Synthesis of 5a-carba-hexopyranoses and hexopyranosylamines, as well as 5a,5a′-dicarbadisaccharides, from 3,8-dioxatricyclo[4.2.1.0 2,4]nonan-9-ol: Glycosidase inhibitory activity of N-substituted 5a-carba-β-gluco- and β-galactopyranosylamines,

Article abstract of DOI:10.1016/j.bmcl.2004.07.091

Since glycosidase and glycosyltransferase inhibitors, composed of carba-sugars, have recently attracted much attention, it is desirable to develop effective preparative routes for provision of new carba-sugar derivatives of potential biological interest.

Full text of DOI:10.1016/j.bmcl.2004.07.091

Bioorganic & Medicinal Chemistry Letters 14 (2004) 5183–5188
Synthesis of 5a-carba-hexopyranoses and hexopyranosylamines,
as well as 5a,5a0-dicarbadisaccharides, from
3,8-dioxatricyclo[4.2.1.02,4]nonan-9-ol: glycosidase
inhibitory activity of N-substituted 5a-carba-b-gluco- and
b-galactopyranosylamines, and derivatives thereof
Seiichiro Ogawa,* Sho Funayama, Kensuke Okazaki, Fumito Ishizuka, Yoko Sakata and
Fuminao Doi
Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Hiyoshi, Kohoku-ku,
Yokohama 223-8522, Japan
Received 10 May 2004; accepted 26 July 2004
Abstract—Since glycosidase and glycosyltransferase inhibitors, composed of carba-sugars, have recently attracted much attention, it
is desirable to develop effective preparative routes for provision of new carba-sugar derivatives of potential biological interest.
1,2:3,6-Dianhydro-5a-carba-a-glucopyranose was here chosen for study of synthetic utility, and demonstrated to be a promising
intermediate for supplying several carba-b-glycosylamines and N-linked dicarba-oligosaccharides. An N-linked 5a,5a0-dicarbalac-
tose derivative obtained here was found to be a strong a-galactosidase inhibitor (IC50 1.2lM, green coffee beans).
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
tion of the potential of 2a as a key compound for several
biologically interesting 5a-carba-sugars (Fig. 1).
In recent years, glycosidase and glycosyltransferase
inhibitors, of carba-glycosylamine1 and N-linked carba-
disaccharide types,2 have attracted much attention,
stimulating us to develop efficient preparative routes for
different carba-sugars of biological interest. We here
chose 1,2:3,6-dianhydro-5a-carba-a-DL-glucopyranose
(2a), (1SR,2RS,4SR,6SR,9RS)-3,8-dioxatricyclo[4.2.1.02,4]-
nonan-9-ol, for examination of its potential as a synthetic
intermediate with general application for further de-
mands of glycobiology. Compound 2a was first pre-
pared3 as a precursor for synthesis of b-validamine and
its 6-amino-6-deoxy derivative, a branched-chain ana-
logue of 2-deoxystreptamine. Recently, this compound
was successfully utilized as an intermediate for synthesis
of 5a-carba-sugars, especially fucose-type validamines.4
The present communication describes a further investiga-
Advantageous chemical features of 2a are as follows: the
3,6-anhydro bridge plays a role both in protecting the 3-
and 6-hydroxyl groups and in causing 5a-carba-a-gluco-
pyranose to adopt the 1C conformation. The anhydro
ring is easily opened by conventional acetolysis or bro-
mination with HBr–AcOH. Furthermore, the 1,2-epox-
ide group is reactive toward common nucleophiles,
being cleaved at C-1 with high regioselectivity. The 4-hy-
droxyl group of 2a is readily oxidized to give rise to the
ketone 4, which can be reduced to regenerate 2a. The 4-
sulfonates 3f and 3i do not undergo nucleophilic displace-
ment even with strong nucleophiles and also remain
unchanged under acetolysis to open the 3,6-anhydro ring.
2. Results and discussion
2.1. Improved synthesis of 1,2:3,6-dianhydro-5a-
carba-a-D-glucopyranose (2a)
*
Corresponding author. Tel.: +81 045 566 1788; fax: +81 045 566
1789; e-mail: ogawa@bio.keio.ac.jp
Initially the dianhydride 2a was prepared from 2,3,4-tri-
O-acetyl-6-bromo-6-deoxy-5a-carba-b-glucopyranosyl
In this paper, the nomenclature of carba-sugar derivatives follows the
IUPAC-IUB Recommendations 1996 (Carbohydr. Res. 1997, 297, 1).
0960-894X/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.07.091

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S. Ogawa et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5183–5188
O
6
5
Br
AcO
O5a
1
Br
AcO
2
3
O
4
OAc
RO
O
RO
1
2a–c
2
2a: R = H
b: R = MOM
c: R = Ms
R = H, MOM, Ms
6
5
X
1
O5a
X
O
O
4
3
2
R2O
3a–i
OR1
O
O
R2O
OR1
4
3
X
R2
X
R1
O
3a
b
c
d
e
OMe
OMe
OMe
OC8H17
OC8H17
OC8H17
N3
H
MOM
MOM
H
MOM
H
Ms
MOM
H
Ms
Bn
Bn
Bn
Bn
Bn
Bn
Bn
Ac
O
OR
5
O
Y
OH
f
Y
OH
g
O
Z
X
HO
NH
h
i
N3
N3
Z
HO
OH
OH
6
5a-Carba-β-Galactose
and β-Glucose Deriva-
tives
X
O
O
X
O
O
O
O
OBn
Y
OH
4
5a–c
OH
NH
Z
HO
5a: X = OMe
b: X = OC8H17
c: X = N3
OH
15
Scheme 1. Preparation of 1,2:3,6-dianhydro-5a-carba-a-glucopyra-
nose and its transformation into synthetic intermediates.
Y
OH
HO
OH
H
N
HO
X
Z
HO
OH
of 3b under the influence of THF and 12M HCl at room
temperature gave the 4-OH unprotected derivative 3c
(ꢀ100%). Similarly, the octyl ether was readily obtained
from 2b by treatment with a slight excess of sodium oct-
oxide in octanol for 2days at reflux temperature, and the
product was isolated8 as the benzyl ether 3d (28% over-all
yield), which was also converted into the 4-hydroxy com-
pound 3e (83%). Azidolysis of 2b with sodium azide
(3molarequiv) in 80% aqueous DMF at 120ꢁC pro-
ceeded smoothly and the resulting sole azide was isolated
as the benzyl ether 3g (86% over-all yield), which was
similarly converted into the 4-hydroxy compound 3h
(91%). Compounds 2a, 3c, 3e, and 3h were found to be
oxidized with DMSO/Ac2O to afford the respective ke-
tones9 4 and 5a–c in ꢀ80% yields, which were used as
acceptors for reductive amination with carba-glycosyl-
amines, affording N-linked 5a,5a0-dicarbadisaccharides.
When compound 2c was treated with sodium azide
(3molarequiv) in DMF at 120ꢁC, this gave, after acetyl-
ation, the azido mesylate 3i (64%), showing that the
4-mesyloxyl group is unreactive toward strong nucleo-
philes. Removal of the 3,6-anhydro bridges of 3f and 3i
would be expected to provide useful precursors for the
preparation of 5a-carba-b-galactopyranose derivatives.
17
N-Linked 5a,5a'-Dicarba-β-Cellobiose
and β-Lactose Derivatives
Figure 1. Possible synthetic routes to 5a-carba-b-galacto- and b-
glucopyranose derivatives, and N-linked 5a,5a0-dicarbadisaccharides
from 1,2:3,6-dianhydro-5a-carba-a-glucopyranose: X = NHR, OR,
etc.; Y, Z = OH, NH2, etc.
bromide5 (1) by treatment with an excess of methanolic
sodium methoxide for 2h at reflux temperature, and the
major product 2a was isolated as the acetate in 65%
yield, accompanied by the methyl ether generated by
cleavage of the 1,2-anhydro ring with a methoxide ion
(Scheme 1). In this work, compound6 2a was obtained
directly as pure crystals in 89% by treatment of 1 with
3molarequiv of solid sodium methoxide in methanol
at 0–5ꢁC for 3h. Compound 2a was readily transformed
into the protected derivatives: the methoxymethyl ether
2b and mesylate 2c.
2.2. Synthesis of 3,6-anhydro-5a-carba-b-glucopyranose
derivatives
Treatment of 2b with methanolic sodium methoxide
(5molarequiv) for 20h at reflux temperature gave the
methyl ether 3a (75%), which was conventionally ex-
posed to benzyl bromide–NaH in DMF (3molarequiv)
at room temperature to afford the benzyl ether7 3b
(95%). Subsequent removal of a methoxymethyl group
2.3. Synthesis of alkyl 5a-carba-b-gluco- and b-galacto-
pyranosides
Conventional acetolysis of 3d and 3f with AcOH/Ac2O/
H2SO4 (40:20:1) at 80ꢁC gave carba-glucopyranoside
derivatives 6a (96%) and 6c (81%), respectively.

S. Ogawa et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5183–5188
5185
O-Deacetylation of 6a gave octyl 5a-carba-b-glucopyr-
N3
O
OAc
anoside10 6b (84%). On the other hand, nucleophilic sub-
stitution of the 4-mesyloxyl group of 6c with potassium
acetate (5molarequiv) readily proceeded in DMF in the
presence of 18-crown-6 ether at 110ꢁC to give8 a sole
tetra-O-acetyl derivative 6d (44%), which was O-deacetyl-
a
MsO
AcO
N3
OAc
6f
b
MsO
OAc
3i
AcO
AcO
OAc
´
ated under Zemplen conditions to give octyl 5a-carba-
b-galactopyranoside10 6e (85%). In this reaction,
formation of other products, initiated by neighboring
participation of the 3-acetoxyl group, was not observed.
The present synthesis significantly improved the preced-
ing routes10 to 6b and 6e, thus constituting a practical
synthetic regimen for alkyl 5a-carba-galacto and gluco-
pyranosides. Very recently some alkyl 5a-carba-glyco-
pyranosides have actually been applied11 as potent
primers for biocombinatorial synthesis12 (Scheme 2).
N3
OAc
6g
c
HO
HO
OH
NHX
OH
6h: X = H
i: X = Ac
d
Scheme 3. Synthesis of 5a-carba-b-galactopyranosylamine and deriv-
ative. Reagents and conditions: (a) AcOH/Ac2O/H2SO4 (40:20:1),
120ꢁC; (b) NaOAc, DMF, 110ꢁC; (c) NaOMe, MeOH; H2, EtOH,
Raney Ni; (d) Ac2O, MeOH.
Acetolysis of compound 3i produced8,13 the mesylate 6f
(26%) and the acetate 6g (5%). The latter appeared to be
formed by further acetolysis of 6f in situ. In fact, nucle-
ophilic substitution of 6f with sodium acetate in DMF
gave 6g (71%). Conventional O-deacetylation of 6g fol-
lowed by hydrogenolysis in ethanol in the presence of
Raney nickel afforded, after purification over a column
of Dowex-50W · 2 (H+) resin with methanolic 5%
6
NH(CH2)nX
O5a
5
1
2a
4
2
3
HO
OH
ammonia,
5a-carba-b-galactopyranosylamine
(6h,
7a–g
85%), which was transformed into the N-acetyl deriva-
tive 6i (ꢀ100%) (Scheme 3).
n
X
7a
b
c
d
e
3
5
7
9
11
1
Me
Me
Me
Me
Me
Ph
Ph
2.4. Synthesis of N-alkyl 3,6-anhydro-5a-carba-b-
glucosylamines and derivatives thereof
f
g
Direct nucleophilic cleavage of the 1,2-anhydro ring of
2a with alkyl and phenylalkyl-amines was attempted in
order to prepare N-substituted derivatives 7a–f, from
which corresponding 5a-carba-b-glucopyranosylamines
might be obtainable (Scheme 4). Treatment with a molar
equivalent of butylamine in 2-propanol in a sealed
tube for 4days at 120ꢁC resulted in preferential cleavage
at C-1 to give, after purification by silica gel chromato-
graphy, N-butyl-3,6-anhydro-5a-carba-b-glucopyrano-
sylamines14 7a (78%). Similarly, by use of hexyl, octyl,
decyl, dodecyl, benzyl, and 2-phenylethyl-amines, the
corresponding N-substituted 3,6-anhydrides 7b–g were
2
Scheme 4. Structures of several N-substituted 3,6-anhydro-5a-carba-
b-glucopyranosylamines.
6
NHX
O5a
5
1
4
OH
2
3
b
HO
HO
HO
OH
a
NHX
7c
OH
9
Br
CH3
c
AcO
AcO
HO
HO
6
Y
NHX
NHX
NHX
OR
4
5a
5
OH
OH
OAc
Z
2
3
1
X
RO
8
10
OR
6a–i
CH2
d
HO
HO
Z
X
Y
R
6a
b
OC8H17
OC8H17
OC8H17
OC8H17 OAc
OC8H17
N3
N3
NH2
H
H
H
OAc
OH
OMs
H
H
OMs
H
H
H
Ac
H
Ac
Ac
H
Ac
Ac
H
H
X = (CH2)7CH3
11
c
d
e
f
g
Scheme 5. Synthesis of some N-octyl-5a-carba-b-glucopyranosylamine
derivatives. Reagents and conditions: (a) 30% HBr–AcOH, 85ꢁC; (b)
Conventional acetolysis of 7c or NaOAc, aq 80% 2-methoxyethanol,
reflux; NaOMe, MeOH; (c) Bu3SnH, AIBN, toluene; NaOMe, MeOH;
(d) NaOAc, DMF, reflux; NaOMe, MeOH.
OH
H
OAc
OH
OH
h
i
NHAc
synthesized in 98%, 97%, 38%,8 94%, 76%, and 83%
yields, respectively.
Scheme 2. Synthesis of 5a-carba-b-galacto- and b-glucopyranose
derivatives.

5186
S. Ogawa et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5183–5188
The N-octyl derivative 7c was chosen, as an example, for
possible further chemical transformation (Scheme 5).
Thus, it was first acetylated and then treated with 30%
HBr–AcOH at 85ꢁC, resulting in the opening of the
3,6-anhydro ring with a bromide ion to give the 6-bromo-
6-deoxy derivative 8, which was debrominated with tri-
butyltin hydride in toluene in the presence of AIBN,
followed by hydrolysis with 4M hydrochloric acid, to
OMe
OMe
OR
O
O
a
MOMO
OH
MOMO
3a
12a: R = H
b: R = Ms
c
b
OR
AcO
AcO
AcO
OMs
d
afford
N-octyl-6-deoxy-5a-carba-b-glucopyranosyl-
RO
RO
OMe
NHAc
OMe
amine 10 on acid resin chromatography with methanolic
ammonia (25% over-all yield). Dehydrobromination of
8 was effected by treatment with sodium acetate (10
molarequiv) in DMF at reflux temperature to give the
6-deoxy-5-eno derivative 11 (ꢀ20% over-all yield). N-
13
14a: R = Ac
b: R = H
e
Scheme 6. Synthesis of methyl 2-acetamido-2-deoxy-5a-carba-b-gluco-
pyranoside. Reagents and conditions: (a) Ac2O, DMSO; L-selectride,
THF; (b) MsCl, pyridine; (c) conventional acetolysis; (d) NaN3, DMF,
120ꢁC; H2, MeOH, Raney Ni, Ac2O; (e) NaOMe, MeOH.
Octyl-5a-carba-b-galactopyranosylamine
9 was pre-
pared in ꢀ50% over-all yield by acetolysis of 7c followed
by hydrolysis with 4M hydrochloric acid and purifica-
tion over an acid resin column, in order to supply a
sample for biological assays (Table 1) for enzyme-inhibi-
tory activity to compare the three structurally related
compounds 9, 10, and 11. Alternatively, starting from
the mesylate 2c, a series of 5a-carba-b-galactopyranosyl-
amine derivatives would be generated through
amination and subsequent acetolysis, followed by
4-epimerization.
ride of 6h was conducted in aqueous methanol in the
presence of sodium cyanoborohydride (2molarequiv)
and anhydrous magnesium sulfate for 19h at reflux
temperature. The product could successfully be isolated
as the tetra-O-acetyl derivative 15a (47%). Similar
coupling of 5a–c with 6h produced the respective
5a,5a0-dicarbadisaccharide derivatives 15b–d in 60%,
41%, and 50% yields, respectively. O-Deacetylation of
15b gave N-linked methyl 3,6-anhydro-5a,5a0-dicarba-
b-D-lactoside16 16 (91%). Acetolysis of 15b and subse-
quent deprotection would provide17 5a,5a0-dicarba-b-
lactose 17.
2.5. Synthesis of alkyl 2-acetamido-2-deoxy-5a-carba-b-
glucopyranoside
Oxidation of 3a with Ac2O–DMSO and successive
reduction with L-selectride gave preferentially the 2-epi-
mer 12a (59%), which was then transformed into the
mesylate 12b (91%). Acetolysis of 12b gave methyl
3,4,6-tri-O-acetyl-2-O-mesyl-5a-carba-b-mannopyrano-
side (13, 82%). Similarly, methyl 5a-carba-b-mannopyr-
anoside could be obtained from 12a. Compound 13 was
then subjected to azidolysis (NaN3, 5molarequiv) in
DMF at 120ꢁC, giving a sole azide, which was similarly
hydrogenolyzed in ethanol containing acetic anhydride,
followed by acetylation, to give the penta-N,O-acetyl
derivative15 14a (52%), O-deacetylation of which affor-
ded methyl 2-acetamido-2-deoxy-5a-carba-b-D-gluco-
pyranoside 14b (81%). This sequence could be
generally utilized for the preparation of alkyl 5a-carba-
b-mannosides and N-acetyl-5a-carba-b-glucosaminides
(Scheme 6).
O
AcO
AcO
OAc
O
+
4
6h
NH
OAc
15a
X
O
AcO
AcO
OAc
6h + 5a–c
OBn
NH
OAc
15b–d
X
2.6. Synthesis of imino-linked 5a,5a0-dicarbalactose
derivatives
15b
c
d
OMe
OC8H17
N3
Reductive amination of the ketones 4 and 5a–c with
5a-carba-hexopyranosylamines has been demonstrated
to proceed readily in stereoselective fashion, affording
N-linked b(1!4)-5a,5a0-dicarbadisaccharide derivatives
containing 3,6-anhydro-5a-carba-glucopyranose resi-
dues (Scheme 7).
OMe
O
HO
HO
OH
OH
NH
OH
16
OMe
HO
HO
HO
OH
H
N
HO
5a-Carba-b-galactopyranosylamine 6h was first con-
verted into the hydrochloride under the influence of
an equimolar amount of 1M hydrochloric acid, and
then subjected to reductive coupling with the ketone
4. Thus, reaction of 4 (2molarequiv) and the hydrochlo-
OH
OH
17
Scheme 7. Synthesis of some 5a,5a0-dicarbalactose derivatives.

S. Ogawa et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5183–5188
5187
Table 1. Inhibitory activity of some 5a-carba-hexopyranosylamine
derivatives against three glycosidases
Oshima, M.; Yamamoto, Y.; Noguchi, A.; Takimoto, K.;
Itoh, M.; Matsuzaki, Y.; Yasuda, Y.; Ogawa, S.; Sakata,
Y.; Nanba, E.; Higaki, K.; Ogawa, Y.; Tominaga, L.;
Ohno, K.; Iwasaki, H.; Watanabe, H.; Brandy, R. O.;
Suzuki, Y. Proc. Natl. Acad. Sci. U.S.A. 2003, 100, 15912.
2. Okazaki, K.; Nishigaki, S.; Ishizuka, F.; Kajihara, Y.;
Ogawa, S. Org. Biomol. Chem. 2003, 1, 2229.
Compd
IC50 (M)
a-Galactosidase
(green coffee beans) (bovine liver)
b-Galactosidase b-Glucosidase
(rat intestine)
6h
6i
2.8
NI
NI
NI
NI
1.2
NI
NI
10
130
14
3. Ogawa, S.; Oya, M.; Toyokuni, T.; Chida, N.; Suami, T.
Bull. Chem. Soc. Jpn. 1983, 56, 1441.
9
NI
NI
NI
NI
4. Ogawa, S.; Mori, M.; Takeuchi, G.; Doi, F.; Watanabe,
M.; Sakata, Y. Bioorg. Med. Chem. Lett. 2002, 12, 2811.
5. Ogawa, S.; Nakamoto, K.; Takahara, M.; Tanno, Y.;
Chida, N.; Suami, T. Bull. Chem. Soc. Jpn. 1979, 52, 1174.
10
11
16
18
30
NI
NI: No inhibition <10ꢂ3 M.
20
6. Compound 2a: ½aꢁD ꢂ 68 (c 1.1, CHCl3); 1H NMR
(300MHz, CDCl3): d 4.62 (d, 1H, J1,2 = 8.7Hz, H-1),
4.26 (dd, 1H, J3,4 = 5.1Hz, J2,3 = 8.3Hz, H-3), 4.20 (dd,
2.7. Glycosidase inhibitory activity
1H, J3,4 = J4,5 = 5.1Hz, H-4), 4.15 (ddd, 1H, J5a(exo),6exo
=
1.8Hz, J5,6exo = 5.4Hz, Jgem = 8.8Hz, H-6exo), 3.83 (d,
1H, Jgem = 8.8Hz, H-6endo), 3.41 (br s, 1H, H-2), 3.32–
3.35 (m, 1H, H-1), 2.46–2.52 (m, 1H, H-5), 2.03–2.32
[m, 1H, H-5a(exo)], 1.99 [ddd, 1H, J1,5a(endo) = 2.0Hz,
J5,5a(endo) = 4.2Hz, Jgem = 16.1Hz, H-5a(endo)].
Some of the new compounds synthesized underwent pre-
liminary assay for enzyme-inhibitory activity against six
glycosidases18 (Table 1). Interestingly, 5a-carba-b-galac-
topyranosylamine (6h) was shown to be a good inhibitor
of a-galactosidase rather than b-galactosidase, while its
N-acetyl derivative 6i exhibited moderate inhibition.19
Seven N-alkyl and phenylalkyl-3,6-anhydro-5a-carba-
b-glucopyranosylamines 7a–g did not show any inhibi-
tory activity against the six enzymes. In view of the
structural relationship between substrates and enzyme
inhibitors, N-octyl-b-gluopyranosylamine 9, and its 6-
deoxy and 6-deoxy-5-eno derivatives (10 and 11) can
be considered to be model compounds for discussion
regarding the hydrophobic nature of the region around
substituents at C-5. The products are all moderate b-
galactosidase inhibitors, being not a- nor b-glucosidase
inhibitors, and substantial structural change around C-
5 did not appreciably alter the activity.
1
7. Compound 3b: H NMR (300MHz, CDCl3): d 7.26–7.35
(m, 5H, Ph), 4.66 and 4.74 (ABq, each 1H, Jgem = 6.7Hz,
OCH2), 4.64 (s, 2H, OCH2), 4.20 (dd, 1H, J3,4
J4,5 = 4.9Hz, H-4), 4.11 (dd, 1H, J2,3 = 2.0Hz, J3,4
4.9Hz, H-3), 3.87 (ddd, 1H, J5,6exo = 3.2Hz, J5a(exo),6exo
=
=
=
4.4Hz, Jgem = 8.1Hz, H-6exo), 3.79 (d, 1H, Jgem = 8.1Hz,
H-6endo), 3.69 (ddd, 1H, J1,2 = 3.7Hz, J1,5a(endo)
=
J1,5a(exo) = 4.9Hz, H-1), 3.55 (ddd, 1H, J2,3 = 2.0Hz,
J1,2 = 3.7Hz, H-2), 3.35, and 3.39 (2 s, each
3H, 2 · OMe), 2.50 [dddd, 1H, J5a(exo),6exo = 3.2Hz,
J1,5a(endo) = 4.9Hz, J5,5a(exo) = 6.1Hz, Jgem = 14.4Hz, H-
5a(exo)], 2.50 (dddd, 1H, J5,5a(endo) = J5,6exo = 4.4Hz,
J4,5 = 4.9Hz, J5,5a(exo) = 6.1Hz, H-5), 1.57 [ddd, 1H,
J5,5a(endo) = 4.4Hz, J1,5a(endo) = 4.9Hz, Jgem = 14.4Hz, H-
5a(endo)].
8. The reaction conditions have not been optimized yet.
1
9. Compound 4: H NMR (300MHz, CDCl3) data for 4; d
Very interestingly, the N-linked dicarbalactose deriva-
tive 16 has been demonstrated to be a strong and specific
a-galactosidase inhibitor (green coffee beans). As ex-
pected,20 N-alkylation of 6h much improved21 the inhib-
itory potential toward a- and b-galactosidases, and
b-glucosidase. However, its characteristic specificity
as a a-galactosidase inhibitor completely disappeared.
Hydrophobic spacer N-alkyl chains seemed to enhance
its affinity for other enzymes, independent of specific
recognition owing to structural mimicking dependent
on the carba-galactopyranose residue. Therefore, in
chemical modification of 6h, the N-linked dicarbadisac-
charide 16 might hopefully be a lead compound for
development of specific a-galactosidase inhibitors of this
kind.
4.32 (ddd, 1H, J5a(eq),6exo = 2.1Hz, J5,6exo = 4.9Hz, Jgem
=
8.5Hz, H-6exo), 4.18 (d, 1H, J2,3 = 3.4Hz, H-3), 4.03 (d,
1H, Jgem = 8.5Hz, H-6endo), 3.60 (dd, 1H, J2,3 = 3.4Hz,
J1,2 = 3.7Hz, H-2), 3.27 (ddd, 1H, J1,5a(endo) = 1.2Hz,
J1,2 = 3.7Hz, J1,5a(exo) = 4.0Hz, H-1), 2.60 (ddd, 1H,
J5,5a(exo) = 2.0Hz, J5,6exo = 4.9Hz, J5,5a(endo) = 6.8Hz,
H-5), 2.44–2.48 [m, 1H, H-5a(endo)], 2.26 [ddd, 1H,
J5,5a(exo) = 2.0Hz,
J1,5a(exo) = 4.0Hz,
Jgem = 15.1Hz,
H-5a(exo)]; for 5a: d 7.27–7.37 (m, 5H, Ph), 4.56 and
4.66 (ABq, each 1H, Jgem = 11.8Hz, OCH2), 4.37 (d,
1H, Jgem = 7.8Hz, H-6endo), 4.15 (dd, 1H, J2,3 = 4.9Hz,
J1,2 = 5.0Hz, H-2), 4.06 (ddd, 1H, J5a(exo),6exo = 2.9Hz,
J5,6exo = Jgem = 7.8Hz, H-6exo), 3.95 (d, 1H, J2,3
4.9Hz, H-3), 3.40 (ddd, 1H, J1,5a(exo) = 2.0Hz,
=
J1,5a(endo) = 4.4Hz, J1,2 = 5.0Hz, H-1), 3.38 (s, 3H, OMe),
2.49 (ddd, 1H, J5,5a(endo) = 3.4Hz, J5,5a(exo) = 3.7Hz,
J5,6exo = 7.8Hz, H-5), 2.34–2.37 (m, 2H, H-5a,5a).
10. Ogawa, S.; Aoyama, H.; Sato, T. Carbohydr. Res. 2002,
337, 1979–1992.
Acknowledgements
11. Aoyama, H.; Ogawa, S.; Sato, T. In preparation.
12. (a) Miura, Y.; Arai, T.; Yamagata, T. Carbohydr. Res.
1996, 289, 193; (b) Miura, Y.; Yamagata, T. Biochem.
Biophys. Res. Commun. 1997, 241, 698; (c) Nakajim, H.;
Miura, Y.; Yamagata, T. J. Biochem. 1998, 124, 148; (d)
Carmelita, M.; Kasuya, Z.; Wang, L. X.; Lee, Y. C.;
Mitsuki, M.; Nakajima, H.; Miura, Y.; Sato, T.; Hata-
naka, K.; Yamagata, S.; Yamagata, T. Cabohydr. Res.
2000, 329, 755–763.
The authors sincerely thank Drs. Atsushi Takahashi and
Akihiro Tomoda (Hokko Chemical Industry Co. Ltd)
for the biological assays, and Ms. Miki Kanto for her
assistance in preparing this manuscript.
References and notes
1. Ogawa, S.; Kobayashi Matsunaga, Y.; Suzuki, Y. Bioorg.
Med. Chem. 2002, 10, 1967; Matsuda, J.; Suzuki, O.;
13. Exhaustive acetolysis of 3i is likely to give 6g selectively;
however, prolonged heating of intermediate 6f and/or 6g

5188
S. Ogawa et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5183–5188
5a0eq), 1.78 [br dd, 1H, J5,5a(exo) = 3.8Hz, Jgem = 15.6Hz,
under these conditions might cause substitution as well as
0 0 0 0
H-5a(exo)], 1.60 (dddd, 1H, J5 ,6 a = 2.7Hz, J5 ,5a eq =
elimination to give rise to aromatic compounds. There-
fore, careful optimization should be worked out for the
acetolysis.
2.9Hz, J4 ,5 = 9.3Hz, J5 ,5a(ax) = 12.0Hz, H-50), 1.32
0
0
0
0
0
0
(ddd, 1H, J1 ,5a ax = 11.8Hz, J5 ,5a ax = 12.0Hz, Jgem =
0
1
14. Compound 7a: H NMR (300MHz, MeOH): d 4.25 (dd,
1H, J4,5 = 4.8Hz, J3,4 = 5.1Hz, H-4), 3.79 (dd, 1H,
J2,3 = 2.4Hz, J3,4 = 5.1Hz, H-3), 3.77 (dd, 1H,
J5,6exo = 2.2Hz, Jgem = 8.3Hz, H-6exo), 3.68 (d, 1H,
Jgem = 8.3Hz, H-6endo), 3.58 (br d, 1H, J2,3 = 2.4Hz,
12.5Hz, H-5a0ax).
17. Preliminary, when 15b was subjected to the conventional
acetolysis [AcOH/Ac2O/H2SO4 (40:20:1), 80–95ꢁC], de-O-
methylation was partly accompanied with opening of the
anhydro ring and the benzyl ether group remained almost
unaffected, contrary to the cases of 3d and 3f. Therefore,
initial removal of the benzyl ether group by hydrogenolysis,
followed by acetolysis, would be an effective route to
furnish free N-linked dicarbadisaccharides. Furthermore,
in order to get the 1-O-alkyl derivatives in acceptable yields,
the acetolysis conditions should be optimized in each cases.
18. All compounds were assayed for activity against six
glycosidases: a-galactosidase (green coffee beans), b-galac-
tosidase (bovine liver), a-glucosidase (BakerÕs yeast),
b-glucosidase (almond), a-fucosidase (bovine kidney), a-
mannosidase (Jack beans). Biological assays were carried
out in a standard manner by Drs. A. Takahashi and A.
Tomoda (Hokko Chemical Industries, Co. Ltd, Toda,
Atsugi, Japan).
19. Some N-alkyl derivatives of 6h were synthesized for the
purpose of comparing their activity with those of 6-deoxy
congeners, the antipodes of a-fucopyranosylamine-type
inhibitors. They have been shown to possess strong
inhibitory activity against b-galactosidase and b-glucosi-
dase, as well as a-galactosidase: Ogawa, S.; Fujieda, M.;
Sakata, Y., in preparation.
20. With a series of N-alkyl-5a-carba-b-galactopyranosylam-
ines, deoxylation at C-6 resulted in drastic change in
potential and specificity of inhibitory activity: Ogawa, S.;
Fujieda, S.; Sakata, Y.; Ishizaki, M.; Hisamatsu, S.;
Okazaki, K. Bioorg. Med. Chem. Lett. 2003, 13,
3461–3463.
H-2), 2.85 (br dd, 1H, J1,5a(endo) = 3.7Hz, J1,5a(exo)
=
8.1Hz, H-1), 2.54–2.59 (m, 2H, NHCH2), 2.33 [ddd, 1H,
J5,5a(exo) = 1.2Hz, J1,5a(exo) = 8.1Hz, Jgem = 14.6Hz,
H-5a(exo)], 2.17 (ddd, 1H, J5,5a(exo) = 1.2Hz, J5,6exo
=
2.2Hz, J4,5 = 4.8Hz, H-5), 1.52 [br d, 1H, Jgem = 14.6Hz,
H-5a(endo)], 1.19–1.46 [m, 4H, (CH2)2CH3], 0.85 (t, 3H,
J = 7.2Hz, CH3).
20
15. Compound 14a: ½aꢁD þ 16 (c 0.5, CHCl3); 1H NMR
(300MHz, CDCl3): d 5.43 (d, 1H, J2,NH = 9.8Hz, NH),
5.05 (dd, 1H, J3,4 = 9.6Hz, J4,5 = 10.7Hz, H-4), 4.93 (dd,
1H, J3,4 = 9.6Hz, J2,3 = 10.5Hz, H-3), 4.10 (dd, 1H,
J5,6b = 3.7Hz, Jgem = 11.2Hz, H-6b), 4.05 (br d, 1H,
J2,NH = 9.8Hz, H-2), 3.97 (dd, 1H, J5,6a = 3.4Hz,
Jgem = 11.2Hz, H-6a), 3.37 (s, 3H, OMe), 3.27 (ddd, 1H,
J1,5a(eq) = 4.2Hz, J1,2 = 10.5Hz, J1,5a(ax) = 11.2Hz, H-1),
2.21 [ddd, 1H, J5,5a(eq) = 3.7Hz, J1,5a(eq) = 4.2Hz,
Jgem = 13.2Hz, H-5a(eq)], 1.97, 2.02, 2.07, and 2.08 (4 s,
each 3H, 4 · Ac), 1.91 (br s, 1H, H-5), 1.50 [ddd,
1H, J1,5a(ax) = 11.2Hz, J5,5a(ax) = 12.9Hz, Jgem = 13.2Hz,
H-5a(ax)].
20
16. Compound 16: ½aꢁD ꢂ 34 (c 0.15, MeOH); 1H NMR
(300MHz, D2O): d 4.06 (br d, 1H, Jgem = 7.3Hz, H-
6endo), 4.03 (br s, 1H, H-2), 3.97 (br s, 1H, H-40), 3.79–
3.83 (m, 2H, H-3, H-6exo), 3.64 (br d, 1H, Jgem = 10.4Hz,
H-6b0), 3.52 (dd, 1H, J5 ,6 a = 2.7Hz, Jgem = 10.4Hz,
0
0
0
H-60), 3.46 (dd, 1H, J2 ,3 = 9.2Hz, J1 ,2 = 9.5Hz, H-2 ),
0
0
0
0
3.33 (s, 1H, OMe), 3.30–3.36 (m, 3H, H-1, H-30, H-4), 2.50
0
0
0
0
0
0
(ddd, 1H, J1 ,5 eq = 4.6Hz, J1 ,2 = 9.5Hz, J1 ,5a ax
=
21. Ogawa, S.; Ashiura, M.; Uchida, C.; Watanabe, S.;
Yamazaki, C.; Yamagishi, K.; Inokuchi, J. Bioorg. Med.
Chem. Lett. 1996, 6, 929; Ogawa, S.; Kobayashi, Y.;
Kabayama, K.; Jimbo, M.; Inokuchi, J. Bioorg. Med.
Chem. 1998, 6, 1955.
11.8Hz, H-10), 2.38 (br dd, 1H, J5,5a(endo) = 3.5Hz,
J5,5a(exo) = 3.8Hz, H-5), 2.20 [ddd, 1H, J5,5a(endo) = 3.5Hz,
J1,5a(endo) = 5.1Hz, Jgem = 15.6Hz, H-5a(endo)], 1.85 (ddd,
0
J5 ,5a eq = 2.9Hz, J1 ,5a eq = 4.6Hz, Jgem
0
0
0
=
12.5Hz, H-