Syntheses of 2-deoxy-2,3-didehydro-N-acetylneuraminic acid analogues modified by α-acylaminoamido groups at the C-4 position using isocyanide-based four-component coupling and biological evaluation as inhibitors of human parainfluenza virus type 1

Article abstract of DOI:10.1248/cpb.c12-00834

Novel sialidase inhibitors 11 having an α-acylaminoamido group at the C-4 position of Neu5Ac2en 1 against human parainfluenza virus type 1 (hPIV-1) were synthesized using one-pot isocyanide-based four-component condensation, and their inhibitory activities against hPIV-1 sialidase were studied. Compound 11b showed inhibitory activity (IC₅₀=5.1 mM) against hPIV-1 sialidase. The degree of inhibition of 11b was much weaker than that of 1 (IC ₅₀=0.3 mM).

Full text of DOI:10.1248/cpb.c12-00834

Regular Article
January 2013
Chem. Pharm. Bull. 61(1) 69–74 (2013)
69
Syntheses of 2-Deoxy-2,3-didehydro-N-acetylneuraminic Acid Analogues
Modified by α-Acylaminoamido Groups at the C-4 Position Using
Isocyanide-Based Four-Component Coupling and Biological Evaluation
as Inhibitors of Human Parainfluenza Virus Type 1
Reiko Nishino,a Takuya Hayakawa,b Tadanobu Takahashi,b Takashi Suzuki,b Masayuki Sato,a and
,c
Kiyoshi Ikeda*
b
a Department of Organic Chemistry, School of Pharmaceutical Sciences, University of Shizuoka; Department of
Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka; 52–1 Yada, Suruga-ku, Shizuoka 422–
c
8526, Japan: and Department of Organic Chemistry, School of Pharmaceutical Sciences, Hiroshima International
University; 5–1–1 Hirokoshingai, Kure, Hiroshima 737–0112, Japan.
Received September 21, 2012; accepted October 29, 2012
Novel sialidase inhibitors 11 having an α-acylaminoamido group at the C-4 position of Neu5Ac2en 1
against human parainfluenza virus type 1 (hPIV-1) were synthesized using one-pot isocyanide-based four-
component condensation, and their inhibitory activities against hPIV-1 sialidase were studied. Compound
11b showed inhibitory activity (IC50=5.1 mm) against hPIV-1 sialidase. The degree of inhibition of 11b was
much weaker than that of 1 (IC50=0. 3 mm).
Key words human parainfluenza virus type 1; sialidase inhibitor; sialic acid; 4-isocyano Neu5Ac2en deriva-
tive; isocyanide-based four-component coupling
Human parainfluenza viruses (hPIVs), members of the been undetermined. In 2004, Portner et al. reported that com-
human parainfluenza viruses (hPIVs), which are part of the pounds BCX 2798 (3) and BCX 2855 (4) with modifications at
Paramyxoviridae family, are important respiratory tract patho- C-4 and C-5 positions of 1, which were designs based on the
gens in infants and children. Four different types of hPIV crystal structure of the HN of Newcastle disease virus (NDV),
have been identified, all of which cause a spectrum of ill- were specific and potent inhibitors of hPIVs.10) We demon-
nesses of the upper and lower respiratory tracts of children.1,2) strated that 4-O-amidinomethyl- 5,11,12) 4-O-thiocarbamamoyl-
There are currently no effective vaccines or specific therapies methyl- 6,11–13) 4-O-ethyl- 7,14) and 4-O-(2-thienyl-2-propynyl)
available for controlling parainfluenza virus infections.3) Para- Neu5Ac2en derivatives 815) have potential inhibitory activities
influenza virus contains 2 spike glycoproteins, hemagglutinin- against the sialidase from hPIV-1.
neuraminidase (HN) glycoproteins, and fusion (F) glycopro-
Multicomponent reactions (MCRs) have become important
tein, embedded in the envelope. HN proteins recognize sialic tools in modern preparative synthetic chemistry owing to
acid-containing glycolipids and glycoproteins of target cells; their exceptional synthetic efficiency.16,17) MCRs have emerged
this recognition allows the virus to bind to target cells. Fur- as valuable tools for the preparation of structurally diverse
thermore, HN proteins act as a sialidase, removing sialic acid chemical libraries of drug-like carbohydrates.18) Recently, we
from virus particles, and thus preventing self-aggregation and reported the synthesis of novel compounds 9 and 10 with an
promoting efficient spread of the virus. The multifunctional N-sulfonylamidino group at the C-4 position of 1, using three-
role of HN in the viral life cycle makes it an attractive tar- component coupling as the key reaction, and the analysis of
get for structure-based design of chemotherapeutics to treat their inhibitory activities against hPIV-1 sialidase19) (Fig. 1).
hPIV infection. Among the diverse array of compounds re-
For further insight into the interaction of sialidase
lated to the sialic acid family,4) 5-acetamido-2,6-anhydro-3,5- with a substituent at C-4 of Neu5Ac2en derivatives, we
dideoxy-d-galacto-d-glycero-non-2-enonic acid (Neu5Ac2en, herein report the synthesis of novel compounds 11 with
1) is known as an inhibitor of sialidases from both bacterial an α-acylaminoamido group at the C-4 position of 1 using
and viral sources, occupying an important position in mod- isocyanide-based four-component reaction20) of 4-isocyano
ern chemistry.5,6) A variety of Neu5Ac2en analogs have been Neu5Ac2en derivative 12 as a key intermediate; we also
synthesized as competitive sialidase inhibitors. By molecular studied their inhibitory activities against hPIV-1 sialidase
modeling techniques, von Itzstein et al. reported the design (Chart 1). Ugi reactions21) are particularly interesting as they
and biological evaluation of 4-deoxy-4-guanidino-Neu5Ac2en are more versatile and diverse than other MCRs. To the best
analogs (2) (zanamivir).7) In sialic acids, C-4 near the of our knowledge, there are no reports on the synthesis of
anomeric center seems to play an important role in enzyme- Neu5Ac2en analogs with an α-acylaminoamido group 11 at
substrate interactions. Neu5Ac2en derivatives with structural the C-4 position of 1 using isocyanide-based multicomponent
modifications at the C-4 position are particular candidates reactions.
for the design of potent inhibitors against anti-paramyxovirus
agents. Although the amino acid sequences of hPIV-1 surface
Results and Discussion
Synthesis of 12 4-Isocyano Neu5Ac2en derivative 12, a
glycoproteins have been described,8,9) the crystal structure
model of a complex of hPIV-1 HN glycoprotein and 1 has not key intermediate for synthesizing target compounds 11, con-
tains an isocyanide group, which was prepared from Neu5Ac
in seven steps (Chart 2). Initially, methyl ester of Neu5Ac,
The authors declare no conflict of interest.
© 2013 The Pharmaceutical Society of Japan
*To whom correspondence should be addressed. e-mail: ikeda@ps.hirokoku-u.ac.jp

70
Vol. 61, No. 1
Fig. 1. The Structure of Sialidase Inhibitors
Chart 1. Synthesis of 11 by Isocyanide-Based Four-Component Coupling
derived from Neu5Ac, was converted to 13 in a quantitative α-acylaminoamido group at the C-4 position of 18a, 18e, and
yield in two steps. Reaction of compound 13 with TMSOTf 18f appeared as two singlets, due to the partial double bond
in AcOEt at 50°C gave 14, followed by subsequent treatment character of the nitrogen–carbonyl carbon bond.
by TMSN3 in t-BuOH, which afforded compound 1522) in 80%
Zemplen O-deacetylation of 18a–d with 0.1m sodium
yield in two steps. Reduction of an azide group of 15 with methoxide in MeOH followed by subsequent hydrolysis with
Lindlar catalyst and NEt3 in AcOEt under H2 atmosphere fol- 0.1 m NaOH–MeOH (1:1) gave the target compounds 11a–d in
lowed by the treatment with acetic formic acid anhydride gave yields ranging from 85% to 98% (Table 2).
compound 17 in 86% yield in two steps. Transformation of a
The formation of 18 can be explained by the mechanism
formyl group to a cyanide group of 17 with CBr4, PPh3, and shown in Chart 3. The carbonyl group could be protonated by
23)
NEt3 in CH2Cl2 at −20°C successfully afforded 12 in 67% carboxylic acid, which could facilitate formation of an imi-
yield.
nium cation A. Nucleophilic addition of isocyanide 12 to imi-
Synthesis of 11 Ugi coupling reaction was performed nium intermediate B, followed by the attack with carboxylate
using the combination of 4-cyano Neu5Ac2en derivative 12, anion, gave intermediate C, which could then be converted to
amines (1.25eq), aldehydes (1.25eq), and carboxylic acids final product 18.
(1.25eq) in MeOH as shown in Table 1. Under the optimized
Biological Evaluation The behavior of compounds 11a–d
conditions, many groups of four components were smoothly toward hPIV-1 sialidase was tested by a fluorometric assay
coupled to afford the corresponding α-acylaminoamido com- using 4-methylumbelliferyl N-acetyl-α-neuraminic acid as
pounds (18a–f) in yields ranging from 52 to 85% (entries per our previously reported method.12) As can be seen in
1–6). In entry 7, when AcOH was added as an acid (2.4eq), Table 2, among synthesized compounds 11a–d, compound
the corresponding product 18g was successfully obtained 11b showed inhibitory activity (IC50=5.1 m m) against hPIV-1
in 71% yield (entry 7). In the nuclear magnetic resonance sialidase. However, the degree of inhibition of 11b was much
(NMR) spectra of the products, N-methyl protons of an weaker than that of 1 (IC50=0.3 m m). The reason for the lower

January 2013
71
Chart 2. Synthesis of 12
Table 1. Synthesis of 18a–g by Isocyanide-Based Four-Component Coupling
Entry
Aldehyde (R1)
Amine (R2)
Acid (R3)
Product
Yield (%)
1
2
3
H
H
H
Me
n-Pr
Bn
Me
Me
Me
18a
18b
18c
85
79
84
4
H
Me
18d
71
5
6
H
H
Me
Me
H
Me
18e
18f
52
52
7
n-Pr
Me
18g
71a)
a) Heated at 60°C for 4h with AcOH (2.4eq).
Table 2. Deprotection of 18a–d and Their Inhibition of hPIV-1 Sialidase
Entry
R1
R2
R3
Product
Yield (%)
IC50 (mm)
1
2
3
H
H
H
Me
n-Pr
Bn
Me
Me
Me
11a
11b
11c
90
98
85
12.3
5.1
7.3
4
H
Me
11d
89
101.1

72
Vol. 61, No. 1
Chart 3. A Possible Mechanism for the Formation of 18
inhibitory activity of compounds 11 is unclear in this study, addition of saturated aqueous NH4Cl (10mL), and extracted
but it was found that the substituent bulkiness at the C-4 al- with CH2Cl2, and then the extract was washed with brine,
cohol of 1 might affect interaction with the cavity of the cata- dried anhydrous MgSO4, and concentrated. The residue was
lytic pocket in HN glycoprotein in sialidase (Table 2, entry purified by silica gel column chromatography (eluent: CHCl3–
4). These studies suggest that diminished activity results from MeOH) to afford 10 (586mg, 67%). [α]D25 +53 (c=1.0, MeOH).
1
fewer favorable interactions between 11 and enzyme.
IR (neat) cm−1: 2143, 1742, 1665, 1539. H-NMR (CDCl3) δ:
6.00 (1H, d, J=7.9Hz), 5.96 (1H, d, J=2.4Hz), 5.40 (1H, dd,
J=6.7, 1.8Hz), 5.34 (1H, dt, J=6.2, 2.6Hz), 5.13 (1H, dd,
Conclusion
In conclusion, the one-pot isocyanide-based four-component J=9.4, 2.7Hz), 4.70 (1H, dd, J=10.4, 1.8Hz), 4.55 (1H, dd,
condensation of 4-cyano-Neu5Ac2en derivative 12, amines, J=12.8, 2.4Hz), 4.22 (1H, dd, J=12.8, 5.5Hz), 3.82 (3H, s),
aldehydes, and carboxylic acids provided 2,3-didehydro sialic 3.59 (1H, td, J=9.7, 7.9Hz), 2.17, 2.07, 2.06, 2.05 (12H, s).
acids having an α-acylaminoamido group at the 4-O-position 13C-NMR (CDCl3) δ: 171.1, 170.6, 170.5, 170.0, 161.1, 158.0,
in MeOH in good yields. This methodology offers several ad- 144.9, 105.5, 74.4, 70.2, 67.6, 61.8, 52.7, 50.4, 49.9, 23.3, 20.8,
vantages, including high product yield, ease of experimental 20.8, 20.7. MS (ESI) m/z: 463 (M+Na)+. HR-MS (ESI) Calcd
procedure, and amenability to large-scale operations.
These findings should provide useful information for the
development of anti-human parainfluenza virus compounds.
for C19H24O10N2Na (M+Na)+: 463.13286; Found: 463.13612.
Methyl 5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-[2-
(acetylmethylamino)acetylamino]-d-glycero-d-galacto-
non-2-enonate (18a) To a solution of formaldehyde solu-
tion (37wt% in H2O) (20mL, 0.25mmol) in MeOH (0.5mL)
Experimental
All melting points are uncorrected. Optical rotations were was added methylamine solution (40wt% in H2O) (25mL,
measured with a JASCO P-1030s (Japan) digital polarimeter. 0.25mmol) at room temperature. After the reaction mixture
IR spectra were recorded on a SHIMADZU IRPrestige-21 was stirred at the same temperature for 10min, the reaction
(Japan) spectrometer. 1H-NMR spectra were recorded with mixture was supplemented with AcOH (15mL, 0.25mmol)
a JEOL ECA-500 (500MHz) (Japan) instrument. 13C-NMR and a solution of compound 11 (90mg, 0.20mmol) in MeOH
spectra were recorded with a JEOL ECA-500 (126MHz) (2.0mL), and the reaction mixture was stirred at room tem-
(Japan) instrument. Chemical shifts are expressed in ppm perature for 30min, and concentrated. The residue was puri-
relative to Me4Si (δ=0) in CDCl3 and in D2O referenced to fied by silica gel column chromatography (eluent: EtOAc–
HOD (4.85ppm) as internal standards. MS and high resolution MeOH) to afford 11a (93mg, 85%). [α]D25 +33 (c=1.0, MeOH).
1
(HR)-FAB-MS data were obtained using a JEOL JMS-700 IR (neat) cm−1: 1741, 1537, 1371, 1215, 1144, 1090. H-NMR
(Japan) spectrometer in the positive mode with an NBA ma- (CDCl3) δ: 6.68 (1H, d, J=7.4Hz), 6.23 (1H, d, J=9.7Hz),
trix. MS and HR-electrospray ionization (ESI) were measured 5.93 (1H, d, J=2.3Hz), 5.50 (1H, dd, J=4.6, 2.3Hz), 5.31 (1H,
on a JEOL JMS-T100LC (Japan) mass spectrometer. Column ddd, J=6.9, 4.6, 2.9Hz), 4.69 (2H, dd, J=12.6, 2.3Hz), 4.34
chromatography was performed on Silica Gel 60 (70–230 (1H, dd, J=10.3, 2.3Hz), 4.11–4.22 (3H, m), 3.78 (3H, s), 3.74
mesh, Merck). All reactions were monitored using TLC (Silica (1H, d, J=16.0Hz), 3.07 (3H, s), 2.17 (3H, s), 2.09, 2.07, 2.06
Gel 60F254, E. Merck, Germany) by charring after spraying (each 3H, s), 1.91 (3H, s). 13C-NMR (CDCl3) δ: 172.2, 171.6,
5% H2SO4 in MeOH and then heating.
170.7, 170.3, 169.9, 161.7, 144.3, 110.3, 71.3, 67.8, 62.2, 52.4,
Methyl 5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-isocy- 52.3, 49.5, 46.4, 37.7, 23.0, 21.6, 20.9, 20.6. MS (FAB) m/z:
ano-d-glycero-d-galacto-non-2-enonate (12) To a solution 544 (M+H)+. HR-MS (FAB) Calcd for C23H34O12N3 (M+H)+:
of 17 (919mg, 2.00mmol), CBr4 (2.00g, 6.03mmol), and tri- 544.2142; Found: 544.2176.
ethylamine (0.80g, 7.94mmol) in CH2Cl2 (2.0mL) was added
Methyl
5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-[2-
a solution of triphenylphosphine (1.57g, 5.99mmol) in CH2Cl2 (acetylpropylamino)acetylamino]-d-glycero-d-galacto-
(3.0mL) at −20°C. The mixture was stirred at the same tem- non-2-enonate (18b) The reaction was carried out using 12
perature for 10min. The reaction mixture was quenched by (73mg, 0.17mmol), formaldehyde solution (37wt% in H2O)

January 2013
73
(16mL, 0.20mmol), n-propylamine (16mL, 0.19mmol), and 8.10 (1H, s), 6.48 (1H, d, J=7.9Hz), 5.96 (1H, d, J=10.4 Hz),
AcOH (10mL, 0.17mmol) in MeOH (2.5mL) in a manner 5.91 (2H, d, J=1.8Hz), 5.50 (1H, dd, J=4.9, 2.4Hz), 5.30 (1H,
similar to the preparation of 18a, to give 18b (69mg, 79%). ddd, J=7.3, 4.9, 3.0Hz), 4.73 (1H, ddd, J=9.7, 7.9, 2.4Hz), 4.68
1
IR (neat) cm−1: 3219, 1734, 1635, 1369, 1213. H-NMR (CDCl3) (1H, dd, J=12.2, 2.4Hz), 4.31 (1H, dd, 10.4, 1.8Hz), 4.22–4.16
δ: 6.74 (1H, d, J=7.9Hz), 5.92 (1H, d, J=2.4Hz), 5.77 (1H, d, (2H, m), 4.11 (1H, d, J=15.8Hz), 3.79 (3H, s), 3.76 (1H, d,
J=9.7Hz), 5.47 (1H, dd, J=4.9, 1.8Hz), 5,31 (1H, ddd, J=6.7, J=15.8Hz), 3.02 (2H, s), 2.09, 2.07, 2.06 (9H, 3s), 1.92 (3H, s).
4.3, 2.4Hz), 4.71 (1H, dd, J=8.5, 1.8Hz), 4.13–4.23 (2H, m), MS (ESI) m/z: 552 (M+Na)+.
4.07 (1H, d, J=15.2Hz), 3.78 (3H, s), 3.74 (1H, d, J=15.8Hz),
Methyl
5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-[2-
3.34–3.27 (1H, m), 3.23–3.17 (1H, m), 2.17 (3H, s), 2.09, 2.07, (acetylmethylamino)butyrylamino]-d-glycero-d-galacto-
2.05 (each 3H, s), 1.91 (3H, s), 0.94–0.87 (3H, m). 13C-NMR non-2-enonate (18f) The reaction was carried out using
(CDCl3) δ: 172.0, 171.7, 170.7, 170.3, 170.2, 170.0, 161.8, 12 (82mg, 0.19mmol), propionaldehyde (95%) (16mL,
144.2, 110.4, 71.3, 67.9, 62.3, 52.4, 52.0, 50.6, 49.7, 46.3, 23.0, 0.21mmol), methylamine solution (40wt% in H2O) (24mL,
21.8, 21.3, 21.0, 20.8, 20.7, 11.1. MS (FAB) m/z: 572 (M+H)+. 0.23mmol), and AcOH (13mL, 0.23mmol) in MeOH (2.5mL)
HR-MS (FAB) Calcd for C25H38O12N3 (M+H)+: 572.2455; in a manner similar to the preparation of 18a, to give 18f
Found: 572.2539.
Methyl
(57mg, 52%). IR (neat) cm−1: 3291, 1740, 1654, 1533, 1369,
5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-[2- 1215. H-NMR (CDCl3) δ: 6.68, 6.66 (1H, d, J=8.5Hz), 6.08,
1
(acetylbenzylamino)acetylamino]-d-glycero-d-galacto- 6.04 (1H, d, J=9.6Hz), 5.85 (1H, dd, J=5.7, 2.3Hz), 5.48
non-2-enonate (18c) The reaction was carried out using 12 (1H, dt, J=4.5, 1.7Hz), 5.30 (1H, tt, J=7.1, 2.6Hz), 4.89, 4.79
(50mg, 0.11mmol), formaldehyde solution (37wt% in H2O) (1H, dd, J=9.1, 6.2Hz), 4.30, 4.25 (1H, dd, J=10.8, 1.7Hz),
(10mL, 0.12mmol), benzylamine (14mL, 0.13mmol), and 4.23–4.10 (1H, m), 3.80 (1H, d, J=1.7Hz), 3.79 (3H, s), 2.96,
AcOH (8mL, 0.14mmol) in MeOH (1.0mL) in a manner 2.80 (3H, s), 2.18, 2.16 (3H, s), 2.10, 2.08, 2.07, 2.06, 2.06
similar to the preparation of 18a, to give 18c (57mg, 84%). (s, 9H), 1.99–1.86 (1H, m), 1.88, 1.86 (3H, s), 1.72–1.57 (1H,
1H-NMR (CDCl3) δ: 7.40–7.34 (2H, m), 7.32 (1H, d, J=7.1Hz), m), 0.93–0.82 (5H, m). 13C-NMR (CDCl3) δ: 173.0, 172.2,
7.18 (2H, d, J=7.3Hz), 6.61 (1H, d, J=7.9Hz), 6.03 (1H, d, 172.0, 171.6, 171.1, 170.6, 170.5, 170.4, 170.3, 170.0, 170.0,
J=9.7Hz), 5.89 (1H, d, J=2.4Hz), 5.50 (1H, q, J=2.4Hz), 5.32 161.7, 161.6, 144.8, 144.5, 110.4, 71.5, 71.5, 67.8, 67.7, 58.2,
(1H, ddd, J=7.3, 4.3, 2.4Hz), 4.72–4.65 (3H, m), 4.47 (1H, 58.1, 57.8, 52.4, 48.7, 48.5, 46.7, 46.6, 31.6, 31.4, 29.6, 28.2,
d, J=17.1Hz), 4.33 (1H, dd, J=10.4, 2.4Hz), 4.17 (2H, ddd, 23.1, 23.0, 22.1, 22.0, 21.3, 20.9, 20.8, 20.7, 20.2, 18.3, 10.5,
J=19.6, 11.1, 6.9Hz), 4.04 (1H, d, J=15.8Hz), 3.79 (3H, s), 10.4. MS (FAB) m/z: 572 (M+H)+. HR-MS (FAB) Calcd for
3.83–3.78 (1H, m), 2.24 (3H, s), 2.10, 2.07, 2.05 (9H, 3s), 1.94 C25H38O12N3 (M+H)+: 572.2455; Found: 572.2492.
(3H, s). 13C-NMR (CDCl3) δ: 172.4, 171.9, 170.7, 170.3, 169.9,
Methyl
5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-[2-
169.9, 161.8, 144.2, 135.6, 129.1, 128.9, 128.5, 128.1, 126.6, (acetylpropylamino)-2-pyridin-3-yl-acetylamino]-d-glycero-
110.4, 71.4, 67.9, 53.4, 52.4, 50.2, 49.6, 46.3, 23.1, 21.5, 21.0, d-galacto-non-2-enonate (18g) To a solution of 3-pyridine-
20.8, 20.7. MS (FAB) m/z: 620 (M+H)+. HR-MS (FAB) Calcd carboxyaldehyde (15mL, 0.16mmol) in MeOH (0.5mL) was
for C29H38O12N3 (M+H)+: 620.2455; Found: 620.2500.
added n-propylamine (12mL, 0.14mmol) at room temperature.
5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-{2- The reaction mixture was stirred at the same temperature
Methyl
[(furan-2-carbonyl)methylamino]acetylamino}-d-glycero-d- for 10min. To the reaction mixture was added AcOH (9mL,
galacto-non-2-enonate (18d) The reaction was carried out 0.15mmol) and a solution of compound 12 (59mg, 0.13mmol)
using 12 (90mg, 0.20mmol), formaldehyde solution (37wt% in MeOH (2mL), and the reaction mixture was stirred at
in H2O) (20mL, 0.25mmol), methylamine solution (40wt% room temperature for 1h. The reaction mixture was heated
in H2O) (25mL, 0.24mmol), and 2-furoic acid (70%) (27mg, at 60°C for 4h, and concentrated. The residue was purified
0.24mmol) in MeOH (2.5mL) in a manner similar to the by silica gel column chromatography (eluent: EtOAc–MeOH)
preparation of 18a, to give 18d (84mg, 71%). [α]D25 −9.8 to afford 11g (60mg, 71%). IR (neat) cm−1: 3283, 1741, 1655,
1
(c=1.0, MeOH). IR (neat) cm−1: 3288, 1736, 1372, 1219, 1022. 1219. H-NMR (CDCl3) δ: 8.65–8.55 (2H, m), 7.80, 7.72 (1H,
1H -NMR (CDCl3) δ: 7.54 (1H, s), 7.12 (1H, d, J=3.4Hz), 6.68 d, J=7.9Hz), 7.33 (1H, dd, J=8.5, 4.5Hz), 6.73, 6.59 (1H,
(1H, s), 6.53–6.49 (1H, m), 5.96 (1H, d, J=9.7Hz), 5.90 (1H, d, J=7.4Hz), 6.45, 6.37 (1H, d, J=9.1Hz), 5.95, 5.89 (1H, d,
s), 5.49 (1H, dd, J=5.2, 1.7Hz), 5.31 (1H, ddd, J=7.4, 4.6, J=2.3Hz), 5.56 (1H, s), 5.51, 5.48 (1H, dd, J=4.5, 2.3Hz),
2.3Hz), 4.82 (1H, t, J=8.3Hz), 4.68 (1H, dd, J=12.3, 2.0Hz), 4.86–4.72 (1H, m), 4.67 (1H, dt, J=19.6, 7.1Hz), 4.41 (1H,
4.33 (1H, dd, J=10.3, 1.7Hz), 4.27 (4H, d, J=16.6Hz), 4.17 dd, J=9.9, 8.2Hz), 4.20–4.15 (1H, m), 4.12 (2H, dd, J=22.4,
(4H, dd, J=12.6, 6.9Hz), 3.90 (1H, s), 3.78 (4H, s), 3.34 (2H, 9.9Hz), 3.79 (3H, s), 3.36–3.22 (1H, m), 3.22–3.08 (1H, m),
s), 2.08, 2.07, 2.06 (each 3H, 3s), 1.87 (3H, s). MS (FAB) m/z: 2.20 (3H, d, J=12.5Hz), 2.07 (9H, dt, J=13.2, 4.3Hz), 1.91
596 (M+H)+. HR-MS (FAB) Calcd for C26H34O13N3 (M+H)+: (3H, d, J=28.3Hz), 1.47 (1H, brs), 1.14 (1H, brs), 0.80–0.68
596.2092; Found: 596.2057.
Methyl 5-Acetylamino-2,6-anhydro-3,5-dideoxy-4-[2- 170.3, 170.2, 170.0, 169.9, 169.8, 161.7, 150.6, 149.7, 149.6,
(3H, m). 13C-NMR (CDCl3) δ: 172.0, 171.9, 171.9, 170.6, 170.4,
(formyl-methylamino)acetylamino]-d-glycero-d-galacto- 144.3, 144.2, 137.5, 137.0, 131.1, 130.9, 123.7, 123.5, 110.3,
non-2-enonate (18e) The reaction was carried out using 12 110.3, 71.5, 71.3, 67.9, 62.2, 62.0, 61.6, 52.4, 50.3, 49.8, 49.7,
(54mg, 0.12mmol), formaldehyde solution (37 wt. % in H2O) 46.3, 46.2, 23.1, 22.9, 22.8, 22.8, 22.0, 21.8, 20.9, 20.9, 20.8,
(11mL, 0.14mmol), methylamine solution (40wt% in H2O) 20.6, 20.6, 11.1, 11.0. MS (ESI) m/z: 671 (M+Na)+.
(15mL, 0.15mmol), and HCOOH (6mL, 0.16mmol) in MeOH
5 -Acet ylamino -2,6 -anhydro -3, 5 - dideoxy- 4 -[2-
(2.5mL) in a manner similar to the preparation of 18a, to give (acetylmethylamino)acetylamino]-d-glycero-d-galacto-
18e (33mg, 52%). [α]D25 −37 (c=1.0, MeOH). IR (neat) cm−1: non-2-enoic Acid (11a) To a solution of 11a (65mg,
1
3283, 1734, 1655, 1541, 1371, 1213, 1142. H-NMR (CDCl3) δ: 0.12mmol) in MeOH (1.0mL) was added a solution of NaOMe

74
Vol. 61, No. 1
(5mol/L in MeOH) (24mL, 0.12mmol) at 0°C, and the mix- HR-MS (FAB) Calcd for C19H26O10N3 (M+H)+: 456.1618;
ture was stirred for 1h at the same temperature. The reaction Found: 456.1603.
mixture was evaporated to dryness, the residue was dissolved
in MeOH (1.0mL), to the mixture was added 1m NaOH
Acknowledgements This work was financially sup-
(1.0mL) at 0°C, and the mixture was stirred for 20min at ported in part by a Grant-in-Aid for Scientific Research (No.
the same temperature. The reaction mixture was treated with 21590117) from the Ministry of Education, Culture, Sports,
Amberlite IRC-120 (H+), the suspension was filtered, and the Science and Technology of Japan. This work was partly sup-
filtrate was evaporated in vacuo. The residue was purified by ported by the Uehara Memorial Foundation.
column chromatography on silica gel using CHCl3–MeOH–
H2O (65:35:5, v/v/v) to give 12a (43mg, 90%). [α]D25 −25
(c=1.0, MeOH) H-NMR (CD3OD) δ: 5.72, 5.70 (1H, d, J=2.3,
2.9Hz), 4.72 (1H, tt, J=9.5, 2.5Hz), 4.17 (2H, d, J=10.9 Hz),
4.11–4.02 (1H, m), 3.99–3.91 (1H, m), 3.86 (1H, d, J=16.6Hz),
References
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1626, 11557, 1250, 732. H-NMR (CD3OD) δ: 5.81, 5.77 (1H,
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1
of 11a, to give 11c (28mg, 85%). H-NMR (CD3OD) δ: 7.39
(1H, t, J=6.9Hz), 7.36–7.28 (2H, m), 7.28–7.23 (2H, m), 5.77,
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3.93 (1H, d, J=16.6Hz), 3.89 (1H, td, J=6.0, 2.9Hz), 3.82 (1H,
dd, J=11.5, 2.9Hz), 3.66 (1H, dd, J=11.5, 5.7Hz), 3.60 (1H,
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1
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(1H, d, J=25.8Hz), 6.97, 6.85 (1H, s), 6.43 (1H, d, J=13.2Hz),
5,65 (1H, d, J=25.8Hz), 4.71–4.65 (1H, m), 4.24 (1H, s), 4.18
(1H, t, J=11.5Hz), 4.01 (2H, d, J=9.7Hz), 3.76–3.70 (1H,
m), 3.68 (1H, d, J=12.0Hz), 3.49–3.41 (2H, m), 3.15 (1H, s),
2.87 (2H, s), 1.79, 1.74 (3H, s). MS (FAB) m/z: 456 (M+H)+.