 mmol) was hydrogenated by the general procedure, and the

3828 J. Am. Chem. Soc., Vol. 118, No. 16, 1996
McDeVitt and Lansbury
resultant amine was dissolved in dichloromethane (1 mL) and tri-
ethylamine (30 µL) and added to 1,3,5-benzenetricarbonyl trichloride.
After 10 min at 25 °C, the solution was concentrated to an oil and
dissolved in chloroform. The organic phase was washed with aqueous
KHSO4 and brine, dried over sodium sulfate, and concentrated to a
crude oil. Further purification was not pursued since this was a model
for library synthesis. IR (film): 3384 (br), 2940, 1739, 1662, 1540,
analyzed by FABMS (all (M + H)+): 983 (Template(5)3), 1061
(T(4)(5)2), 1075 (T(8)(5)2), 1139 (T(4)2(5)), 1154 (T(4)(5)(8)), 1167
(T(8)2(5)), 1217 (T(4)3), 1231 (T(4)2(8)), 1246 (T(4)(8)2). A peak at
1260 (T(8)3) was not detected.
Acknowledgment. This work was supported by grants from
the National Institutes of Health (R29-HL42416) and the
National Science Foundation (Presidential Young Investigator
Award). P.L. is the Firmenich Associate Professor of Chem-
istry.
1
1438, 1207, 1089 cm-1; H NMR (300 MHz, CDCl3) δ 8.14 (s, 3H),
7.68 (br t, 3H, J ) 5.9), 4.88 (dd, 3H, J ) 5.6, 3.2), 4.76 (dd, 3H, J
) 5.6, 4.2), 4.2 (m, 6H), 4.0 (m, 3H), 3.85 (m, 3H), 3.70 (s, 9H), 3.56
(m, 6H), 2.8 (m, 6H), 1.49 (s, 9H), 1.32 (s, 9H); HRMS Calcd for
C45H63N3O21 (M + H)+: 982.4032, found: 982.4035.
Synthesis of a Template-Directed Library. A mixture of gly-
cosazido esters 5 (2.7 mg, 9.0 µmol), 4 (4.2 mg, 11.1 µmol), and 8
(2.0 mg, 5.1 µmol) was hydrogenated in accordance with the general
procedure for 30 min. The products of hydrogenation were dissolved
in dichloromethane (1.5 mL) and added to a mixture of triethylamine
(10 µL, 72 µmol) and 1,3,5-benzenetricarbonyl trichloride (0.5 mg,
2.6 µmol). After 10 min, the solution was concentrated to an oil and
taken up in chloroform (1 mL). The chloroform solution was washed
with KHSO4 (2 × 1 mL) and brine (1 × 1 mL), dried over sodium
sulfate, filtered, and concentrated to an oil. The crude mixture was
Supporting Information Available: 1H NMR spectra for
the compounds in Figures 1 and 2 and Scheme 1 (17 pages).
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