Chemical modification of the α-mannosidase inhibitor mannostain A: Synthesis of a potent inhibitor 1L-(1,2,3,5/4)-5-amino-4-O-methyl-1,2,3,4- cyclopentanetetrol

Article abstract of DOI:10.1002/ejoc.200500118

Demethylthio-, S-demethyl-, and S-ethyl derivatives of the α-mannosidase inhibitor, mannostasin A, were synthesized and evaluated for their inhibition of Jack bean α-mannosidase with the prime objective of elucidating the role of the methylthio group. All

Full text of DOI:10.1002/ejoc.200500118

FULL PAPER
Chemical Modification of the α-Mannosidase Inhibitor Mannostain A:
Synthesis of a Potent Inhibitor 1 -(1,2,3,5/4)-5-Amino-4-O-methyl-1,2,3,4-
L
cyclopentanetetrol[‡]
Seiichiro Ogawa*[a] and Takayuki Morikawa[a]
Keywords: Cyclitols / Aminocyclopentitols / Glycosidase inhibitors / α-Mannosidase inhibitors / Mannostatin A analogues
Demethylthio-, S-demethyl-, and S-ethyl derivatives of the α-
mannosidase inhibitor, mannostasin A, were synthesized and
evaluated for their inhibition of Jack bean α-mannosidase
with the prime objective of elucidating the role of the meth-
ylthio group. All methylthio derivatives had significantly
lowered inhibitory potentials. However, one mannostatin A
analogue with a methoxyl instead of the methylthio group
exhibited about twofold enhancement of the activity. The
structure and inhibitory activity relationships of mannostatin
A and related compounds are discussed in light of our results.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Introduction
Identification of a potent and specific α-mannosidase in-
hibitor, mannostatin A[2–10] [1, 1-(1,2,3,4/5)-4-amino-5-
methylthio-1,2,3-cyclopentanetriol],[11] has stimulated us to
develop new glycosidase inhibitors of the aminocyclopent-
itol type. These inhibitors are thought to act as transition
state mimics of the glycopyranosyl cations that are pos-
tulated to be formed during hydrolysis of glycosides.[12,13] It
appears rather difficult to correlate clearly the structures of
known α-mannosidase inhibitors[14] with the conforma-
tional features of the transition state of mannopyranosyl
cations. Recently, Winkler and Holan[15,16] proposed two
conformational models (flap-up and -down) for mannopyr-
anosyl cations, and suggested that comparison of the struc-
ture of mannostatin A to the former is pertinent, having a
good overlap of the 1- and 2-hydroxy groups in 1 with the
respective 3- and 2-hydroxy groups of the flap-up model
(Figure 1).
Identification of the potent and specific inhibition of α-
mannosidase by mannostatin A (1) has led us to investigate
novel glycosidase inhibitors of the 5-amino-1,2,3,4-cyclo-
pentanetetrol type, with elucidation of their structure–in-
hibitory activity relationships. In a preceding paper, the
synthesis and evaluation of the α-mannosidase inhibitory
activity of three deoxy derivatives, 2–4, of 1 were de-
scribed,[17,18] pointing to the clear significance of each hy-
droxy group (Figure 2). The 3-hydroxy groups of 1 and re-
lated compounds were found to be essential, conceivably
Figure 1. Mannostatin A (1) and mannopyranosyl cation. Com-
parison of preferred conformations (flap-up and -down) of the pos-
tulated transition-state mannopyranosyl cation with those of man-
nostatin A.
[‡] Part of this work was previously reported: Ref.[1]
[a] Department of Biosciences and Informatics, Faculty of Science
and Technology,
Keio University, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Ja-
pan
Fax: +81-45-566-1789
E-mail: ogawa@bio.keio.ac.jp
corresponding to the 2-hydroxy group of the mannopyrano-
syl cation. The amino groups located on the β-faces be-
tween the ring oxygen atoms and anomeric carbon atoms
Eur. J. Org. Chem. 2005, 4065–4072
DOI: 10.1002/ejoc.200500118
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S. Ogawa, T. Morikawa
FULL PAPER
of these derivatives were also found to be essential. Thus, diepimer[22] are moderate α-mannosidase inhibitors, and no
among the 24 known stereoisomers[19] of 5-amino-1,2,3,4- other isomers[21,23] lacking vicinal cis-hydroxy groups show
cyclopentanetetrol, only
5-C-methyl derivatives,[20] DL-6 and 8, were found to possess
moderate inhibitory activity against Jack bean α-mannosid- cation[1] of the methylthio functionality of mannostatin A
ase (Table 1). Comparison of the activities of -5 and -9 (1), with the focus on the synthesis and evaluation of the
L-5 and 7, and the corresponding inhibitory activity.
In this paper we describe the details of chemical modifi-
L
L
suggests the role of the 3-hydroxy groups. All compounds inhibitory activity of demethylthio (11), de-S-methyl (12),
containing cis-1,2-dihydroxy groups are likely to be and ethylthio (13) derivatives (Figure 3). Furthermore, in
matched with the 2- and 3-hydroxy groups of the mannopy- order to assess the role of the sulfur atom of 1, attempts
ranosyl cation. This consideration is in line with the find- were made to replace the methylthio group with a methoxy
ings that only mannostatin A isomer[21]
D
-10 and the 2,3- group, preparing 4-O-methyl-, 1,4-di-O-methyl-, and epi-4-
O-methylaminocyclopentanetetrols (14, 15 and 16), which
led to finding a very strong α-mannosidase inhibitor, 14,
comparable to the parent 1.
Figure 3. Chemical modification of the methylthio functionality of
mannostatin A.
Results and Discussion
Reaction of the 2,3-O-cyclohexylidene derivative[24,25] of
(1,2,3,4,5/0)-5-acetamido-1,2,3,4-cyclopentanetetrol with
Figure 2. Three deoxy derivatives of mannostatin A and analogous
aminocyclopentitol α-mannosidase inhibitors.
(2R)-O-acetylmandelic acid in the presence of DCC and
DMAP in CH2Cl2 diastereoselectively afforded 1R(2R)-O-
Table 1. Inhibitory activity (IC50, µ) against α-mannosidase (Jack
beans); NI: no inhibition Ͻ 10–3 .
acetylmandelate[26]
L-17 (56%) together with the (1S) ester
Compound[a]
Inhibitory activity
D
-17 (8%) (Figure 4). Compound -17 was converted into
L
the phenylthiocarbonyl ester 18 (71%) by treatment with
DMAP (6 equiv.) and phenyl chlorothionocarbonate (5
equiv.) in CH3CN at room temperature. Reaction of 18 with
tributyltin hydride in the presence of AIBN gave the deoxy
derivative 20 (71%). Deprotection of 20 with 2  HCl at
80 °C, followed by conventional acetylation, gave the tetra-
N,O-acetyl derivative 11a (ca. 100%), the structure of which
1
2
3
4
0.35
28
31
NI
110
10
83
29
56
NI
250
17[b]
11
36
5
0.16
NI
NI
D
-5
L
-5
-6
L
7
8
1
was characterized on the basis of its H NMR spectrum.
D
-9
-9
-10
Compound L-17 was treated with triflic anhydride in pyr-
L
idine/CH2Cl2 at –15 °C, and the resulting triflate 19 was
then subjected to nucleophilic substitution with potassium
thioacetate/18-crown-6 ether in dry benzene to give the ace-
tylthio derivative 21 (61%). Acid hydrolysis of 21 followed
by acetylation gave the penta-N,O,S-acetyl derivative 12a
(ca. 100%). In addition, 21 was de-S-acetylated with meth-
anolic sodium methoxide and the resulting crude thiol was
treated with iodoethane to give the ethylthio derivative 22
D
11
12
13
14
15
16
[a] Only inhibitory activity against α-mannosidase is listed. [b] The
Ki value was shown.[21]
4066
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chemical Modification of the α-Mannosidase Inhibitor Mannostain A
FULL PAPER
Figure 4. Synthesis of demethylthio, S-demethyl, and S-ethyl deriv-
atives of mannostatin A.
Figure 5. Synthesis of 1-(1,2,3,5/4)-5-amino-4-O-methyl-1,2,3,4-
cyclopentanetetrol (14).
(ca. 100%), which was purified by conversion into the tetra-
N,O-acetyl derivative 13a (ca. 100%).
Diastereoselective acylation of the 2,3-O-cyclohexylidene
derivative[26] of (1,4/2,3,5)-5-acetamido-1,2,3,4-cyclopen-
tanetetrol (23) with (2S)-O-acetylmandelic acid afforded a
mixture (ca. 4:1) of the esters
directly treated with triethylsilyl triflate in CH2Cl2 to give a
separable mixture of the triethylsilylates -25 (77%) and
25 (23%) (Figure 5). Compound -25 was de-O-acylated
L-24 and D-24, which was
L
D-
L
under Zemplén conditions to give 26, which was sub-
sequently treated with iodomethane/Ag2O in acetonitrile to
give the methyl ether 27 (ca. 100%). Desilylation of 27 with
tetrabutylammonium fluoride in THF to give 28 (69%),
was followed by conventional transformation into the mes-
ylate 29. Crude mesylate 29 was hydrolyzed by heating in
80% aq. DMF at 110 °C to give, through neighboring-
group participation, the 4-epimeric alcohol 30 (76% overall
yield). Acid hydrolysis of 30 and successive acetylation gave
the tetra-N,O-acetyl derivative 14a (53%).
The alcohol L-26 derived from
D-25 was mesylated and
the resulting crude sulfonate was treated with sodium ace-
Figure 6. Synthesis of the 1-O-methyl derivative 15a and 4-epimer
16a of 14a.
tate in aqueous DMF to give the 4(1)-epimer 31 (80%) of
1
23 (Figure 6). The structure of 31 was confirmed by the H
NMR spectrum of its di-O-acetyl derivative 32. Compound
31 was then methylated in a conventional manner to give (97%). Conventional deprotection of 35 followed by acety-
the dimethyl ether 33 (68%), which was converted conven- lation gave the tetra-N,O-acetyl derivative 16a (87%).
tionally into the tri-N,O-acetyl derivative 15a (86%).
Compound -17 was silylated and deacylated to give 34 ment of the corresponding peracetyl derivatives 11a–13a
(68%), and then methylated to give the methyl ether 35 with 2  hydrochloric acid at 80 °C, and purified on a col-
Mannostatin A analogues 11–13 were prepared by treat-
D
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S. Ogawa, T. Morikawa
FULL PAPER
umn of Dowex-50 W×2 (H+) resin with 1% aqueous am- droxy groups adjacent to the amino group should match
monia as the eluent. The analogues 14–16 were also ob- with the 2- and 3-hydroxy groups of the cation adopting
tained by hydrolysis of 14a–16a with 1  aqueous Ba(OH)2 the flap-up conformation, as roughly depicted in Figure 1.
at 90 °C, followed by a similar purification. The free bases Although studies[31] on a moderate α-mannosidase inhibi-
thus obtained were directly subjected to assays of α-manno- tor, deoxymannonojirimycin, demonstrated that 5-hy-
sidase inhibition.
droxymethyl branching is not indispensable for inhibitory
action, we found the strong inhibitory activity of com-
pounds 36 and 37 to depend on the presence of 4-hy-
droxymethyl groups, matching the 5-hydroxymethyl group
of the mannopyranosyl cation. In the cases of compounds
1 and 14, the methylthio and methoxy groups seem to act as
hydroxymethyl equivalents to provide a certain hydrophobic
region of space, increasing their potency.
Biological Assay
Listed in Table 1 are the Jack bean α-mannosidase inhibi-
tory activities[27] for newly prepared compounds 11–16, to-
gether with those of deoxy- (2–4), C-methyl- (6 and 8), and
hydroxymethyl (9 and 10) aminocyclopentitol derivatives
(Table 1). The moderate inhibitor 4-amino-1,2,3-cyclopen-
tanetriol (11) appeared to have the minimum core structure
for exhibiting inhibitory activity against α-mannosidase,
suggesting that possible enhancement of activity could be
achieved by chemical modification, for example, through N-
substitution with alkyl or phenylalkyl functionalities.[28] In-
corporation of the appropriate functionalities at the 5-car-
bon atom of 11 with methylthio and methoxy groups, as
shown in compounds 1 and 14, increased the activity dra-
matically. In contrast, derivatives having hydrophilic sub-
Conclusions
We obtained a strong α-mannosidase inhibitor amino-O-
methylcyclopentanetriol 14, the activity of which was com-
parable to that of the parent 1, providing a lead compound
for further development. The configuration of the hydro-
phobic S- or O-methyl functionality was shown to be very
important, and the significance of a free 1-hydroxy group
adjacent to the amino group was again verified by compar-
ing the activities of the pairs 14 and 16, and 14 and 15,
respectively. Strong inhibitory activity was demonstrated to
be generated by an essential core structure composed of the
5-O-(or S-)methyl functionality and consecutive 1-, 2-, and
3-hydroxy, and 4-amino groups on the cyclopentane ring.
Vicinal 2- and 3-hydroxy groups in a cis relationship match
the 3- and 2-hydroxy groups of the postulated mannopyr-
anosyl cation, and the amino functionality locates on the
α- or β-face between pyranoid oxygen atom and anomeric
carbon atoms. N-Substitution with normal or modified
alkyl and phenylalkyl groups might improve inhibitory po-
tential, as suggested by previous results.[28,30]
stituents at C-5, such as L-5 and 7, exhibited decreased ac-
tivity, indicating that the presence of a hydrophobic region
of space around C-5 is essential. Furthermore, the fact that
the 4-epimer (16) of 14 completely lacked activity suggests
that substituents located on the β-face at C-5 are important.
It became apparent that the more the structures resembled
mannostatin A (1), the greater their inhibitory potential.
Farr[29] reported the synthesis of a strong mannosidase in-
hibitor, amino(hydroxymethyl)cyclopentanetriol 36, with a
1-(1,2,4/3,5N) configuration, and demonstrated good over-
lap between 36 and the mannopyranosyl cation by molecu-
lar modeling (Figure 1 and Table 2).[16] Recently, Jäger[30]
described the synthesis of two stereoisomers, 37 and 38,
having 1-(1,2,4,5N/3) and 1 L-(1,2/3,4,5N) configurations,
respectively. From a structural viewpoint, the cis-vicinal hy-
Experimental Section
General: Melting points: Mel-Temp capillary melting-point appara-
tus, uncorrected values. Specific rotations: Jasco DIP-370 polarime-
ter, 1-dm cells. IR spectra: Hitachi FT/IR-200 and BIORAD DIGI-
TAL FT-65 spectrometers. 1H NMR spectra: Jeol JNM EX-90
(90 MHz); Jeol GSX-270 f.t. (270 MHz), and Jeol Lambda-300
(300 MHz) spectrometers; solvent CDCl3: internal tetramethylsi-
lane (TMS) standard. CD3OD: external acetone standard; D2O:
external acetone standard. Mass spectra: positive-ion electrospray
ionization with a Micromass Zab Hybrid Spec Sector-TOF mass
spectrometer. TLC: Silica Gel 60 GF (E. Merck Darmstadt); detec-
tion by charring with concentrated H2SO4. Column chromatog-
raphy: Wakogel C-300 (silica gel, 300 mesh, Wako Chemical
Osaka). Organic solutions, after drying with anhydrous Na2SO4,
were concentrated at Ͻ50 °C under reduced pressure.
Table 2. Present data for inhibitory activity (IC50 [µ]) of mannos-
tatin A (1) and 14, and those reported for isomeric amino(hy-
droxymethyl)cyclopentanetriols 36–38 against α-mannosidase (Jack
beans) (reference compound 1: IC50 = 0.02; 0.07 µM].
IC50
[µ]
Compd. R1
R2
R3
R4
X
Y
2,3-O-Cyclohexylidene Derivative of (1R,2S,3R,4S,5S)-5-Acetamido-
1-O-[(2R)-2-O-acetylmandelyl]-4-O-phenoxythiocarbonyl-1,2,3,4-
1
OH
OH
H
H
H
H
H
H
H
SMe
OMe
H
NH2
NH2
H
NH3Br
H
H
H
0.32
0.16
cyclopentanetetrol (18): To a solution of L
-17[26] (1.83 g, 4.1 mmol)
14
36
37
38
OH CH2OH
OH CH2OH
OH
NH3Br 0.39
H
NH3Br
in acetonitrile (18 mL) were added DMAP (3.0 g, 24.5 mmol, 6
equiv.) and phenyl chlorothioformate (2.83 mL, 20.5 mmol, 5
equiv.), and the reaction mixture was stirred at room temperature
H
0.17
5.8
H
CH2OH
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 4065–4072

Chemical Modification of the α-Mannosidase Inhibitor Mannostain A
FULL PAPER
for 3 h. The mixture was diluted with ethyl acetate (200 mL), the
solution was washed with water, dried, and the solvents were evapo-
rated. The residual product was purified by chromatography on a
silica gel column (240 g, acetone/toluene, 1:10) to give 18 (1.69 g,
and then iodoethane (9 µL, 1.1 mmol) was added. After stirring at
room temperature for 1 h, the reaction mixture was concentrated
and the residue was purified by chromatography on a column of
silica gel (0.5 g, acetone/toluene, 1:3) to give 22 (3.6 mg, ca. 100%)
as a syrup. TLC (acetone/toluene, 1:2): Rf = 0.27. [α]2D2 = +1.7 (c =
71%) as a syrup. TLC (acetone/toluene, 1:3): Rf = 0.43. [α]1D8 = –
1
30 (c = 0.64, CHCl3). H NMR (270 MHz, CDCl3): δ = 1.22–1.77 0.35, CHCl3). 1H NMR (300 MHz, CDCl3): δ = 1.29 (t, J = 7.3 Hz,
(m, 10 H, C6H10), 1.93, 2.21 (2 s, each 3 H, 2×Ac), 4.76 (dd, J1,2
= 5.1, J1,5 = 5.8 Hz, 1 H, 1-H), 4.82 (dd, J3,4 = 5.1, J2,3 = 5.5 Hz, (q, J = 7.3 Hz, 2 H, CH2CH3), 3.17 (dd, J3,4 = 3.9, J4,5 = 8.8 Hz,
1 H, 3-H), 4.94 (ddd, J4,5 = 5.6, J1,5 = 5.8, J5,NH = 9.2 Hz, 1 H, 5- 1 H, 4-H), 4.16 (dd, J1,5 = 4.4, J1,2 = 4.9 Hz, 1 H, 1-H), 4.34 (ddd,
H), 5.01 (dd, J1,2 = 5.1, J2,3 = 5.5 Hz, 1 H, 2-H), 5.47 (dd, J3,4 J1,5 = 4.4, J4,5 = 8.8, J5,NH = 9.0 Hz, 1 H, 5-H), 4.51 (dd, J3,4
5.1, J4,5 = 5.6 Hz, 1 H, 4-H), 6.01 [s, 1 H, PhCH(OAc)CO], 6.33 3.9, J2,3 = 7.1 Hz, 1 H, 3-H), 4.58 (dd, J1,2 = 4.9, J2,3 = 7.1 Hz, 1
3 H, CH2CH3), 1.38–1.77 (m, 10 H, C6H10), 2.03 (s, 3 H, Ac), 2.70
=
=
(d, J5,NH = 9.2 Hz, 1 H, NH), 7.12–7.59 (m, 10 H, 2×Ph) ppm.
H, 2-H), 6.08 (d, J5,NH = 9.0 Hz, 1 H, NH) ppm. HRMS: calcd.
HRMS: calcd. for C30H33NO9S 583.1876; found 583.1871 [M+].
for C15H25NO4S 315.1504; found 315.1506 [M+].
Tetra-N,O-acetyl-(1R,2R,3R,4S,5S)-4-amino-5-ethylthio-1,2,3-cy-
clopentanetriol (13a): Compound 22 (6.0 mg, 19 µmol) was hy-
drolyzed as in the preparation of 11, and the product was acety-
lated in the usual manner. The product was purified by a column
of silica gel (0.7 g, acetone/toluene, 1:2) to give 13a (6.9 mg, ca.
1,2-O-Cyclohexylidene Derivative of (1S,2S,3R,4R)-4-Acetamido-3-
O-[(2R)-2-O-acetylmandelyl]-1,2,3-cyclopentanetetrol (20): To a
solution of AIBN (3.4 mg, 0.021 mmol, 0.3 equiv.) in toluene (0.5
mL) was added tributyltin hydride (55.4 µL, 0.21 mmol, 3 equiv.)
dropwise, followed by a mixture of 18 (40 mg, 0.07 mmol) and tolu-
ene (3.5 mL). The reaction mixture was heated at reflux for 2 h,
then concentrated to dryness, and the product was purified by
chromatography on a silica gel column (10 g, acetone/toluene,
1:4.5) to give 20 (21 mg, 71%) as a syrup. TLC (acetone/toluene,
1:3): Rf = 0.18. [α]2D2 = +21 (c = 0.54, CHCl3). 1H NMR (300 MHz,
CDCl3): δ = 1.25–1.52 (m, 10 H, C6H10), 1.98–2.04 (m, 2 H, 5a-H,
5b-H), 1.87, 2.20 (2 s, each 3 H, 2×Ac), 4.57 (m, 1 H, 4-H), 4.63
(ddd, J1,5a = 2.4, J1,5b = 5.4, J1,2 = 6.1 Hz, 1 H, 1-H), 4.70 (dd, J2,3
= 4.9, J1,2 = 6.1 Hz, 1 H, 2-H), 4.87 (dd, J2,3 = J3,4 = 4.9 Hz, 1 H,
3-H), 5.99 [s, 1 H, PhCH(OAc)CO], 6.26 (d, J4,NH = 9.0 Hz, 1 H,
NH), 7.40–7.52 (m, 5 H, Ph) ppm. HRMS: calcd. for C23H30NO9
431.1944; found 431.1949 [M+].
100%) as a syrup. TLC (acetone/toluene, 1:1): Rf = 0.40. [α]2D5
=
1
+15 (c = 0.07, CHCl3). H NMR (300 MHz, CDCl3): δ = 1.25 (t,
J = 7.3 Hz, 3 H, CH2CH3), 2.04, 2.06, 2.08, 2.11 (4 s, each 3 H,
4×Ac), 2.45 (br. q, J = 7.3 Hz, 2 H, CH2CH3), 3.17 (dd, J1,5 = 5.6,
J4,5 = 7.6 Hz, 1 H, 5-H), 4.53 (ddd, J3,4 = 5.6, J4,5 = 7.6, J4,NH
8.8 Hz, 1 H, 4-H), 5.16 (t, J1,2 = J1,5 = 5.6 Hz, 1 H, 1-H), 5.35 (dd,
J2,3 = 4.4, J3,4 = 5.6 Hz, 1 H, 3-H), 5.42 (dd, J2,3 = 4.4, J1,2
=
=
5.6 Hz, 1 H, 2-H), 5.70 (d, J4,NH = 8.8 Hz, 1 H, NH) ppm. HRMS:
calcd. for C15H24NO7S 362.1273; found 362.1270 [M+].
2,3-O-Cyclohexylidene Derivatives of (1S,2S,3R,4R,5R)- and
(1R,2R,3S,4S,5S)-5-Acetamido-1-O-[(2S)-2-O-acetylmandelyl]-4-O-
triethylsilyl-1,2,3,4-cyclopentanetetrol (
1- and 1-(1,4/2,3,5)-5-acetamido-1-O-[(2S)-2-O-acetylmandelyl]-
1,2,3,4-cyclopentanetetrol ( -24 and -24, 336 mg, 0.752 mmol) de-
D-25 and L-25): A mixture of
Tetra-N,O-acetyl-(1S,2S,3R,4R)-4-amino-1,2,3-cyclopentanetriol
(11a): A mixture of 20 (8.2 mg, 19 µmol) and 2  hydrochloric acid
(1.0 mL) was heated at 80 °C for 1 h, and then concentrated to
dryness. The residue was treated with acetic anhydride (0.5 mL)
and pyridine (1 mL) at room temperature overnight. The reaction
mixture was coconcentrated with toluene, and the residue was puri-
fied by chromatography on a column of silica gel (0.7 g, acetone/
toluene, 1:2) to give 11a (5.7 mg, ca. 100%) as a syrup. TLC (ace-
tone/toluene, 1:1): Rf = 0.39. [α]2D5 = +16 (c = 0.42, CHCl3). 1H
NMR (300 MHz, CDCl3): δ = 1.77 (m, 1 H, 5a-H), 2.01, 2.05, 2.07,
2.13 (4 s, each 3 H, 4×Ac), 2.66 (m, 1 H, 5b-H), 4.57 (m, 1 H, 4-
H), 5.20–5.28 (m, 3 H, 1-H, 2-H, 3-H), 5.74 (d, J4,NH = 8.5 Hz, 1 H,
NH) ppm. HRMS: calcd. for C13H20NO7 302.1239; found 302.1229
[M+].
D
L
rived[26] from the diol 23, triethylsilyl triflate (255 µL, 1.13 mmol,
1.5 equiv.), and 2,6-lutidine (262 µL, 2.25 mmol, 3 equiv.) in dichlo-
romethane (3.5 mL) was stirred under argon at 0 °C for 90 min. To
the reaction mixture was then added saturated aqueous NaHCO3
(60 mL), and the aqueous layer was thoroughly extracted with chlo-
roform (3 ×20 mL). The extracts were dried, and the solvents were
evaporated. The residue was purified by chromatography on a silica
gel column (40 g, ethyl acetate/toluene, 1:7) to give
77%) and -25 (94 mg, 23%), each as a syrup.
L-25 (326 mg,
D
L
-25: TLC (acetone/toluene, 1:4): Rf = 0.48. [α]2D5 = +37 (c = 1.14,
1
CHCl3). H NMR (300 MHz, CDCl3): δ = 0.59 [dd, J = 7.8, Jgem
= 16.1 Hz, 6 H, Si(CH2CH3 )3 ], 0.93 [t, J = 7.8 Hz, 9 H,
Si(CH2CH3)3], 1.39–1.70 (m, 10 H, C6H10), 1.85, 2.18 (2 s, each 3
H, 2×Ac), 4.02 (dd, J1,2 = 2.2, J1,5 = 4.4 Hz, 1 H, 1-H), 4.12 (ddd,
Penta-N,O,S-acetyl-(1R,2R,3R,4S,5S)-4-amino-5-thio-1,2,3-cyclo-
pentanetriol (12a): A mixture of 21[26] (12.0 mg, 24 µmol) and 2 
hydrochloric acid (1.0 mL) was stirred at 80 °C for 1 h, and then
coconcentrated with EtOH. The residue was acetylated in the usual
manner and the product was purified by chromatography on a col-
umn of silica gel (0.7 g, acetone/toluene, 1:4) to give 12a (8.9 mg,
ca. 100%) as a syrup. TLC (acetone/toluene, 1:1): Rf = 0.48. [α]2D5
J1,5 = 4.4, J4,5 = 4.6, J5,NH = 9.0 Hz, 1 H, 5-H), 4.41 (dd, J1,2
=
2.2, J2,3 = 6.6 Hz, 1 H, 2-H), 4.57 (dd, J3,4 = 2.2, J2,3 = 6.6 Hz, 1
H, 3-H), 5.04 (dd, J3,4 = 2.2, J4,5 = 4.6 Hz, 1 H, 4-H), 5.63 (br. d,
J5,NH = 9.0 Hz, 1 H, NH), 5.87 [s, 1 H, PhCH(OAc)CO], 7.36–7.46
(m, 5 H, Ph) ppm. HRMS: calcd. for C27H38NO8Si 532.2367;
found 532.2367 [M+].
1
= +26 (c = 0.37, CHCl3). H NMR (300 MHz, CDCl3): δ = 1.99,
-25: TLC (acetone/toluene, 1:4): Rf = 0.44. [α]2D5 = +28 (c = 1.12,
2.03, 2.07, 2.15, 2.37 (5 s, each 3 H, 5×Ac), 3.91 (dd, J1,5 = 6.8,
D
1
J4,5 = 10.5 Hz, 1 H, 5-H), 4.52 (ddd, J3,4 = 4.4, J4,NH = 8.5, J4,5
=
CHCl3). H NMR (300 MHz, CDCl3): δ = 0.63 [dd, J = 8.1, Jgem
= 15.4 Hz, 6 H, Si(CH2CH3 )3 ], 0.96 [t, J = 8.1 Hz, 9 H,
Si(CH2CH3)3], 1.37–1.71 (m, 10 H, C6H10), 1.92, 2.17 (2 s, each 3
H, 2×Ac), 4.07 (m, 1 H, 1-H), 4.26 (m, 1 H, 5-H), 4.33 (m, 2 H,
2-H, 3-H), 5.10 (m, 1 H, 4-H), 5.72 (br. d, J5,NH = 9.0 Hz, 1 H,
NH), 5.90 [s, 1 H, PhCH(OAc)CO], 7.37–7.48 (m, 5 H, Ph) ppm.
HRMS: calcd. for C27H38NO8Si 532.2367; found 532.2388 [M+].
10.5 Hz, 1 H, 4-H), 5.26 (dd, J1,5 = 6.8, J1,2 = 7.1 Hz, 1 H, 1-H),
5.40 (dd, J2,3 = 3.9, J1,2 = 7.1 Hz, 1 H, 2-H), 5.42 (dd, J2,3 = 3.9,
J3,4 = 4.4 Hz, 1 H, 3-H), 5.79 (d, J4,NH = 8.5 Hz, 1 H, NH) ppm.
HRMS: calcd. for C15H24NO7S 376.1066; found 376.1068 [M+].
1,2-O-Cyclohexylidene Derivative of (1R,2S,3R,4S,5R)-4-Acet-
amido-5-ethylthio-1,2,3-cyclopentanetriol (22): A solution of 21
(5.7 mg, 11 µmol) in MeOH (0.2 mL) was treated with 1  meth-
anolic sodium methoxide (17 µL) at room temperature for 10 min,
2,3-O-Cyclohexylidene Derivative of (1R,2S,3S,4S,5R)-5-Acet-
amido-1-O-triethylsilyl-1,2,3,4-cyclopentanetetrol (D-26): A solution
Eur. J. Org. Chem. 2005, 4065–4072
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 4069

S. Ogawa, T. Morikawa
FULL PAPER
of the S-acetylmandelate
L-25 (159 mg, 0.28 mmol) in CH2Cl2 (1.6
and the residue was purified by chromatography on a silica gel
mL) was treated with 1  methanolic sodium methoxide (57 µL, 57
µM) at 0 °C for 3 h. The product was purified by chromatography
on a column of silica gel (10 g, acetone/toluene, 1:2) to give the
column (1.5 g, acetone/toluene, 1:3) to give the alcohol 30 (12.6 mg,
76%) as a syrup. TLC (acetone/toluene, 1:1): Rf = 0.42. [α]2D5
=
1
–29 (c = 0.8, CHCl3). H NMR (300 MHz, CDCl3): δ = 1.38–1.76
(m, 10 H, C6H10), 2.03 (s, 3 H, Ac), 3.23 (d, J4,OH = 3.7 Hz, 1 H,
OH), 3.43 (s, 3 H, Me), 3.68 (dd, J1,2 = 2.7, J1,5 = 6.6 Hz, 3 H, 1-
H), 4.11 (ddd, J4,OH = 3.7, J4,5 = 4.6, J3,4 = 4.9 Hz, 1 H, 4-H), 4.41
(ddd, J4,5 = 4.6, J1,5 = 6.6, J5,NH = 8.5 Hz, 1 H, 5-H), 4.45 (dd, J1,2
= 2.7, J2,3 = 7.1 Hz, 1 H, 2-H), 4.58 (dd, J3,4 = 4.9, J2,3 = 7.1 Hz,
alcohol D-26 (109 mg, ca. 100%) as a syrup. TLC (acetone/toluene,
1:2): Rf = 0.41. [α]2D5 = +10 (c = 1.65, CHCl3). 1H NMR (300 MHz,
CDCl3): δ = 0.69 [dd, J = 8.1, Jgem = 15.9 Hz, 6 H, Si(CH2CH3)3],
0.99 [t, J = 8.1 Hz, 9 H, Si(CH2CH3)3], 1.36–1.77 (m, 10 H, C6H10),
1.97 (s, 3 H, Ac), 3.79 (d, J4,OH = 8.1 Hz, 1 H, OH), 4.00–4.07 (m,
3 H, 1-H, 4-H, 5-H), 4.50 (m, 1 H, 2-H), 5.64 (m, 1 H, 3-H), 5.90 1 H, 3-H), 6.12 (br. d, J5,NH = 8.5 Hz, 1 H, NH) ppm. HRMS:
(m, 1 H, NH) ppm. HRMS: calcd. C19H35NO5Si 385.2285; found
m/z = 285.1575 [M+]. C14H23NO5 (285.1576).
385.2303 [M+].
(1R,2R,3S,4R,5R)-5-Acetamido-1,2,3-O-acetyl-4-O-methyl-1,2,3,4-
cyclopentanetetrol (14a): A mixture of 30 (31.4 mg, 0.11 mmol) and
aqueous acetic acid (60%, 1.0 mL) was stirred at 60 °C for 5.5 h
and then concentrated to dryness. The residual product was acety-
lated in the usual manner, and the product was purified by
chromatography on a silica gel column (3 g, acetone/toluene, 1:3)
to give the acetyl derivative 14a (19.2 mg, 53%) as a syrup. TLC
2,3-O-Cyclohexylidene Derivative of (1S,2R,3R,4R,5S)-5-Acet-
amido-1-O-triethylsilyl-1,2,3,4-cyclopentanetetrol (L-26):
(149 mg, 0.26 mmol) was deacylated as in the preparation of
D
-25
-26
D
to give L-26 (167 mg, ca. 100%) as a syrup. TLC (acetone/toluene,
1:2): Rf = 0.41. [α]2D5 = –7.4 (c = 1.0, CHCl3). HRMS: calcd. for
1
C19H36NO5Si 386.2363; found 386.2354 [M+]. The H NMR spec-
1
trum was found to be superimposable on that of -26.
(acetone/toluene, 1:1): Rf = 0.32. [α]2D3 = –3.1 (c = 0.5, CHCl3). H
NMR (300 MHz, CDCl3): δ = 2.04, 2.08, 2.10 (3 s, 3 H, 6 H, 3 H,
4×OAc), 3.42 (s, 3 H, Me), 3.77 (t, J3,4 = J4,5 = 4.6 Hz, 1 H, 4-H),
4.57 (ddd, J4,5 = 4.6, J1,5 = 6.1, J5,NH = 9.0 Hz, 1 H, 5-H), 5.14 (t,
J2,3 = J3,4 = 4.6 Hz, 1 H, 3-H), 5.34 (dd, J1,2 = 3.9, J1,5 = 6.1 Hz,
1 H, 1-H), 5.46 (dd, J1,2 = 3.9, J2,3 = 4.6 Hz, 1 H, 2-H), 5.82 (br.
d, J5,NH = 9.0 Hz, 1 H, NH) ppm. HRMS: calcd. for C14H22NO8
332.1345; found 332.1371 [M+].
2,3-O-Cyclohexylidene Derivative of (1S,2S,3S,4S,5R)-5-Acetamido-
1-O-methyl-4-O-triethylsilyl-1,2,3,4-cyclopentanetetrol (27): To a
solution of
D-26 (12.3 mg, 2 mmol) in acetonitrile (0.5 mL) were
added silver oxide (11.4 mg, 48 µM) and iodomethane (0.2 mL,
3.19 mmol), and the mixture was refluxed for 6 h. An insoluble
material was removed by filtration, and the filtrate was concen-
trated to dryness. The residue was purified by chromatography on
a silica gel column (0.7 g, acetone/toluene, 1:7) to give the methyl
ether 27 (12.7 mg, ca. 100%) as a syrup. TLC (acetone/toluene,
1:1): Rf = 0.71. [α]2D5 = –0.1 (c = 0.7, CHCl3). 1H NMR (300 MHz,
CDCl3): δ = 0.63 [dd, J = 8.1, Jgem = 14.9 Hz, 6 H, Si(CH2CH3)3],
0.96 [t, J = 8.1 Hz, 9 H, Si(CH2CH3)3], 1.32–1.70 (m, 10 H, C6H10),
1.97 (s, 3 H, Ac), 3.42 (s, 3 H, Me), 3.71 (m, 1 H, 4-H), 4.06–4.11
2,3-O-Cyclohexylidene Derivative of (1S,2R,3S,4R)-5-Acetamido-
1,2,3,4-cyclopentanetetrol (31): Alcohol L-26 (167 mg, 0.433 mmol)
was mesylated as in the preparation of 29. During the above pro-
cessing, when the reaction mixture was concentrated and coconcen-
trated with toluene, a partial removal of the triethylsilyl group was
observed. The resulting crude mesylate was treated with sodium
acetate (178 mg, 2.16 mmol) in aqueous 80% DMF (2.0 mL) at
110 °C overnight, and then the mixture was concentrated and co-
concentrated with ethanol and toluene. The residue was purified
by chromatography on a column of silica gel (10 g, acetone/toluene,
1:1) to give the diol 31 (94 mg, 80%) as a syrup. TLC (acetone/
toluene, 2:1): Rf = 0.28. [α]2D1 = –28 (c = 1.0, CHCl3). 1H NMR
(300 MHz, CDCl3): δ = 1.34–1.76 (m, 10 H, C6H10), 2.03 (s, 3 H,
Ac), 4.13–4.21 (m, 3 H, 3-H, 4-H, 5-H), 4.49 (d, J1,2 = 7.1 Hz, 1
H, 1-H), 4.65 (dd, J2,3 = 4.9, J1,2 = 7.1 Hz, 1 H, 2-H), 6.52 (br. s,
1 H, NH) ppm. HRMS: calcd. for C13H21NO5 271.1420; found
271.1413 [M+].
(m, 2 H, 1-H, 5-H), 4.41 (m, 1 H, 2-H), 4.52 (dd, J2,3 = 2.2, J3,4
=
6.6 Hz, 1 H, 3-H), 5.73 (br. d, J5,NH = 7.6 Hz, 1 H, NH) ppm.
HRMS: calcd. for C20H37NO5Si 399.2441; found 399.2441 [M+].
2,3-O-Cyclohexylidene Derivative of (1R,2S,3R,4S,5S)-5-Acet-
amido-1-O-methyl-1,2,3,4-cyclopentanetetrol (28): A solution of 27
(83 mg, 0.21 mmol) in THF (1.6 mL) was treated with TBAF
(59 µL, 0.25 mmol) at room temperature for 1.5 h, and then the
reaction mixture was concentrated to dryness. The residue was dis-
solved in ethyl acetate (15 mL), and the solution was washed with
1  hydrochloric acid, saturated aqueous NaHCO3, and water,
dried, and the solvents were evaporated. The residual product was
purified by chromatography on a silica gel column (5 g, acetone/
2,3-O-Cyclohexylidene Derivative of (1S,2S,3R,4R)-5-Acetamido-
toluene, 1:1) to give 28 (40.5 mg, 69%) as a syrup. TLC (acetone/ 1,4-di-O-acetyl-1,2,3,4-cyclopentanetetrol (32): Diol 31 (91 mg, 0.34
1
toluene, 1:1): Rf = 0.34. [α]2D7 = +12 (c = 0.82, CHCl3). H NMR
(300 MHz, CDCl3): δ = 1.31–1.75 (m, 10 H, C6H10), 2.01 (s, 3 H,
Ac), 3.48 (s, 3 H, Me), 3,62 (m, 1 H, 1-H), 4.03 (m, 2 H, 4-H, 5-
mmol) was acetylated with acetic anhydride in pyridine in the usual
manner, and the product was purified by chromatography on a col-
umn of silica gel (10 g, acetone/toluene, 1:4) to give the di-O-acetyl
H), 4.29 (m, 1 H, OH), 4.56 (br. s, 2 H, 2-H, 3-H), 5.99 (br. s, 1 H, derivative 32 (119 mg, ca. 100%) as a syrup. TLC (acetone/toluene,
NH) ppm. HRMS: calcd. for C14H23NO5 285.1576; found 285.1589
1:1): Rf = 0.50. [α]2D3 = +38 (c = 1.5, CHCl3). 1H NMR (300 MHz,
CDCl3): δ = 1.25–1.82 (m, 10 H, C6H10), 1.99, 2.08, 2.16 (3 s, each
3 H, 3×Ac), 4.48 (dd, J3,4 = 1.7, J2,3 = 6.3 Hz, 1 H, 3-H), 4.54
(ddd, J4,5 = 4.6, J1,5 = 5.1, J5,NH = 8.5 Hz, 1 H, 5-H), 4.77 (dd, J1,2
= 5.1, J2,3 = 6.3 Hz, 1 H, 2-H), 5.11 (dd, J3,4 = 1.7, J4,5 = 4.6 Hz,
[M+].
2,3-O-Cyclohexylidene Derivative of (1R,2R,3S,4R,5S)-5-O-Acet-
amido-4-O-methyl-1,2,3,4-cyclopentanetetrol (30): To a solution of
28 (16.5 mg, 58 µmol) in pyridine (0.4 mL) was added mesyl chlo-
ride (22.4 µL, 0.29 mmol) at 0 °C. The mixture was stirred at room
temperature for 1 h, and then coconcentrated with toluene. The
residue was diluted with CHCl3 (15 mL), and the solution was
washed thoroughly with water, dried, and the solvents were evapo-
rated. The resulting crude mesylate 29 was dissolved in aqueous
DMF (80%, 3.0 mL) and, after addition of sodium acetate (18 mg,
2.2 mmol), the mixture was stirred at 110 °C overnight. The reac-
tion mixture was then coconcentrated with ethanol and toluene,
1 H, 4-H), 5.18 (t, J1,2 = J1,5 = 5.1 Hz, 1 H, 1-H), 6.17 (d, J5,NH
=
8.5 Hz, 1 H, NH) ppm. HRMS: calcd. for C17H25NO7 355.1631;
found 355.1612 [M+].
2,3-O-Cyclohexylidene Derivative of (1S,2R,3S,4R)-5-Acetamido-
1,4-di-O-methyl-1,2,3,4-cyclopentanetetrol (33): Diol 31 (76 mg,
0.28 mmol) was methylated with silver oxide (194 mg, 0.837 mmol)
and iodomethane (1.74 mL, 27.9 mmol) in acetonitrile (1.0 mL) at
80 °C for 5 h. The product was purified by chromatography on a
4070
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 4065–4072

Chemical Modification of the α-Mannosidase Inhibitor Mannostain A
FULL PAPER
column of silica gel (3 g, acetone/toluene, 1:5) to give ether 33
(57 mg, 68%) as a syrup. TLC (acetone/toluene, 2:1): Rf = 0.62.
[α]2D2 = –31 (c = 1.4, CHCl3). 1H NMR (300 MHz, CDCl3): δ =
1.25–1.81 (m, 10 H, C6H10), 3.44, 3.44 (2 s, each 3 H, 2×Me), 3.62
(t, J3,4 = J4,5 = 5.4 Hz, 1 H, 4-H), 3.46 (s, 3 H, Me), 3.92 (t, J1,2 =
J1,5 = 5.4 Hz, 1 H, 1-H), 4.44 (t, J1,2 = J2,3 = 5.4 Hz, 1 H, 2-H),
4.60 (t, J2,3 = J3,4 = 5.4 Hz, 1 H, 3-H), 4.62 (ddd, J1,5 = J4,5 = 5.4,
J5,NH = 9.8 Hz, 1 H, 5-H), 6.27 (d, J5,NH = 9.8 Hz, 1 H, NH) ppm.
(s, 1 H, 4-H), 3.88 (t, J1,2 = J1,5 = 4.9 Hz, 1 H, 1-H), 4.41 (d, J2,3 HRMS: calcd. for C20H37NO5Si 399.2441; found 399.2427 [M+].
= 4.9 Hz, 1 H, 3-H), 4.44 (dd, J1,5 = 4.9, J5,NH = 7.1 Hz, 1 H, 5-
(1R,2R,3S,4S,5R)-5-Acetamido-1,2,3-tri-O-acetyl-4-O-methyl-
H), 4,73 (t, J1,2 = J2,3 = 4.9 Hz, 1 H, 2-H), 6.34 (d, J5,NH = 7.1 Hz,
1,2,3,4-cyclopentanetetrol (16a): A mixture of 35 (10 mg, 25 µmol)
1 H, NH) ppm. HRMS: calcd. for C15H26NO5 300.1811; found
and aqueous acetic acid (60%, 2.0 mL) was stirred at 80 °C for 9 h,
and then coconcentrated with ethanol and toluene. The residue was
300.1816 [M+].
treated with acetic anhydride (0.5 mL) and pyridine (1.0 mL) at
room temperature overnight. The reaction mixture was concen-
trated, and the residue was purified by chromatography on a col-
(1S,2R,3S,4R)-5-Acetamido-2,3-di-O-acetyl-1,4-di-O-methyl-
1,2,3,4-cyclopentanetetrol (15a): Compound 33 (54 mg, 0.18 mmol)
was hydrolysed with 60% aqueous acetic acid at 80 °C for 2 h. The
umn of silica gel (0.7 g, acetone/toluene, 1:3) to give the acetyl
product was acetylated in the usual manner, and the acetyl deriva-
derivative 16a (7.3 mg, 87 %) as a syrup. TLC (acetone/toluene,
tive was purified by chromatography on a column of silica gel (3
g, acetone/toluene, 1:3) to give the di-O-acetyl derivative 15a
1:1): Rf = 0.41. [α]2D2 = +36 (c = 0.4, CHCl3). 1H NMR (300 MHz,
CDCl3): δ = 2.05, 2.08, 2.09, 2.14 (4 s, each 3 H, 4×Ac), 3.40 (s, 3
(46.5 mg, 86%) as a syrup. TLC (acetone/toluene, 1:1): Rf = 0.39.
[α]2D2 = –44 (c = 1.2, CHCl3). 1H NMR (300 MHz, CDCl3): δ =
2.06, 2.06, 2.14 (3 s, each 3 H, 3×Ac), 3.37, 3.45 (2 s, each 3 H,
2×Me), 3.72 (dd, J4,5 = 3.7, J3,4 = 5.6 Hz, 1 H, 4-H), 3.89 (dd, J1,2
= 3.6, J1,5 = 6.8 Hz, 1 H, 1-H), 4.44 (ddd, J4,5 = 3.7, J1,5 = 6.8,
J5,NH = 8.5 Hz, 1 H, 5-H), 5.02 (t, J2,3 = J3,4 = 5.6 Hz, 1 H, 3-H),
H, Me), 3.86 (m, 1 H, 4-H), 4,74 (m, 1 H, 5-H), 5.22–5.29 (m, 3
H, 1-H, 2-H, 3-H), 5.97 (d, J5,NH = 9.0 Hz, 1 H, NH) ppm. HRMS:
calcd. for C14H22NO8 332.1345; found 332.1331 [M+].
(1S,2S,3R,4R)-4-Amino-1,2,3-cyclopentanetriol (11): A mixture of
11a (8.3 mg, 28 µmol) and 2  hydrochloric acid (1 mL) was stirred
at 80 °C for 1 h, and the solvents were evaporated to dryness. The
residual product was purified by chromatography on a column of
Dowex-50 W×2 (H+) resin (1 mL, 1  aqueous ammonia) to give
the free base 11 (3.7 mg, ca. 100 %). TLC (H2O/AcOH/tBuOH,
1:1:4): Rf = 0.33. [α]2D4 = +46 (c = 0.4, MeOH). 1H NMR
5.48 (dd, J1,2 = 3.6, J2,3 = 5.6 Hz, 1 H, 2-H), 6.05 (d, J5,NH
=
8.5 Hz, 1 H, NH) ppm. HRMS: calcd. for C13H22NO7 304.1396;
found 304.1402 [M+].
2,3-O-Cyclohexylidene Derivative of (1R,2S,3S,4S,5R)-5-Acet-
amido-1-O-triethylsilyl-1,2,3,4-cyclopentanetetrol (34): To a solu-
(300 MHz, D2O): δ = 1.46 (ddd, J1,5a = 6.1, J4,5a = 6.8, Jgem
14.6 Hz, 1 H, 5a-H), 2.35 (ddd, J1,5b = 7.6, J4,5b = 8.5, Jgem
14.6 Hz, 1 H, 5b-H), 3.24 (ddd, J3,4 = 5.6, J4,5a = 6.8, J4,5b
=
=
=
tion of
D
-17[24] (114 mg, 0.254 mmol) in CH2Cl2 (1.5 mL) were
added 2,6-lutidine (89 µL, 0.763 mmol) and triethylsilyl triflate
(86 µL, 0.38 mmol) at 0 °C under argon, and the mixture was
stirred at 0 °C for 30 min. Saturated aqueous NaHCO3 (20 mL)
was added, and the mixture was extracted with chloroform (3×10
mL). The extracts were washed with water, dried, and the solvents
were evaporated. The residual product was treated with 1  meth-
anolic sodium methoxide (50 µL) in CH2Cl2 (1.0 mL) at 0 °C for
30 min. After neutralization with aqueous acetic acid, an insoluble
material was removed by filtration and washed with acetone. The
filtrate and washings were combined and the solvents were evapo-
rated to dryness. The residue was purified by chromatography on
a column of silica gel (10 g, acetone/toluene, 1:4) to give the alcohol
34 (66 mg, 68%) as a syrup. TLC (acetone/toluene, 1:1): Rf = 0.48.
[α]2D1 = +25 (c = 1.0, CHCl3). 1H NMR (300 MHz, CDCl3): δ =
0.63 [dd, J = 8.1, Jgem = 15.1 Hz, 6 H, Si(CH2CH3)3], 0.97 [t, J =
8.1 Hz, 9 H, Si(CH2CH3)3], 1.36–1.83 (m, 10 H, C6H10), 2.04 (s, 3
H, Ac), 3.06 (d, J4,OH = 10.0 Hz, 1 H, OH), 4.00 (ddd, J3,4 = J4,5
= 6.6, J4,OH = 10.0 Hz, 1 H, 4-H), 4.08 (t, J1,2 = J1,5 = 4.4 Hz, 1
H, 1-H), 4.15 (ddd, J1,5 = 4.4, J4,5 = 6.6, J5,NH = 7.8 Hz, 1 H, 5-
H), 4.44 (dd, J1,2 = 4.4, J2,3 = 6.6 Hz, 1 H, 2-H), 4.53 (t, J2,3 = J3,4
= 6.6 Hz, 1 H, 3-H), 6.37 (d, J5,NH = 7.8 Hz, 1 H, NH) ppm.
HRMS: calcd. for C19H35NO5Si 385.2285; found 385.2284 [M+].
8.5 Hz, 1 H, 4-H), 3.80 (t, J1,2 = J2,3 = 4.4 Hz, 1 H, 2-H), 3.87 (dd,
J2,3 = 4.4, J3,4 = 5.6 Hz, 1 H, 3-H), 3.97 (ddd, J1,2 = 4.4, J1,5a
=
6.1, J1,5b = 7.6 Hz, 1 H, 1-H) ppm. HRMS: calcd. for C5H12NO3
134.0817; found 134.0798 [M+].
(1R,2R,3R,4S,5R)-4-Amino-5-thio-1,2,3-cyclopentanetriol (12):
Compound 12a (8.9 mg) was hydrolyzed as in the preparation of
11, and the product was purified on a column of Dowex-50 W×2
(H+) resin (1 mL, 1  aqueous ammonia) to give 12 (2.9 mg, 74%)
as a syrup. TLC (H2O/AcOH/tBuOH, 1:1:2): Rf = 0.24. [α]2D4 = +66
1
(c = 0.1, MeOH). H NMR (300 MHz, D2O): δ = 3.12 (dd, J1,5
=
5.6, J4,5 = 7.8 Hz, 1 H, 5-H), 3.88–3.98 (m, 3 H, 1-H, 2-H, 3-H),
3.95 (m, 1 H, 4-H) ppm. HRMS: calcd. for C5H13NO3S 167.0616;
found 167.0633 [M+].
(1R,2R,3R,4S,5R)-4-Amino-5-ethylthio-1,2,3-cyclopentanetriol (13):
Compound 13a (5.9 mg, 16 µmol) was hydrolyzed as in the prepa-
ration of 11, and the product was purified by a column of Dowex-
50 W × 2 (H+) resin (1 mL, 1  aqueous ammonia) to give 13
(2.9 mg, ca. 100%) as a syrup. TLC (MeOH/chloroform, 1:2): Rf =
1
0.23. [α]2D4 = –54 (c = 0.15, MeOH). H NMR (300 MHz, D2O): δ
= 1.11 (t, J = 7.3 Hz, 3 H, CH2CH3), 2.54 (br. q, J = 7.3 Hz, 2 H,
CH2CH3), 2.84 (dd, J3,4 = 6.3, J4,5 = 7.8 Hz, 1 H, 4-H), 3.00 (dd,
2,3-O-Cyclohexylidene Derivative of (1R,2S,3S,4S,5R)-5-Acet-
amido-1-O-methyl-4-O-triethylsilyl-1,2,3,4-cyclopentanetetrol (35):
To a solution of 34 (57 mg, 0.15 mmol) in acetonitrile (1.0 mL)
were added silver oxide (51 mg, 0.22 mmol) and a large excess of
iodomethane (0.9 mL, 14.7 mmol), and the suspension was refluxed
at 80 °C overnight. After cooling, an insoluble material was re-
moved by filtration, and the filtrate was concentrated. The residue
was purified by chromatography on a column of silica gel (3 g,
acetone/toluene, 1:6) to give the methyl ether 35 (57 mg, 97%) as
a syrup. TLC (acetone/toluene, 1:1): Rf = 0.56. [α]2D1 = +8.3 (c =
J1,5 = 5.6, J4,5 = 7.8 Hz, 1 H, 5-H), 3.82 (dd, J2,3 = 5.4, J3,4
=
6.3 Hz, 1 H, 3-H), 3.90 (t, J1,2 = J2,3 = 5.4 Hz, 1 H, 2-H), 3.96
(dd, J1,2 = 5.4, J1,5 = 5.6 Hz, 1 H, 1-H) ppm. HRMS: calcd. for
C7H15NO3S 193.0773; found 193.0781 [M+].
(1R,2R,3R,4R,5S)-5-Amino-4-O-methyl-1,2,3,4-cyclopentanetetrol
(14): Compound 14a (9.2 mg, 28 µmol) was treated with 2  aque-
ous barium hydroxide (1 mL) at 90 °C for 5 h. After neutralization
with carbon dioxide, the reaction mixture was filtered through a
pad of Celite and the filtrate was concentrated to dryness. The pro-
duct was purified on a column of Dowex-50 W×2 (H+) resin (1
1
1.0, CHCl3). H NMR (300 MHz, CDCl3): δ = 0.63 [dd, J = 8.1,
Jgem = 15.6 Hz, 6 H, Si(CH2CH3)3], 0.97 [t, J = 8.1 Hz, 9 H, mL, 1% aqueous ammonia) to give the free base 14 (1.9 mg, 42%)
Si(CH2CH3)3], 1.32–1.84 (m, 10 H, C6H10), 2.00 (s, 3 H, Ac), 3.44
as a syrup. TLC (H2O/AcOH/BuOH, 1:1:2): Rf = 0.46. [α]2D0 = +53
Eur. J. Org. Chem. 2005, 4065–4072
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4071

S. Ogawa, T. Morikawa
FULL PAPER
(c = 0.1, MeOH). H NMR (300 MHz, D2O): δ = 2.92 (m, 1 H, 5-
H), 3.32 (s, 3 H, Me), 3.48 (m, 1 H, 4-H), 3.81 (m, 1 H, 3-H), 3.89
(m, 2 H, 1-H, 2-H) ppm. HRMS: calcd. for C6H14NO4 164.0923;
found 164.0922 [M+].
1
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(1R,2S,3R,4R)-5-Amino-1,4-di-O-methyl-1,2,3,4-cyclopentanetetrol
(15): Compound 15a (7.4 mg, 24 µmol) was treated with 1  aque-
ous barium hydroxide (1 mL) at 90 °C overnight. After neutraliza-
tion with CO2, an insoluble material was removed by filtration
through a Celite pad, and the filtrate was concentrated to dryness.
The residue was purified by chromatography on a column of
Dowex-50 W×2 (H+) resin (1 mL, 1  aqueous ammonia) to give
the di-O-methyl ether 15 (4.3 mg, ca. 100%) as a syrup. TLC (H2O/
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Cyclitols (Pure Appl. Chem. 1974, 37, 285–297). In the Exp.
Sect., the (R,S) notation is generally used instead to describe
absolute configurations.
AcOH/BuOH, 1:1:2): Rf = 0.41. [α]2D2 = +23 (c = 0.3, MeOH). H
NMR (300 MHz, D2O): δ = 3.13 (dd, J4,5 = 5.4, J1,5 = 6.3 Hz, 1
H, 5-H), 3.31, 3.32 (2 s, each 3 H, 2×Me), 3.50 (t, J3,4 = J4,5
5.4 Hz, 1 H, 4-H), 3.58 (dd, J1,2 = 3.7, J1,5 = 6.3 Hz, 1 H, 1-H),
3.77 (t, J2,3 = J3,4 = 5.4 Hz, 1 H, 3-H), 4.03 (dd, J1,2 = 3.7, J2,3
1
=
=
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5.4 Hz, 1 H, 2-H) ppm. HRMS: calcd. for C7H16NO4 178.1079;
found 178.1087 [M+].
[14] G. C. Lock, C. H. Fotsch, C. H. Wong, Acc. Chem. Res. 1993,
(1S,2R,3R,4R,5S)-5-Amino-1-O-methyl-1,2,3,4-cyclopentanetetrol
(16): Compound 16a (57 mg, 17 µmol) was treated with 1  aque-
ous barium hydroxide (1 mL) at 90 °C overnight. After neutraliza-
tion with carbon dioxide, the mixture was filtered through a pad
of Celite which was washed with water thoroughly. The filtrate and
washings were concentrated and the residue was purified by
chromatography on a column of Dowex-50 W×2 (H+) resin (1 mL,
1  aqueous ammonia) to give the amine 16 (2.8 mg, ca. 100%) as
a syrup. TLC (H2O/AcOH/BuOH, 1:1:3): Rf = 0.19. [α]2D0 = –16 (c
26, 182–190.
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1
= 0.14, MeOH). H NMR (300 MHz, D2O): δ = 3.32 (m, 4 H, 5-
H, Me), 3.60 (dd, J1,2 = 4.9, J1.5 = Ϸ 5 Hz, 1 H, 1-H), 3.81 (t, J2,3
= J3,4 = 5.1 Hz, 1 H, 3-H), 3.92 (t, J3,4 = J4,5 = 5.1 Hz, 1 H, 4-H),
3.99 (dd, J1,2 = 4.9, J2,3 = 5.1 Hz, 1 H, 2-H) ppm. HRMS: calcd.
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Acknowledgments
The authors would like to thank Drs. Atsushi Takahashi and
Akihiro Tomoda (Hokko Chemical Industry, Co. Ltd., Atsugi, Ja-
pan) for the biological assays, and Ms. Miki Kanto for her assist-
ance in preparing this manuscript.
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Received: February 15, 2005
Published Online: August 10, 2005
4072
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 4065–4072