A convenient synthesis of C-galactofuranosylic compounds (C-galactofuranosides)

Article abstract of DOI:10.1016/S0008-6215(02)00133-7

Galactofuranose sugar units are essential for the production of the cell coat of many pathogenic microorganisms. This sugar is not found in mammals, and so compounds that may interfere with the biosynthetic processing of this sugar unit provide interesting targets for drug design. This paper describes the use of a cyanation reaction for the production of a one-carbon extension of a galactofuranosylic unit at C-1, giving 2,5-anhydro-3,4,6,7-tetra-O-benzoyl-D-glycero-L-manno-heptononitrile. A procedure for the efficient hydrolysis of the introduced nitrile group to produce the methyl ester is reported, along with procedures for the synthesis of both the corresponding α,β-unsaturated, and 3-deoxy ester derivatives.

Full text of DOI:10.1016/S0008-6215(02)00133-7

Carbohydrate Research 337 (2002) 2017–2022
www.elsevier.com/locate/carres
A convenient synthesis of C-galactofuranosylic compounds
(C-galactofuranosides)
David J. Owen,a Robin J. Thomson,b Mark von Itzsteinb,*
aDepartment of Medicinal Chemistry, Monash Uni6ersity (Park6ille Campus), 381 Royal Parade, Park6ille, Victoria 3052, Australia
bCentre for Biomolecular Science and Drug Disco6ery, Griffith Uni6ersity (Gold Coast Campus), PMB 50 Gold Coast Mail Centre,
Queensland 9726, Australia
Received 2 April 2002; accepted 30 May 2002
Dedicated to Professor Derek Horton on the occasion of his 70th birthday
Abstract
Galactofuranose sugar units are essential for the production of the cell coat of many pathogenic microorganisms. This sugar
is not found in mammals, and so compounds that may interfere with the biosynthetic processing of this sugar unit provide
interesting targets for drug design. This paper describes the use of a cyanation reaction for the production of a one-carbon
extension of a galactofuranosylic unit at C-1, giving 2,5-anhydro-3,4,6,7-tetra-O-benzoyl-D-glycero-L-manno-heptononitrile. A
procedure for the efficient hydrolysis of the introduced nitrile group to produce the methyl ester is reported, along with procedures
for the synthesis of both the corresponding a,b-unsaturated, and 3-deoxy ester derivatives. © 2002 Elsevier Science Ltd. All rights
reserved.
Keywords: Galactofuranose; C-Glycosylic compounds; C-Glycosides; Cyanation
1. Introduction
can found in the cell coat of many pathogenic microor-
ganisms, including Mycobacterium tuberculosis.4–6 This
peptidoglycan layer is essential for viability of the mi-
croorganism and provides a tough wall that is responsi-
ble, not only for preventing access of many
antibacterial compounds, but is also thought to be
responsible for the virulence of the organism. Since
Galf is not found in mammals, compounds that mimic
Galf and interfere with the biosynthetic enzymes that
produce and utilise Galf may provide interesting targets
for the development of new drug treatments.
Poor socioeconomic conditions in many third-world
countries have led to the reoccurrence of many mi-
crobacterial diseases that were once thought to be on
the decline. One such disease, tuberculosis, is responsi-
ble for an estimated three million deaths worldwide
every year.1 Furthermore, incomplete drug treatment of
many sufferers has resulted in the emergence of drug-
resistant strains of the microorganism, Mycobacterium
tuberculosis, that causes this disease.2,3 The significant
mortality associated with tuberculosis, as well as ap-
pearance of new drug-resistant strains, has resulted in
the urgent need for new, cost-effective treatments to
combat this disease.
Galactofuranose 1 (Galf ) is one of the sugar units
which is essential for the production of the peptidogly-
C-Glycosylic compounds (C-glycosides) form one
class of compounds that have often shown interesting
biological properties.7,8 With regard to C-glycosides of
Galf, Kovensky et al. reported methods to gain access
to a- and b-phosphonic acid derivatives of Galf,
* Corresponding author. Tel.: +61-7-55527016; fax: +61-
7-55529040
E-mail address: m.vonitzstein@mailbox.gu.edu.au (M. von
Itzstein).
0008-6215/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(02)00133-7

2018
D.J. Owen et al. / Carbohydrate Research 337 (2002) 2017–2022
C-glycoside analogues of Galf 1-phosphate.9 For the
synthesis of the b-difluoromethylenephosphonate deriva-
tive 2, introduction of the carbon substituent at C-1 was
achieved through olefination of protected galactono-1,4-
lactone 3.9 Wheatley et al. have described the synthesis
of the 1-a-ester derivative of Galf 4, from a rearrange-
reaction whereby 1-O-acyl sugars react with TMSCN
under Lewis acidic conditions to introduce a cyano group
into the anomeric position of the sugar.12,18,19 This
reaction when applied to perbenzoylated Galf 820,21
resulted in the production of the desired nitrile 9 in a
satisfying 80% yield (Scheme 1). This reaction not
unexpectedly furnished the b-isomer exclusively. As our
initial goal was to make a methyl ester at the C-1 position,
we required a method to hydrolyse the nitrile to the acid,
which we could subsequently methylate to produce the
desired methyl ester. Unfortunately, under standard
acidic or basic hydrolysis conditions, elimination oc-
curred to produce a furan derivative, for example, the
benzoylated furan nitrile 13 from attempted acidic hy-
drolysis. A similar result has previously been reported by
Albrecht et al. who had attempted to perform reductive
hydrolysis of a C-1 cyano function in ribose.22 A report
by Poonian and Nowoswiat,23 who had formed the
methyl imidate 14 from benzoylated ribosyl cyanide that
was then utilised in a heterocyclisation, prompted us to
examine the formation of the corresponding methyl
imidate of Galf under anhydrous conditions. The methyl
imidate should be easily hydrolysed to the desired methyl
ester under relatively mild conditions. Reaction of the
nitrile 9 with anhydrous sodium methoxide overnight†
furnished the fully deprotected methyl imidate 10. This
compound could be easily isolated from the reaction by
neutralisation, followed by removal of the solvent, or
alternatively, it could be hydrolysed in situ with a small
amount of Dowex 50 (H+) resin and water to give the
crude methyl ester 12. The deprotected ester 12 was most
readily purified and characterised as the corresponding
peracetylated derivative. Accordingly, peracetylation of
the crude ester yielded the acetylated C-1 ester 11 in a
respectable 68% yield (after flash chromatography) from
9 over three steps. O-Deacetylation of 11 gave the desired
Galf ester 12.
ment of the 2-O-trifluoromethanesulfonyl-D-glycero-D-
gulo-heptono-1,4-lactone (5) in the presence of acidic
methanol.10 Rearrangement of sugar g- and d-lactone
2-triflates in acidic10 or basic11 methanol has been applied
to the synthesis of a range of C-1 methyl ester derivatives.
The introduction of a nitrile at C-1, however, offers a
useful handle, which can subsequently be manipulated to
arrive at a number of interesting C-glycosidic ana-
logues.12–16 Ko¨ll et al. have previously accessed the
1-b-cyano derivative 6 of peracetylated Galf by reduc-
tion, with phosphorus trichloride, of the corresponding
1-b-nitromethyl Galf derivative 7.17 The yield of 6 over
three steps from galactose was, however, only 5%,
principally due to a low (13%) yield in the preparation
of 7 from galactose. Herein we report the use of the
cyanation reaction to make the versatile, one-carbon
homologated Galf derivative, 2,5-anhydro-3,4,6,7-tetra-
O-benzoyl-D-glycero-L-manno-heptononitrile (9). In this
work, we were initially interested in forming a methyl
ester at the C-1 position in order to arrive at a sialic
acid–Galf-type hybrid molecule. Thus, we have devel-
oped a method that efficiently converts the protected
nitrile 9 into the desired, deprotected Galf methyl ester
12. Further elaboration from nitrile
the a,b-unsaturated ester 18 and the 3-deoxy derivative
20.
9 led into
Having established an efficient route to one of our
target compounds, we set about making two further
derivatives, namely the corresponding a,b-unsaturated
ester derivative 18 and the 3-deoxy derivative 20. Elim-
ination of the C-3 benzoyl group in 9, to produce the
a,b-unsaturated derivatives, was easily achieved via a
simple two-step procedure (Scheme 2). Firstly, reaction
of the nitrile 9 with DBU24 at room temperature for three
days, furnished the desired intermediate 15 in virtually
† If the reaction was left for only 4 h compared with 20 h,
a 1:1 mixture of the desired methyl ester 11 as well as the
peracetylated Galf nitrile 617 was subsequently isolated. This
result shows that the methyl imidate 10 was slow to form.
2. Results and discussion
Previous workers have shown that access to one-car-
bon extensions of sugars is best achieved by a cyanation

D.J. Owen et al. / Carbohydrate Research 337 (2002) 2017–2022
2019
Scheme 1. Reagents and conditions: (a) TMSCN, BF3·OEt2, CH3NO2, rt, (80%); (b) 1 M NaOMe–MeOH, rt; (c) i. Dowex 50
(H+) resin, H2O, rt; ii. Ac2O, pyridine, rt (68% over 3 steps, b and c); (d) 1 M NaOMe–MeOH, rt (95%).
the saturated 3-deoxy derivative 20. Standard
hydrogenation25 of the a,b-unsaturated ester derivative
17 in ethyl acetate with palladium-on-carbon provided
the 3-deoxy derivative 19 in quantitative yield (Scheme
3). Standard O-deacetylation gave the target 3-deoxy-
Galf derivative 20.
The work outlined here illustrates an expedient entry
into a number of interesting galactofuranosyl C- gly-
cosides. These compounds are of interest as potential
drug candidates in the fight against Mycobacterium
tuberculosis, the biological pathogen responsible for the
disease tuberculosis. Biological testing of these com-
pounds is presently being undertaken and will be re-
ported elsewhere.
quantitative yield. In the second step, it was assumed
that addition of methanol to the nitrile, followed by
hydrolysis with Dowex 50 (H+) using the conditions
described above, and finally acetylation, should furnish
the protected a,b-unsaturated methyl ester 17. Unfortu-
nately, using the standard conditions, only the methyl
imidate 16 was isolated from the reaction in 61% yield,
even after prolonged exposure to the Dowex 50 (H+)–
water mixture. This result was rather surprising; how-
ever, it was subsequently found that the
a,b-unsaturated imidate 16 could be relatively easily
hydrolysed in situ by treatment with a slight excess of
20% aqueous acetic acid. Acetylation of the crude
product from this reaction furnished the peracetylated
a,b-unsaturated ester 17 in an overall yield of 89% over
three steps. Standard O-deacetylation gave the target
Galf a,b-unsaturated ester 18.
3. Experimental
The protected glycal 17 provides a potential entry
point into a range of other Galf derivatives, including
General methods.—Perbenzoylated galactofuranose 8
was prepared as per known literature methods using
Scheme 2. Reagents and conditions: (a) DBU, CH2Cl2, rt (97%); (b) 1 M NaOMe–MeOH, rt; (c) i. Dowex 50 (H+) resin, H2O,
rt; ii. Ac2O, pyridine, rt; (d) i. 20% HOAc, rt; ii Ac2O, pyridine, rt; (e) 1 M NaOMe–MeOH, rt (95%).

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D.J. Owen et al. / Carbohydrate Research 337 (2002) 2017–2022
Scheme 3. Reagents and conditions: (a) H2, 60 psi, 10% Pd/C (quant); (b) 1 M NaOMe–MeOH, rt (95%).
either the one-step procedure reported by D’Accorso et
al.,20 or the three-step procedure of Kohn et al.21 via
reduction of galactonolactone using disiamyl borane.26
The latter method21 proved to give better overall yields
of 8 in our hands. 1H and 13C NMR spectra were
recorded in CDCl3 using a Bruker AM 300 spectrome-
ter. Chemical shifts are given in ppm relative to the
left to stir at room temperature overnight. The reaction
was neutralised with Dowex 50W×8 (H+) resin, and
water (100 mL was added). After stirring for 1 h the
resin was filtered off and washed thoroughly with a 3:1
mixture of MeOH and water. Solvent was removed in
6acuo, and the residue was dried under high vacuum
overnight. Pyridine (10 mL), followed by acetic anhy-
dride (5 mL), was added and the reaction was left to
stir for 12 h. After this time the solvent was removed in
6acuo, and the residue was purified by silica gel chro-
matography to yield 131 mg (68% yield) of the desired
methyl ester 11 as a colourless oil: Rf 0.28 (3:2 hexane–
1
solvent used [CDCl3: 7.26 for H; 77.0 for 13C]. ESI
mass spectra (ESIMS) were obtained using a Micro-
mass Platform II electrospray-ionization spectrometer,
and HRMS were obtained using a Bruker BioApex II
FTMS. Reactions were monitored by TLC on alu-
minium plates coated with Silica Gel 60 F254 (E. Merck)
and visualised with either 10% H2SO4 in EtOH, I2, or
ninhydrin. All compounds were purified by flash chro-
matography using E. Merck Silica Gel 60 (0.040–0.063
mm). All new compounds gave the expected spectro-
scopic data.
1
EtOAc); H NMR (CDCl3): l 5.43 (dd, 1 H, J3,2 2.7,
J3,4 2.1, Hz, H-3), 5.36 (m, 1 H, H-6), 5.12 (dd, 1 H, J4,5
4.0 Hz, H-4), 4.60 (d, 1 H, H-2), 4.39 (dd, 1 H, J7,6 4.3,
J7,7% 11.8 Hz, H-7), 4.36 (br.d, 1 H, H-5), 4.18 (dd, 1 H,
J7%,6 6.9 Hz, H-7%), 3.80 (s, 3 H, OCH3), 2.14, 2.13, 2.05
(3×s, 12 H, 4×OCOCH3); 13C NMR (CDCl3): l
170.3, 169.9, 169.5, 169.4, 169.3 (4×OCOCH3 and
C-1), 82.4 (C-5), 80.9 (C-3), 79.4 (C-2), 77.2 (C-4), 69.6
(C-6), 62.5 (C-7), 52.4 (OCH3), 21.4, 20.8, 20.6 (4×
OCOCH3); ESIMS: m/z (relative intensity, %) 413
[(M+Na)+, 10], 408 [(M+NH4)+, 40], 391 [(M+H)+,
5], 331 (M+-OCOCH3, 100); HRMS: Calcd for
C16H26NO11 (M+NH4)+ 408.15058; found 408.15001.
2,5-Anhydro-3,4,6,7-tetra-O-benzoyl-D -glycero-L-
manno-heptononitrile (9).—To a solution of perbenzoy-
lated galactofuranose 820,21 (9.6 g, 13.7 mmol) in dry
CH3NO2 (50 mL) stirring at room temperature under
an atmosphere of N2 was added TMS-CN (8.2 mL, 4.5
equiv) followed by boron trifluoride diethyl etherate
(350 mL, 0.2 equiv). After 30 min TLC showed the
reaction was complete. The solvent was removed in
6acuo, and the resulting black oil was purified by flash
chromatography to yield 6.6 g (80% yield) of the com-
pound 9 as a white crystalline solid: Rf 0.66 (2:1 hex-
ane–EtOAc); 1H NMR (CDCl3): l 7.30–8.10 (m, 20 H,
4×OCOC6H5), 6.03 (m, 1 H, H-6), 5.86 (br.s, 1 H,
H-4), 5.79 (br.s, 1 H, H-3), 5.12 (br.s, 1 H, H-2), 4.85
(dd, 1 H, J7,6 3.9, J7,7% 12.0 Hz, H-7), 4.80 (m, 1 H,
H-5), 4.70 (dd, 1 H, J7%,6 6.6 Hz, H-7%); 13C NMR
(CDCl3): l 165.9, 165.6, 165.2, 165.1 (4×OCOC6H5),
133.9, 133.3, 133.1, 130.0, 129.9, 129.6, 129.3, 129.1,
128.6, 128.5, 128.5, 128.4, 128.3, 127.8, (aromatic C),
115.2 (C-1), 84.5 (C-5), 80.7 (C-3), 77.4 (C-4), 71.5
(C-2), 70.2 (C-6), 63.3 (C-7); ESIMS: m/z (relative
intensity, %) 623 [(M+NH4)+, 100], 606 [(M+H)+,
5], 484 (M+-C6H5CO2, 20); HRMS: Calcd for
C35H31N2O9 (M+NH4)+ 623.20295; found 623.2022.
3,4,6,7 - Tetra - O - acetyl - 2,5 - anhydro - D - g lycero - L-
manno-heptononitrile (6).—To a solution of the nitrile
9 (300 mg, 0.5 mmol) in dry MeOH (20 mL) under an
atmosphere of N2 was added one equiv of NaOMe (0.5
mL of a 1 M solution in dry MeOH). The reaction was
left to stir for 4 h at room temperature. After this time
the reaction was neutralised with Dowex 50W×8 (H+)
resin, and water (100 mL) was added. After stirring for
1 h the resin was filtered off and washed thoroughly
with a 3:1 mixture of MeOH and water. Solvent was
removed in 6acuo, and the residue dried under high
vacuum overnight. Pyridine (10 mL), followed by acetic
anhydride (5 mL), was added, and the reaction was left
to stir for 12 h. After this time the solvent was removed
in 6acuo, and two compounds were separated by silica
gel chromatography, giving 86.5 mg of methyl 3,4,6,7-
tetra-O-acetyl-2,5-anhydro-
D-glycero-L-manno-hep-
Methyl 3,4,6,7-tetra-O-acetyl-2,5-anhydro-
D-glycero-
tanoate (11) (44% yield) and 89 mg of
L
-manno-heptanoate (11).—To a solution of the nitrile
3,4,6,7-tetra-O-acetyl-2,5-anhydro-D-glycero-L-manno-
9 (300 mg, 0.5 mmol) in dry MeOH (25 mL) under an
atmosphere of N2 was added one equiv of NaOMe (0.5
mL of a 1 M solution in dry MeOH). The reaction was
heptononitrile (6)17 (46% yield). The acetylated nitrile 6
was obtained as a colourless oil: Rf 0.44 (3:2 hexane-
1
EtOAc); H NMR (CDCl3): l 5.36 (m, 2 H, H-3 and

D.J. Owen et al. / Carbohydrate Research 337 (2002) 2017–2022
2021
H-6), 5.16 (dd, 1 H, J 1.0, 2.7 Hz, H-4), 4.78 (br.s, 1 H,
H-2), 4.33 (m, 2 H, H-5 and H-7), 4.17 (dd, 1 H, J7%,6 6.6,
J7%,7 12.0 Hz, H-7%), 2.15, 2.14, 2.12, 2.06 (4×s, 12 H,
4×OCOCH3); ESIMS: m/z (relative intensity, %) 380
[(M+Na)+, 25], 375 [(M+NH4)+, 60], 331 (M+-CN,
35), 298 (M+-CH3CO2H, 100); HRMS: Calcd for
C15H23N2O9 (M+NH4)+ 375.14035; found 375.13981.
was added. After stirring for 1 h the resin was filtered off
and washed thoroughly with a 3:1 mixture of MeOH and
water. Solvent was removed in 6acuo, and the residue
dried under high vacuum overnight. Pyridine (5 mL),
followed by acetic anhydride (2.5 mL), was added, and
the reaction was left to stir for 12 h. After this time the
solvent was removed in 6acuo, and the residue was
purified by silica gel chromatography to yield 65.1 mg
(61% yield) of the imidate 16 as a colourless oil: Rf 0.36
Methyl 2,5-anhydro-D-glycero-L-manno-heptanoate
(12).—To a solution of the acetylated ester 11 (411 mg,
1.05 mmol) in dry MeOH (10 mL) under an atmosphere
of N2 was added NaOMe (0.26 mL of a 1 M solution in
dry MeOH, 0.25 equiv). The reaction was left to stir at
room temperature for 2 h. After this time the reaction
was neutralised with aqueous acetic acid (20% solution),
all volatile compounds were removed in 6acuo, and the
residue was dried under high vacuum overnight to yield
222 mg (95% yield) of the desired deprotected methyl es-
ter 12 as a slightly yellow oil: 1H NMR (D2O): l 4.48 (d,
1 H, J2,3 4.5 Hz, H-2), 4.32 (t, 1 H, J3,4 4.5 Hz, H-3), 4.17
(dd, 1 H, J4,5 5.4 Hz, H-4), 3.98 (dd, 1 H, J5,6 4.0 Hz, H-
5), 3.81 (m, 1 H, H-6), 3.77 (s, 3 H, OCH3), 3.69 (dd, 1 H,
J7,6 4.5, J7,7% 11.7 Hz, H-7), 3.62 (dd, 1 H, J7%,6 7.3 Hz, H-
7%); 13C NMR (D2O): l 173.1 (C-1), 84.0 (C-5), 81.3 (C-
3), 79.2 (C-2), 76.6 (C-4), 70.7 (C-6), 62.6 (C-7), 52.8
(OCH3).
1
(1:1 hexane–EtOAc); H NMR (CDCl3): l 7.94 (br.s, 1
H, NH), 5.75 (br.apparent t, 1 H, J 3.0 Hz, H-4), 5.65 (d,
1 H, J3,4 3.0 Hz, H-3), 5.35 (m, 1 H, H-6), 4.69 (br.dd, 1
H, J 3.6, 3.9 Hz, H-5), 4.35 (dd, 1 H, J7,6 4.6, J7,7% 11.7
Hz, H-7), 4.21 (dd, 1 H, J7%,6 6.6 Hz, H-7%), 3.84 (s, 3 H,
OCH3), 2.08, 2.07, 2.06 (3×s, 9 H, 3×OCOCH3); 13C
NMR (CDCl3): l 170.2, 169.9, (3×OCOCH3), 140.4
(C-1), 123.7 (C-2), 100.7 (C-3), 84.3 (C-5), 78.8 (C-4),
70.7 (C-6), 61.7 (C-7), 53.2 (OCH3), 20.8, 20.6 (3×
OCOCH3); ESIMS: m/z (relative intensity, %) 352
[(M+Na)+, 10], 330 [(M+H)+, 100], 270 (M+-
CH3CO2H, 30), 210 (M+-2×CH3CO2H, 80).
Methyl
4,6,7-tri-O-acetyl-2,5-anhydro-3-deoxy-D-
glycero- -manno-hep-2-enoate (17).—To a solution of
L
the a,b-unsaturated nitrile derivative 15 (310 mg, 0.64
mmol) in dry MeOH (20 mL) under an atmosphere of N2
was added NaOMe (0.48 mL of a 1 M solution in dry
MeOH, 0.75 equiv). The reaction was left to stir at room
temperature overnight before being neutralised with an
aqueous acetic acid solution (20%). After stirring for 1 h
the solvent was removed in 6acuo, and the residue was
dried under high vacuum overnight. Pyridine (10 mL),
followed by acetic anhydride (5 mL), was added, and the
reaction was left to stir for 12 h. After this time the sol-
vent was removed in 6acuo, and the residue was purified
by silica gel chromatography to yield 190 mg (89% yield)
of the desired a,b-unsaturated methyl ester 17 as a
2,5-Anhydro-4,6,7-tri-O-benzoyl-3-deoxy-
manno-hept-2-enonitrile (15).—To a solution of 2,5-an-
hydro-3,4,6,7-tetra-O-benzoyl- -glycero- -manno-hepto
D-glycero-L-
D
L
nonitrile (9) (1.024 g, 1.7 mmol) in dry CH2Cl2 (30 mL)
stirring at room temperature under an atmosphere of N2
was added 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU,
506 mL, 2 equiv). After 72 h TLC showed reaction was
complete. The solvent was removed in 6acuo, and the
residue was purified by flash chromatography to yield
794 mg (97% yield) of 15 as a slightly off-white foam: Rf
1
0.63 (3:1 hexane–EtOAc); H NMR (CDCl3): l 7.38–
1
8.10 (m, 20 H, 4×OCOC6H5), 6.11 (m, 2 H, H-3 and H-
4), 5.95 (m, 1 H, H-6), 5.10 (br.t, 1 H, J 3.3 Hz, H-5),
4.76 (dd, 1 H, J7,6 5.1, J7,7% 11.7 Hz, H-7), 4.70 (dd, 1 H,
J7%,6 6.4 Hz, H-7%); 13C NMR (CDCl3): l 165.8, 165.7,
165.3 (4×OCOC6H5), 135.4 (C-2), 133.7, 133.2, 129.8,
129.7, 129.6, 129.2, 128.8, 128.6, 128.5, 128.4, (aromatic
C), 113.3 (C-3), 110.3 (C-1), 85.7 (C-5), 78.0 (C-4), 70.8
(C-6), 62.4 (C-7); ESIMS: m/z (relative intensity, %) 506
[(M+Na)+, 5], 501 [(M+NH4)+, 100]; HRMS: Calcd
for C28H25N2O7 (M+NH4)+ 501.16617; found
501.16567.
colourless oil: Rf 0.6 (1:1 hexane–EtOAc); H NMR
(CDCl3): l 5.97 (d, 1 H, J3,4 2.8 Hz, H-3), 5.73
(br.apparent t, 1 H, J4,5 3.3 Hz, H-4), 5.35 (m, 1 H, H-6),
4.73 (br.dd, 1 H, J 3.6, 4.2 Hz, H-5), 4.34 (dd, 1 H, J7,6
4.6, J7,7% 11.8 Hz, H-7), 4.24 (dd, 1 H, J7%,6 6.4 Hz, H-7%),
3.84 (s, 3 H, OCH3), 2.07, 2.05 (3×s, 9 H, 3×
OCOCH3); 13C NMR (CDCl3): l 170.3, 170.1, 169.9,
(3×OCO2CH3), 159.5 (C-1), 152.4 (C-2), 107.5 (C-3),
84.6 (C-5), 77.9 (C-4), 70.0 (C-6), 61.7 (C-7), 52.4
(OCH3), 20.7, 20.6, 20.5 (3×OCOCH3); ESIMS: m/z
(relative intensity, %) 331 [(M+H)+, 5]; HRMS: Calcd
for C14H22NO9 (M+NH4)+ 348.12946; found
348.12894.
Methyl
glycero- -manno-hept-2-enoimidate (16).—To a solu-
tion of 2,5-anhydro-4,6,7-tri-O-benzoyl-3-deoxy-
glycero- -manno-hept-2-enonitrile (15) (157 mg, 0.3
4,6,7-tri-O-acetyl-2,5-anhydro-3-deoxy-D-
L
D-
Methyl
2,5-anhydro-3-deoxy-D-glycero-L-manno-
L
hep-2-enoate (18).—To a solution of the protected ester
17 (456 mg, 1.38 mmol) in dry MeOH (10 mL) under an
atmosphere of N2 was added NaOMe (0.34 mL of a 1 M
solution in dry MeOH, 0.25 equiv). The reaction was left
to stir at room temperature for 2 h. After this time
the reaction was neutralised with aqueous acetic acid
mmol) in dry MeOH (10 mL) under an atmosphere of N2
was added NaOMe (0.24 mL of a 1 M solution in dry
MeOH, 0.75 equiv). The reaction was left to sir at room
temperature overnight. The reaction was neutralised
with Dowex 50W×8 (H+) resin, and water (100 mL)

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D.J. Owen et al. / Carbohydrate Research 337 (2002) 2017–2022
(20% solution), all volatile compounds were removed in
6acuo, and the residue was dried under high vacuum
overnight to yield 267 mg (95% yield) of the desired
deprotected a,b-unsaturated methyl ester 18 as a
Acknowledgements
This work was supported by the Australian Research
Council through an ARC fellowship to DO. We thank
Milton Kiefel for helpful discussions and assistance in
the preparation of this manuscript.
1
slightly yellow oil: H NMR (D2O): l 6.08 (d, 1 H, J3,4
3.0 Hz, H-3), 5.07 (dd, 1 H, J4,5 3.9 Hz, H-4), 4.46 (t, 1
H, J 3.9 Hz, H-5), 3.82 (br.s, 4 H, H-6, OCH3), 3.71
(dd, 1 H, J7,6 4.8, J7,7% 11.7 Hz, H-7), 3.64 (dd, 1 H, J7%,6
7.2 Hz, H-7%); 13C NMR (D2O): l 162.0 (C-1), 149.7
(C-2), 112.2 (C-3), 88.9 (C-5), 75.2 (C-4), 72.0 (C-6),
61.8 (C-7), 52.8 (OCH3).
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4,6,7-tri-O-acetyl-2,5-anhydro-3-deoxy-D-
glycero- -manno-heptanoate (19).—To a solution of
L
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1
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(CDCl3): l 5.24 (m, 1 H, H-6), 5.17 (apparent pent, 1
H, J 2.4 Hz, H-4), 4.66 (t, 1 H, J2,3 8.1 Hz, H-2), 4.38
(dd, 1 H, J7,6 4.5, J7,7% 11.7 Hz, H-7), 4.23 (br.dd, 1 H,
J 2.4, 3.9 Hz, H-5), 4.22 (dd, 1 H, J7%,6 6.6 Hz, H-7%),
3.78 (s, 3 H, OCH3), 2.32 (m, 2 H, H-3 and H-3%), 2.08,
2.07, 2.05 (3×s, 9 H, 3×OCOCH3); 13C NMR
(CDCl3): l 171.3 (C-1), 170.4, 170.0, 169.8 (3×
OCOCH3), 83.5 (C-2), 77.0, 75.4 (C-4 and C-5), 70.5
(C-6), 62.2 (C-7), 52.2 (OCH3), 35.9 (C-3), 20.9, 20.7,
20.6 (3×OCOCH3); ESIMS: m/z (relative intensity, %)
355 [(M+Na)+, 20], 350 [(M+NH4)+, 100]; 333
[(M+H)+, 40]; 273 (M+-CH3CO2H, 70); HRMS:
Calcd for C14H24NO9 (M+NH4)+ 350.14511; found
350.14442.
Methyl
2,5-anhydro-3-deoxy-D-glycero-L-manno-
heptanoate (20).—To a solution of the protected 3-de-
oxy ester 19 (490 mg, 1.47 mmol) in dry MeOH (25
mL) under an atmosphere of N2 was added NaOMe
(0.5 mL of a 1 M solution in dry MeOH, 0.3 equiv).
The reaction was left to stir at room temperature for 2
h. After this time the reaction was neutralised with
aqueous acetic acid (20% solution), all volatile com-
pounds were removed in 6acuo, and the residue was
dried under high vacuum overnight to yield 304 mg
(100% yield) of the desired deprotected 3-deoxy methyl
1
ester 20 as a slightly yellow oil: H NMR (D2O): l 4.38
(br.s, 1 H, H-6), 3.90 (br.s, 1 H, H-4), 3.75 (s, 3 H,
OCH3), 3.50–3.70 (m, 3 H, H-5, H-7 and H-7%), 2.25
(br.s, 2 H, H-3 and H-3%), H-2 not observed (probably
hidden under HOD peak at 4.74 ppm); 13C NMR
(D2O): l 174.7 (C-1), 87.1 (C-5), 76.1 (C-2), 72.1 (C-4),
71.3 (C-6), 62.6 (C-7), 52.7 (OCH3), 38.1 (C-3); ESIMS:
m/z (relative intensity, %) 229 [(M+Na)+, 35], 207
[(M+H)+, 100]; HRMS: Calcd for C8H15O6 (M+H)+
207.08686; found 207.08634.