Synthetic studies on the carbohydrate moiety of amipurimycin

Article abstract of DOI:10.1080/07328300802030787

The carbohydrate core of amipurimycin in its fully acetylated form was synthesized in 24 steps starting from commercially available methyl 4,6-O-benzylidene-α-D-glucopyranoside to give an overall yield of 1.5%. The late-stage intermediates involved were suitable for total synthesis of amipurimycin. It was further discovered that the branches and the protecting groups on the sugar rings of involved intermediates had a significant influence on their conformations, which in turn resulted in new and interesting cyclization reactions. Copyright Taylor & Francis Group, LLC.

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Synthetic Studies on the Carbohydrate Moiety
of Amipurimycin
Jie Xue a & Zhongwu Guo a
a Department of Chemistry , Wayne State University , Detroit, MI, USA
Published online: 28 May 2008.
To cite this article: Jie Xue & Zhongwu Guo (2008) Synthetic Studies on the Carbohydrate Moiety of
Amipurimycin, Journal of Carbohydrate Chemistry, 27:2, 51-69, DOI: 10.1080/07328300802030787
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Journal of Carbohydrate Chemistry, 27:51–69, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0732-8303 print 1532-2327 online
DOI: 10.1080/07328300802030787
Synthetic Studies
on the Carbohydrate Moiety
of Amipurimycin
Jie Xue and Zhongwu Guo
Department of Chemistry, Wayne State University, Detroit, MI, USA
The carbohydrate core of amipurimycin in its fully acetylated form was synthesized in
24 steps starting from commercially available methyl 4,6-O-benzylidene-a-D-glucopyra-
noside to give an overall yield of 1.5%. The late-stage intermediates involved were
suitable for total synthesis of amipurimycin. It was further discovered that the
branches and the protecting groups on the sugar rings of involved intermediates had
a significant influence on their conformations, which in turn resulted in new and inter-
esting cyclization reactions.
Keywords Amipurimycin, Antibiotics, Nucleoside, Carbohydrate, Conformation
INTRODUCTION
Amipurimycin is a nucleoside antibiotic isolated from Streptomyces novogui-
neensis by Iwasa et al.[1,2] in 1977, that was shown to be particularly active
toward Pyricularia oryzae. Several years later, Goto et al.[3] proposed its
primary structure. Amipurimycin has a unique carbohydrate core (i.e., an
a-amino glycuronic acid having a two-carbon branch on C-3) and has the
nucleic base b-linked to its anomeric center. Amipurimycin also contains a
b-amino acid attached to the carbohydrate amino group. However, the stereo-
chemistry of carbohydrate C-6 has not been determined. Amipurimycin is
representative of a unique class of natural nucleosides, thus its carbohydrate
core has drawn significant attention, as demonstrated by a number of
reports on its synthesis.[4–10] Garner and coworkers[4–6] prepared the carbo-
hydrate core of amipurimycin based on cyclocondensation of penaldic acid
and an electron-rich diene. Others used readily accessible carbohydrates as
the synthetic precursors, which could make use of the carbohydrate skeleton
Received August 1, 2007; accepted November 19, 2007.
Address correspondence to Zhongwu Guo, Department of Chemistry, Wayne State
University, 5101 Cass Avenue, Detroit, MI 48202, USA. E-mail: zwguo@chem.wayne.edu
51

J. Xue and Z. Guo
52
and chirality.[7–10] However, only Garner and coworkers[6] obtained the intact
carbohydrate moiety of amipurimycin, and others were focused on partial or
model structures.
Herein, we report a synthesis of the fully acetylated carbohydrate moiety 1
of amipurimycin with a commercially available and inexpensive derivative of
D-glucose as the starting material. In this synthesis, we have observed the
critical influence of side chains and protecting groups on the ring conformation
of carbohydrates and novel reactions that were determined by the ring confor-
mation. The results should be generally useful for the synthesis of branched
sugars.
RESULTS AND DISCUSSION
The synthesis started from commercially available D-glucose derivative 2
(Sch. 1). Unbiased monobenzylation of 2 led to compound 3[11] and its regio-
isomer with little discrimination, but the two products were easily separable.
Acetylation of 3 was followed by removal of the benzylidene group under mild
acidic conditions and then selective protection of the 6-OH by a trityl group to
afford 5 in an excellent overall yield (95%). To deoxygenate the 4-position, 5
was first converted to the corresponding triflate and then treated with
NaBH4.[12] The product was then deacetylated to give 6 (74%, last three steps).
Oxidation of 6 using PCC gave ketone 7, to which the two-carbon branch
was introduced to C-3 through reaction with [(ethoxycarbonyl)methylene]triphe-
nylphosphorane (Sch. 2). This Wittig reaction turned out to be extremely slow but
highly stereoselective to afford only the (E)-isomer 8, which was isolated in a 99%
yield. The (E)-configuration of 8 was characterized by means of 1H NMR. Similar
Scheme 1: Reagents and conditions. (a) BnBr, NaOH, n-Bu4NI, rt, overnight, 54%; (b) Ac2O,
DMAP, pyridine, rt, 95%; (c) HOAc, H2O, 808C, 2 h; (d) TrCl, pyridine, 408C, 36 h, 100%; (e) Tf2O,
pyridine, 08C, 1 h; (f) NaBH4, DMF, rt, 2 h; (g) NaOH, MeOH, H2O, rt, 2 h, 74% three steps).

Carbohydrate Moiety of Amipurimycin
53
˚
Scheme 2: Reagents and conditions. (a) PCC, MS 4A, DCM, rt, 3 h, 84%; (b) Ph3P55CHCO2Et,
CHCl3, reflux, 3 d, 99%; (c) OsO4, NMO, Acetone, THF, water, rt, overnight, 98%; (d) BnBr, NaH,
DMF, rt, 1 h, 100%; (e) LiAlH4, THF, rt, 4 h; (f) BnBr, NaH, DMF, rt, 2 h; (g) HCOOH, Et2O, rt, 1 h, 93%;
.
;;
(h) SO3 Pyr, Et3N, DMSO, DCM, 08C, 45 min; (i) HC CMgBr, THF, 40% each.
1
to what was reported by Rauter et al.[8] the H NMR signal of the equatorial
proton on C-4 shifted downfield to d 3.91 due to strong deshielding effect of the
adjacent ethoxycarbonyl group, while the axial proton on C-4 was at d 1.97.
The preferred formation of the (E)-isomer was probably due to the presence of
a rather bulky benzyl group at the 2-O-position which was likely to point away
from the methoxyl group on C-1. Treatment of 8 with 4-methylmorpholine
N-oxide and osmium tetraoxide, gave the cis-dihydroxylation product 9 stereo-
specifically in a 98% yield. While the cis selectivity was determined by the mech-
anisms of the oxidation reaction, the facial selectivity was possibly due to steric
effect, as the bottom side of the C55C bond might be shielded by the adjacent
benzyl and the anomeric methoxyl groups, which forces the oxidizing reagent
to approach C55C bond from the top only. Thereafter, 9 was benzylated to
afford 10. We noticed that the coupling constants between H-5 and H-4/40 in
10 were substantially different from that of 8, 9, and other compounds that
have the conventional 4C1 conformation. For example, J4a,5 and J4e,5 for 9 were
12.4 and 2.0 Hz, respectively, but they were 4.8 and 6.4 Hz for 10. Based on
these results, we suggested that 10 might adopt the C1 conformation or that
4
the 4C1 and 4C1 conformers were in rapid equilibrium. Other subsequent inter-
mediates also adopted C1 conformation, which might account for many new
4
and interesting reactions observed in this research.
The carboxyl group in 10 was reduced to alcohol by lithium aluminum
hydride smoothly, which was followed by benzylation of the product using
benzyl bromide and removal of the trityl group under mild acidic conditions
to yield 11 (93%). Swern oxidation of 11 gave aldehyde 12, which was treated
with an excess of ethynylmagnesium bromide at 08C to afford 13 and 14 in a
nearly 1:1 ratio. The stereochemistry of 13 and 14 was assigned later on.
The efforts to directly azidonate C-6 of 13 and 14 via activation of 6-OH and
azido substitution were unsuccessful, because the reactions always led to

J. Xue and Z. Guo
54
Scheme 3: Reagents and conditions. (a) Tf2O, pyridine, rt, 100%; (b) Ts2O, pyridine, rt, 100%,
(c) NaN3, DMF, 808C; (d) H2SO4, Ac2O, AcOH, 08C; (e) BCl3, Ac2O, THF, 2508C.
intramolecular substitution (Sch. 3). Treating 13 and 14 with triflic anhydride
gave 15 and 16 quantitatively and stereospecifically, instead of the desired tri-
flates, even at low temperature. We believe that triflates were formed, but they
were prone to intramolecular substitution with simultaneous 3-O-debenzyla-
tion to give 15 and 16. Trying to overcome this problem, we transformed 14
into tosylate 17, in which the C-6 should be less electrophilic. The tosylation
reaction indeed gave isolable 17; however, treatment of 17 with sodium azide
in DMF still produced 16 as the major product. We believe that the 4C1 confor-
mation of 13 and 14 made O-3 perfectly situated to attack C-6 to facilitate
intramolecular substitution. Consequently, intermolecular substitution reac-
tions would not happen. These results were disappointing for the target syn-
thesis, but the reactions were new and interesting. Moreover, because the
products 15 and 16 had rigid structures, they were useful for assignments of
the sterochemistry of 13 and 14. For example, strong NOEs between H-6 and
H-1 in 15 and strong NOEs between H-6 and H-4 in 16 all supported the
assigned structures of 13 and 14. Considering that benzyl group, which can
depart as a stabilized cation, might have enabled the intramolecular
reaction, we then attempted to substitute all benzyl groups in 17 with acetyl
groups. For acetolysis of benzyl ethers, 17 was treated with BCl3 or sulfuric
acid in acetic acid and acetic anhydride, but neither of these conditions
would afford the desired products. Instead, cyclization products 18, 19, and
20, which were also derived from an intramolecular reaction, were obtained.
After these frustrations, we decided to attempt a procedure involving oxi-
dation of the triple bond first and then replacement of benzyl groups with
acetyl groups in two steps including catalytic hydrogenolysis and acetylation
(Sch. 4). Oxidation of 14 by NaIO4 using osmium tetraoxide as the catalyst

Carbohydrate Moiety of Amipurimycin
55
Scheme 4: Reagents and conditions. (a) OsO4, NaIO4, THF, H2O, 408C, overnight; (b) CH2N,
CH2Cl2, rt, 66% two steps); (c) TsCl, pyr., CH2Cl2, 08C to rt, quant.; (d) 10% Pd/C, H2, THF, 1 d; (e)
Ac2O, pyr. (1:3), rt, overnight, 89% two steps); (f) H2SO4, AcOH, Ac2O, EtOAc, 08C, overnight,
60%; (g) NaN3, DMF, 308C, 1 d, 51%.
and methylation of the resultant carboxylic group afforded a moderate yield
(66%) of 21. Subsequent tosylation of 21 gave 22 quantitatively. Hydrogenoly-
sis to remove the benzyl groups in 22 and peracetylation of the product went
smoothly to give 23, in which the 3-OH could not be acetylated even after pro-
longed reaction, probably because of the severe steric hindrance at this
position. When 23 reacted with sodium azide in DMF, an inseparable
mixture was obtained, and it seemed that the 3-OH was involved. To avoid
this problem, we subjected 23 to acetylation using acetic anhydride and a
catalytic amount of sulfuric acid. The reaction indeed gave a 3-O-acetyl
product with acetolysis of the anomeric center, but this product was identified
as 24 with inverted stereochemistry at C-3, which was probably derived from
an acid-catalyzed and thermodynamically controlled SN1 reaction.
Compound 24 was then used as a model to study the reaction conditions for
C-6 azidonation. We found that the reaction of 24 with sodium azide in DMF
at 308C afforded an acceptable yield (51%) of 25.
Next, we examined the 3-O-acetylation and anomeric acetolysis of 23 with
Lewis acid SnCl4 as catalyst (Sch. 5). This reaction turned out to be rather
complex, but the desired compound 26 (28%) and a side product 27 (11%)
were isolated as the major products. It should be possible to optimize this
Scheme 5: Reagents and conditions. (a) SnCl4, Ac2O, CH2Cl2, 08C to rt, overnight, 11% and
28%, respectively; (b) NaN3, DMF, 308C, 1 d, 85%; (c) 10% Pd/C, H2, THF, MeOH, overnight; (d)
Ac2O, pyr., rt, overnight, 92% (two steps).

J. Xue and Z. Guo
56
reaction by carefully monitoring the reaction progress and promptly quenching
the reaction. For subsequent azidonation of 26, the reaction conditions estab-
lished in the preparation of 25 were utilized to offer a good yield (85%) of 28.
It was assumed that the azidonation reaction under basic condition would
follow an SN2 mechanism with configurational inversion of C-6. It is worth
noting that the azidonation product 28 resumed conventional 4C1 confor-
mation, supported by its J4a,5 and J4e,5 values of 12.4 and 2.4 Hz, respectively.
Compound 28 with an azido group as a latent amino group can be very useful
for total synthesis of amipurimycin. For instance, 28 may be directly glycosi-
dated to introduce the nucleic base, which would be followed by reduction of
the azido group and regioselective N-acylation to introduce the b-amino acid
to eventually afford amipurimycin. In this research, 28 was subjected to hydro-
genation and then N-acetylation to give 1, the peracetylated carbohydrate
moiety of amipurimycin. In conclusion, 1 was synthesized from commercially
available 2 in 24 steps and in an overall yield of 1.5%.
EXPERIMENTAL
NMR spectra were recorded on a 200-, 300-, 400- or 600-MHz machine.
Chemical shifts of protons are reported in ppm (d) downfield from tetramethyl-
silane (TMS) if not specified otherwise, and chemical shifts of carbons are
reported in ppm (d) in reference to the solvent peak of CDCl3 (d 77.16).
Coupling constants (J) are reported in hertz (Hz). Thin layer chromatography
(TLC) was performed on silica gel GF254 plates detected by charring with phos-
phomolibdic acid/EtOH or 5% H2SO4/EtOH solutions. Molecular sieves were
dried under high vacuum at 170 to 1808C for 6 to 10 h before use. Commercial
anhydrous solvents and other reagents were used without further purification.
Methyl 2-O-Benzyl-4,6-O-benzylidene-a-D-glucopyranoside
(3)[11]
A mixture of 2 (25 g, 88.6 mmol), n-Bu4NI (7.4 g, 20 mmol), and benzyl
bromide (13 mL, 109 mmol) in CH2Cl2 (600 mL) and aq. NaOH solution
(0.68 M, 200 mL) was stirred at rt for 24 h. The organic phase was separated
and washed once with water and dried over Na2SO4. The solvent was
removed under reduced pressure to give the crude product, which was
purified by silica gel column chromatography to yield 3 as a major product
1
17.9 g (48 mmol, 54%). H NMR (CDCl3, 200 MHz): 7.32–7.54 (m, 10H), 5.53
(s, 1H), 4.80 (d, J ¼ 12.2 Hz, 1H), 4.71 (d, J ¼ 12.2 Hz, 1H), 4.62 (d, J ¼ 3.6 Hz
1H), 4.28 (dd, J ¼ 9.2, 4.0 Hz, lH), 4.17 (t, J ¼ 9.2 Hz, 1H), 3.81 (m, 1H), 3.71
(t, J ¼ 9.6 Hz, 1H), 3.50 (m, 2H), 3.39 (s, 3H).

Carbohydrate Moiety of Amipurimycin
57
Methyl 3-O-Acetyl-2-O-benzyl-4,6-O-benzylidene-a-D-
glucopyranoside (4)[13]
The mixture of 3 (17.9 g, 48 mmol), acetic anhydride (100 mmol), and
dimethylaminopyridine (61 mg, 0.5 mmol) in pyridine (150 mL) was stirred
at rt overnight. The reaction was quenched with water and the mixture was
extracted with CH2Cl2. After washing with water and saturated NaHCO3
solution, the organic phase was dried over Na2SO4 and then condensed in
vacuum. The residue was subjected to column chromatography to give 4
1
(19 g, 45.8 mmol, 95%) as a white solid. H NMR (CDCl3, 200 MHz): 7.32–
7.48 (m, 10H), 5.57 (t, J ¼ 9.6 Hz, 1H), 5.46 (s, 1H), 4.70 (d, J ¼ 3.6 Hz, 1H),
4.66 (s, 2H), 4.2 (dd, J ¼ 9.9, 4.6 Hz, 1H), 3.90 (td, J ¼ 9.9, 4.6 Hz, 1H), 4.73
(d, J ¼ 9.9 Hz, 1H), 3.58 (m, 2H), 3.41 (s, 3H), 2.05 (s, 3H).
Methyl 3-O-Acetyl-2-O-benzyl-6-O-trityl-a-D-glucopyranoside (5)
Compound 4 (19 g, 45.8 mmol) was dissolved in a mixture of HOAc and
H2O (150 mL, 1:1), The solution was stirred at 808C for 2 h and then concen-
trated to dryness. The resulting residue was dissolved in 150 mL of pyridine.
To this solution was added trityl chloride (15.3 g, 55 mmol) at rt and the
mixture was stirred at 408C for 36 h, when TLC indicated the completion of
reaction. After the mixture was concentrated, to the mixture was added
CH2Cl2, and the solution was washed with water, dried over Na2SO4, and
then concentrated. The resulting syrup was purified with a silica gel column
1
to afford 5 (26 g, 100%). [a]¼þ42 (1.0, CHCl3); H NMR (CDCl3, 200 MHz):
7.20–7.50 (m, 20H), 5.25 (t, J ¼ 9.5 Hz, 1H, H-3), 4.71 (d, J ¼ 3.5 Hz, 1H,
H-1), 4.66 (s, 2H, H-Bn), 3.72 (m, 1H, H-5), 3.48–3.58 (m, 2H), 3.42 (s, 3H,
OMe), 3.33–3.38 (m, 2H), 2.08 (s, 3H, Ac); HR FAB MS (m/z): calc. for
C35H36NaO7(M þ Naþ) 591.2359, found 591.2354.
Methyl 2-O-Benzyl-4-deoxy-6-O-trityl-a-D-xylo-
hexopyrnaoside (6)
To the solution of 5 (2.4 g, 4.22 mmol) in CH2Cl2 (30 mL) and pyridine
(1 mL) at 2108C was added triflic anhydride (1.0 mL, 5.9 mmol). The
mixture was allowed to warm n-Bu4NI to rt gradually and then stirred for
1 h. The mixture was subsequently washed with diluted HCl solution, aq.
NaHCO3 solution and water, dried over Na2SO4, and concentrated to give
the crude product as syrup. After this crude product was dissolved in 20 mL
of anhydrous DMF, NaBH4 (1.6 g, 42.2 mmol) was added at rt. The reaction
mixture was stirred at rt for 2 h and then diluted with CH2Cl2. The organic
layer was washed with water, dried over Na2SO4, and concentrated. The
residue was dissolved in a mixture of MeOH and H2O, and to this solution
was added NaOH. After the solution was stirred at rt for 2 h, the reaction

J. Xue and Z. Guo
58
mixture was concentrated and diluted with CH2Cl2. The organic phase was
washed with water, dried over Na2SO4, and concentrated. The resulting
syrup was subjected to silica gel column chromatography to afford 6 (1.6 g,
74%) 6: [a] ¼ þ48.6 (1.0, CHCl3); 1H NMR (CDC13, 400 MHz): 7.20–7.45
(m, 20H), 4.73 (d, J ¼ 3.6 Hz, 1H, H-1), 4.69 (d, J ¼ 12.0 Hz, 1H, H-Bn),
4.64 (d, J ¼ 12.0 Hz, 1H, H-Bn), 4.04 (m, 1H, H-3), 3.90 (m, 1H, H-5), 3.38
(s, 3H, OMe), 3.30 (dd, J ¼ 9.6, 3.6 Hz, 1H, H-2), 3.21 (dd, J ¼ 9.6, 6.0 Hz,
1H, H-6), 3.03 (dd, J ¼ 9.6, 4.8 Hz, 1H), 2.35 (d, J ¼ 2.0 Hz, 1H, OH), 2.04
(ddd, J ¼ 12.4, 5.2, 2.4 Hz, 1H, H-4e), 1.43 (q, J ¼ 12.0 Hz, lH, H-4a); 13C
NMR (CDCl3, 100 MHz): 144.2, 138.2, 128.9, 128.8, 128.3, 128.0, 127.2, 98.0,
86.7, 82.1, 72.8, 67.1, 66.4, 55.2, 35.4; HR FAB MS (m/z): calc. for
C33H34NaO5 (M þ Naþ) 533.2304, found 533.2307.
Methyl 2-O-BenzyI-4-deoxy-6-O-trityl-a-D-erythro-
hexopyranoside-3-ulose (7)
To a mixture of 6 (1.6 g, 3.14 mmol) and molecular sieves 4A (3.0 g) in dry
˚
DCM (20 mL) was slowly added PCC (1.7 g, 7.85 mmol). After stirring at rt for
3 h, the reaction mixture was diluted with CH2Cl2, washed with water, dried
over Na2SO4, and then concentrated. Column chromatography of the
1
residue afforded 7 (1.35 g, 84%). [a] ¼ 222.6 (1.0, CHCl3); H NMR (CDCl3,
400 MHz): 7.20–7.45 (m, 20H), 5.03 (d, J ¼ 4.0 Hz, 1H, H-1), 4.93
(d, J ¼ 12.4 Hz, 1H, H-Bn) 4.54 (d, J ¼ 12.4 Hz, 1H, H-Bn), 4.12 (m, 1H,
H-5), 4.04 (d, J ¼ 4.0 Hz, 1H, H-2), 3.40 (s, 3H OMe), 3.24 (dd. J ¼ 10.0,
6.0 Hz, 1H, H-6), 3.14 (dd, J ¼ 10.0, 4.4 Hz, 1H, H-6), 2.43 (d, J ¼ 6.4 Hz,
2 H, H-4); 13C NMR (CDCl3, 100 MHz); 202.9, 143.9, 137.6, 128.9, 128.7,
128.3, 128.1, 127.3, 101.5, 86.9, 81.0, 72.8, 69.1, 65.9, 55.5, 44.4; HR FAB MS
(m/z): calc. for C33H32NaO5 (M þ Naþ) 531.2147, found 531.2146.
Methyl 2-O-Benzyl-4-dexoy-3-C-[(E)-(ethoxycarbonyl)
methylene]-6-O-trityl-a-D-erythro-hexopyranoside (8)
After [(ethoxycarbonyl)methylene]triphenylphosphorane (20 g, 57.4 mmol)
was added to a solution of 7 (8.0 g, 15.7 mmol) in dry CHCl3 (200 mL), the
mixture was stirred under reflux for 3 d. Evaporation of the solvent in
vacuum and purification of the crude product by column chromatography
1
afforded 8 (9.0 g, 99%). [a] ¼ þ1.6 (1.0, CHCl3); H NMR (CDCl3, 400 MHz):
7.20–7.43 (m, 20H), 6.18 (t, J ¼ 2.0 Hz, 1H, 55CH), 4.88 (d, J ¼ 3.6 Hz, 1H,
H-1), 4.78 (d, J ¼ 12.4 Hz, 1H, H-Bn), 4.56 (d, J ¼ 12.4 Hz, 1H H-Bn), 4.15
(m, 2-H, Et), 4.01 (dd, J ¼ 3.6, 2.0 Hz, 1H, H-2), 3.97 (m, 1H, H-5), 3.91 (dd,
J ¼ 12.0, 2.0 Hz, 1H, H-4e), 3.47 (s, 3H, OMe), 3.18 (dd, J ¼ 10.0, 6.0 Hz, 1H,
H-6), 3.08 (dd, J ¼ 10.0, 3.2 Hz, 1H, H-6), 1.97 (t, J ¼ 12.0 Hz, 1H, H-4a),
1.27 (t, J ¼ 7.2 Hz, 3H, Et); 13C NMR (CDCl3, 100 MHz): 166.8, 152.8, 144.2,

Carbohydrate Moiety of Amipurimycin
59
137.9. 128.9, 128.7, 128.2, 128.0, 127.2, 113.8, 99.7, 86.6, 78.1, 72.4, 69.4, 66.4,
60.0, 55.3, 31.9, 14.5; HR FAB MS (m/z): calc. for C37H38NaO6 (M þ Naþ)
601.2566, found 601.2567.
Methyl 2-O-Benzyl-4-deoxy-3-C-[(R)-(ethoxycarbonyl)
hydroxymethyI]-6-O-trityl-a-D-xylo-hexopyranoside (9)
After 8 (9.0 g, 15.5 mmol) and 4-methylmorpholine N-oxide (3.63 g,
31 mmol) were dissolved in a mixture of acetone, THF, and water (250 mL,
8:2:1), osmium tetraoxide (197 mg, 0.775 mmol) was added, and the reaction
mixture was stirred overnight at rt. The mixture was then poured into H2O
and extracted with CHCl3. The organic layer was washed with water, dried
over Na2SO4, and concentrated to dryness. The residue was purified with
flash column chromatography to give 9 (9.3 g, 98%) as syrup. [a] ¼ þ26.6
(1.0, CHCl3); lHNMR (CDCl3, 400 MHz): 7.20–7.45 (m, 20H), 4.82
(d, J ¼ 5.2 Hz, 1H, CH-CO2Et), 4.81 (d, J ¼ 3.6 Hz, lH, H-l), 4.65 (s, 2H,
H-Bn), 4.51 (d, J ¼ 5.2 Hz, 1H, OH), 4.31 (s, lH, OH), 4.17 (m, 1H, H-5), 4.08
(qd, J ¼ 7.2, 1.2 Hz, 2H, Et), 3.70 (d, J ¼ 3.6 Hz, 1H, H-2), 3.47 (s, 3H, OMe),
3.16 (dd, J ¼ 9.6, 6.0 Hz, 1H, H-6), 3.02 (dd, J ¼ 9.6, 4.4 Hz, 1H, H-6), 1.92
(dd, J ¼ 14.0, 2.0 Hz, 1H, H-4e), 1.68 (dd, J ¼ 14.0, 12.4 Hz, 1H, H-4a), 1.16
(t, J ¼ 7.2 Hz, 3H, Et); 13C NMR (CDCl3, 100 MHz): 172.0, 144.1, 137.4,
128.9, 128.8, 128.4, 128.3, 128.0, 127.2, 98.1, 86.7, 84.6, 75.2, 74.1, 73.2, 67.2,
66.3, 61.4, 55.7, 38.5, 14.3; HR FAB MS (m/z): calc. for C37H40NaO8
(M þ Naþ) 635.2621, found 635.2641.
Methyl 2,3-di-O-Benzyl-4-deoxy-3-C-[(R)-(ethoxycarbonyl)
benzyloxymethyl]-6-O-trityl-a-D-xylo-hexopyranoside (10)
To the solution of 9 (50 mg, 0.079 mmol) and benzyl bromide (24 mg,
0.2 mmol) in DMF (3 mL) was added NaH (8 mg, 0.2 mmol) at 08C. The
mixture was stirred at rt for 1 h. The reaction was quenched with methanol
and diluted with CH2Cl2. The reaction mixture was washed with water,
dried over Na2SO4, and concentrated. The residue was purified with flash
column chromatography to give 10 (64 mg, 100%) as white foam. [a] ¼ þ43.0
(1.0, CHCl3); 1H NMR (CDCl3, 400 MHz): 7.05–7.40 (m, 30H), 5.08
(d, J ¼ 11.6 Hz, 1H, H-Bn), 5.01 (d, J ¼ 11.2 Hz, 1H, H-Bn), 4.76
(d, J ¼ 2.0 Hz, 1H, H-1), 4.54 (d, J ¼ 10.4 Hz, 1H, H-Bn), 4.53
(d, J ¼ 10.8 Hz, 1H, H-Bn), 4.48 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.45 (s, 1H,
CH-CO2Et), 4.41 (m, 1H, H-5), 4.18 (qd, J ¼ 7.2, 10.8 Hz, 1H, Et), 4.16
(d, J ¼ 2.0 Hz, 1H, H-2), 4.15 (d J ¼ 10.8 Hz 1H-Bn), 4.01 (qd, J ¼ 7.2,
10.8 Hz, 1H, Et), 3.55 (s, 3 H, OMe), 3.49 (dd, J ¼ 10.4, 8.0 Hz, 1H, H-6), 2.81
(dd, J ¼ 10.4, 3.6 Hz, 1H, H-6), 2.20 (dd, J ¼ 14.0, 6.4 Hz, 1H, H-4e), 1.73

J. Xue and Z. Guo
60
(dd, J ¼ 14.0, 4.8 Hz, 1H, H-4a), 1.06 (t, J ¼ 7.2 Hz, 3H, Et); HR FAB MS (m/z);
calc. for C51H52NaO8 (M þ Naþ) 815.3560, found 815.3563.
Methyl 2,3-di-O-Benzyl-4-deoxy-3-C-[(S)-1,2-
dibenzyloxyethyl]-a-D-xylo-hexopyranoside (11)
Lithium aluminum hydride (3.8 g, 100 mmol) was added to a solution of 10
(14.9 mmol) in dry THF (200 mL) at 08C, and the mixture was warmed to rt and
.
stirred for 4 h. Then, the reaction was quenched with Na2SO4 10H2O, and the
reaction mixture was filtered off, dried over Na2SO4 and concentrated. The
residue was dissolved in dry DMF (100 mL), and to this solution was added
benzyl bromide (4.5 mL, 37.5 mmol) and NaH (40%, 2.0 g, 50 mmol) at 08C.
The reaction mixture was stirred at rt for 2 h and quenched with methanol.
The mixture was poured into H2O and extracted with CH2Cl2. The organic
layer was washed with water, dried over Na2SO4, and concentrated. The
residue was dissolved in a mixture of HCOOH and Et2O (100 mL, 1:1). After
stirring at rt for 1 h, evaporation of the solvent and purification of the
product by chromatography afforded 11 (8.3 g, 93%). [a] ¼ þ55.2 (1.0,
CHCl3); 1H NMR (CDCl3, 400 MHz): 7.20–7.40 (m, 20H), 5.05
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.95 (d, J ¼ 11.2 Hz, 1H H-Bn), 4.90
(d, J ¼ 12.0 Hz, 1H, H-Bn), 4.87 (d, J ¼ 2.4 Hz, 1H, H-l), 4.63 (d, J ¼ 6 Hz,
1H, H-Bn), 4.46 (s, 2H, H-Bn), 4.42 (d, J ¼ 10.0 Hz, 1H, H-Bn), 4.39
(d, J ¼ 11.2 Hz, 1H, H-Bn), 4.29 (d, J ¼ 2.0 Hz, 1H, H-2), 4.25 (m, 1H, H-5),
4.13 (dd, J ¼ 6.0, 3.6 Hz, 1H, H-l0), 3.91 (dd, J ¼ 10.4, 3.6 Hz, 1H, H-20), 3.73
(dd, J ¼ 10.4, 6.0 Hz, 1H, H-20), 3.69 (m, 1H, H-6), 3.53 (ddd, J ¼ 11.2. 4.0,
3.2 Hz, 1H, H-6) 3.44 (s, 3H, OMe), 2.04 (m, 1H, OH), 2.00 (dd, J ¼ 14.0,
6.0 Hz, 1H, H-4e), 1.66 (dd, J ¼ 14.0, 6.4 Hz, 1H, H-4a), 1.06 (t, J ¼ 7.2 Hz,
3 H, Et); 13C NMR (CDCl3, 100 MHz): 139.5, 139.3, 139.0, 138.3, 128.6,
128.4, 128.3, 127.9, 27.6, 127.5, 127.4, 127.2, 127.1, 98.7, 83.2, 79.8, 74.8,
74.0, 73.6, 71.9, 70.9, 67.3, 65.1, 56.4, 33.0; HR FAB MS (m/z): calc. for
C37H43O7 (M þ Hþ) 599.3009, found 599.2992.
Methyl (6R)-2,3-di-O-Benzyl-4-deoxy-3-C-[(S)-l,2-
dibenzyloxyethyl]-6-C-ethynyl-a-D-xylo-hexopyranoside
(13) and Methyl (6S)-2,3-di-O-benzyl-4-deoxy-3-C-[(S)-
l,2-dibenzyloxyethyl]-6-C-ethynyl-a-D-xylo-
hexopyranoside (14)
To a solution of 11 (8.3 g, 13.9 mmol) and Et3N (19.5 mL, 139 mmol) in
.
DCM (75 mL) at 08C was added SO3 Pyr (17.8 g, 111.2 mmol) in DMSO
(150 mL). After the reaction mixture was stirred at 08C for 45 min, it was
diluted with ethyl acetate, washed with aqueous NaHCO3 and brine, dried

Carbohydrate Moiety of Amipurimycin
61
over Na2SO4, and then concentrated. The residue was dissolved in THF
;;
(50 mL) and directly treated with HC CMgBr (100 mL, 0.5 M) at 08C. The
reaction mixture was stirred at 08C until the starting material disappeared
(monitored by TLC). Evaporation of the solvent under vacuum and purification
of the product by column chromatography afforded 13 (3.5 g, 40%) and 14
(3.5 g, 40%). 13 (more polar product): [a] ¼ þ53.3 (1.0, CHCl3); 1H NMR
(CDCI3, 400 MHz): 7.20–7.40 (m, 20H), 5.07 (d, J ¼ 11.2 Hz, 1H, H-Bn), 4.99
(d, J ¼ 12.0 Hz, 1H, H-Bn), 4.90 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.84
(d, J ¼ 2.4 Hz, 1H, H-1), 4.65 (d, J ¼ 12.0 Hz, 1H, H-Bn), 4.59 (ddd, J ¼ 6.4,
4.0, 2.0 Hz, 1H, H-6), 4.48 (s, 2H, H-Bn), 4.42 (d, J ¼ 11.2 Hz, 1H, H-Bn),
4.38 (d, J ¼ 11.6 Hz, lH, H-Bn), 4.31 (d. J ¼ 1.6 Hz, 1H, H-2), 4.19
(q, J ¼ 6.0 Hz, 1H H-5), 4.12 (dd, J ¼ 6.0, 3.6 Hz, 1H, H-10), 3.94 (dd,
J ¼ 10.4, 3.6 Hz, 1H, H-20), 3.74 (dd, J ¼ 10.4, 6.0 Hz, 1H, H-20), 3.46 (s, 3H,
;;
OMe), 2.61 (d, J ¼ 4.4 Hz, 1H, OH), 2.42 (d, J ¼ 2.4 Hz, 1H, HC C), 2.13
(dd, J ¼ 14.0, 6.4 Hz, 1H, H-4e), 1.97 (dd, J ¼ 14.0, 5.6 Hz, 1H, H-4a); 13C
NMR (CDCl3, 100 MHz): 139.3, 139.2, 139.0, 138.2, 128.6, 128.5, 128.4,
127.9, 127.6, 127.4, 127.2, 127.1, 98.6, 83.0, 82.3, 80.0, 74.9, 74.2, 73.8, 73.7,
73.6, 73.4, 71.7, 67.1, 64.2, 56.6, 32.2; HR FAB MS (m/z): calc. for C39H43O7
(M þ Hþ) 623.3003, found 623.3008. 14 (less polar product): [a] ¼ þ56.5
(1.0, CHCl3); 1H NMR (CDCl3, 400 MHz): 7.20–7.40 (m, 20 H), 5.07 (d,
J ¼ 11.6 Hz. 1H, H-Bn), 5.01 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.96 (d, J ¼ 2.4 Hz,
1H, H-1), 4.93 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.66 (d, J ¼ 11.6 Hz, 1H, H-Bn),
4.57 (ddd, J ¼ 7.2, 5.2, 2.4 Hz, 1H, H-6), 4.52 (d, J ¼ 12.0 Hz, 1H, H-Bn), 4.49
(d, J ¼ 12.0 Hz, 1H, H-Bn), 4.44 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.42
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.30 (d, J ¼ 2.0 Hz, 1H, H-2), 4.27 (q, J ¼ 6.0 Hz,
1H, H-5), 4.18 (dd, J ¼ 6.0, 3.6 Hz, 1H, H-l0), 3.98 (dd, J ¼ 10.4, 3.6 Hz, 1H,
H-20), 3.79 (dd, J ¼ 10.4, 6.0 Hz, 1H, H-20), 3.48 (s, 3H, OMe), 2.83
;;
(d, J ¼ 7.2 Hz, 1H, OH), 2.43 (d, J ¼ 2.4 Hz, 1H, HC C), 2.09 (d, J ¼ 6.4 Hz,
2H, H-4); 13C NMR (CDCl3 100 MHz): 139.4, 139.2, 138.6, 138.2, 128.7,
128.6, 128.4, 128.3, 127.9, 127.8, 127.6, 127.4, 127.2, 127.1, 98.2, 83.0,
82.5, 79.9, 74.8, 74.3, 73.7, 73.6, 72.4, 71.9, 67.5, 64.8, 56.5, 31.0; HR FAB
MS (m/z): calc. for C39H43O7 (M þ Nþ) 623.3003, found 623.3009.
(1S,3S,4R,5R,7R)-4-Benzyloxy-5-[(S)-l,2-dibenzyloxyethyl]-7-
ethynyl-3-methoxy-2,6-dioxabicyclo[3.2.1]octane (15)
To the solution of 13 (120 mg, 0.2 mmol) in pyridine (0.1 mL) and dichloro-
methane (5 mL) was added triflic anhydride (67.3 mL, 0.4 mmol) at 08C. After
the mixture was stirred for 0.5 h, water was added to quench the reaction.
The mixture was extracted with CH2Cl2, and the organic layer was washed
with water, dried over Na2SO4, and concentrated. The residue was subjected to
column chromatography to afford 15 (99 mg, 100%) [a] ¼ þ86.3 (1.0, CHCl3);
1H NMR (CDCl3, 400 MHz): 7.20–7.35 (m, 15H), 4.97 (d, J ¼ 11.6 Hz, 1H,

J. Xue and Z. Guo
62
H-Bn), 4.79 (d, J ¼ 2.4 Hz, 1H, H-l), 4.75 (d, J ¼ 2.0 Hz, 1H, H-6), 4.71
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.51 (s, 2H, H-Bn), 4.50 (m, 1H, H-5), 4.31
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.24 (d, J ¼ 11.6 Hz, 1H, H-Bn), 3.98 (br, 1H, H-2),
3.95 (m, 2H, H-10,20), 3.72 (dd, J ¼ 12.0, 6.0 Hz, 1H, H-20), 3.54 (s, 3H, OMe),
;;
2.47 (d, J ¼ 2.0 Hz, 1H, HC C), 2.47 (ddd, J ¼ 12.4, 1.2, 1.2 Hz, 1H, H-4e),
2.12 (ddd J ¼ 12.4, 2.8, 1.2 Hz, 1H, H-4a); 13C NMR (CDCl3, 100 MHz): 139.1,
138.5, 138.3, 128.6, 128.5, 128.3, 128.1, 128.0, 127.9, 127.7, 127.6, 127.5, 101.3,
87.5, 80.8, 79.3, 77.2, 75.9, 75.2, 74.6, 73.6, 73.1, 72.7, 70.0, 57.7, 32.1; HR
FAB MS (m/z): calc. for C32H35O6 (M þ Hþ) 515.2434, found 515.2430.
(1S,3S,4R,5R,7S)-4-Benzyloxy-5-[(1S)-1,2-dibenzyloxyethyl]-
7-ethynyl-3-methoxy-2,6-dioxa bicyclo[3.2.1]octane
(16)
To the solution of 14 (120 mg, 0.2 mmol) in pyridine (0.1 mL) and dichlor-
omethane (5 mL) was added triflic anhydride (67.3 mL, 0.4 mmol) at 08C. After
the mixture was as stirred for 0.5 h, water was added to quench the reaction.
The mixture was extracted with CH2Cl2, and the organic layer was washed
with water, dried over Na2SO4, and concentrated. The resides was subjected
to column chromatography to afford 16 (100 mg, 100%). [a] ¼ þ110.2
(1.0, CHCl3); 1H NMR (CDCl3, 400 MHz): 7.20–7.38 (m, 15H), 5.40
(d, J ¼ 2.4 Hz, 1H, H-l), 5.00 (d, J ¼ 11.2 Hz, 1H, H-Bn), 4.69 (d,
J ¼ 11.6 Hz, 1H, H-Bn), 4.49 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.48 (d, J ¼ 2.4 Hz,
1H, H-6), 4.43 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.41 (m, 1H, H-5), 4.33
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.24 (d, J ¼ 11.6 Hz, 1H, H-Bn), 3.96
(d, J ¼ 2.0 Hz, 1H, H-2), 3.89 (dd, J ¼ 5.2, 4.8 Hz, 1H), 3.78 (dd, J ¼ 6.4,
4.8 Hz, 1H), 3.64 (dd, J ¼ 6.4, 5.2 Hz, 1H), 3.58 (s, 3H, OMe), 2.62
;;
(d, J ¼ 2.8 Hz, 1H, HC C), 2.52 (dd, J ¼ 12.4, 1.2 Hz, 1H, H-4e), 1.82 (dd,
J ¼ 12.4, 1.6 Hz, 1H, H-4a); HR FAB MS (m/z): calc. for C32H35O6 (M þ Hþ)
515.2434, found 515.2430.
Methyl (6S)-2,3-di-O-Benzyl-4-deoxy-3-C-[(S)-l,2-
dibenzyloxyethyl]-6-C-ethynyl-6-O-tosyl-a-D-xylo-
hexopyranoside (17)
To a solution of 14 (120 mg, 0.2 mmol) in pyridine (0.1 mL) and dichloro-
methane (5 mL) was added TsCl (0.8 mmol) at 08C. After the reaction
mixture was warmed to rt, it was stirred overnight, and then water was
added to quench the reaction. The mixture was extracted with CH2Cl2, and
the organic layer was washed with water, dried over Na2SO4, and concen-
trated. The residue was subjected to column chromatography to afford 17
1
(150 mg, 100%). [a] ¼ þ36.7 (1.0, CHCl3); H NMR (CDC13, 400 MHz): 7.67

Carbohydrate Moiety of Amipurimycin
63
(d, J ¼ 7.6 Hz, 2H, Ts), 7.24–7.38 (m, 20H), 7.19 (d, J ¼ 7.6 Hz, 2H, Ts), 5.53
(d, J ¼ 6.8 Hz, 1H, H-6), 5.09 (d, J ¼ 11.2 Hz, 1H, H-Bn), 4.99
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.95 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.71 (br, 1H,
H-l), 4.66 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.51 (d, J ¼ 12.0 Hz, 1H, H-Bn), 4.45
(d, J ¼ 12.0 Hz, 1H, H-Bn), 4.40 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.37
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.28 (br, 1H, H-2), 4.24 (dd, J ¼ 12.0, 6.0 Hz, 1H,
H-5) 4.06 (dd, J ¼ 2.8, 2.0 Hz, 1H, H-10), 3.90 (dd, J ¼ 10.4, 2.8 Hz, 1H, H-20),
3.76 (dd, J ¼ 10.4, 2.0 Hz, 1H, H-20), 3.38 (s, 3H, OMe), 2,43 (s, 3H, CH3),
;;
2.40 (br, 1H, HC C), 2.08 (dd, J ¼ 14.4, 4.8 Hz, 1H, H-4), 1.93 (dd, J ¼ 14.4,
4.4 Hz, 1H, H-4); HR FAB MS (m/z): calc. for C46H49O9S (M þ Hþ) 777.3097,
found 777.3114.
(1S,3S,5R,6S,8R)-5-Acetoxy-8-benzyloxy-6-
benzyloxymethyl-3-[(R)-(ethynyl)tosyloxymethyl]-2,7-
dioxabicyclo[3.2.1]octane (18)
To a solution of 17 (80 mg, 0.1 mmol) in acetic acid and acetic anhydride (1:1,
5 mL) was added sulfuric acid (1 drop) at 08C. The reaction mixture was stirred
at 08C for 0.5 h and then diluted with CH2C12. The mixture was washed with
water, dried over Na2SO4, and concentrated. The residue was finally subjected
to column chromatography to afford 18. 1H NMR (CDCl3, 600 MHz): 7.81
(d, J ¼ 7.8 Hz, 2H, Ts), 7.20–7.38 (m, 12H), 5.35 (s, 1H, H-l), 5.22
(t, J ¼ 3.6 Hz, 1H, H-6), 4.64 (d, J ¼ 12.0 Hz, 1H, H-Bn), 4.60 (dd, J ¼ 12.0,
2.4 Hz, 1H, H-20), 4.55 (d, J ¼ 10.8 Hz, 1H, H-Bn), 4.54 (d, J ¼ 12.0 Hz, 1H,
H-Bn), 4.45 (d, J ¼ 10.8 Hz, 1H, H-Bn), 4.43 (dd, J ¼ 12.0, 9.0 Hz, 1H, H-20),
4.25 (dd, 9.0, 2.4 Hz, 1H, H-10), 4.09 (dt, J ¼ 10.8, 3.6 Hz, 1H, H-5), 3.58
;;
(S, 1H, H-2), 2.47 (d, J ¼ 1 3.6 H2, 1H, HC C), 2.44 (S, 3H, CH3), 2.23
(t, J ¼ 13.2 Hz, 1H, H-4a), 1.93 (dd, 13.2, 6.0 Hz, 1H, H-4e), 2.05 (s, 3H, Ac).
(1S,3S,5R,6S,8R)-5,8-di-Acetoxy-6-acetoxymethyl-3-[(R)-
(ethynyl)tosyloxymethyl]-2,7-dioxabicyclo[3.2.1]
octane (19) and (1S,3S,5R,6S,8R)-5,8-di-Acetoxy-6-
benzyloxymethyl-3-[(R)-(ethynyl)tosyloxymethyl]-2,7-
dioxabicyclo[3.2.1]octane (20)
To the solution of 17 (160 mg, 0.2 mmol) in THF and acetic anhydride (9:1,
10 mL) was added BCl3, at 2508C. After it was stirred for 1 h, CH2CI2 was
added, and the mixture was washed with water, dried over Na2SO4, and con-
centrated. The residue was subjected to column chromatography to give 19
and 20. 19: [a] ¼ 249.0 (0.6, CHCl3); 1H NMR (CDCl3, 400 MHz): 7.81
(d, J ¼ 8.0 Hz, 2 H, Ts), 7.34 (d, J ¼ 8.0 Hz, 2H, Ts), 5.20 (s, 1H, H-1), 5.18
(dd, J ¼ 3.6, 2.4 Hz, 1H, H-6), 4.97 (s, 1H, H-2), 4.62 (dd, J ¼ 7.2, 4.0 Hz, IH,

J. Xue and Z. Guo
64
H-20), 4.27 (dd, J ¼ 12.0, 7.2 Hz, 1H, H-l0), 4.24 (dd, J ¼ 12.0, 4.0 Hz, lH, H-l0),
4.09 (dt, J ¼ 11.2, 4.0 Hz, 1H, H-5), 2.61 (dd, J ¼ 12.8, 4.4 Hz, 1H, H-40), 2.50
(d, J ¼ 2.0 Hz, 1H, HC;C), 2.44 (s, 3H, CH3), 2.28 (t, J ¼ 12.8 Hz, lH, H-4a),
2.12 (s, 3H, Ac), 2.09 (s, 3H, Ac), 2.08 (s, 3H, Ac); HR FAB MS (m/z): cacl. for
C23H27O11S (M þ Hþ) 511.1274, found 511.1262. 20: [a] ¼ 250.0 (0.3, CHCl3);
1H NMR (CDCl3, 400 MHz): 7.80 (d, J ¼ 8.0 Hz, 2H, Ts), 7.27–7.36 (m, 7 H),
5.22 (s, lH, H-l), 5.18 (dd, J ¼ 3.6, 2.0 Hz, 1H, H-6), 4.58 (s, 2H, H-Bn), 4.44
(dd, J ¼ 8.4, 2.8 Hz, 1H, H-l0), 4.39 (dd, J ¼ 12.0, 3.2 Hz, 1H, H-20), 4.31 (dd,
J ¼ 12.0, 8.4 Hz, lH, H-20), 4.04 (m, 1H, H-5), 3.92 (s, 1H, H-2), 2.45
;;
(d, J ¼ 2.4 Hz, lH, HC C), 2.43 (s, 3H, CH3), 2.37 (dd, J ¼ 14.4, 12.8 Hz,
1H, H-4a), 2.34 (d, J ¼ 14.4 Hz, 1H, H-4e), 2.08 (s, 3H, Ac), 2.07 (s, 3H, Ac);
HR FAB MS (m/z): calc. for C28H31O10S (M þ Hþ) 559.1638, found 559.1637.
Methyl {Methyl 2,3-di-O-Benzyl-4-deoxy-3-C-[(S)-(l,2-
dibenzyloxyethyl)]-a-D-gluco-heptopyranosid}
uronate (21)
After 14 (2.0 g, 3.21 mmol) and NaIO4 (3.2 g, 15 mmol) were dissolved in a
mixture of THF and water (5:3, 160 mL), osmium tetraoxide (76 mg, 0.3 mmol)
was added, and the reaction mixture was stirred at 458C overnight. After the
mixture was concentrated to remove THF, the residue was poured into water
and extracted with CH2Cl2. The organic layer was washed with H2O, dried
over Na2SO4, and concentrated. The crude product was directly subjected to
methylation using freshly prepared CH2N2 in CH2Cl2 to give 21 (1.4 g, 66%).
1
[a] ¼ þ69.7 (1.0, CHCl3); H NMR (CDCl3, 400 MHz): 7.20–7.38 (m, 20 H),
5.05 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.97 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.92
(d, J ¼ 2.0 Hz, 1H, H-l), 4.89 (d, J ¼ 12.0 Hz, 1H, H-Bn), 4.65 (d, J ¼ 11.6 Hz,
1H, H-Bn), 4.52 (m, 1H, H-6), 4.48 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.45
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.41 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.35
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.26 (d, J ¼ 2.0 Hz, 1H, H-2), 4.22 (m, 1H, H-5),
4.09 (dd, J ¼ 6.4, 3.2 Hz, 1H, H-10), 3.95 (dd, J ¼ 10.8, 3.2 Hz, 1H, H-20), 3.73
(dd, J ¼ 10.8, 6.4 Hz, 1H, H-20), 3.71 (s, 3H, OMe), 3.42 (s, 3H, OMe), 2.79
(d, J ¼ 8.0 Hz, 1H, OH), 1.99 (m, 2H, H-4e, H-4a); HR FAB MS (m/z): calc.
for C39H45O9 (M þ Hþ) 657.3064, found 657.3017.
Methyl {Methyl 2,3-di-O-Benzyl-4-deoxy-3-C-[(S)-(1,2-
dibenzyloxyethyl)]-6-O-tosyl-a-D-gluco-heptopyranosid}
uronate (22)
To the solution of 21 (0.6 g, 0.91 mmol) in pyridine and CH2Cl2 (1:1, 20 mL)
was added TsCl (5 eq., 4.5 mmol) at 08C. The reaction mixture was allowed to
warm to rt and stirred overnight. Then, CH2Cl2 was added to dilute the
reaction mixture, and the mixture was washed with water, dried over

Carbohydrate Moiety of Amipurimycin
65
Na2SO4, and concentrated. The residue was subjected to column chromato-
1
graphy to give 22 (0.74 g, 100%). [a] ¼ þ36.8 (1.0, CHCl3); H NMR (CDCl3,
400 MHz): 7.49 (d, J ¼ 8.4 Hz, 2H, Ts), 7.20–7.44 (m, 20H), 7.08
(d, J ¼ 8.4 Hz, 2H, Ts), 5.46 (d, J ¼ 9.2 Hz, 1H, H-6), 5.08 (d, J ¼ 11.6 Hz,
1H, H-Bn), 4.90 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.86 (d, J ¼ 2.0 Hz, 1H, H-1),
4.85 (d, J ¼ 11.2 Hz, 1H, H-Bn), 4.69 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.49
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.44 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.37
(d, J ¼ 11.6 Hz, 1H, H-Bn), 4.28 (d, J ¼ 11.6 Hz, 1H, H-Bn), 4.28 (m, 2H, H-2,
H-5), 3.96 (dd, J ¼ 6.0, 3.6 Hz, 1H, H-10), 3.73 (dd, J ¼ 10.4, 3.6 Hz, 1H,
H-20), 3.68 (dd, J ¼ 10.4, 6.0 Hz, 1H, H-20), 3.61 (s, 3H, OMe), 3.34 (s, 3H,
OMe), 2.36 (s, 3H, CH3), 2.04 (dd, J ¼ 14.4, 6.8 Hz, 1H, H-4e), 2.04
(d, J ¼ 14.4 Hz, 1H, H-4a), HR FAB MS (m/z): calc. for C46H51O11S
(M þ Hþ). 811.3152, found 811.3151.
Methyl {Methyl 2-O-Acetyl-4-deoxy-3-C-[(S)-(1,2-
diacetyloxyethyl)]-6-O-tosyl-a-D-gluco-heptopyranosid}
uronate (23)
To the solution of 22 (0.73 g, 0.9 mmol) in THF (15 mL) was added 10%
Pd/C (0.2 g). After stirred under hydrogen atmosphere for 1 d, the reaction
mixture was filtered off, and the filtrate was concentrated. The residue was dis-
solved in the mixture of pyridine and acetic anhydride (3:1, 12 mL), and a cat-
alytic amount of DMAP was added. The reaction mixture was stirred at rt
overnight. The reaction mixture was diluted with CH2Cl2, washed with
water, dried over Na2SO4, and then concentrated. The residue was subjected
to column chromatography to give 23 (460 mg, 89% yield). [a] ¼ þ16.5 (1.0,
CHCl3); 1H NMR (CDCl3), 400 MHz): 7.81 (d, J ¼ 8.0 Hz, 2H, Ts), 7.37
(d, J ¼ 8.0 Hz, 2H, Ts), 5.39 (d, J ¼ 8.8 Hz, 1H, H-6), 5.13 (dd, J ¼ 6.8,
3.6 Hz, 1H, H-l0), 4.96 (br, 1H, H-2) 4.94 (d, J ¼ 2.0 Hz, 1H, H-S). 4.31
(m, 2H, H-5, H-20), 4.04 (dd, J ¼ 12.0, 6.8 Hz, 1H, H-20), 3.66 (s, 3H, OMe),
3.36 (s, 3H, OMe), 2.75 (s, 1H, OH), 2.46 (s, 3H, CH3), 2.08 (s, 3H, Ac), 2.07
(s, 3H, Ac), 2.05 (s, 3H, Ac), 1.99 (dd, J ¼ 14.4, 6.4 Hz, 1H, H-4e), 1.85 (dd,
J ¼ 14.4, 3.2 Hz, 1H, H-4a); HR FAB MS (m/z): calc. for C24H33O14S
(M þ Hþ) 577.1591, found 577.1590.
Methyl {Methyl 2,3-di-O-Acetyl-4-deoxy-3-C-[(S)-(l,2-
diacetyloxyethyl)]-6-O-tosyl-a-D-allo-heptopyranosid}
uronate (24)
To the solution of 23 (0.45 g, 0.78 mmol) in the mixture of ethyl acetate,
acetic anhydride, and acetic acid (35 mL, 8:3:2) was added sulfuric acid
(0.03 mL) under nitrogen atmosphere at 08C. The reaction mixture was
stirred overnight and then poured into water and extracted with ethyl

J. Xue and Z. Guo
66
acetate. The organic layer was washed with water, dried over Na2SO4, and con-
centrated. The residue was purified with flash column chromatography to give
24 (0.305 g, 60%). 1H NMR (CDCl3, 400 MHz): 7.81 (d, J ¼ 8.0 Hz, 2H, Ts), 7.35
(d, J ¼ 8.0 Hz, 2H, Ts), 6.01 (d, J ¼ 4.0 Hz, 1H, H-1), 5.94 (dd, J ¼ 8.8, 2.8 Hz,
1H, H-10), 5.45 (d, J ¼ 4.0 Hz, 1H, H-2), 5.04 (d, J ¼ 4.4 Hz, 1H, H-6), 4.58 (dd,
J ¼ 12.0, 2.8 Hz, 1H, H-20), 4.56 (m, 1H, H-5), 4.06 (dd, J ¼ 12.0, 8.8 Hz, 1H,
H-20), 3.71 (s, 3H, OMe), 2.46 (s, 3H, CH3), 2.44 (m, 2H, H-4e, H-4a), 2.10
(s, 3H, Ac), 2.06 (s, 3H, Ac), 2.03 (s, 3H, Ac), 2.02 (s, 3H, Ac), 2.00 (s, 3H, Ac);
HR FAB MS (m/z): calc. for C25H31O14S (Mþ 2 OAc) 587.1435, found 587.1438.
Methyl {Methyl 2,3-di-O-Acetyl-6-C-azido-3-C-[(S)-(1,2-
diacetyloxyethyl)]-4,6-dideoxy-a-L-talo-
heptopyranosid}urinate (25)
To the solution of 24 (220 mg, 0.34 mmol) in dry DMF (10 mL) was added
NaN3 (218 mg, 3.4 mmol) and NH4Cl (22 mg). The reaction mixture was
stirred at 308C for 1 d and then poured into water and extracted with ethyl
acetate. The organic layer was washed with water, dried over Na2SO4, and con-
centrated. The residue was purified with flash column chromatography to give
1
25 (90 mg, 51%). [a] ¼ –4.5 (1.0, CHCl3); H NMR (CDCl3, 400 MHz): 6.25
(d, J ¼ 4.4 Hz, 1H, H-l), 5.93 (dd, J ¼ 8.4, 2.4 Hz, 1H, H-l0), 5.64
(d, J ¼ 4.4 Hz, 1H, H-2), 4.67–4.72 (m, 2H, H-5, H-20). 4.09 (dd, J ¼ 12.0,
8.8 Hz, 1H, H-20), 3.83 (s, 3H, OMe), 2.76 (dd, J ¼ 10.4, 7.2 Hz, 1H, H-4e),
2.47 (dd, J ¼ 10.4, 4.0 Hz, 1H, H-4a), 2.11 (s, 3H, Ac), 2.09 (s, 3H, Ac), 2.08
(s, 3H, Ac), 2.06 (s, 3H, Ac), 2.04 (s, 3H, Ac); HR FAB MS (m/z): calc. for
C18H24N3O11 (Mþ 2 OAc) 458.1411, found 458.1418.
Methyl {l,2,3-tri-O-Acety-4-deoxy-3-C-[(S)-(l,2-
diacetoxhyl)]-6-O-tosyl-a-O-tosoyl-a-D-gluco-
heptopyranosid}uronate (26)
To the solution of 23 (300 mg, 0.52 mmol) in acetic anhydride (2.6 mmol) and
anhydrous dichloromethane (20 mL) was added SnCl4 (0.52 mmol) at 08C. The
mixture was allowed to warm to rt and stirred at rt overnight. The mixture
was neutralized with triethyl amine and then poured into H2O and extracted
with CH2Cl2. The organic layer was washed with water, dried over Na2SO4,
and concentrated under reduced pressure. The residue was finally purified
by silica gel column chromatography to afford 26 (90 mg, 28%) and (1S,
3S,5R,6S,8R)-5,8-di-acetoxy-6-acetoxymethyl-3-[(S)-(methoxycarbonyl)tosyloxy-
methyl]-2,7-dioxabicyclo[3.2.1]octane 27 (30 mg, 11%). 26: [a] ¼ 24.4 (1.0,
CHCl3); 1H NMR (CDCl3, 400 MHz): 7.78 (d, J ¼ 8.4 Hz, 2H, Ts), 7.31
(d, J ¼ 8.4 Hz, 2H, Ts), 5.84 (d, J ¼ 2.4 Hz, 1H, H-1), 5.80 (dd, J ¼ 6.8, 4.0 Hz,
1H, H-10), 5.39 (d, J ¼ 1.2 Hz, 1H, H-2), 4.97 (d, J ¼ 4.8 Hz, 1H, H-6), 4.49 (dd,

Carbohydrate Moiety of Amipurimycin
67
J ¼ 12.4, 4.0 Hz, 1H, H-20), 4.32 (ddd, J ¼ 11.6, 4.8, 2.8 Hz, 1H, H-5), 3.94 (dd,
J ¼ 12.0, 6.8 Hz, 1H, H-20), 3.68 (s, 3H, OMe), 2.44 (s, 3H, CH3), 2.31 (dd,
J ¼ 14.4, 4.0 Hz, 1H, H-4e), 2.22 (dd, J ¼ 14.4, 2.4 Hz, 1H, H-4a), 2.08 (s, 3H,
Ac), 2.04 (s, 3H, Ac), 2.03 (s, 3H, Ac), 2.02 (s, 3H, Ac), 2.01 (s, 3H, Ac);
13C NMR (CDCl3, 100 MHz): 171.0, 169.9, 169.1, 168.9, 168.5, 166.6, 145.6,
133.2, 129.8, 128.5, 90.7, 79.8, 78.2, 71.0, 68.1, 66.8, 62.9, 53.3, 29.8, 21.9, 21.8,
21.1, 20.9, 20.8, 20.8; HR FAB MS (m/z): calc. for C25H31O14S (Mþ 2 OAc)
587.1435, found 587.1438. 27: [a] ¼ 218.4 (1.0, CHCl3); 1H NMR (CDCl3,
400 MHz): 7.79 (d, J ¼ 8.4 Hz, 2H, Ts), 7.33 (d, J ¼ 8.4 Hz, 2H, Ts), 5.70
(s, 1H, H-l), 5.14 (s, 1H, H-2), 4.87 (d, J ¼ 4.4 Hz, 1H, H-6), 4.39–4.45 (m, 2H,
H-5, H-10), 4.26 (dd, J ¼ 8.4, 3.2 Hz, 1H, H-20), 4.14 (dd, J ¼ 12.0, 8.4 Hz, 1H,
H-20), 3.63 (s, 3H, OMe), 2.43 (m, 2H, H-4e, H-4a), 2.41 (s, 3H, CH3), 2.09
(s, 3H, Ac), 2.04 (s, 3H, Ac), 2.03 (s, 3H, Ac); 13C NMR (CDCl3, 100 MHz):
170.6, 169.4, 169.3, 166.6, 145.6, 132.8, 129.9, 128.7, 100.4, 78.5, 78.0, 77.7,
72.7, 67.3, 63.5, 53.2, 30.1, 21.9, 21.4, 21.0, 20.8; HR FAB MS (m/z): cacl. for
C23H29O13S (M þ Hþ) 545.1329, found 545.1325.
Methyl {1,2,3-tri-O-Acetyl-3-C-[(S)-(l,2-diacetyloxyethyl)]-4,6-
dideoxy-6-C-azido-a-L-ido-heptopyranosid}uronate (28)
To the solution of 26 (80 mg, 0.14 mmol) in dry DMF (5 mL) was added
NaN3 (91 mg, 1.4 mmol) and NH4Cl (10 mg). The reaction mixture was
stirred at 308C for 1 d and was then poured into water and extracted with
ethyl acetate. The organic layer was washed with water, dried over Na2SO4,
and concentrated. The residue was purified with flash column chromatography
to afford 28 (62 mg, 85%). [a] ¼ þ6.5 (1.0, CHCl3); 1H NMR (CDC13, 400 MHz):
6.04 (d, J ¼ 2.4 Hz, 1H, H-1), 5.89 (dd, J ¼ 7.6, 3.2 Hz, 1H, H-10), 5.47
(d, J ¼ 1.6 Hz, 1H, H-2), 4.62 (dd, J ¼ 12.4, 3.2 Hz, 1H, H-20), 4.50 (dt,
J ¼ 12.4, 2.8 Hz, 1H, H-5), 3.97 (dd, J ¼ 12.4, 7.6 Hz, 1H, H-20), 3.80 (s, 3H,
OMe), 3.78 (d, J ¼ 3.2 Hz, 1H, H-6), 2.56 (dd, J ¼ 14.0, 12.4 Hz, 1H, H-4a),
2.30 (dd, J ¼ 14.0, 2.4 Hz, 1H, H-4a), 2.13 (s, 3H, Ac), 2.12 (s, 3H, Ac), 2.07
(s, 3H, Ac), 2.07 (s, 3H, Ac), 2.06 (s, 3H, Ac); HR FAB MS (m/z): calc. for
C20H27N3NaO13 (M þ Naþ) 540.1442, found 540.1450.
Methyl {6-C-Acetamido-1,2,3-tri-O-acetyl-3-C-[(S)-1,2-
diacetyloxyethyl)]-4,6-dideoxy-a-L-ido-
heptopyranosid}uronate (1)
To a solution of 28 (10 mg, 0.02 mmol) in a mixture of MeOH, THF, and
DCM (6 mL, 1:1:1) was added 10% Pd/C (5 mg) under hydrogen atmosphere,
and the mixture was stirred overnight. After filtration of the reaction
mixture to remove the catalyst, the filtrate was concentrated, and the
residue was dissolved in pyridine and acetic anhydride (3:1, 4 mL) containing

J. Xue and Z. Guo
68
a catalytic amount of DMAP. The reaction mixture was stirred at rt overnight
and then diluted with CH2Cl2, washed with water, dried over Na2SO4, and
finally concentrated. The residue was subjected to column to chromatography
1
give, (9 mg, 92%). [a] ¼ 23.6 (0.5, CHCl3); H NMR (CDCl3, 400 MHz): 6.17
(d, J ¼ 9.2 Hz, 1H, NH), 5.97 (d, J ¼ 2.0 Hz, 1H, H-l), 5.88 (dd, J ¼ 6.8,
4.0 Hz, 1H, H-10). 5.54 (d, J ¼ 2.0 Hz, 1H, H-2), 4.83 (dd, J ¼ 8.8, 2.4 Hz, 1H,
H-6), 4.58 (dd, J ¼ 12.0, 3.6 Hz, 1H, H-20), 4.52 (ddd, J ¼ 9.6, 4.8, 2.8 Hz, 1H,
H-5), 3.99 (dd, J ¼ 12.0, 6.8 Hz, 1H, H-20), 3.73 (s, 3H, OMe), 2.15–2.19
(m, 2H, H-4a, H-4e), 2.11 (s, 6 H, 2 Ac), 2.08 (s, 3H, Ac), 2.07 (s, 3H, Ac), 2.06
(s, 3H, Ac), 2.04 (s, 3H, Ac); HMQC (CDCl3, 1H 400 MHz/13C 100 MHz):
5.97/91.0 (H-1/C-2), 5.88/71.5, (H-10/C-10), 5.54/66.5 (H-2/C-2), 4.83/54.5
(H-6/C-6), 4.58/62.5 (H-20/C-20), 4.52/68.5 (H-5/C-5), 3.99/62.5 (H-20/C-20),
3.73/52.5 (OMe), 2.17/32.0 (H-4/C-4); HR FAB MS (m/z): calc. for
C22H32NO14 (M þ Hþ) 534.1823, found 534.1830.
ACKNOWLEDGMENT
This work is supported by research grants from the National Science Foundation
(CHE-0407144 and CHE-0715275). Z.G. thanks Professor Philip Garner for
helpful and stimulating suggestions and discussion about this project.
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