Bromohydroxylation of glycals - An investigation into the reaction of some 4-N-acylated derivatives of methyl 5-acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-3,4,5-trideoxy-D-glycero-D-galacto-no n-2-enonate and its 4-epimer

Article abstract of DOI:10.1081/CAR-100105710

Bromohydroxylation of some 4-N-acylated derivatives of the glycals of N-acetylneuraminic acid, methyl 5-acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-3,4,5-trideoxy-D-glycero-D-galacto-no n-2-enonate (4) and methyl 5-acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-3,4,5-trideoxy-D-glycero-D-talo-non-2 -enonate (the 4-epimer of 4), with N-bromosuccinimide (NBS) and water in the presence of a co-solvent has provided a range of new glycosyl donors. The stereoselectivity of the halohydroxylation reaction was found to be governed by solvent composition, reaction temperature and the stereoelectronic nature of the substituent at C-4.

Full text of DOI:10.1081/CAR-100105710

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BROMOHYDROXYLATION OF GLYCALS—AN
INVESTIGATION INTO THE REACTION OF SOME
4-N-ACYLATED DERIVATIVES OF METHYL
5-ACETAMIDO-7,8,9-TRI-O-ACETYL-2,6-
ANHYDRO-3,4,5-TRIDEOXY-D-GLYCERO-D-GALACTO-
NON-2-ENONATE AND ITS 4-EPIMER
Gaik B. Kok a , Tho van Phan a & Mark von Itzstein b
a Department of Medicinal Chemistry, Monash University (Parkville Campus), 381 Royal
Parade, Parkville, Victoria, 3052, Australia
b Department of Medicinal Chemistry, Monash University (Parkville Campus), 381 Royal
Parade, Parkville, Victoria, 3052, Australia
Available online: 16 Aug 2006
To cite this article: Gaik B. Kok, Tho van Phan & Mark von Itzstein (2001): BROMOHYDROXYLATION OF GLYCALS—AN
INVESTIGATION INTO THE REACTION OF SOME 4-N-ACYLATED DERIVATIVES OF METHYL 5-ACETAMIDO-7,8,9-TRI-
O-ACETYL-2,6-ANHYDRO-3,4,5-TRIDEOXY-D-GLYCERO-D-GALACTO-NON-2-ENONATE AND ITS 4-EPIMER, Journal of
Carbohydrate Chemistry, 20:5, 359-374
To link to this article: http://dx.doi.org/10.1081/CAR-100105710
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J. CARBOHYDRATE CHEMISTRY, 20(5), 359–374 (2001)
BROMOHYDROXYLATION OF GLYCALS—AN
INVESTIGATION INTO THE REACTION OF SOME
4-N-ACYLATED DERIVATIVES OF METHYL
5-ACETAMIDO-7,8,9-TRI-O-ACETYL-2,6-
ANHYDRO-3,4,5-TRIDEOXY-D-GLYCERO-
D-GALACTO-NON-2-ENONATE AND ITS 4-EPIMER
Gaik B. Kok,1 Tho van Phan,1 and Mark von Itzstein1,2,
*
1Department of Medicinal Chemistry, Monash University (Parkville
Campus), 381 Royal Parade, Parkville 3052, Victoria, Australia
2Centre for Biomolecular Science and Drug Discovery (Gold Coast
Campus), Griffith University, PMB 50 Gold Coast Mail Centre,
Queensland 9726, Australia
ABSTRACT
Bromohydroxylation of some 4-N-acylated derivatives of the glycals of N-
acetylneuraminic acid, methyl 5-acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-
3,4,5-trideoxy-D-glycero-D-galacto-non-2-enonate (4) and methyl 5-aceta-
mido-7,8,9-tri-O-acetyl-2,6-anhydro-3,4,5-trideoxy-D-glycero-D-talo-non-2-
enonate (the 4-epimer of 4), with N-bromosuccinimide (NBS) and water in the
presence of a co-solvent has provided a range of new glycosyl donors. The
stereoselectivity of the halohydroxylation reaction was found to be governed
by solvent composition, reaction temperature and the stereoelectronic nature of
the substituent at C-4.
Key Words: N-acetylneuraminic acid; Sialosyl donor; Ulosonic acids; Glycal;
Halohydroxylation
*Corresponding author. E-mail: m.vonitzstein@mailbox.gu.edu.au
359
Copyright © 2001 by Marcel Dekker, Inc.
www.dekker.com

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KOK, VAN PHAN, AND VON ITZSTEIN
INTRODUCTION
Ulosonic acids, in particular, N-acetylneuraminic acid (Neu5Ac, 1) are
widespread in nature. As constituents of glycoconjugates such as glycoproteins,
glycolipids and oligosaccharides, these carbohydrate structures are involved in
many biological processes including molecular recognition, cell adhesion and in-
flammation.1 There has been therefore considerable interest over the years both in
the glycobiology and chemistry of this class of carbohydrates. As part of our con-
tinuing research interest in ulosonic acid-recognising proteins and their role in car-
bohydrate metabolism, we required a series of 4-N-acylated and 4-epi-N-acylated
derivatives of Neu5Ac as sialosyl donors in O-glycosylation reactions.
We envisaged that the most direct entry into a range of such compounds
would be via successive acylation and halohydroxylation of the well-known amine,
methyl 5-acetamido-7,8,9-tri-O-acetyl-4-amino-2,6-anhydro-3,4,5-trideoxy-D-
glycero-D-galacto-non-2-enonate (2)2 or its 4-epimer 3. Indeed, it has been previ-
ously demonstrated3 by Okamoto and coworkers that glycals such as the methyl es-
ter of peracetylated Neu5Ac2en 4 can be converted into the corresponding glycosyl
donors such as 2,3-dibromo- and 2-halo-3-hydroxyl-N-acetylneuraminic acid
derivatives by the electrophilic addition of bromine or halohydroxylation. In the
latter case, in the absence of any neighbouring group participation and serious
steric constraints, halohydroxylation reactions on 4 appear to proceed with high re-
giocontrol according to Markovnikov’s rule.4 Herein we report our findings when
we extend this methodology to some C-4 N-acylated derivatives of 4.
RESULTS AND DISCUSSION
The amines 2 and its 4-epimer 3 used in this study were prepared by reduc-
tion of the corresponding azides 52 and 6,5 respectively under catalytic hy-
drogenolysis conditions as previously described. Acylation of these amines with
either acetic or benzoic anhydride and DMAP in pyridine afforded the corre-
sponding 4-N-acylated glycals 7–9. The 4-epi-N-(9ꢀ-fluorenylmethoxycarbonyl)
(Fmoc)-protected amine 10 and its C-4 epimer 11 were prepared by respectively
treating 3 and 2 with Fmoc-ONSu under standard conditions. Coupling of the
amine 2 with 4-hydroxyphenylacetic acid in the presence of dicyclohexylcarbodi-

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361
Table 1. Reaction of Glycals 7–11 and 13 with NBS and Water in the Presence of a Co-solvent
Reaction Conditions
Temp.
(ꢂC)
Time
(h)
Entry
Substrate
Solvent System
Product (% Yield)
1
2
3
7
8
9
H2O/CH3CH (1:9)
H2O/CH3CN (1:9)
H2O/CH3CN (1:9)
20
20
20
2
2
2
14a:14b ꢃ 1:1 (85)
15a:15b ꢃ 7:1 (72)
16a:16b ꢃ 2:1 (34)
16d (33)
4
9
H2O/CH3CN (1:1)
20
2
16a:16b ꢃ 1:2 (35)
16d (39)
5
6
7
8
9
9
7
H2O/CH3CN (1:9)
H2O/DMSO (1:1)
H2O/CH3CN (1:9)
H2O/CH3CN (1:4)
80
ꢄ20
60
0.5
6
0.5
2
16d (84)
16a:16b ꢃ 1:5 (56)
14b (83)
17a:17b ꢃ 3:1 (17)
17c (79)
10
20
9
10
H2O/CH3CN (1:1)
60
0.5
17a:17b ꢃ 4:1 (37)
17c (55)
10
11
12
13
11
11
11
13
H2O/CH3CN (1:4)
H2O/CH3CN (1:4)
H2O/CH3CN (1:4)
H2O/CH3CN (1:9)
0
20
60
20
72
2
0.5
2
18a:18b ꢃ 3:1 (72)
18a:18b ꢃ 3:1 (72)
18a:18b ꢃ 3:1 (70)
19a:19b ꢃ 1:1 (60)
imide (DCC) and 1-hydroxybenzotriazole (HOBT) hydrate gave, after conven-
tional workup, the 4-(4ꢀ-hydroxyphenyl)acetamido compound 12 in 96% yield.
Subsequent acetylation of 12 under standard conditions gave, after column chro-
matography, the 4-(4ꢀ-acetoxyphenyl)acetamido-4-deoxy glycal 13 in 83% yield.
This series of 4-N-acylated amines were then used in halohydroxylation re-
actions employing varying reaction conditions such as temperature and solvent
composition. These results are summarised in Table 1.
Halohydroxylation of glycal 7 with NBS and aqueous acetonirile at rt for 2 h
proceeded uneventfully to provide the two bromohydrins 14a and 14b in a 1:1 ra-
1
tio (by H NMR spectroscopy) (Table 1, entry 1). The two adducts were chro-
matographically inseparable on silica gel for all of the different solvent combina-
tions investigated and, as a consequence, the spectral data of the product
composition were not easy to interpret due to overlapping signals. Notwithstand-
ing these difficulties, bromohydroxylation, in mechanistic terms, should yield ei-
ther a mixture of the bromohydrins, or if there is stereocontrol in the addition pro-
cess a preferred bromohydrin. Clearly the possibilities are either the
trans-2,3-diaxial isomer 14a and/or the 2,3-diequatorial isomer. In this system,
however, it is to be expected that the initially formed 2,3-diequatorial adduct, given
time, would equilibrate or mutarotate to the thermodynamically more stable 2-ax-
ial-3-equatorial isomer 14b due to the anomeric effect.6
In some systems (vide infra), the 2,3-diequatorial adduct can be observed (by
TLC analysis or 1H NMR spectroscopy) in the crude reaction product mixture. As
can be expected, mutarotation to the more stable ꢁ-anomer then occurs with pro-

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KOK, VAN PHAN, AND VON ITZSTEIN

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363
longed handling of the reaction product such as column purification, a process that
complicates the physical analysis and spectral interpretation even further. It may
be speculated therefore that where both diaxial and diequatorial adducts are formed
in a reaction, the adducts obtained after chromatographic purification are the ther-
modynamically more stable ꢁ-anomers. In the case of products from the D-glycero-
D-galacto system (e.g. 7), the smaller coupling constant for 3J3,4 (ca. 3 Hz) is more
characteristic of the diaxial adduct (e.g. 14a) while a larger 3J3,4 coupling constant
(ca. 10 Hz) is more characteristic of the adduct with an equatorial Br at C-3. For
products derived from the D-glycero-D-talo system (e.g. 8), the two adducts (eg 15a
and b) are not discernible on the basis of the 3J3,4 coupling constant with both be-
ing about 3 Hz in magnitude. For either system however, the long range coupling
4J3,OH-C(2) (ca. 1 Hz) can sometimes be observed in the 1H NMR spectrum. In con-
formational terms this can only be fulfilled by an axially-oriented OH at C-2 and
an equatorial Br at C-3.
While an approximate 1:1 stereochemical outcome of the halohydroxylation
reaction can be expected for glycals with no serious steric influences at C-4 such
as 7 (Table 1, entry 1), stereoselectivity in favour of the diaxial adduct (15a) was
obtained for its epimer 87 (Table 1, entry 2). In the latter situation, an inherent con-
formational bias due to the substituent at C-4 residing in an axial orientation, forces
mainly anti addition to the double bond.
While halohydroxylation of the glycals 7 and 8 with NBS in aqueous CH3CN
at rt appears straightforward, this is not the case for the other 4-N-acylated glycals
such as 9–11. Thus, treatment of the 4-benzamido-4-deoxy glycal 9 with NBS in
10% aqueous CH3CN at rt for 2 h gave the desired bromohydrins 16a and 16b as
a mixture [Rƒ (EtOAc) ꢃ 0.55] in only 34% yield (Table 1, entry 3). A slower mi-
grating component [by TLC analysis; Rƒ (EtOAc) ꢃ 0.38] was also isolated after
1
column chromatography and was determined (by both H NMR and mass spec-
troscopy) to be the oxazine 16d (33%), formed by competitive intramolecular nu-
cleophilic attack on the intermediate bromonium ion intermediate 16c (Scheme 1).
The absence of the second NH resonance in the 1H NMR spectrum and a (M ꢅ H)ꢅ
peak m/z at 615/613 in the mass spectrum are in accord with the assigned structure
of 16d. Furthermore, aqueous acid hydrolysis (HOAc:H2O:EtOAc ꢃ 1:2:2, 50°C,
40 h) of 16d at 50°C afforded only the bromohydrin 16b (41% isolated yield after
chromatography on silica). A coupling constant of 10.5 Hz for 3J3,4 in the 1H NMR
spectrum of this compound (16b) is consistent for H-3 being axial. From this re-
sult, an analysis of the spectral information for the earlier mixture of bromohydrins
revealed that the diaxial bromohydrin 16a was the major product formed from the
intermolecular reaction (16a:16b ꢃ 2:1).
As shown by previous studies,4 and as our subsequent experiments demon-
strate, besides the polar and steric requirements of the substituent, the nature of the
solvent composition and the reaction temperature can also influence the course of
the reaction. Hence, in the halohydroxylation reaction of 9 with NBS and aqueous
CH3CN, when the proportion of H2O was increased from 10% to 50%, the major
bromohydrin formed was 16b rather than 16a (16a:16b ꢃ 1:2; combined yield of
35%) (Table 1, entry 4). The oxazine 16d was also formed in the reaction (39%).

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KOK, VAN PHAN, AND VON ITZSTEIN
Scheme 1.
With an increase in temperature (Table 1, entry 5), halohydroxylation of 9 with
NBS in 10% aqueous CH3CN at 80°C for 30 min, gave the oxazine 16d exclusively
(84% isolated yield after chromatography on silica). On the other hand, the reac-
tion when conducted at ꢄ20°C in a 1:1 mixture of DMSO/H2O (Table 1, entry 6)
gave no detectable amount of oxazine 16d; rather a 1:5 mixture of 16a and 16b be-
ing formed in 56% yield. It is worth noting that the 1H NMR spectrum taken of the
crude product of this reaction showed no resonances that correspond to the bro-
mohydrin 16b suggesting that mutarotation of the initially formed 2,3-diequatorial
adduct may have occurred during the purification process.
These results suggested that it would be of value to investigate halohydroxy-
lation of the 4-acetamido-4-deoxy glycal 7 with NBS in aqueous CH3CN at a
higher temperature. As Table 1, entry 7 shows, only the 2-axial-3-equatorial adduct
14b was obtained when the temperature was increased to 60°C, implying that at a
higher temperature, the thermodynamically more stable reaction intermediate was
the 2,3-diequatorial bromonium ion adduct.
Next, we investigated halohydroxylation of the 4-epi-Fmoc-amino-4-deoxy
glycal 10 with NBS/aqueous CH3CN. When 10 was treated with NBS in 20%
aqueous CH3CN at rt for 2 h (Table 1, entry 8), the desired bromohydrins 17a and
17b were formed as an inseparable mixture in very low yield (17%). A faster mi-
grating component (by TLC analysis), isolated after chromatography on silica, was
found to be the oxazine 17c (79%). Aqueous acid hydrolysis of the oxazine 17c
gave the diaxial bromohydrin 17a in approximately 50% yield, contaminated with
approximately 20% of the glycal starting material 10 (by 1H NMR spectroscopy).
In the light of this result, the major bromohydrin formed in the intermolecular ver-
sion of the reaction was the diaxial adduct 17a. The yield of the desired bromohy-
drins 17a and 17b improved to 37% (17a:17b ꢃ 4:1) when the reaction was con-
ducted at 60°C for 30 min, with a concomitant increase in the amount of water in
the reaction (Table 1, entry 9). The oxazine 17c was formed as the major product
of this reaction (55%).
In contrast to its 4-epimer, the reaction of the glycal 11 with NBS in aqueous
CH3CN over a range of temperatures (0°C, rt and 60°C) (Table 1 entries 10–12)
did not result in any formation of the corresponding oxazine analogue. Only the de-
sired bromohydrins 18a and 18b were produced. In this situation, with the more

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365
sterically-demanding Fmoc group at C-4, the course of the reaction was biased in
favour of the diaxial adduct 18a in all three cases.
When the 4-(4ꢀ-acetoxyphenyl)acetamido)-4-deoxy glycal 13 was treated
with NBS in aqueous CH3CN at rt for 2 h (Table 1, entry 13), a 1:1 mixture of the
bromohydrins 19a and 19b was obtained, with no oxazine being formed. Thus,
compared to the 4-benzamido-4-deoxy glycal 9, the intramolecular version of the
addition reaction is, in this case, not observed for a weaker nucleophile.
Finally, in a reaction reminiscent of that involving the introduction8 of nu-
cleophiles such as azide and sulfur at the C-4 position of Neu5Ac2en via the oxa-
zoline analogue, 7,8,9-tri-O-acetyl-2,6-anhydro-3,4,5-trideoxy-2ꢀ-methyl(methyl
D-glycero-D-talo-non-2-enonate)[5,4-d]oxazole, the 1,3-oxazine analogue 16d
was also found to be amenable to attack by nucleophiles at the activated C-2 posi-
tion. Thus, treatment of the oxazine 16d with n-Bu3SnH/AIBN furnished the cor-
responding debrominated oxazine 20. Subsequent treatment of 20 with TMSN3
gave, after column chromatography, the 2-ꢁ-azide 21 in 52% yield. The glycal 9
was also obtained as a by-product (16%).
In conclusion, several novel 4-N-acylated sialosyl donors have been prepared
via halohydroxylation of the corresponding glycal with NBS and aqueous CH3CN.
Depending upon the nature of the substituent at C-4 a competing intramolecular
version of the process leading to oxazine analogues was also observed with the

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KOK, VAN PHAN, AND VON ITZSTEIN
amount formed being temperature and solvent-composition dependent. These ox-
azine analogues can, however, be readily hydrolysed into the desired bromohy-
drins. Further study employing these bromohydrins in glycosylation reactions is
presently underway.
EXPERIMENTAL
General Methods. 1H NMR (300 MHz) and 13C NMR (75 MHz) spectra
(in ꢆppm) were obtained using a Bruker AMX-300 spectrometer. All NMR spec-
tra were recorded in CDCl3 (unless otherwise stated) and referenced using solvent
residues. J-Values are given in hertz (Hz). Low resolution (LR) electrospray ion-
ization (ESI) mass spectra were recorded on a Micromass Platform II mass spec-
trometer and high resolution (HR) mass spectra were recorded on a Bruker BIO-
APEX II Fourier Transform Ion Cyclotron Resonance mass spectrometer with
“Analytica” ESI source. Reactions were monitored by TLC on Kieselgel 60 F254
plate (Merck 5554) and detection of the spots was carried out by spraying with a
95% aqueous solution containing 5% H2SO4 and charring of the plates at 180°C.
Hexane refers to the fraction of petroleum ether that boils in the range 60–80°C.
All solvents and reagents were distilled and NBS (purchased from Aldrich) was re-
crystallised from H2O, before use.
Preparation of the 4-N-acylated-4-deoxy glycals 7–13. The amine 2 was
prepared from the azide 5 according to literature methods.2 Acylation of the amine
2 under standard conditions (Ac2O, py, DMAP, rt, 24 h) provided compound 7 in
54% yield. The 1H NMR spectral data for 7 were consistent with the literature.7 Acy-
lation of the amine 2 with benzoic anhydride in pyridine gave, after chromatogra-
phy on silica gel (EtOAc/hexane, 1.3–1:1), the 4-benzamido-4-deoxy compound 9
in 89% yield. The azide 6 was prepared from Neu5Ac 1 following published pro-
cedures,5 and following catalytic hydrogenolysis (10% Pd/C, atmospheric H2, rt, 50
min) in MeOH, the amine 3 was obtained in 92% yield. Acetylation of 3 under stan-
dard conditions (Ac2O, py) provided the 4-acetamido-4-deoxy glycal 8 in 35%
yield. The Fmoc-protected amines 10 and 11 were prepared by treating the amines
3 and 2 respectively with Fmoc-ONSu at 0°C until TLC analysis indicated complete
consumption of starting material. In each case, the product was isolated after chro-
matography on silica gel (EtOAc/hexane, 2:1), 10 (72%), 11 (97%). For the prepa-
ration of 13, the amine 2 was added to a mixture containing a molar equivalent each
of DCC, HOBT-hydrate and 4-hydroxyphenylacetic acid. Conventional workup
followed by chromatography on silica (EtOAc) furnished the corresponding 4-(4ꢀ-
hydroxyphenyl)acetamido-4-deoxy glycal 12 in 96% yield. This compound was
then treated with Ac2O/DMAP/py under standard conditions affording, after chro-
matography on silica (EtOAc), the desired glycal 13 in 83% isolated yield.
Methyl 4,5-diacetamido-7,8,9-tri-O-acetyl-2,6-anhydro-3,4,5-trideoxy-
1
D-glycero-D-talo-non-2-enonate (8). Rƒ 0.29 (EtOAc/MeOH, 9:1); H NMR ꢆ

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6.03 (1 H, d, J3,4 4.8, H-3), 5.63 (2 H, m, NHa and NHb), 5.46 (1 H, dd, J7,6 3.9, J7,8
3.9, H-7), 5.29 (1 H, m, H-8), 4.77 (1 H, ddd, J4,5 4.8, J4,NH 7.8, H-4), 4.68 (1 H,
dd, J9,8 3.0, J9,9ꢀ 12.6, H-9), 4.42 (1 H, ddd, J5,6 9.0, J5,NH 9.0, H-5), 4.20 (1 H, dd,
J9ꢀ,8 5.4, H-9ꢀ), 4.18 (1 H, dd, H-6), 3.80 (3 H, s, COOCH3), 2.12, 2.09, 2.06, 2.04,
1.95 (each 3 H, s, OCOCH3 ꢇ 3, NHCOCH3 ꢇ 2); 13C NMR ꢆ 171.1, 170.8, 170.7,
169.9, 162.0 (carbonyls), 144.4 (C-2), 108.8 (C-3), 74.1, 71.5, 68.4 (C-6, C-7, C-
8), 62.1 (C-9), 52.4, 45.8, 42.8 (C-4, C-5, COOCH3), 22.9 (NHCOCH3 ꢇ 2), 20.7,
20.6, 20.5 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 472 (MHꢅ, 100%); HRMS:
Calcd for C20H29N2O11:[Mꢅ ꢅ 1], 473.1760. Found: m/z, 473.1756.
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-4-benzamido-3,4,5-
trideoxy-D-glycero-D-galacto-non-2-enonate (9). Rƒ 0.60 (EtOAc); [ꢈ]D ꢅ98°
1
(c 1.00, CHCl3); H NMR ꢆ 7.74–7.40 (5 H, m, aromatic protons), 6.54 (1 H, d,
JNHa,5 8.4, NHa), 6.05 (1 H, d, J3,4 2.4, H-3), 5.93 (1 H, d, JNHb,4 9.9, NHb), 5.55 (1
H, dd, J7,61.0, J7,8 5.1, H-7), 5.35 (1 H, ddd, J8,9 2.7, J8,9ꢀ 7.2, H-8), 4.99 (1 H, m,
H-4), 4.71 (1 H, dd, J9,9ꢀ 12.3, H-9), 4.41–4.36 (2 H, m, H-5, H-6), 4.20 (1 H, dd,
H-9ꢀ), 3.79 (3 H, s, COOCH3), 2.11, 2.09, 2.07, 1.85 (each 3 H, s, NHCOCH3,
OCOCH3 ꢇ 3); 13C NMR ꢆ 171.6, 170.6, 170.3, 169.8, 168.4, 161.7 (carbonyls),
144.4 (C-3), 133.3, 131.9, 128.7, 126.9 (aromatic carbons), 110.7 (C-2), 77.1, 71.5,
68.1 (C-6, C-7, C-8), 62.3 (C-9), 52.3, 49.7, 46.5 (C-4, C-5, COOCH3), 22.6
(NHCOCH3), 20.8, 20.7, 20.5 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 535
(MHꢅ, 100%), 338 (8), 60 (5); HRMS: Calcd for C25H31N2O11:[Mꢅ ꢅ 1],
535.1928. Found: m/z, 535.1902.
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-4-N-(9ꢀ-fluorenyl-
methoxycarbonyl)amino-3,4,5-trideoxy-D-glycero-D-talo-non-2-enonate (10).
Rƒ 0.50 (EtOAc/hexane, 3:1); [ꢈ]D ꢄ92° (c 1.40, CHCl3); 1H NMR ꢆ 7.80–7.26 (8
H, m, aromatic protons, 6.00 (1 H, d, J3,4 5.1, H-3), 5.55 (1 H, br s, NHa), 5.45 (1
H, dd, J7,63.3, J7,8 4.2, H-7), 5.26 (1 H, ddd, J8,9 3.0, J8,9ꢀ 7.5, H-8), 4.75 (1 H, d,
JNHb,4 7.8, NHb), 4.69 (1 H, dd, J9,9ꢀ 12.6, H-9), 4.50–4.40 (4 H, m, H-4, H-5, -CH-
CH2O-), 4.18 (1 H, dd, H-9ꢀ), 4.03 (1 H, dd, J6,5 9.6, H-6), 3.80 (3 H, s, COOCH3),
2.10, 2.09, 2.06, 1.89 (each 3 H, s, NHCOCH3, OCOCH3 ꢇ 3); 13C NMR ꢆ 170.6,
170.0, 161.9, 156.1 (carbonyls), 144.5, 143.6, 143.4, 141.2, 127.8, 127.1, 127.0,
124.8, 120.0 (C-2 and aromatic carbons), 108.3 (C-3), 73.7, 71.4, 68.4 (C-6, C-7,
C-8), 66.9, 62.1 (C-9, -CH2OC(O)-), 52.4, 47.0, 45.7, 44.8 (C-4, C-5, COOCH3, -
CH-CH2O-), 23.0 (NHCOCH3), 20.8, 20.7, 20.5 (OCOCH3 ꢇ 3); LRMS (cone
voltage 30V): 653 (MHꢅ, 50%), 431 (10), 414 (100); HRMS: Calcd for
C33H37N2O12:[Mꢅ ꢅ 1], 653.2347. Found: m/z, 653.2344.
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-4-N-(9ꢀ-fluorenyl-
methoxycarbonyl)amino-3,4,5-trideoxy-D-glycero-D-galacto-non-2-enonate
1
(11). Rƒ 0.50 (EtOAc/hexane, 3:1); [ꢈ]D ꢅ46° (c 1.00, CHCl3); H NMR ꢆ
7.76–7.27 (8 H, m, aromatic protons), 6.00 (1 H, d, JNHb,4 9.3, NHa), 5.94 (1 H, br
s, H-3), 5.52 (1 H, m, H-7), 5.31 (2 H, m, H-8, NHb), 4.72 (1 H, dd, J9,8 2.4, J9,9ꢀ12.3,
H-9), 4.53 (1 H, m, H-4), 4.15–4.40 (6 H, m, H-5, H-6, H-9ꢀ, -CHCH2O-), 3.78 (3

ORDER
REPRINTS
368
KOK, VAN PHAN, AND VON ITZSTEIN
H, s, COOCH3), 2.12, 2.06, 2.05, 2.02 (each 3 H, s, NHCOCH3, OCOCH3 ꢇ 3);
LRMS (cone voltage 30V): 653 (MHꢅ, 100%), 414 (10), 338 (20), 60 (8); HRMS:
Calcd for C33H37N2O12:[Mꢅ ꢅ 1], 653.2347. Found: m/z, 653.2308.
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-2,6-anhydro-4-(4ꢀ-hydroxyphe-
nyl)acetamido-3,4,5-trideoxy-D-glycero-D-galacto-non-2-enonate (12). Rƒ
0.22 (EtOAc/hexane, 3:1); [ꢈ]D ꢄ14° (c 0.98, CHCl3); 1H NMR ꢆ 7.04–6.73 (4 H,
m, aromatic protons), 6.11 (1 H, d, JNHa,5 9.9, NHa), 5.90 (1 H, d, JNHb,4 9.0, NHb),
5.82 (1 H, d, J3,4 2.4, H-3), 5.47 (1 H, dd, J7,61.9, J7,8 4.8, H-7), 4.69 (1 H, ddd, J8,9
2.8, J8,9ꢀ 7.5, H-8), 4.85 (1 H, ddd, J4,5 9.6, H-4) 4.69 (1 H, dd, J9,9ꢀ12.5, H-9), 4.27
(1 H, dd, J6,5 9.6, H-6), 4.18 (1 H, ddd, H-5), 4.16 (1 H, dd, H-9ꢀ), 3.79 (3 H, s,
COOCH3), 3.44 (1 H, d, J10,10ꢀ15.3, CH10-Ph), 3.37 (1 H, d, CH10ꢀ-Ph), 2.08, 2.07,
2.06, 1.63 (each 3 H, m, NHCOCH3, OCOCH3 ꢇ 3); 13C NMR ꢆ 173.3, 172.0,
170.7, 170.3, 170.0, 161.8 (carbonyls), 155.8, 144.6, 130.3, 125.6, 115.9 (C-2, aro-
matic carbons), 110.6 (C-3), 77.2, 71.4, 68.0 (C-6, C-7, C-8), 62.2 (C-9), 52.4,
48.3, 46.5 (C-4, C-5, COOCH3), 33.8 (-CH2-C6H4-), 22.4 (NHCOCH3), 20.8, 20.7,
20.5 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 565 (MH ꢅ, 100%), 225 (20).
Methyl 5-Acetamido-4-(4ꢀ-acetoxyphenyl)acetamido-7,8,9-tri-O-acetyl-
2,6-anhydro-3,4,5-trideoxy-D-glycero-D-galacto-non-2-enonate (13). Rƒ 0.31
(EtOAc); 1H NMR ꢆ 7.27–7.04 (4 H, m, aromatic protons), 5.98 (1 H, d, JNHa,5 8.1,
NHa), 5.96 (1 H, d, JNHb,4 9.3, NHb), 5.84 (1 H, d, J3,4 2.4, H-3), 5.48 (1 H, dd, J7,6
2.1, J7,8 4.8, H-7), 5.30 (1 H, ddd, J8,9 2.7, J8,9ꢀ 7.2, H-8), 4.83 (1 H, ddd, J4,5 9.6,
H-4), 4.70 (1 H, dd, J9,9ꢀ 12.3, H-9), 4.29 (1 H, dd, J6,5 10.2, H-6), 4.15 (1 H, ddd,
H-5), 4.16 (1 H, dd, H-9ꢀ), 3.78 (3 H, s, COOCH3), 3.52 (1 H, d, J10,10ꢀ 15.0, CH10-
Ph) 3.46 (1 H, d, CH10ꢀ-Ph), 2.29, 2.09, 2.07, 2.06, 1.69 (each 3 H, s, NHCOCH3,
OCOCH3 ꢇ 4); 13C NMR ꢆ 172.0, 171.3, 170.6, 170.3, 169.8, 169.4, 161.7 (car-
bonyls), 144.6 (C-2), 149.8, 132.0, 130.3 (aromatic carbons), 110.4 (C-3), 77.4,
71.5, 67.9 (C-6, C-7, C-8), 62.2 (C-9), 52.3, 48.6, 46.4 (C-4, C-5, COOCH3), 42.6
(-CH2-C6H4-), 22.6 (NHCOCH3), 21.0, 20.8, 20.7, 20.5 (OCOCH3 ꢇ 4); LRMS
(cone voltage 30V): 642 (MNaꢅ, 55%), 607 (MHꢅ, 100), 327 (10), 60 (12);
HRMS: Calcd for C28H38N3O13:[M ꢅ NH4ꢅ], 624.2404. Found: m/z, 624.2404.
Representative Procedure for the Reaction of the 4-N-Acylated-4-deoxy
Glycals 7–11 and 13 with NBS and H2O in a Co-solvent. To a stirring solution
of the glycal (0.2 mmol) in H2O and a co-solvent (see Table 1) was added NBS (1.1
molar equivalents). After stirring at the temperature and time as specified in Table
1, the reaction mixture was concentrated to dryness under diminished pressure. The
resulting residue was purified by flash chromatography on silica gel affording the
adducts as specified in Table 1.
Methyl 4,5-Diacetamido-7,8,9-tri-O-acetyl-3-bromo-3,4,5-trideoxy-D-
erythro-ꢀ-L-manno-2-nonulopyranosonate (14a) and Methyl 4,5-diacetamido-
7,8,9-tri-O-acetyl-3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-gluco-2-nonulopyra-
nosonate (14b).

ORDER
REPRINTS
BROMOHYDROXYLATION OF GLYCALS
369
1
14a: Rƒ 0.72 (EtOAc/MeOH, 4:1); H NMR ꢆ 7.03 (1 H, d, JNHa,5 9.3,
NHa), 6.32 (1 H, d, JNHb,4 8.4, NHb), 5.44 (1 H, m, H-7), 5.33 (1 H, ddd, J8,7 6.6,
J8,9 2.1, J8,9ꢀ 6.6, H-8), 4.85 (1 H, dd, J9,9ꢀ 12.3, H-9), 4.63 (1 H, m, H-4), 4.60 (1
H, d, J3,4 3.0, H-3), 4.40 (1 H, m, ddd, J5,4 9.0, J5,6 9.0, H-5), 4.36 (1 H, m, H-6),
4.19 (1 H, dd, H-9ꢀ), 3.81 (3 H, s, COOCH3), 2.14, 2.11, 2.06, 2.05, 1.93 (each 3
H, s, NHCOCH3 ꢇ 2, OCOCH3 ꢇ 3).
14b: Rƒ 0.72 (EtOAc/MeOH, 4:1); 1H NMR ꢆ 8.79 (1 H, br, OH), 6.77 (1
H, d, JNHa,5 9.9, NHa), 6.38 (1 H, d, JNHb,4 9.9, NHb), 5.34 (1 H, dd, J7,6 2.4, J7,8
6.6, H-7), 5.21 (1 H, ddd, J8,9 2.4, J8,9ꢀ 6.6, H-8), 4.57 (1 H, ddd, J4,5 10.8, H-4),
4.37 (1 H, dd, J6,5 10.5, H-6), 4.32 (1 H, dd, J9,9ꢀ 12.6, H-9), 4.23 (1 H, d, J3,4 11.4,
H-3), 4.11 (1 H, ddd, H-5), 4.01 (1 H, dd, H-9ꢀ), 3.92 (3 H, s, COOCH3), 2.12, 2.10,
2.02, 1.97, 1.91 (each 3 H, s, NHCOCH3 ꢇ 2, OCOCH3 ꢇ 3); 13C NMR ꢆ 178.5,
171.7, 171.4, 170.7, 170.3, 169.8, 167.8 (carbonyls), 95.4 (C-2), 70.6, 69.8, 67.7
(C-6, C-7, C-8), 62.4 (C-9), 53.9, 52.9, 50.5, 50.3 (C-3, C-4, C-5, COOCH3), 22.9,
22.8 (NHCOCH3 ꢇ 2), 20.8, 20.6, 20.5 (OCOCH3 ꢇ 3); LRMS (cone voltage
30V): 571, 569 (MHꢅ, 5%), 490 (15), 419 (25), 374 (60), 83 (100); HRMS: Calcd
for C20H33N3O1279Br:[M ꢅ NH4ꢅ], 586.1247. Found: m/z, 586.1247.
Methyl 4,5-Diacetamido-7,8,9-tri-O-acetyl-3-bromo-3,4,5-trideoxy-D-
erythro-ꢀ-L-altro-2-nonulopyranosonate (15a) and Methyl 4,5-Diacetamido-
7,8,9-tri-O-acetyl-3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-allo-2-nonulopyra-
nosonate (15b).
15a: Rƒ 0.36 (CH2Cl2/MeOH, 9:1); 1H NMR ꢆ 7.45 (1 H, br, NHa), 6.80 (1
H, br, NHb), 5.37 (1 H, m, H-7), 5.29 (1 H, m, H-8), 5.02 (1 H, m, H-4), 4.75–4.55
(4 H, m, H-5, H-6, H-9, OH), 4.39 (1 H, m, H-3), 4.07 (1 H, dd, J9ꢀ,8 8.1, J9ꢀ,9 13.2,
H-9ꢀ), 3.78 (3 H, s, COOCH3), 2.16, 2.09, 2.04, 2.03, 1.97 (each 3 H, s, OCOCH3
ꢇ 3, NHCOCH3 ꢇ 2); 13C NMR (CDCl3/CD3OD, 20:1): ꢆ 171.2, 171.0, 170.7,
170.2, 168.9, 167.4 (carbonyls), 95.8 (C-2), 72.6, 69.0, 68.2 (C-6, C-7, C-8), 62.9
(C-9), 52.7, 51.2, 47.1, 41.0 (C-3, C-4, C-5, COOCH3), 23.1, 22.6 (NHCOCH3
ꢇ 2), 20.8, 20.7, 20.6 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 593, 591
(MNaꢅ, 30%), 571, 569 (MHꢅ, 100), 490 (10); HRMS: Calcd for
C20H30N2O1279Br:[Mꢅ ꢅ 1], 568. 8982. Found: m/z, 569.0997.
1
15b: Rƒ 0.42 (CH2Cl2/MeOH, 9:1); H NMR ꢆ 6.13 (1 H, d, JNHa,5 9.9,
NHa), 5.94 (1 H, br s, NHb), 5.36 (1 H, dd, J7,6 4.8, J7,8 6.3, H-7), 5.18 (1 H, m, H-
8), 4.88 (1 H, m, H-4), 4.50 (1 H, m, H-5), 4.42 (1 H, dd, J9,8 3.6, J9,9ꢀ 12.3, H-9),
4.19 (1 H, dd, J9ꢀ,8 6.3, H-9ꢀ), 4.06 (1 H, dd, J6,5 6.3, H-6), 3.96 (1 H, d, J3,4 2.7, H-
3), 3.93 (1 H, br s, OH), 3.81 (3 H, s, COOCH3), 2.12, 2.08, 2.05, 2.03, 1.99 (each
3 H, s, OCOCH3 ꢇ 3, NHCOCH3 ꢇ 2); 13C NMR (CDCl3/CD3OD, 20:1): ꢆ 170.9,
170.6, 170.8 (carbonyls), 96.0 (C-2), 73.2, 71.0, 68.6 (C-6, C-7, C-8), 61.7 (C-9),
57.8, 53.2, 44.8, 42.9 (C-3, C-4, C-5, COOCH3), 22.7, 22.6 (NHCOCH3 ꢇ 2),
20.6, 20.5, 20.4 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 490 (MHꢅ - Br,
100%).

ORDER
REPRINTS
370
KOK, VAN PHAN, AND VON ITZSTEIN
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-4-benzamido-3-bromo-3,4,5-
trideoxy-D-erythro-ꢀ-L-manno-2-nonulopyranosonate (16a), Methyl 5-ac-
etamido-7,8,9-tri-O-acetyl-4-benzamido-3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-
L-gluco-2-nonulopyranosonate (16b) and 2-Phenyl(Methyl 5-acetamido-
7,8,9-tri-O-acetyl-3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-gluco-2-nonulopyra-
nosonate)4H-1,3-oxazine (16d).
16a: Rƒ 0.55 (EtOAc); selected 1H NMR ꢆ 5.52 (1 H, dd, J7,6 1.5 J7,8 4.2,
H-7), 5.38 (1 H, ddd, J8,9 2.4, J8,9ꢀ 6.9, H-8), 4.87 (1 H, dd, J9,9ꢀ 12.3, H-9), 4.79 (1
H, d, J3,4 3.3, H-3), 4.22 (1 H, dd, H-9ꢀ), 3.81 (3 H, s, COOCH3); selected 13C
NMR ꢆ 172.4, 172.1, 170.3, 169.2, 168.0, 167.9, 167.7 (carbonyls), 73.0, 71.8,
68.6 (C-6, C-7, C-8), 62.9 (C-9), 54.6, 52.9, 50.8, 44.8 (C-3, C-4, C-5, COOCH3).
1
16b: Rƒ 0.55 (EtOAc); H NMR ꢆ 7.66–7.31 (5 H, m, aromatic protons),
6.64 (1 H, d, JNHa,5 10.2, NHa), 6.44 (1 H, d, JNHb,4 9.9, NHb), 5.34 (1 H, dd, J7,6
2.4, J7,8 7.5, H-7), 5.19 (1 H, ddd, J8,9 2.4, J8,9ꢀ 6.3, H-8), 4.92 (1 H, d, JOH,3 0.9,
OH), 4.85 (1 H, ddd, J4,3 10.5, J4,5 10.5, H-4), 4.44 (1 H, dd, J6,5 10.5, H-6), 4.33
(1 H, dd, H-3), 4.24 (1 H, ddd, H-5), 4.26 (1 H, dd, J9,9ꢀ 12.6, H-9), 3.96 (1 H, dd,
H-9ꢀ), 3.87 (1 H, s, COOCH3), 2.04, 2.03, 2.02 (each 3 H, s, OCOCH3 ꢇ 3), 1.70
(3 H, s, NHCOCH3); 13C NMR (CDCl3): ꢆ 171.6, 170.6, 170.0, 169.8, 168.5, 167.7
(carbonyls), 133.7, 131.9, 128.7, 127.0 (aromatic carbons), 95.4 (C-2), 70.8, 69.6,
67.7 (C-6, C-7, C-8), 62.4 (C-9), 54.0, 53.7, 50.7, 50.6 (C-3, C-4, C-5, COOCH3),
22.7 (NHCOCH3), 20.8, 20.6 (OCOCH3 ꢇ 3); LRMS for (cone voltage 30V): 655,
653 (MNaꢅ, 12%), 633, 631 (MHꢅ, 30), 551 (100); HRMS: Calcd for
C25H32N2O1279Br:[Mꢅ ꢅ1], 631.1139. Found: m/z, 631.1140.
1
16d: Rƒ 0.38 (EtOAc); H NMR ꢆ 7.92–7.35 (5 H, m, aromatic protons),
5.84 (1 H, br, NH), 5.32 (1 H, ddd, J8,7 6.9, J8,9 2.4, J8,9ꢀ 5.7, H-8), 5.25 (1 H,
dd, J7,6 1.5, H-7), 4.68 (1 H, d, J3,4 3.9, H-3), 4.49 (1 H, dd, J9,9ꢀ 12.3, H-9),
4.47–4.44 (2 H, m, H-5, H-6), 4.12–4.07 (2 H, m, H-4, H-9ꢀ), 3.93 (3 H, s,
COOCH3), 2.11, 2.07, 2.04 (each 3 H, s, OCOCH3), 1.79 (NHCOCH3); 13C
NMR ꢆ 170.6, 169.7, 169.4, 169.1, 164.6 (carbonyls), 152.3 (CꢃN), 131.5,
130.9, 128.1, 127.6 (aromatic carbons), 94.7 (C-2), 70.1, 69.6, 68.5 (C-6, C-7,
C-8), 62.0 (C-9), 55.4, 53.4, 47.9, 42.0 (C-3, C-4, C-5, COOCH3), 23.3
(NHCOCH3), 20.8, 20.7, 20.0 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 615,
613 (MHꢅ, 100%), 537 (20); HRMS: Calcd for C25H30N2O1179Br:[Mꢅ ꢅ 1],
613.1033. Found: m/z, 613.1005.
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-3-bromo-3,4,5-trideoxy-4-N-(9ꢀ-
Fluorenylmethoxycarbonyl)amino-D-erythro-ꢀ-L-altro-2-nonulopyra-
nosonate (17a), Methyl 5-Acetamido-7,8,9-tri-O-acetyl-3-bromo-3,4,5-
trideoxy-4-N-(9ꢀ-Fluorenylmethoxycarbonyl)amino-D-erythro-ꢀ-L-allo-2-non
ulopyranosonate (17b) and 2-Fluorenylmethoxy(Methyl 5-Acetamido-7,8,9-
tri-O-acetyl-3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-altro-2-nonulopyra-
nosonate)4H-1,3-oxazine (17c).

ORDER
REPRINTS
BROMOHYDROXYLATION OF GLYCALS
371
1
17a: Rƒ 0.46 (CH2Cl2/MeOH, 19:1); H NMR ꢆ 7.85–7.30 (8 H, m, aro-
matic protons), 5.50 (1 H, br, NHa), 5.32–5.25 (2 H, m, H-7, H-8), 5.20 (1 H, d,
JNHb,5 10.2, NHb), 4.95 (1 H, ddd, J5,4 3.0, J5,6 10.5, H-5), 4.64 (1 H, dd, J9,8 2.1,
J9,9ꢀ 12.3, H-9), 4.56–4.24 (4 H, m, OH and -CHCH2O-), 4.20 (1 H, m, H-9ꢀ), 3.89
(3 H, s, COOCH3), 3.87 (1 H, dd, J6,7 1.5, H-6), 3.75 (1 H, m, H-4), 2.16, 2.08, 2.06
(each 3 H, s, OCOCH3 ꢇ 3), 1.86 (3 H, s, NHCOCH3); 13C NMR ꢆ 172.0, 171.8,
171.4, 170.2, 167.6, 156.3 (carbonyls), 143.4, 141.2, 127.8, 127.0, 124.9, 124.8,
120.0 (aromatic carbons), 95.6 (C-2), 72.6, 72.2, 68.8 (C-6, C-7, C-8), 67.6, 62.8
(C-9, -CH2OC(O)-), 54.5, 52.9, 51.4, 46.8, 45.0 (C-3, C-4, C-5, COOCH3,
-CHCH2O-), 23.0 (NHCOCH3), 21.0, 20.8, 20.7 (OCOCH3 ꢇ 3); LRMS
(cone voltage 30V): 733, 731 (MHꢅ, 100%), 555, 553 (15). HRMS: Calcd for
C33H38N2O1379Br:[Mꢅ ꢅ 1], 749.1557. Found: m/z, 749.1559.
1
17b: Rƒ 0.46 (CH2Cl2/MeOH, 19:1); H NMR ꢆ 7.79–7.30 (8 H, m, aro-
matic protons), 6.02 (1 H, d, JNHa,5 9.3, NHa), 5.40 (1 H, br, NHb), 5.33 (1 H, dd,
J7,6 1.8, J7,8 4.5, H-7), 5.25 (1 H, m, H-8), 5.03 (1 H, m, H-9), 4.74 (1 H, m, H-5),
4.55–4.20 (7 H, m, H-3, H-4, H-6, -CH-CH2-, OH), 4.04 (1 H, dd, J9ꢀ,8 7.8, J9ꢀ,9
12.6, H-9ꢀ), 3.85 (3 H, s, COOCH3), 2.18, 2.10, 2.04 (each 3 H, s, OCOCH3 ꢇ 3),
1.87 (3 H, s, NHCOCH3).
1
17c: Rƒ 0.56 (CH2Cl2/MeOH, 19:1); H NMR ꢆ 7.85–7.30 (8 H, m, aro-
matic protons), 5.35–5.25 (2 H, m, H-7, H-8), 5.20 (1 H, d, JNHb,5 10.2, NHb), 4.95
(1 H, ddd, J5,4 3.0, J5,6 10.5, H-5), 4.64 (1 H, dd, J9,8 2.1, J9,9ꢀ 12.3, H-9), 4.56–4.30
(4 H, m, H-3, -CHCH2O-), 4.12 (1 H, dd, J9ꢀ,8 7.5, H-9ꢀ), 3.90 (3 H, s, COOCH3),
3.86 (1 H, dd, J6,7 1.5, H-6), 3.76 (1 H, dd, J4,3 3.3, H-4), 2.16, 2.08, 2.06 (each 3
H, s, OCOCH3 ꢇ 3), 1.86 (3 H, s, NHCOCH3); 13C NMR ꢆ 171.1, 170.6, 169.9,
167.6, 156.8 (carbonyls), 143.7, 143.5, 141.2, 127.7, 127.1, 125.1, 125.0, 120.0
(CꢃN, aromatic carbons), 95.4 (C-2), 71.0, 70.2, 67.7 (C-6, C-7, C-8), 67.4, 62.4
(-CHCH2O-, C-9), 55.2, 54.0, 51.0, 50.3, 46.9 (C-3, C-4, C-5, COOCH3, -
CHCH2O-), 22.9 (NHCOCH3), 20.8, 20.7, 20.6 (OCOCH3 ꢇ 3); LRMS (cone
voltage 30V): 733, 731 (MHꢅ, 100%), 555, 553 (18); HRMS: Calcd for
C33H36N2O1279Br:[Mꢅ ꢅ 1], 731.1452. Found: m/z, 731.1443.
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-4-N-(9ꢀ-Fluorenylmethoxycar-
bonyl)amino-3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-manno-2-nonulopyra-
nosonate (18a) and Methyl 5-Acetamido-7,8,9-tri-O-acetyl-4-N-(9ꢀ-Fluorenyl-
methoxycarbonyl)amino-3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-gluco-2-nonu
lopyranosonate (18b).
1
18a: Rƒ 0.50 (EtOAc/hexane, 2:1); H NMR ꢆ 7.76–7.28 (8 H, m, aro-
matic protons), 6.23 (1 H, d, JNHa,5 8.4, NHa), 5.86 (1 H, br, NHb), 5.44–5.42 (2
H, m, H-7, OH), 5.31 (1 H, m, H-8), 4.93 (1 H, dd, J9,8 2.1, J9,9ꢀ 12.6, H-9), 4.58
(1 H, br, H-3), 4.40–4.15 (6 H, m, H-5, H-6, H-9ꢀ, -CHCH2O-), 3.82 (3 H, s,
COOCH3), 2.17, 2.06, 2.01 (each 3 H, s, OCOCH3 ꢇ 3), 1.82 (3 H, s,
NHCOCH3); 13C NMR ꢆ 172.0, 171.8, 171.6, 170.2, 167.6, 156.3 (carbonyls),

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KOK, VAN PHAN, AND VON ITZSTEIN
143.4, 141.1, 127.8, 127.1, 125.4, 119.9 (aromatic carbons), 95.6 (C-2), 72.6,
72.2, 68.8 (C-6, C-7, C-8), 67.6, 62.8 (C-9, -CH2OC(O)-), 54.5, 52.9, 51.4, 46.8,
45.0 (C-3, C-4, C-5, -CHCH2O-, COOCH3), 22.9 (NHCOCH3), 21.0, 20.9, 20.7
(OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 751, 749 (MNaꢅ, 80%), 609 (35),
491 (15), 338 (40), 181 (100).
18b: Rƒ 0.60 (EtOAc/hexane, 2:1); 1H NMR ꢆ 7.75–7.29 (8 H, m, aromatic
protons), 5.95 (1 H, d, JNHa,5 9.3, NHa), 5.34 (1 H, dd, J7,6 1.8, J7,8 6.9, H-7), 5.21
(1 H, m, H-8), 5.02 (1 H, br, NHb), 4.90 (1 H, br, OH), 4.40–4.15 (8 H, m, H-3, H-
4, H-5, H-6, H-9, -CHCH2-), 3.99 (1 H, dd, J9ꢀ,8 6.3, J9ꢀ,9 12.3, H-9ꢀ), 3.94 (3 H, s,
COOCH3), 2.17, 2.08, 2.02 (each 3 H, s, OCOCH3 ꢇ 3), 1.82 (3 H, s, NHCOCH3);
13C NMR ꢆ 171.2, 170.7, 170.3, 170.0, 167.7, 156.9 (carbonyls), 143.7, 143.6,
141.2, 127.8, 127.3, 125.2, 125.0, 120 (aromatic carbons), 95.4 (C-2), 71.0, 70.3,
67.8 (C-6, C-7, C-8), 67.5, 62.5 (C-9, -CH2OC(O)-), 54.1, 51.0, 50.4, 46.9, 45.8
(C-3, C-4, C-5, -CHCH2O-, COOCH3), 29.6 (C-3), 23.0 (NHCOCH3), 20.9, 20.7,
20.6 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 773, 771 (MNaꢅ, 100%), 751,
749 (55), 669 (80); HRMS: Calcd for C33H38N2O1379Br:[Mꢅ ꢅ1], 749.1557.
Found: m/z, 749.1526
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-4-(4ꢀ-Acetoxyphenyl)acetamido-
3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-manno-2-nonulopyranosonate (19a)
and Methyl 5-Acetamido-7,8,9-tri-O-acetyl-4-(4ꢀ-Acetoxyphenyl)acetamido-
3-bromo-3,4,5-trideoxy-D-erythro-ꢀ-L-gluco-2-nonulopyranosonate (19b).
1
19a/19b: Rƒ 0.40 (EtOAc); H NMR ꢆ 7.22–7.03 (4 H, m, aromatic pro-
tons), 6.32, 6.29, 5.99 (2 H, d, J 7.8, 9.9, 9.6 respectively, NHa, NHb), 5.40–5.17
(2 H, m, H-7, H-8), 4.90–3.95 (6 H, m, H-3, H-4, H-5, H-6, H-9, H-9ꢀ), 3.92, 3.83
(3 H, s, COOCH3), 3.47 (2 H, m, -CH2-C6H4-), 2.29, 2.81, 2.12, 2.09, 2.06, 2.03,
2.02, 1.72, 1.70 (15 H, s, NHCOCH3, OCOCH3 ꢇ 4); 13C NMR ꢆ 170.6, 170.0,
169.9, 169.7, 169.6, 169.5, 168.1, 167.9, 167.5 (carbonyls), 149.8, 148.7, 132.0,
131.9, 130.4, 130.1 121.9 (aromatic carbons), 95.4, 95.3 (C-2), 71.8, 71.2, 70.8,
69.8, 68.5, 67.6 (C-6, C-7, C-8), 62.9, 62.4 (C-9), 54.2, 54.0, 53.0, 52.9, 50.5, 50.3,
50.1, 44.5 (C-3, C-4, C-5, COOCH3), 42.8, 42.5 (-CH2-C6H4-), 22.6, 21.0, 21.9,
20.8, 20.7, 20.6 (NHCOCH3, OCOCH3 ꢇ 4); LRMS (cone voltage 30V): 705, 703
(MHꢅ, 100%), 641 (55), 623 (20); HRMS: Calcd for C28H36N2O1479Br:[Mꢅ ꢅ 1],
703.1350. Found: m/z, 703.1315.
2-Phenyl(Methyl 5-Acetamido-7,8,9-tri-O-acetyl-3,4,5-trideoxy-D-glyc-
ero-ꢈ-D-galacto-2-nonulopyranosonate)4H-1,3-oxazine (20). A stirring solu-
tion of the oxazine 16d (180 mg, 0.294 mmol), n-Bu3SnH (257 mg, 0.882 mmol)
and AIBN (5 mg) in anhydrous THF (5 mL) was heated under reflux for 2 h, and
cooled. The volatiles were removed in vacuo and the resulting residue gave, after
column chromatography on silica (EtOAc), the title compound 20 as a colourless
amorphous mass, 150 mg (96%); Rƒ 0.13 (EtOAc); 1H NMR ꢆ 7.95–7.35 (5 H, m,
Ph), 6.09 (1 H, d, JNH,5 6.9, NH), 5.40 (1 H, m, H-8), 5.23 (1 H, d, J 8.1, H-7), 4.37

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373
(1 H, dd, J9,8 1.0, J9,9ꢀ 12.6, H-9), 4.22 (1 H, dd, J9ꢀ,8 4.5, H-9ꢀ), 4.20–4.17 (3 H, m,
H-4, H-5, H-6), 3.87 (3 H, s, COOCH3), 3.23 (1 H, m, H-3), 2.94 (1 H, dd, J3ꢀ,3
10.8, J3ꢀ,4 7.2, H-3ꢀ), 2.07, 2.05, 2.04, 1.99 (each 3 H, s, NHCOCH3, OCOCH3
ꢇ 3); 13C NMR ꢆ 171.0, 170.5, 170.4, 169.5, 167.0, 152.9 (carbonyls, CꢃN),
132.4, 131.0, 128.0, 127.3 (aromatic carbons), 95.7 (C-2), 68.9, 67.8, 65.2 (C-6, C-
7, C-8), 62.0 (C-9), 54.5, 53.0, 49.0 (C-4, C-5, COOCH3), 25.1 (C-3), 23.5
(NHCOCH3), 20.8, 20.5, 20.4 (OCOCH3 ꢇ 3); LRMS (cone voltage 30V): 535
(MHꢅ, 100%), 338 (8), 60 (5); HRMS: Calcd for C25H31N2O11:[Mꢅ ꢅ 1],
535.1928. Found: m/z, 535.1927.
Methyl 5-Acetamido-7,8,9-tri-O-acetyl-2-azido-4-benzamido-2,3,4,5-
tetradeoxy-D-glycero-ꢀ-D-galacto-2-nonulopyranosonate (21). A stirring so-
lution of the oxazine 20 (50 mg, 0.094 mmol) and azidotrimethylsilane (0.037 mL,
0.279 mmol) in anhydrous THF (5 mL) was heated under reflux for 16 h, and
cooled. The volatiles were removed under diminished pressure and the resulting
residue purified by column chromatography on silica gel (EtOAc/hexane, 2:1) af-
fording the 2-ꢁ-azide 21 as a colourless syrup, 28 mg (52%). Further elution of the
column gave the glycal 9, 8 mg (16%); Rƒ (EtOAc/hexane, 2:1): Rƒ (21) ꢃ 0.20;
Rƒ (9) ꢃ 0.15.
21: [ꢈ]D ꢄ40° (c 2.02, CHCl3); 1H NMR ꢆ 7.70–7.39 (5 H, m, Ph), 6.63 (1
H, d, J 8.1, NHa), 6.20 (1 H, d, J 9.6, NHb), 5.56 (1 H, dd, J7,6 1.8, J7,8 6.0, H-7),
5.26 (1 H, ddd, J8,9 2.4, J8,9ꢀ 6.0, H-8), 4.57 (1 H, dd, J9,9ꢀ 12.6, H-9), 4.54 (1 H, m,
H-4), 4.35 (1 H, dd, J6,5 10.2, H-6), 4.13 (1 H, dd, H-9ꢀ), 4.08 (1 H, m, H-5), 3.88
(3 H, s, COOCH3), 2.45 (1 H, dd, J3eq,3ax 4.2, J3eq,4 13.5, H-3eq), 2.13, 2.09, 2.06,
1.80 (each 3 H, s, NHCOCH3, OCOCH3 ꢇ 3), 1.99 (1 H, m, H-3ax); 13C NMR ꢆ
172.1, 170.5, 170.1, 169.6, 168.0, 166.4 (carbonyls), 133.4, 131.9, 128.7, 126.9
(aromatic carbons), 90.2 (C-2), 73.1, 70.8, 67.8 (C-6, C-7, C-8), 62.0 (C-9), 53.3,
49.0, 48.5 (C-4, C-5, COOCH3), 36.4 (C-3), 22.7 (NHCOCH3), 20.9, 20.6, 20.5
(OCOCH3 ꢇ 3); IR (ꢉmax, KBr): 2106 cmꢄ1 (N3); LRMS (cone voltage 30V): 578
(MHꢅ, 80%), 73 (28), 60 (100); HRMS: Calcd for C25H32N5O11:[Mꢅ ꢅ 1],
578.2098. Found: m/z, 578.2096.
ACKNOWLEDGMENTS
We gratefully acknowledge the support provided by Glaxo-Wellcome, U.K,
the Australian Research Council and the National Health and Medical Research
Council.
REFERENCES
1. See for example: Biology of the Sialic Acids, Rosenberg, R.A (ed), Plenum Press, New
York (1995); von Itzstein, M.; Thomson, R.J. The synthesis of novel sialic acids as bi-
ological probes, Top. Curr. Chem. 1997, 186, 119–170.

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KOK, VAN PHAN, AND VON ITZSTEIN
2. von Itzstein, M.; Wu, W.-Y.; Jin, B. The synthesis of 2,3-didehydro-2,3-dideoxy-4-
guanidinyl-N-acetylneuraminic acid: a potent influenza virus sialidase inhibitor, Car-
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3. Okamoto, K.; Kondo, T.; Goto, T. Functionalisation of 2-deoxy-2,3-dehydro-N-acetyl-
neuraminic acid methyl ester, Bull. Chem. Soc. Jpn., 1987, 60, 631–636.
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5. Kok, G.B.; von Itzstein, M. A new facile synthesis of C-4 nitrogen-containing deriva-
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6. See for example: Angyal, S. Composition and conformation of sugars in solution.
Angew. Chem. Int. Ed. Engl., 1969, 8, 157–166.
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Received March 21, 2001
Accepted May 1, 2001

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