Synthesis of neamine-derived pseudodisaccharides by stereo- and regio-selective functional group transformations

Article abstract of DOI:10.1039/b907518f

Neamine is normally found as a core structure of aminoglycoside antibiotics. In order to understand the relationship between the antibiotic activity and the configurations of the functional groups of neamine, a series of novel neamine analogues with funct

Full text of DOI:10.1039/b907518f

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis of neamine-derived pseudodisaccharides by stereo- and
regio-selective functional group transformations†
Li-Juan Pang, Dan Wang, Jian Zhou, Li-He Zhang and Xin-Shan Ye*
Received 14th April 2009, Accepted 24th July 2009
First published as an Advance Article on the web 12th August 2009
DOI: 10.1039/b907518f
Neamine is normally found as a core structure of aminoglycoside antibiotics. In order to understand the
relationship between the antibiotic activity and the configurations of the functional groups of neamine,
a series of novel neamine analogues with functional group manipulations on the 2-deoxystreptamine
(2-DOS) ring or the sugar ring were designed and synthesized. The synthetic approach involved the
construction of 2-DOS derivatives by catalytic Ferrier II rearrangement, stereo- and regio-selective
functional group transformations, glycosyl coupling reaction, and global deprotection. Of the synthetic
neamine analogues, four compounds showed comparable 16S rRNA binding affinities with neamine,
whereas they displayed lower binding affinities towards 18S rRNA than neamine, implying a lower
toxicity to mammals. This strategy might have applications in the chemical synthesis of other neamine
derivatives and new aminoglycoside antibiotics with improved biological activities.
Introduction
As a group of clinically important antibiotics, 2-deoxystreptamine
(2-DOS) aminoglycosides function by selectively binding to the
decoding aminoacyl site (A-site) of the bacterial 16S ribosomal
RNA, which leads to interference with protein biosynthesis.1
However, the rapid spread of antibiotic resistance towards this
family of antibiotics and their relatively high toxicity to mammals
are critical problems that greatly limit intensive clinical use of
these drugs. To overcome these problems, a wide variety of
aminoglycoside modifications have been developed in the last
few decades.2 Aminoglycosides can also serve as a paradigm for
exploration of small molecule–RNA interactions, which has led
to further investigations into this type of compound.3
The main subgroup of aminoglycosides, which includes the
widely used drugs gentamicin, neomycin B and kanamycin,
Fig. 1 The structures of neamine (1) and 2-deoxystreptamine (2) found
have a pseudodisaccharide core known as neamine (Fig. 1).
More generally, the carbocyclic 2-DOS core is included in
most aminoglycoside antibiotics. Accordingly, numerous chemical
modifications of aminoglycosides are based on neamine or 2-
DOS core structures.4–7 It was found by X-ray crystallography that
neamine or 2-DOS alone indeed play a central role in the recog-
nition of RNA with aminoglycosides.8 The reported structural
modifications vary, from different substitution on neamine (such
as simple amino-containing acyclic or cyclic structures,4 aromatic
heterocyclic compounds,5 and glycosides6) to dimerizations of
neamine or 2-DOS.9 The common strategy for the preparation
of aminoglycoside analogues comprises the derivatization10 of
natural aminoglycosides or their substructures, thus limiting
neamine or 2-DOS structures strictly to their natural forms.11
in most aminoglycoside antibiotics.
More structural diversity can be also achieved by changing the
stereochemistry or manipulating the amino or hydroxyl func-
tionalities on neamine or 2-DOS. Since the hydroxyl and amino
groups of aminoglycosides are regarded as key binding groups
for targeting RNA,8 it is important to explore the structure–
activity relationships between the configurations or changes of the
functional groups of the aminoglycosides and their antibacterial
activities.
For this purpose, based on the structure of neamine, a series of
pseudodisaccharides 3–14, with various configurations of amino
or hydroxyl groups either on the sugar ring or on the 2-DOS ring,
were designed and synthesized (Fig. 2).
As shown in Fig. 2, the natural sugar ring was retained, but the
amino groups in positions 1 and 3 of 2-DOS ring were altered
in configuration or changed into a series of 1,3-dihydroxyl or
1-methoxyl groups. These manipulations may mimic the natural
2-DOS structure and improve the binding affinity with RNA. In
addition, to investigate the influence of glycoforms towards
RNA binding, the sugar ring was changed from glucose into
State Key Laboratory of Natural and Biomimetic Drugs, Peking University
and School of Pharmaceutical Sciences, Peking University, Xue Yuan Rd
#38, Beijing, 100191, China. E-mail: xinshan@bjmu.edu.cn; Fax: +86 10
62014949; Tel: +86 10 82801570
† Electronic supplementary information (ESI) available: Experimental
procedures, 1H and 13C NMR spectra for compounds. See DOI:
10.1039/b907518f
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Fig. 2 The structures of pseudodisaccharides 3–14.
galactose- or mannose-type amino sugars, with the natural
2-DOS structure unchanged. We herein report the synthesis of
pseudodisaccharides 3–14 using the Ferrier II rearrangement as
a key step, which can be regarded as mimic of the biosynthetic
pathway of 2-DOS.12 The RNA binding affinities and antibacterial
activities of synthetic compounds 3–14 are also reported.
1:1 mixture of axial and equatorial products was produced, and
the total yield was low (35%). Thus, the rearrangement was
performed with 16 and 17 to produce compounds 18–20, with
the 5-axial hydroxyl isomer as the major isomer.15 To reduce the
carbonyl group, triisobutylaluminium (TIBAL) was employed to
promote the reaction using 16 as reactant, leading to a mixture of
1-OMe cyclohexanol products 21 and 22 in high yield with 5-axial
hydroxyl isomer as the major product.
Results and discussion
Stereoselective reduction of the Ferrier II rearrangement prod-
ucts provided a series of cyclitol analogues. Reduction of 18 under
various conditions16 led to 1,5-trans diol and 1,5-cis diol with
high stereoselectivity (Scheme 2). To make purification easier, the
1,5-trans diol was benzoylated to produce 23. Based upon the
strong leaving ability of the OTf group, we considered that elimi-
nation should be suppressed in SN2 reactions, and this was indeed
the case, compound 24 being obtained after several functional
group transformations via the triflate intermediate. However, 26
could not be obtained by a similar substitution process from 25
due to the elimination reaction, and likewise, mesylation of 18
gave the elimination product 27. Luche reduction17 of enone 27
afforded allylic alcohol 28 with high stereoselectivity.
The preparation of 26, in which the 1,5-hydroxyls are established
at two equatorial positions, proved to be arduous. The SN2 reaction
of the corresponding triflate of 25 by n-Bu4NOAc gave elimination
products exclusively. Epoxidation of 28 by either Sharpless asym-
metric epoxidation or vanadium-catalyzed epoxidation provided
27, not the epoxide which might have been further modified to give
26. Finally, the PMB-protected cyclohexanone 20 was reduced to
yield diols. After testing several reduction conditions including
NaBH4·Et2BOMe, LiAlH4, and NaBH4 in MeOH, it was found
that only NaBH4 in dioxane18 was able to reduce 20, producing
1,5-cis diol 29 as the major product with moderate stereoselectivity
Synthesis of 2-DOS and its analogues as glycosyl acceptors
The designed pseudodisaccharides 3–14 were retrosynthetically
disconnected into two building blocks: a monosaccharide moiety
and a 2-DOS moiety. Coupling of these two moieties followed by
global deprotection would complete the synthesis of the target
molecules. According to this retrosynthetic analysis, construction
of the 2-DOS moiety is the key issue. Although there are numerous
methods available for the synthesis of 2-DOS and its analogues,11
synthesis of a 2-DOS framework with various structural modifi-
cations remains a problem. Inspired by the biosynthetic route to
2-DOS,12 we chose the Ferrier II rearrangement13 as the key reac-
tion to build the cyclohexanol framework starting from D-glucose,
with the suitable functionalities exposed for further modifications.
As shown in Scheme 1, two precursors 16 and 17 were easily
prepared from compound 15 in a similar manner to the published
procedure.14 To carry out the rearrangement, various metal
catalysts, including PdCl2, HgCl2, Hg(OAc)2 and Hg(OCOCF3)2,
were screened. Considering the yield, stereoselectivity, and rate of
reaction, we decided to use Hg(OCOCF3)2 (0.1 equivalent) as the
catalyst. In addition to allyl- and p-methoxybenzyl (PMB) groups,
the t-butyldimethylsilyl (TBDMS) group was also introduced
to the 4-OH position. Unfortunately, when the rearrangement
precursor with the TBDMS group was treated with PdCl2, a
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Scheme 1 Synthesis of the cyclohexanol framework by the Ferrier II rearrangement. Reagents and conditions: (a) allylBr, NaH, DMF, 87% for 16; or
PMBCl, NaH, DMF, 92% for 17. (b) Hg(OCOCF3)2, acetone/water (1:1), 74% for 18, 90% for 19 and 20 with the ratio of 19/20 (5:1). (c) TIBAL, PhMe,
97%, 21/22 (1:3).
Scheme 2 Stereoselective reduction of compound 18. Reagents and conditions: (a) i. Me4NBH4, HOAc, THF, CH3CN; ii. BzCl, DMAP, pyridine, 80%.
(b) i. NaOMe, MeOH; ii. Tf2O, pyridine, CH2Cl2; iii. n-Bu4NOAc, DMF, 35%. (c) NaBH4, MeOH, 82%. (d) MsCl, Et3N, CH2Cl2, 60%. (e) NaBH4,
CeCl3·7H2O, MeOH, 90%.
(Scheme 3). Compound 29 was further benzoylated to give 30, the
PMB-analogue of 26.
and allyl groups. In a similar way, cyclohexanol 33 was also
prepared starting from diol 25. To avoid the low efficiency of
allyl group deprotection, a PMB group was employed instead
of the allyl group, and high yield of deprotected product was
achieved. In the same manner, other cyclohexanols 37 and 38
with configuration changes at 1,5-positions were also obtained
in acceptable yields starting from rearrangement product 19 and
Next, the hydroxyl group of the 1-OMe cyclohexanol 22 was
converted to an azido group by SN2 substitution; however, the
yield for the subsequent deprotection of the allyl group was
low (Scheme 4). The low efficiency of the deprotection might
arise from an intramolecular cycloaddition between the azido
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Scheme 3 Selective reduction of 20 to produce diols 29 and 31. Reagents and conditions: (a) NaBH4, dioxane, r.t. 98%, 29/31 (3:1). (b) BzCl, pyridine,
89%.
Similar to the preparation of compound 34, other 2-DOS
derivatives without amino functionalities (39 and 41–44) were pre-
pared smoothly from the corresponding precursors via protection–
deprotection operations (Scheme 6). The use of benzoyl in-
stead of acetyl as the protective group suppressed the possi-
ble migration of the acyl group during the selective allyl or
PMB group deprotection. The structures of compounds 39 and
42–44 were unambiguously identified by NMR analysis. However,
the structure of compound 41 was difficult to identify by its
NMR spectra due to the overlap of proton signals. To exclude
the possibility of benzoyl migration and to confirm its structure,
compound 41 was subjected to re-allylation to yield 40*, whose
NMR spectra were identical to that of 40. Thus the structure of
cyclohexanol derivative 41 was verified.
When compound 21 was treated with triflic anhydride followed
by sodium azide, the desired product 45 was not produced.
Similarly, the diaxial diazide product was not obtained by starting
from diol 29, although several approaches such as using tosylate
as the intermediate and sequential introduction of the azido
group were tried. This might be explained by the 1,3-diaxial
hindrance between the attacking azide and the OMe group or the
Scheme 4 Preparation of acceptors 32 and 33 starting from 22 and 25.
existing azido group. However, when compound 21 was treated
Reagents and conditions: (a) i. Tf2O, pyridine, CH2Cl2, 0 ◦C; ii. NaN3,
with triflic anhydride, the oxo-bridged product 46 was obtained
DMF, 0 ◦C. (b) PdCl2, MeOH, 35% over three steps. (c) Pd(PPh3)4, TsOH,
(Scheme 7).
CH2Cl2, r.t., 35% over three steps. (d) i. BzCl, pyridine, 0 ◦C to r.t.; ii.
Thus, altogether ten 2-DOS analogues as glycosyl acceptors
PdCl2, MeOH, 88% over two steps. (e) PMBOC(NH)CCl3, BF3·OEt2,
CH2Cl2, 56%. (f) i. NaOMe, MeOH; ii. Tf2O, pyridine, CH2Cl2, 0 ◦C; iii.
NaN3, DMF, 0 ◦C; iv. DDQ, CH2Cl2/water (18:1), 61% over four steps.
were prepared using the Ferrier II rearrangement followed by
functional group manipulations (Fig. 3). The configurations of
newly generated chiral centers of compounds in Fig. 3 were
determined by analyzing the coupling constants in their 1H NMR
spectra (Table 1).
the reduction product 31 via functional group manipulations
(Scheme 5).
Scheme 5 Preparation of cyclohexanol derivatives 37 and 38. Reagents and conditions: (a) i. Me4NBH4, HOAc, THF, CH3CN; ii. BzCl, DMAP, pyridine,
88% over two steps. (b) i. NaOMe, MeOH; ii. Tf2O, pyridine, CH2Cl2, 0 ◦C; iii. NaN3, DMF, 0 ◦C, 41% over three steps. (c) i. Tf2O, pyridine, CH2Cl2,
0
◦C; ii. NaN3, DMF, 0 ◦C; iii. DDQ, CH2Cl2/water (18:1), 40% over three steps.
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Scheme 6 Preparation of cyclohexanols 39 and 41–44. Reagents and conditions: (a) i. BzCl, DMAP, pyridine; ii. PdCl2, MeOH, 98% over two steps.
˚
(b) BzCl, DMAP, pyridine, 98%. (c) PdCl2, MeOH, 87%. (d) allylOC(NH)CCl3, CH2Cl2/cyclohexane (1:2), TfOH, 4 A molecular sieves, 70%. (e) PdCl2,
MeOH, 98%. (f) i. NaOMe, MeOH; ii. BzCl, DMAP, pyridine; iii. PdCl2, MeOH, 89% over three steps. (g) DDQ, CH2Cl2/water (18:1), 62%.
donors 51 and 52 were synthesized from galactosamine and
mannosamine derivatives following published procedures (refs.
20 and 21, respectively). The introduction of an acetal to 51
greatly facilitated the isolation of the product from the subsequent
glycosylation reactions. The use of an acetyl protecting group
at positions 3 and 4 for mannosamine donor 52 proved to be
better than a benzyl group in stereoselectivity control for the
glycosylation reaction.
Synthesis of pseudodisaccharides 3–14
With all the glycosyl donors and acceptors in hand, we tried to
Scheme 7 Formation of oxo-bridged compound 46. Reagents and condi-
assemble the pseudodisaccharides. The N-iodosuccinimide/triflic
acid (NIS/TfOH) system was chosen as the promoter for the
tions: (a) Tf2O, pyridine, CH2Cl2, 0 ◦C, 99%.
glycosyl coupling reactions. Thus, 2-DOS analogues 34, 39 and
41-44 were glycosylated with thioglycoside donor 50, providing
Synthesis of glycosyl donors 50–52
Scheme 8 outlines the preparation of the glycosyl donors used for
the synthesis of pseudodisaccharides 3–14. The azido-containing
donor 50 was smoothly synthesized from the known thioglycoside
4719 by benzylation of the free hydroxyl groups. Similarly, glycosyl
the pseudodisaccharides 53–58 as the pure a-isomers in 70–86%
yield after debenzoylation. The anomeric selectivity of glycosy-
lations was improved by decreasing the reactivity of acceptors
using the electron-withdrawing benzoyl group in place of the
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Fig. 3 2-DOS analogues as glycosyl acceptors.
Table 1 The 1H NMR coupling constantsa of glycosyl acceptors 32–34,
37–39 and 41–44
J3 (Hz)
J1 (Hz)
Compound
J3,2a
J3,2e
J3,4
J1,2a
J1,2e
J1,6
32b
33c
34b
37c
38c
39b
41b
42b
43c
44b
12.0
12.5
3.5
4.5
obscd
obsc
3.5
3.5
9.5
9.0
3.6
8.7
3.0
—
12.5
—
12.5
2.5
—
—
—
11.2
—
—
obsc
—
4.5
4.5
—
—
—
4.5
—
—
obsc
—
obsc
7.0
—
—
—
9.0
—
obsc
obsc
4.5
4.5
4.5
obsc
4.8
4.5
2.5
12.0
11.0
3.6
11.1
2.5
12.0
obsc
obsc
a The coupling constants for axial–axial coupling are in the range 8.7–
12.5 Hz, whereas axial–equatorial or equatorial–equatorial couplings
are in the range 2.5–4.8 Hz. To make the comparison clear, all the
atom positions of compounds in this table are assigned according to
compound 33. b The configurations at position 1 were fixed after Ferrier
rearrangement, so the configurations at position 3 were needed to
determine them. c The two chiral centers were generated by SN2 reaction
at position 1 and 3 simultaneously. d “obsc” means the coupling constant
was obscured by overlap with other proton signals.
Scheme 8 Synthesis of glycosyl donors 50–52. Reagents and conditions:
(a) BnBr, NaOH, TBAI, THF, 0 ◦C to r.t., 95%. (b) DMP, CSA, r.t., 50%.
(c) i. NaOMe, MeOH; ii. TsCl, pyridine, 0 ◦C to r.t.; iii. NaN3, DMF,
80 ◦C; iv. Ac2O, pyridine, 0 ◦C to r.t., 51% over four steps.
drogenolysis in a single step. In these cases, a two-step protocol was
used. The azido groups were first reduced with hydrogen sulfide,
and the benzyl groups then cleaved by catalytic hydrogenolysis. In
this manner, the target pseudodisaccharides 10–14 and neamine 1
were successfully synthesized.
electron-donating benzyl group. The pseudodisaccharides 53–58
were subjected to catalytic hydrogenolysis over Pd/C to afford the
target compounds 3–8 in 96–99% yield (Scheme 9).
As in the formation of 46 from 21 in Scheme 7, when the
pseudodisaccharide 57 was treated with triflic anhydride, the
oxo-bridged product 59 resulted (Scheme 10). Compound 59
was debenzylated and reduced by hydrogenolysis to provide
pseudodisaccharide 9 very smoothly.
Using the same promoter (NIS/TfOH) for glycosylation, the
other six pseudodisaccharides 60–65 were also assembled from
other glycosyl acceptors and donors (Schemes 9 and 11). Theoret-
ically, azido and benzyl groups could be reduced and deprotected
simultaneously by hydrogenolysis. Unfortunately, this was not
always true in our operations. In the case of compounds 60–
65 containing more than two azido groups, complex products
were obtained if azido and O-benzyl groups were reduced by hy-
RNA binding affinities and antibacterial activities
The RNA binding affinities of synthetic pseudodisaccharides
3–14 and neamine (1) were evaluated by surface plasmon res-
onance (SPR) assay with Escherichia coli 16S rRNA, which is
implicated in the antibiotic activity, and human 18S rRNA, which
may reflect the toxicity to mammals. The dissociation constants
(Kd) were calculated from the equilibrium curves by a nonlinear
curve-fitting method developed previously.10,22 The resulting values
are listed in Table 2. As can be seen, four compounds, 10, 11, 13
and 14, showed comparable RNA binding affinities to that of
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Scheme 9 Synthesis of pseudodisaccharides 3–8, 10–12, and neamine 1. Reagents and conditions: (a) glycosyl acceptors (32, 33, 34, 39, 37, 38, 41–44),
NIS, TfOH, CH2Cl2, 4 A molecular sieves, -40 ◦C to -20 ◦C, 56% for 60, 50% for 61, 86% for 62, 80% for 63. (b) NaOMe, MeOH, isolated yields over
˚
two steps: 53 (80%), 54 (77%), 55 (70%), 56 (86%), 57 (70%), 58 (70%). (c) H2, Pd/C, 1 N HCl, MeOH, isolated yields: 3 (98%), 4 (98%), 5 (99%), 6 (99%),
7 (96%), 8 (99%). (d) H2S, pyridine/H2O/Et3N (3:2:1); then H2, Pd/C, 1 N HCl, MeOH, yield over two steps: 10 (90%), 11 (90%), 12 (70%), neamine 1
(90%).
Scheme 10 Synthesis of pseudodisaccharide 9. Reagents and conditions: (a) Tf2O, pyridine, CH2Cl2, 0 ◦C, 99%. (b) H2, Pd/C, 1 N HCl, MeOH, 96%.
˚
Scheme 11 Synthesis of pseudodisaccharides 13 and 14. Reagents and conditions: (a) glycosyl donors 51 or 52, NIS, TfOH, CH2Cl2, 4 A molecular
sieves, -40 ◦C to -20 ◦C, 84% for 64 (pure a form). (b) NaOMe, MeOH. (c) 80% AcOH/H2O, 60 ◦C, 60% for pure a product 65 over two steps. (d) H2S,
pyridine/H2O/Et3N (3:2:1). (e) H2, Pd/C, 1 N HCl, MeOH, 96% for 13 over three steps, 95% for 14 over two steps.
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Table 2 Dissociation constants of synthetic pseudodisaccharides and
inhibitory effects on Pseudomonas aeruginosa
calcium hydride. Methanol was dried by heating under reflux with
magnesium and then distilled. N,N-Dimethylformamide was dried
over P2O5 and distilled under vacuum. Reactions were monitored
by analytical thin-layer chromatography (TLC) on Merck silica gel
60F254 plates (0.25 mm), visualized by ultraviolet light and/or by
staining with ceric ammonium molybdate or ninhydrin. Optical
rotations were measured at ambient temperature (25 ◦C) using
RUDOLPH AUTOPOL III. 1H NMR spectra were obtained
on Varian INOVA-500 or JEOL JNM-AL300 spectrometer at
ambient temperature. Data were reported as follows: chemical
shift on the d scale (using either TMS or residual proton solvent
as internal standard), multiplicity (br = broad, s = singlet, d =
doublet, t = triplet, q = quartet, m = multiplet), integration, and
coupling constant(s) in Hertz. 13C NMR spectra were obtained
with proton decoupling on a Varian INOVA-500 (125 MHz) or
JEOL JNM-AL-300 (75 MHz) spectrometer and were reported in
ppm with residual solvent for internal standard (77.0 for CDCl3).
High-resolution mass spectra were obtained on a PE SCLEX
QSTAR spectrometer. Elemental analysis data were recorded on
a PE-2400C elemental analyzer.
Kd (mM)
Inhibition ratio (%)
towards P. aeruginosa
at 500 mg/mL
Compound
16S rRNA
18S rRNA
1
22 0.3
26 2.0
34 0.7
62 1.7
68 6.0
41 3.0
286 29
100
45.5
35
31
39
10
11
13
14
6
0.5
123 16
37 2.0
neamine (1); the other compounds did not show any significant
RNA binding affinities. It seems that the number of amino
groups in the pseudodisaccharides is essential for binding to 16S
rRNA. Compounds 10, 11, 13 and 14 displayed lower binding
affinities to 18S rRNA than neamine, implying a lower toxicity.
The antibacterial activities of compounds 1, 10, 11, 13, and
14 were also evaluated against Escherichia coli and Pseudomonas
aeruginosa standard strains. Neamine (1) is still the most active
compound. The synthetic compounds did not show any inhibitory
effects on the E. coli strain (neamine showed activity against E. coli
with a minimum inhibitory concentration (MIC) of 65 mg/mL).
For P. aeruginosa, compounds 10, 11, 13 and 14 showed 45.5,
35%, 31% and 39% inhibition when tested at the MIC of neamine
(500 mg/mL) (Table 2).
2L-(2,4,5/3)-2-O-(4-Methoxybenzyl)-3,4-di-O-benzyl-2,3,4,5-
tetrahydroxycyclohexanone (19) and 2L-(2,4/5,3)-2-O-(4-methoxy-
benzyl)-3,4-di-O-benzyl-2,3,4,5-tetrahydroxycyclohexanone (20).
To a stirred solution of 17 (4.64 g, 9.7 mmol) in acetone–water
(2:1, 90 mL) was added Hg(OCOCF3)2 (0.42 g, 0.98 mmol) at
room temperature. After stirring for 3 h, sat. NaHCO3 was added
to neutralize the mixture to pH 6–7. The mixture was partially
evaporated, the suspension was extracted with EtOAc (50 mL
¥2), the organic layer was collected and sequentially washed with
water and brine (50 mL), dried over Na2SO4, filtered, concentrated
in vacuo. The residue was purified by column chromatography on
silica gel (petroleum ether–EtOAc 3:1) to give 20 (696 mg, 15%)
Conclusion
To explore the substitution and configuration effects of neamine,
neamine (1) and 12 analogues (pseudodisaccharides 3–14) were
designed and synthesized via the glycosylations of 2-DOS deriva-
tives. The construction of 2-DOS derivatives was based on the
Ferrier II rearrangement as a key step followed by a series of
stereoselective functional group manipulations. In the synthetic
process, linear sequences for 10 glycosyl acceptors (cyclohexanol
derivatives) range from 5 to 15 steps from the common starting
material, namely methyl a-D-glucoside. For the preparation of 13
target pseudodisaccharides, the number of synthetic steps range
from 15 to 27. Using the synthetic strategy described here, various
protected and unsymmetrical aminocyclitols and cyclitols with
high stereo-variability can be prepared efficiently. The preliminary
RNA binding and antibacterial results showed that four synthetic
pseudodisaccharides, 10, 11, 13 and 14, exhibited comparable
activities with neamine, which may serve as a useful starting point
in the discovery of new antibiotic entities. The approach described
here may have wide applications in the chemical synthesis of
other neamine derivatives and new aminoglycoside antibiotics
with improved biological activities.
as a white solid: Rf = 0.42 (petroleum ether–EtOAc 1:1); [a]D
=
◦
1
-9.3 (c = 0.4, EtOAc); H NMR (500 MHz, CDCl3, 40 C) d =
7.36–7.24 (m, 12H, Ar), 6.86–6.83 (m, 2H, Ar), 4.99 (d, 1H, J =
11.5 Hz, PhCH2), 4.92 (d, 1H, J = 11.0 Hz, PhCH2), 4.83 (d, 1H,
J = 11.0 Hz, PhCH2), 4.73 (d, 1H, J = 11.0 Hz, PhCH2), 4.69 (d,
1H, J = 11.5 Hz, PhCH2), 4.47 (d, 1H, J = 11.0 Hz, PhCH2), 4.13
(d, 1H, J = 8.0 Hz, H-2), 3.79 (s, 3H, OCH3), 3.73–3.62 (m, 3H,
H-3, H-4, H-5), 2.74 (dd, 1H, J = 4.5, 13.5 Hz, H-6eq), 2.48 (t, 1H,
J =13.5 Hz, H-6ax), 2.43 (s, 1H, OH); 13C NMR (75 MHz, CDCl3)
=
d = 203.20 (C O), 159.43 (PMB), 138.01, 129.90, 129.47, 128.72,
128.44, 128.07, 127.98, 127.84, 113.83, 85.68, 84.65, 81.90, 75.60,
75.44, 73.30, 67.99, 55.26 (OCH3), 44.08 (C-6); HRMS(ESI) m/e
calcd for C28H30O6 (M + Na+) 485.1935, found: 485.1931. Further
elution gave isomer 19 (3.33 g, 75%) as a white solid: Rf = 0.35
(petroleum ether–EtOAc 1:1); [a]D = -22.4 (c = 0.7, EtOAc); 1H
NMR (500M Hz, CDCl3) d = 7.33–7.26 (m, 12H, Ar), 6.83 (d,
2H, J = 8.5 Hz, Ar), 4.93–4.69 (m, 6H, PhCH2, H-5), 4.50 (d, 1H,
J = 11.5 Hz, PhCH2), 4.23–4.22 (m, 1H, H-2), 4.02–4.01 (m, 2H,
H-1, H-3), 3.80–3.76 (m, 4H, H-4, OCH3), 2.66 (dd, 1H, J = 4.0,
15.0 Hz, H-6eq), 2.48 (dd, 1H, J = 4.0, 15.0 Hz, H-6ax); 13C NMR
Experimental
General procedures
=
(75 MHz, CDCl3) d = 203.97 (C O), 159.28, 138.36, 137.58,
Unless otherwise noted, all reactions were carried out in oven-
dried glassware under an atmosphere of argon or nitrogen.
Tetrahydrofuran and toluene were dried and distilled from sodium
metal. Acetonitrile and dichloromethane were distilled from
129.81, 129.71, 128.56, 128.34, 128.06, 127.88, 127.69, 113.73,
84.87, 81.67, 81.45, 75.92, 73.20, 73.09, 66.47, 55.23 (OCH3), 42.50
(C-6); HRMS (ESI) m/e calcd for C28H30O6 (M + Na+) 485.1935,
found: 485.1937.
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1D-(1,2,4/3,5)-4-O-Allyl-2,3-di-O-benzyl-1-O-methyl-5-hydro-
xylcyclohexanepentol (21) and 1D-(1,2,4,5/3)-4-O-allyl-2,3-di-O-
benzyl-1-O-methyl-5-hydroxylcyclohexanepentol (22). To a solu-
tion of 1614 (1.73 g, 4.37 mmol) in toluene (10 mL), was added
TIBAL (1 M in toluene, 43.7 mL) dropwise under argon at
room temperature. When the addition◦of TIABL was finished, the
mixture was heated by oil bath at 50 C. After stirring for 3.5 h,
NaOH (2M aqueous solution, 100 mL) was added to quench the
reaction, the mixture was diluted with EtOAc (50 mL), washed
with water (50 mL) and brine (50 mL). The organic layer was
collected and dried over Na2SO4, concentrated and purified by
column chromatography on silica gel (petroleum ether–EtOAc 4:1)
to give 21 (402 mg, 24%) as a white solid: Rf = 0.48 (petroleum
ether–EtOAc 1:2); [a]D = +31.3 (c = 2.3, EtOAc); 1H NMR
(300 MHz, CDCl3) d = 7.38–7.28 (m, 10H, Ar), 5.95 (ddt, 1H, J =
5.7, 10.2, 17.4 Hz, =CH-), 5.27 (dq, 1H, J = 1.5, 17.4 Hz, =CH2),
5.17 (dq, 1H, J = 1.5, 10.2 Hz, =CH2), 4.94 (d, 1H, J = 10.5 Hz,
PhCH2), 4.75 (d, 1H, J = 10.5 Hz, PhCH2), 4.71 (2d, 2H, J =
temperaure. The mixture was concentrated, diluted with EtOAc
(50 mL), washed successively with sat. NaHCO3 (50 mL) and water
(50 mL). The organic layer was collected and dried over Na2SO4,
concentrated, and purified by column chromatography on silica
gel (petroleum ether–EtOAc 16:1) to give 23 (1.36 g, 80% over two
steps) as colorless solids: Rf = 0.36 (EtOAc/petroleum ehter 1:4);
1
[a]D = +42 (c = 2.0, EtOAc); H NMR (300 MHz, CDCl3) d =
8.12–8.02 (m, 4H, Ar), 7.60–7.42 (m, 7H, Ar), 7.33–7.16 (m, 9H,
Ar), 5.89–5.76 (m, 2H, H-1, H-5), 5.58–5.49 (m, 1H, =CH-), 5.16
(dd, 1H, J = 1.5, 17.1 Hz, =CH2), 5.06 (d, 1H, J = 10.2 Hz, =CH2),
4.92–4.81 (m, 3H, PhCH2), 4.60 (d, 1H, J = 11.7 Hz, PhCH2),
=
4.37 (dd, 1H, J = 5.7, 12.0 Hz, C C-CH2), 4.24 (dd, 1H, J = 6.3,
=
12.0 Hz, C C-CH2), 4.00 (t, 1H, J = 9.3 Hz, H-4), 3.67–3.60 (m,
2H, H-2, H-3), 2.49 (dt, 1H, J = 4.5, 14.1 Hz, H-6eq), 1.71 (ddd,
1H, J = 2.1, 12.0, 14.1 Hz, H-6ax); 13C NMR (75 MHz, CDCl3)
d = 165.65(PhCO), 165.56(PhCO), 138.53, 137.82, 134.85, 133.18,
133.08, 130.02, 129.92, 129.57, 128.46, 128.40, 128.30, 128.14,
128.00, 127.65, 117.32, 82.91, 81.52, 80.69, 76.09, 74.68, 72.15,
71.57, 66.95, 31.07 (C-6); MS (FAB) m/z calcd for C37H36O7: 592,
found: 592 (M+); elemental analysis calcd (%) for C37H36O7: C
74.98, H 6.12; found: C 74.70, H 6.40.
=
12.0 Hz, PhCH2), 4.47 (ddt, 1H, J = 1.5, 5.7, 12.3 Hz, C C-
=
CH2-), 4.19 (ddt, 1H, J = 1.5, 5.7, 12.3 Hz, C C-CH2-), 3.87–
3.76 (m, 2H, H-3, H-5), 3.63–3.62 (m, 1H, H-1), 3.44–3.40 (m,
4H, H-2, OCH3), 3.14 (t, 1H, J = 9.3 Hz, H-4), 2.41 (br, 1H,
OH), 2.30 (dt, 1H, J = 4.5, 14.1 Hz, H-6eq), 1.20 (ddd, 1H,
J = 2.1, 12.0, 14.1 Hz, H-6ax); 13C NMR (75 MHz, CDCl3) d =
138.72, 138.30, 135.05, 128.33, 128.05, 127.83, 127.65, 127.55,
117.02, 85.98, 82.84, 81.68, 75.67, 75.06, 74.11, 72.66, 67.82,
57.34 (OCH3), 30.76 (C-6); HRMS (ESI) m/e calcd for C24H30O54
(M + Na+) 421.1985, found: 421.1945. Further elution gave isomer
22 (1.27 g, 73%) as a colorless oil: Rf = 0.37 (petroleum ether–
EtOAc 1:2); [a]D = +7.5 (c = 2.1, MeOH); 1H NMR (300 MHz,
CDCl3) d = 7.41–7.26 (m, 10H, Ar), 5.97 (ddt, 1H, J = 6.0, 10.5,
17.5 Hz, =CH-), 5.30 (dq, 1H, J = 1.5, 17.5 Hz, =CH2), 5.17 (dq,
1H, J = 1.5, 10.5 Hz, =CH2), 4.92–4.67 (4¥d, 4H, J = 12.0 Hz,
1L-(1,2,4/3,5)-1,5-Di-O-acetyl-2-O-allyl-3,4-di-O-benzyl-
cyclohexanepentol (24). To a solution of 23 (150 mg, 0.25 mmol)
in MeOH (5 mL), 30% NaOMe (0.1 mL) was added at room
temperature. After stirring for 1 h, the mixture was neutralized to
pH = 6–7 with ion-exchange resin (Dowex 50, strong acid form)
at room temperature. The mixture was filtered and concentrated
to give colorless oil. To the crude oil, CH2Cl2 (2 mL) and pyridine
(204 mL, 2.5 mmol) were added, followed by addition of Tf2O
(174 mL, 1.0 mmol) at 0 ◦C. After stirring for 10 min, sat. NaHCO3
(20 mL) was added to the mixture. The mixture was diluted with
CH2Cl2 (20 mL) and washed with water (20 mL). The organic layer
was collected, dried over Na2SO4, concentrated in vacuo and co-
evaporated with toluene (3 mL) for three times to afford a yellow
oil. The crude product was dissolved in DMF (2 mL), n-Bu4NOAc
(226 mg, 0.75 mmol) was added to the mixture at 0 ◦C under argon,
and stirred for 5 h at r.t. The mixture was concentrated, the residue
was purified by column chromatography on silica gel (petroleum
ether–EtOAc 9:1) to give 24 (42 mg, 35% over three steps) as a
white solid: Rf = 0.32 (petroleum ether–EtOAc 3:1); [a]D = -2.4
(c = 2.5, MeOH); 1H NMR (300 MHz, CDCl3) d = 7.34–7.26 (m,
10H, Ar), 5.95 (ddt, 1H, J = 5.7, 10.8, 17.4 Hz, =CH-), 5.43–5.42
(m, 1H, H-1), 5.29 (ddt, 1H, J = 1.2, 1.2, 17.4 Hz, =CH2), 5.23–
5.14 (m, 2H, =CH2, H-5), 4.92–4.67 (m, 4H, PhCH2), 4.18 (dd, 1H,
=
PhCH2), 4.23–4.20 (m, 2H, C C-CH2), 4.11–4.04 (m, 2H, H-3,
H-5), 3.71–3.70 (m, 1H, H-1), 3.60 (d, 1H, J = 9.9 Hz, OH), 3.52
(s, 3H, OCH3), 3.39 (dd, 1H, J = 3.0, 9.3 Hz, H-2), 3.27 (dd,
1H, J = 3.3, 9.3 Hz, H-4), 2.28 (dt, 1H, J = 3.3, 15.0 Hz, H-
6eq), 1.33 (dt, 1H, J = 2.7, 15.0 Hz, H-6ax); 13C NMR (75 MHz,
CDCl3) d = 138.90, 138.45, 135.18, 128.35, 128.28, 128.21, 127.75,
127.65, 127.53, 117.09, 82.47, 82.20, 78.95, 78.82, 75.97, 73.19,
71.64, 68.32, 59.01 (OCH3), 29.54 (C-6); HRMS (ESI) m/z calcd
for C24H30O5 (M + Na+) 421.1985, found: 421.1945.
1D-(1,2,4/3,5)-4-O-Allyl-1,5-di-O-benzoyl-2,3-di-O-benzyl-
cyclohexanepentol (23). To one portion of powdered Me4NBH4
(1.16 g, 0.013 mol) in round-bottomed flask under argon, freshly
distilled AcOH (2.6 ml, 0.045 mol) was added dropwise at room
temperature and stirred for 30 min. THF (8 mL) was then added,
the mixture was stirred at the same temperature for additional 3 h
to ensure complete conversion of Me4NBH4 to Me4NBH(OAc)3.
To the above mixture, a solution of 18 (1.108 g, 2.78 mmol) in
CH3CN (10 mL) was added dropwise. After stirring for 13 h
at room temperature, sat. NH4Cl aqueous solution was added
to quench the reaction. The mixture was extracted with EtOAc
(50 mL), washed with sat. KHCO3 (50 mL), then dried over
Na2SO4, concentrated to produce a colorless oil (899 mg). To
a mixture of the colorless oil and DMAP (14 mg, 0.12 mmol) in
pyridine (20 mL), BzCl (1.63 mL, 14.03 mmol) was added slowly
at 0 ◦C. The mixture was allowed to stir for 6 h from 0 ◦C to room
=
=
J = 5.7, 12.6 Hz, C C-CH2), 4.06 (dd, 1H, J = 6.0, 12.6 Hz, C C-
CH2), 3.85 (t, 1H, J = 9.3 Hz, H-4), 3.51 (t, 1H, J = 9.6 Hz, H-3),
3.42 (dd, 1H, J = 3.0, 9.6 Hz, H-2), 2.20 (dt, 1H, J = 4.5, 14.1 Hz,
H-6eq), 2.13 (s, 3H, COCH3), 1.95 (s, 3H, COCH3), 1.47 (ddd,
1H, J = 2.7, 12.3, 14.1 Hz, H-6ax); 13C NMR (75 MHz, CDCl3)
d = 170.19 (COCH3), 170.09 (COCH3), 138.57, 138.50, 134.55,
128.37, 128.15, 127.74, 127.69, 127.64, 117.45, 83.31, 81.57, 80.36,
76.09, 75.62, 71.36, 70.69, 66.66, 30.80 (C-6), 21.14 (COCH3),
21.06 (COCH3); HRMS (ESI) m/z calcd for C27H32O7 (M + Na+)
491.2040, found: 491.2039.
1D - (1,2,4,5/3)- 4- O -Allyl -2,3-di - O -benzyl -1,5- dihydroxy-
lcyclohexanepentol (25). To a solution of 18 (571 mg, 1.49 mmol)
in methanol (15 mL) at 0 ◦C was added portion-wise NaBH4
(225 mg, 5.96 mmol). After stirring for 10 min, sat. NH4Cl
4260 | Org. Biomol. Chem., 2009, 7, 4252–4266
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aqueous solution was added to quench the reaction. The mixture
was concentrated and extracted with EtOAc (30 mL) and water
(30 mL). The organic layer was dried over Na2SO4, filtered, and
concentrated. The residue was purified by column chromatogra-
phy on silica gel (petroleum ether–acetone 4:1) to give 25 (467 mg,
82%) as a colorless oil: Rf = 0.28 (petroleum ether–acetone 2:1);
[a]D = +15.4 (c = 2.6, EtOAc); 1H NMR (300 MHz, CDCl3, D2O
exchange) d = 7.41–7.26 (m, 10H, Ar), 5.94 (ddt, 1H, J = 5.4,
10.5, 17.1 Hz, =CH-), 5.29 (dd, 1H, J = 1.8, 17.1 Hz, =CH2),
5.18 (dd, 1H, J =1.8, 10.2 Hz, =CH2), 5.16–4.73 (m, 4H, PhCH2),
d = 138.54, 138.24, 134.97 (=CH-), 129.36 (C-2), 128.42, 128.36,
127.94, 127.80, 127.72, 127.45, 127.05 (C-3), 117.32 (=CH2), 84.08
(C-6), 83.27 (C-5), 80.48 (C-4), 75.24 (PhCH2), 74.12 (=C-CH2),
72.28 (PhCH2), 71.93 (C-1); MS (ESI) m/z calcd. for C23H26O4: 389
(M + Na+), found: 389; elemental analysis calcd (%) for C23H26O4:
C 75.38, H 7.15; found: C 75.29, H 7.23.
1D-(1,3,5/2,4)-1,5-Di-O-benzoyl-2,3-di-O-benzyl-4-O-(4-meth-
oxybenzyl)-cyclohexanepentol (30) and 1L-(1,2,4/3,5)-3,4-di-O-
benzyl-2-O-(4-methoxybenzyl)-1,5-dihydroxylcyclohexanepentol
(31). To a solution of 20 (150 mg, 0.32 mmol) in dry dioxane
(6 mL), was added NaBH4 (65 mg, 1.72 mmol) under argon. After
stirring for 4 h, water was added to quench the reaction at 0 ◦C. The
reaction mixture was continued to stir until no bubble spreading
out. Then the mixture was concentrated in vacuo, the residue was
dissolved in EtOAc (20 mL), washed with water and brine, dried
over Na2SO4, concentrated, purified by column chromatography
on silica gel (CH2Cl2/MeOH 100:1) to give 31 (34 mg, 22%): Rf =
=
4.22–4.14 (m, 4H, H-1, H-5, C–CH2–), 4.05 (t, 1H, J = 9.3 Hz,
H-3), 3.40–3.62 (m, 2H, H-2 or H-4, OH), 3.30 (dd, 1H, J = 3.3,
9.3 Hz, H-2 or H-4), 2.33 (dt, 1H, J = 3.6, 15.0 Hz, H-6eq), 1.46
(dt, 1H, J = 2.7, 15.0 Hz, H-6ax); 13C NMR (75 MHz, CDCl3)
d = 138.80, 138.10, 134,82, 128.39, 128.30, 128.12, 127.84, 127.75,
127.56, 117.31, 82.26, 78.66, 76.06, 72.62, 71.70, 68.53, 31.23 (C-
6); HRMS (ESI) m/z calcd for C23H28O5 (M + Na+) 407.1829,
found: 407.1831.
1
0.52 (CH2Cl2/MeOH 20:1); [a]D = -2.2 (c = 0.5, EtOAc); H
2L-(2,4/3)-2-O-Allyl-3,4-di-O-benzyl-2,3,4-trihydroxy-5-cyclo-
hexen-1-one (27). To a solution of 18 (260 mg, 0.6 mmol) in
CH2Cl2 (5 mL), MsCl (156 mg, 1.4 mmol) was added dropwise at
NMR (500 MHz, CDCl3) d = 7.36–7.24 (m, 12H, Ar), 6.86 (d,
J = 8.5 Hz, Ar), 5.00 (d, 1H, J = 11.5 Hz, PhCH2), 4.90 (d, 1H, J =
10.5 Hz, PhCH2), 4.82 (d, 1H, J = 10.5 Hz, PhCH2), 4.76 (2br,
2H, OH), 4.69–4.60 (m, 3H, PhCH2), 4.08 (q, 1H, J = 3.0 Hz,
H-1), 4.95 (ddd, 1H, J = 5.0, 9.5, 12.0 Hz, H-5), 3.83–3.80 (m,
4H, H-3, OCH3), 3.48 (dd, 1H, J = 3.0, 9.0 Hz, H-2), 3.26 (t, 1H,
J = 9.5 Hz, H-4), 2.24 (dt, 1H, J = 4.5, 14.0 Hz, H-6eq), 1.37
(ddd, 1H, J = 2.5, 12.0, 14.0 Hz, H-6ax); 13C NMR (75 MHz,
CDCl3) d = 159.42 (PMB), 138.61, 129.91, 129.52, 128.60, 128.41,
127.92, 127.83, 127.65, 113.92, 86.12, 82.93, 81.50, 75.68, 75.40,
72.45, 67.67, 65.78, 55.27 (OCH3), 33.42 (C-6); HRMS (ESI) m/z
calcd. for C28H32O6 (M + Na+) 487.2091, found: 487.2094. Another
component 29 (116 mg) was collected as a colorless oil: Rf = 0.45
(CH2Cl2/MeOH 20:1), but its purity was not satisfactory in the
1H NMR spectrum. To the above crude oil (116 mg, 0.25 mmol)
in pyridine (5 mL), was added BzCl (209 mg, 1.4 mmol) at
0 ◦C. After stirring for 5 h, pyridine was evaporated under vacuum.
The residue was diluted with EtOAc, washed with sat. NaHCO3
and water. The organic layer was collected, dried over Na2SO4,
concentrated, purified by column chromatography on silica gel
(petroleum ether–EtOAc 12:1) to give 30 (150 mg, 89%) as a white
solid: Rf = 0.30 (petroleum ether–EtOAc 3:1); [a]D = +3.2 (c =
1.3, EtOAc); 1H NMR (500 MHz, CDCl3) d = 8.14–6.66 (m, 24H,
Ar), 5.30 (ddd, 2H, J = 4.5, 9.0, 11.5 Hz, H-1, H-5), 4.89 (d,
2H, J = 11.5 Hz, PhCH2), 4.86–4.69 (m, 4H, PhCH2), 3.82 (t,
1H, J = 9.0 Hz, H-2), 3.79 (t, 1H, J = 9.0 Hz, H-4), 3.73 (t,
1H, J = 9.0 Hz, H-3), 3.71 (s, 3H, OCH3), 2.58 (dt, 1H, J = 5.0,
12.5 Hz, H-6eq), 1.77 (q, 1H, J = 12.0 Hz, H-6ax); 13C NMR
(75 MHz, CDCl3) d = 165.39 (PhCO), 159.11 (PMB), 138.35,
137.94, 133.08, 130.14, 129.87, 129.62, 128.37, 128.26, 127.94,
127.70, 127.63, 113.64, 83.07, 82.71, 76.10, 75.52, 75,13, 70.85,
70.79, 55.13 (OCH3), 32.16 (C-6). HRMS (ESI) m/z calcd. for
C42H40O8 (M + Na+) 695.2615, found: 695.2615.
◦
0 C, followed by addition of triethylamine (0.5 mL, 3.6 mmol).
The mixture was stirred at 0 ◦C for 2 h, diluted with CH2Cl2
(50 mL), washed successively with 0.5 M H2SO4, sat. NaHCO3,
and brine. The organic layer was dried over Na2SO4 and concen-
trated. The residue was purified by column chromatography on
silica gel (petroleum ether–EtOAc 12:1) to give 27 (148 mg, 60%)
as a colorless oil: Rf = 0.28 (petroleum ether–EtOAc 3:1); [a]D =
+21.0 (c = 0.6, EtOAc); 1H NMR (500 MHz, CDCl3) d = 7.40–
7.30 (m, 10H, Ar), 6.80 (dd, 1H, J = 2.0, 10.5 Hz, H-6), 6.02 (dd,
1H, J =2.0, 10.0 Hz, H-5), 6.04–5.95 (m, 1H, =CH-), 5.35 (dd, 1H,
J = 1.5, 17.0 Hz, =CH2), 5.21 (dd, 1H, J = 1.5, 10.5 Hz, =CH2),
4.97 (d, 1H, J = 11.0 Hz, PhCH2), 4.83(d, 1H, J = 11.5 Hz,
PhCH2), 4.81 (d, 1H, J = 10.5 Hz, PhCH2), 4.74 (d, 1H, 12.0 Hz,
=
PhCH2), 4.51 (ddt, 1H, J = 1.5, 5.5, 12.5 Hz, C–CH2–), 4.35 (dt,
1H, J = 2.0,7.5 Hz, H-4), 4.25 (ddt, 1H, J = 1.5, 5.5, 12.5 Hz,
C–CH2–), 3.97–3.91 (m, 2H, H-2, H-3); 13C NMR (125 MHz,
=
=
CDCl3) d = 197.34 (C O), 148.06, 138.17, 137.62, 134.39, 128.54,
128.40, 128.19, 128.03, 127.89, 127.82, 117.80, 84.72, 83.60, 78.89,
75.76, 73.66, 29.69; HRMS (ESI) m/z calcd for C23H24O4 (M + H+)
365.1770, found: 365.1770.
1L-(1,5/4,6)-6-O-Allyl-4,5-di-O-benzyl-cyclohex-2-en-1-ol (28).
To a mixture of 27 (86 mg, 0.24 mmol) and CeCl3·7H2O (132 mg,
0.35 mmol) in methanol (5 mL) was added NaBH4 (13 mg,
0.34 mmol) at 0 ◦C. After stirring for 15 min, the reaction was
quenched with water and extracted with EtOAc (50 mL), washed
with brine, dried over Na2SO4. The organic layer was concentrated
and purified by column chromatography on silica gel (petroleum
ether–EtOAc 4:1) to give 28 (78 mg, 90%) as a light yellow oil:
Rf = 0.22 (petroleum ether–acetone 2:1); [a]D = +90.3 (c = 3.9,
1
MeOH); H NMR (500 MHz, CDCl3) d = 7.38–7.27 (m, 10H,
Ar), 5.95 (ddt, 1H, J = 6.0, 10.5, 17.5 Hz, =CH-), 5.72–5.67 (m,
2H, H-2, H-3), 5.28 (ddt, 1H, J = 1.5, 17.5 Hz, =CH2), 5.19
(ddt, 1H, J = 1.5, 10.0 Hz, =CH2), 4.89–4.65 (m, 4H, PhCH2),
4.46 (ddt, 1H, J = 1.5, 5.0, 12.5 Hz, =C-CH2), 4.30 (d, 1H, J =
7.0 Hz, H-1), 4.23 (dd, 1H, J = 5.0, 12.5 Hz, =C-CH2), 4.22–
4.19 (m, 1H, H-4), 3.71 (dd, 1H, J = 7.5, 10.5 Hz, H-5), 3.41
(dd, 1H, J = 7.5, 10.0 Hz, H-6); 13C NMR (125 MHz, CDCl3)
1D-(1,2,4/3,5)-5-Azido-2,3-di-O-benzyl-1-O-methyl-1,2,3,4-
cyclohexanetetrol (32). To a solution of 22 (34 mg, 0.085 mmol)
in CH2Cl2 (1 mL), pyridine (28 mL, 0.34 mmol) was added and
followed by the addition of Tf2O (29 mL, 0.17 mmol) at 0 ◦C. After
stirring for 10 min, sat. NaHCO3 was added toquench thereaction,
diluted with EtOAc, washed with water and brine. The extract was
dried over Na2SO4, concentrated; the residue was co-evaporated
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with toluene for three times before dissolved in DMF (1 mL). To
the mixture, NaN3 (1.5 mg, 0.34 mmol) was added at 0 ◦C. After
5 h, the mixture was evaporated in vacuo, diluted with EtOAc,
concentrated to give a yellow oil. Mixed the oil with MeOH (1 mL),
PdCl2 (3 mg, 0.022 mmol) was added at r.t. After stirring for
12 h, the mixture was diluted with CH2Cl2, filtered, concentrated.
The residue was purified by column chromatography on silica gel
(petroleum ether–EtOAc 4:1) to give 32 (9 mg, 35% for 3 steps)
temperature, filtered, and concentrated to give 53 (96 mg, 80%
for two steps) as a white solid: Rf = 0.5 (petroleum ether–EtOAc
1:2); [a]D = +19.9 (c = 3.2, EtOAc); 1H NMR (500 MHz, CDCl3)
d = 7.41–7.25 (m, 20H, Ar), 5.28 (d, 1H, J = 3.5 Hz, H-1¢), 5.02
(d, 1H, J = 10.0 Hz, PhCH2), 4.92–4.85 (m, 4H, PhCH2), 4.74
(d, 1H, J = 12.0 Hz, PhCH2), 4.69 (d, 1H, J = 11.5 Hz, PhCH2),
4.59 (d, 1H, J = 11.5 Hz, PhCH2), 4.18–4.10 (m, 4H, H-1 or H-5,
H-2 or H-4, H-3 H-5¢), 4.05 (dd, 1H, J = 9.0, 10.0 Hz, H-3¢),
3.58 (dd, 1H, J = 3.5, 10.0 Hz, H-2¢), 3.52–3.44 (m, 5H, H-1
or H-5, H-2 or H-4, H-4¢, H-6a¢, OH), 3.33 (dd, 1H, J = 6.0,
13.5 Hz, H-6b¢), 3.12 (d, 1H, J = 2.5 Hz, OH), 2.32 (dt, 1H, J =
3.5, 15.5 Hz, H-6eq), 1.53 (d, 1H, J =15.5 Hz, H-6ax); 13C NMR
(75 MHz, CDCl3) d = 138.74, 137.75, 137.58, 128.53, 128.36,
128.12, 127.98, 127.90, 127.83, 127.74, 127.53, 99.14 (C-1¢), 82.10,
82.16, 80.37, 78.94, 78.18, 75.84, 75.59, 75.13, 72.78, 70.93, 70.34,
68.50, 63.86, 51.10, 31.52 (C-6); MS (ESI-TOF) m/z calcd. for
1
as a colorless oil: Rf = 0.34; [a]D = -9.3 (c = 0.4, EtOAc); H
NMR (500 MHz, CDCl3) d = 7.37–7.29 (m, 10H, Ar), 5.02 (d,
1H, J = 11.1 Hz, PhCH2), 4.71 (s, 2H, PhCH2), 4.69(d, 1H, J =
11.1 Hz, PhCH2), 3.76 (t, 1H, J = 9.0 Hz, H-3), 3.66–3.61 (m,
2H, H-4, H-5), 3.45–3.41 (m, 4H, H-1,OCH3), 3.39 (dd, 1H, J =
3.0, 9.0 Hz, H-2), 2.58 (d, 1H, J = 2.5 Hz, OH), 2.21 (dt, 1H,
J = 4.0, 14.5 Hz, H-6eq), 1.19 (ddd, 1H, J = 2.5, 12.0, 14.5 Hz,
H-6ax); 13C NMR (75 MHz, CDCl3) d = 138.51, 137.98, 128.62,
128.46, 127.99, 127.93, 127.86, 82.05, 81.40, 76.49, 75.71, 74.86,
72.46, 58.93, 57.76 (OCH3), 29.69 (C-6); IR u = 2103.6 cm-1 (-N3);
+
C40H44N6O8 754 (M + NH4 ), found 754; elemental analysis calcd
(%) for C40H44N6O8: C 65.20, H 6.02, N 11.41, found: C, 65.09,
H, 6.00, N, 11.19.
+
HRMS (ESI) m/z calcd. for C21H25N3O4 (M + NH4 ) 401.2183,
found: 401.2189.
1D-(1,3,5/2,4)-2-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-3,4-di-O-benzyl-1,2,3,4,5-cyclohexanepentol
(54). Yield: 77%; [a]D = +0.6 (c = 0.3, EtOAc); 1H NMR
(500 MHz, CDCl3) d = 7.38–7.27 (m, 20H, Ar), 5.37 (d, 1H, J =
3.5 Hz, H-1¢), 5.02 (d, 1H, J = 11.0 Hz, PhCH2), 4.94 (d, 1H, J =
11.0 Hz, PhCH2), 4.88–4.86 (m, 4H, PhCH2), 4.67 (d, 1H, J =
11.5 Hz, PhCH2), 4.59 (d, 1H, J = 11.0 Hz, PhCH2), 4.21 (ddd,
1H, J = 2.5, 5.5, 10.0 Hz, H-5¢), 3.97 (dd, 1H, J = 9.0, 10.0 Hz,
H-4¢), 3.64–3.46 (m, 7H, H-1, H-2, H-3 or H-4, H-5, H-2¢, H-3¢,
H-6a¢), 3.37–3.33 (m, 2H, H-3 or H-4, H-6b¢), 2.96 (br, 1H, OH),
2.24 (dt, 1H, J = 4.5, 12.5 Hz, H-6eq), 1.62 (br, 1H, OH), 1.48
(q, 1H, J = 12.5 Hz, H-6ax); 13C NMR (125 MHz, CDCl3) d =
138.36, 138.20, 137.44, 137.38, 128.69, 128.59, 128.49, 128.42,
128.16, 128.10, 128.02, 127.92, 127.87, 127.54, 127.29, 98.28
(C-1¢), 86.17, 85.48, 82.68, 80.27, 78.74, 75.57 (¥2), 75.47, 75.28,
70.82, 68.51, 68.26, 63.76, 51.22, 36.43 (C-6); HRMS (ESI) m/z
calcd. for C40H44N6O8 (M + Na+) 759.3113, found: 759.3124.
General procedure for the preparation of pseudodisaccharides
53–58 and 60–65
Donor 5018 (0.2 mmol) and acceptor (0.3 mmol) were coevapo-
rated twice with toluene and further dried under vacuum. To a
solution of donor and acceptor in CH2Cl2 (5 mL), 4 A molecular
˚
sieves (600 mg) and N-iodosucccinimide (0.2 mmol) were added,
and ◦the mixture was stirred for 30 min before being cooled to
-40 C under argon. Trifluoromethanesulfonic acid (0.02 mmol,
1 N in Et2O) was added, the temperature was then allowed to
rise to -20 ◦C, and maintained at this temperature for 30 min
to 3 h until donor disappeared by TLC monitoring. Et3N was
added to quench the reaction. The reaction mixture was filtered,
washed with CH2Cl2, and concentrated. The residue was purified
by column chromatography on silica gel. To the disaccharides with
a benzoyl protective group, 30% NaOMe in MeOH was added to
give 53–58. Compound 65 was obtained by the coupling of donor
51 and acceptor 33 followed by the deprotection of acetal group
with 80% AcOH/H2O at 60 ◦C for 2 h.
1D-(1,2,4/3,5)-4-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-2,3-di-O-benzyl-1,2,3,4,5-cyclohexanepentol
(55). Yield: 70%; [a]D = +76.5 (c = 0.3, EtOAc); 1H NMR
(300 MHz, CDCl3) d = 7.40–7.24 (m, 20H, Ar), 5.39 (d, 1H,
J = 3.6 Hz, H-1¢), 4.97–4.85 (m, 4H, PhCH2), 4.71–4.66 (m, 2H,
PhCH2), 4.56 (d, 1H, J = 11.0 Hz, PhCH2), 4.26–4.22 (m, 1H,
H-5¢), 4.13–4.07 (m, 1H, H-1), 4.12–3.96 (m, 2H, H-3 or H-4,
H-3¢), 3.85 (t, 1H, J = 9.0 Hz, H-4¢), 3.56–3.43 (m, 5H, H-2,
H-3 or H-4, H-5, H-2¢, H-6a¢), 3.33 (dd, 1H, J = 5.1, 13.2 Hz,
H-6b¢), 2.25 (dt, 1H, J = 4.2, 13.8 Hz, H-6eq), 1.53 (ddd, 1H,
J = 2.4, 13.0, 13.8 Hz, H-6ax). 13C NMR (75 MHz, CDCl3) d =
138.70, 137.65, 137.50, 137.43, 128.56, 128.49, 128.34, 128.11,
128.01, 127.87, 127.52, 127.45, 98.14 (C-1¢), 85.13, 83.01, 80.49,
80.24, 78.75, 75.55, 75.24, 72.73, 70.74, 67.41, 65.60, 63.76,
51.13, 34.47 (C-6); MS (ESI-TOF) m/z calcd. for C40H44N6O8
1L-(1,2,4,5/3)-2-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-3,4-di-O-benzyl-1,2,3,4,5-cyclohexanepentol
(53). A mixture of donor 50 (85 mg, 0.16 mmol), acceptor 34
(149 mg, 0.27 mmol), N-iodosucccinimide (37 mg, 0.16 mmol),
˚
and powdered 4 A molecular sieves (600 mg) in CH2Cl2 (5 mL)
was stirred at room◦temperature for 30 min. The reaction mixture
was cooled to -40 C and trifluoromethanesulfonic acid (16 mL,
1 N in Et2O) was added. The reaction temperature was allowed
to rise to -20 ◦C. After stirring at -20 ◦C for 1 h, the reaction
was diluted with CH2Cl2 (10 mL) and Et3N (0.1 mL) was
added to quench the reaction, filtered, and washed successively
with sat. Na2S2O3 (10 mL) and sat. NaHCO3 (10 mL). The
organic layer was collected, dried over Na2SO4, concentrated,
purified by column chromatography on silica gel (petroleum
ether–EtOAc 8:1) to give the glycosylation product (124 mg).
To a solution of the glycosylation product (124 mg) in MeOH
(5 mL), 30% NaOMe (0.1 mL) was added at room temperature.
After stirring for 1 h, the mixture was neutralized to pH = 6–7
with ion-exchange resin (Dowex 50, strong acid form) at room
+
754 (M + NH4 ), found: 754; elemental analysis calcd (%) for
C40H44N6O8: C 65.20, H 6.02, N 11.41, found: C 65.07, H 5.99, N
11.19.
1L-(1,2,4/3,5)-2-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-3,4-di-O-benzyl-1,2,3,4,5-cyclohexanepentol
(56). Yield: 86%; [a]D = +8.7 (c = 0.3, EtOAc); 1H NMR
4262 | Org. Biomol. Chem., 2009, 7, 4252–4266
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(300 MHz, CDCl3) d = 7.39–7.25 (m, 20H, Ar), 5.35 (d, 1H,
J = 3.9 Hz, H-1¢), 5.02–4.95 (m, 2H, PhCH2), 4.91–4.84 (m, 4H,
PhCH2), 4.70 (d, 1H, J = 11.7 Hz, PhCH2), 4.58 (d, 1H, J =
11.1 Hz, PhCH2), 4.11–4.12 (m, 1H, H-1), 4.03–3.89 (m, 4H, H-3
or H-4, H-3¢, H-4¢, H-5¢), 3.72 (dd, 1H, J = 2.7, 9.6 Hz, H-2),
3.50–3.42 (m, 3H, H-3 or H-4, H-5, H-6a¢), 3.34–3.27 (m, 2H,
H-2¢, H-6b¢), 2.39-2.33 (2¥br, 2H, OH), 2.22 (dt, 1H, J = 4.2,
13.8 Hz, H-6eq), 1.45 (ddd, 1H, J = 2.0, 12.0, 13.5 Hz, H-6ax);
13C NMR (75 MHz, CDCl3) d = 138.43, 138.38, 137.33, 137.19,
128.59, 128.49, 128.40, 128.18, 128.05, 127.88, 127.74, 127.50,
98.59 (C-1¢), 86.54, 81.20, 81.10, 80.22, 78.76, 75.58, 75.44, 75.38,
75.29, 71.23, 68.10, 67.76, 63.59, 51.09, 34.24 (C-6); HRMS (ESI)
m/z calcd. for C40H44N6O8 (M + Na+) 759.3113, found: 759.3116.
3.36 (dd, 1H, J = 4.5, 13.0 Hz, H-6b¢), 3.31 (dd, 1H, J = 4.0,
10.0 Hz, H-3), 2.15 (dt, 1H, J = 4.5, 14.5 Hz, H-5eq), 1.47 (ddd,
1H, J = 3.0, 12.0, 14.5 Hz, H-5ax); 13C NMR (125 MHz, CDCl3)
d = 138.24, 137.68 (¥2), 137.22, 128.59, 128.48, 128.41, 128.14,
128.05, 128.01, 127.90, 127.74, 127.58, 127.45, 97.74 (C-1¢), 82.93,
81.71, 80.04, 78.71, 78.26, 75.47, 75.35, 75.00, 73.19, 70.89, 63.28,
58.28, 57.27, 51.00, 31.17 (C-5); HRMS (ESI) m/z calcd. for
C40H42N12O6 (M + Na+) 809.3242, found: 809.3241.
1L-(1,3,6/2,4)-1-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-4,6-diazido-2,3-di-O-benzyl-1,2,3-cyclohexa-
netriol (61). Yield: 50%; [a]D = +82.1 (c = 0.6, EtOAc); 1H
NMR (500 MHz, CDCl3) d = 7.36–7.25 (m, 20H, Ar), 5.37 (d,
1H, J = 4.0 Hz, H-1¢), 5.01 (d, 1H, J = 11.0 Hz, PhCH2), 4.93 (d,
1H, J = 10.5 Hz, PhCH2), 4.88–4.82 (m, 5H, PhCH2), 4.56 (d,
1H, J = 11.5 Hz, PhCH2), 4.06 (dd, 1H, J = 3.0, 6.0 Hz, H-6),
4.03 (dd, 1H, J = 9.0, 10.5 Hz, H-3¢), 3.97 (t, 1H, J = 9.0 Hz,
H-4¢), 3.91 (ddd, 1H, J = 2.5, 7.0, 9.5 Hz, H-5¢), 3.85 (dd, 1H,
J = 3.5, 9.5 Hz, H-2¢), 3.71 (ddd, 1H, J = 4.5, 9.5, 12.5 Hz, H-4),
3.45–3.32 (m, 4H, H-1, H-2, H-3, H-6a¢), 3.27 (dd, 1H, J = 7.0,
12.5 Hz, H-6b¢), 2.11 (dt, 1H, J = 4.0, 14.0 Hz, H-5eq), 1.45 (ddd,
1H, J = 2.0, 11.5, 13.5 Hz, H-5ax); 13C NMR (75 MHz, CDCl3)
d = 138.24, 137.56, 137.44, 137.39, 128.56, 128.44, 128.16, 128.05,
127.88, 127.60, 127.32, 99.02 (C-1¢), 85.04, 81.64, 79.79, 79.41,
78.72, 75.81, 75.61, 75.53, 75.06, 71.87, 63.27, 59.96, 59.43, 51.10,
31.72 (C-5); HRMS (ESI) m/z calcd. for C40H42N12O6 (M + Na+)
809.3242, found: 809.3232.
1D-(1,2,4/3,5)-4-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-2,3-di-O-benzyl-1-O-methyl-1,2,3,4,5-cyclo-
hexanepentol (57). Yield: 70%; [a]D = +72.7 (c = 4.4, EtOAc);
1H NMR (300 MHz, CDCl3) d = 7.38–7.26 (m, 20H, Ar), 5.37 (d,
1H, J = 3.6 Hz, H-1¢), 4.99–4.84 (m, 5H, PhCH2), 4.74–4.65 (m,
2H, PhCH2), 4.59 (d, 1H, J = 11.0 Hz, PhCH2), 4.18 (ddd, 1H,
J = 2.4, 5.1, 10.2 Hz, H-5¢), 4.00 (dd, 1H, J = 9.0, 10.2 Hz, H-4¢),
3.91 (t, 1H, J = 9.0 Hz, H-3¢), 3.84–3.80 (m, 1H, H-1), 3.60 (m,
1H, H-5), 3.56–3.41 (m, 8H, H-2, H-3, H-4, H-2¢, H-6a¢, OCH3),
3.33 (dd, 1H, J = 5.1, 13.2 Hz, H-6b¢), 2.90 (d, 1H, J = 3.9 Hz,
OH), 2.28 (dt, 1H, J = 4.5, 14.4 Hz, H-6eq), 1.23 (t, 1H, J =
14.4 Hz, H-6ax); 13C NMR (75 MHz, CDCl3) d = 138.85, 138.13,
137.47, 137.42, 128.56, 128.49, 128.36, 128.27, 128.12, 127.99,
127.90, 127.86, 127.71, 127.63, 127.34, 98.21 (C-1¢), 85.97, 82.70,
80.44, 80.14, 78.76, 75.53, 75.21, 74.75, 72.69, 70.75, 67.62, 63.76,
57.54 (OCH3), 51.17, 31.97 (C-6); HRMS (ESI) m/z calcd. for
C41H46N6O8 (M + Na+) 773.3269, found: 773.3262.
1L-(1,3,4/2,5)-1-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-6-azido-2,3-di-O-benzyl-4-O-methyl-1,2,3,4-cyclo-
hexanetetrol (62). Yield: 86%; [a]D = +47.7 (c = 0.3, EtOAc);
1H NMR (300 MHz, CDCl3) d = 7.37–7.26 (m, 20H, Ar), 5.62
(d, 1H, J = 4.0 Hz, H-1¢), 5.07 (d, 1H, J = 10.5 Hz, PhCH2),
4.91–4.86 (m, 4H, PhCH2), 4.70–4.60 (m, 3H, PhCH2), 4.28
(ddd, 1H, J = 2.5, 4.0, 10.0 Hz, H-5¢), 4.03 (t, 1H, J = 9.0 Hz,
H-3¢), 4.00 (t, 1H, J = 9.0 Hz, H-4¢), 3.67–3.36 (m, 10H, H-1,
H-2, H-3, H-4, H-6, H-2¢, H-6a¢, OCH3), 3.30 (dd, 1H, J = 4.0,
10.5 Hz, H-6b¢), 2.32 (dt, 1H, J = 4.0, 14.0 Hz, H-5eq), 1.32
(ddd, 1H, J = 2.0, 13.5, 14.0 Hz, H-5ax); 13C NMR (75 MHz,
CDCl3) d = 138.52, 137.82, 137.70, 128.44, 128.35, 128.03,
127.93, 127.87, 127.73, 127.45, 97.74 (C-1¢), 82.86, 81.75, 79.98,
78.70, 78.61, 75.43, 75.15, 74.98, 74.35, 72.73, 70.74, 63.23, 58.28,
57.90 (OCH3), 50.97, 29.74 (C-5); HRMS (ESI) m/z calcd. for
1L-(1,2,4,5/3)-2-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D-glucopyranosyl)-3,4-di-O-benzyl-5-O-methyl-1,2,3,4,5-cyclo-
hexanepentol (58). Yield: 70%; [a]D = +34.8 (c = 2.4, EtOAc);
1H NMR (300 MHz, CDCl3) d = 7.42–7.24 (m, 20H, Ar), 5.23
(d, 1H, J = 3.6 Hz, H-1¢), 5.02 (d, 1H, J = 10.5 Hz, PhCH2),
4.91–4.83 (m, 4H, PhCH2), 4.77 (d, 1H, J = 12.0 Hz, PhCH2),
4.67 (d, 1H, J = 11.7 Hz, PhCH2), 4.59 (d, 1H, J = 11.4 Hz,
PhCH2), 4.22–4.06 (m, 4H, H-1 or H-3, H-3¢, H-4¢, H-5¢),
3.70–3.65 (m, 2H, H-1 or H-3, OH), 3.54–3.41 (m, 8H, H-4, H-5,
H-6, H-2¢, H-6a¢, OCH3), 3.34 (dd, 1H, J = 5.1, 13.2 Hz, H-6b¢),
2.27 (d, 1H, J = 15.0 Hz, H-6eq), 1.23 (d, 1H, J = 14.4 Hz,
H-6ax); 13C NMR (75 MHz, CDCl3) d = 138.80, 138.14, 137.66,
128.41, 128.28, 128.09, 127.92, 127.87, 127.82, 127.75, 127.64,
127.44, 99.33 (C-1¢), 82.99, 82.70, 80.35, 78.99, 78.61, 78.35,
75.77, 75.52, 75.00, 73.13, 70.76, 70.17, 63.97, 59.06 (OCH3),
51.10, 29.71 (C-6); HRMS (ESI) m/z calcd. for C41H46N6O8
(M + Na+) 773.3269, found: 773.3254.
+
C41H45N9O7 (M + NH4 ) 793.3780, found: 793.3786.
5,6,3¢,4¢-Tetra-O-benzyl-1,3,2¢,6¢-tetraazidoneamine
(63).
Yield: 80%; [a]D = +55.1 (c = 1.3, EtOAc); 1H NMR (300 MHz,
CDCl3) d = 7.38–7.26 (m, 20H, Ar), 5.58 (d, 1H, J = 3.9 Hz,
H-1¢), 5.02 (d, 1H, J = 11.1 Hz, PhCH2), 4.94–4.80 (m, 6H,
PhCH2), 4.61 (d, 1H, J = 11.1 Hz, PhCH2), 4.27 (m, 1H, H-5¢),
4.00 (t, 1H, J = 9.0 Hz, H-3¢), 3.65–3.29 (m, 9H, H-1, H-3,
H-4, H-5, H-6, H-2¢, H-4¢, H-6a¢, H-6b¢), 2.32 (dt, 1H, J = 4.2,
13.2 Hz, H-2eq), 1.49 (q, 1H, J = 13.2 Hz, H-2ax). The 1H NMR
data coinside with the previous report.23
1L-(1,3,4/2,6)-1-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-
a-D -glucopyranosyl)-2,3-di-O-benzyl-4,6-diazido-1,2,3-cyclo-
hexanetriol (60). Yield: 56%; [a]D = +60.0 (c = 0.3, EtOAc);
1H NMR (500 MHz, CDCl3) d = 7.37–7.24 (m, 20H, Ar), 5.59
(d, 1H, J = 4.0 Hz, H-1¢), 5.05 (d, 1H, J = 10.5 Hz, PhCH2),
4.91–4.86 (m, 4H, PhCH2), 4.70 (s, 2H, PhCH2), 4.61 (d, 1H,
J = 11.0 Hz, PhCH2), 4.07 (ddd, 1H, J = 2.5, 4.0, 9.5 Hz, H-5¢),
4.01 (dd, 1H, J = 9.0, 10.0 Hz, H-3¢), 3.99 (dd, 1H, J = 3.5,
7.7 Hz, H-2¢), 3.95 (t, 1H, J = 9.5 Hz, H-4¢), 3.65–3.58 (m, 2H,
H-1 or H-2, H-4), 3.53–3.46 (m, 3H, H-1 or H-2, H-6, H-6a¢),
4-O-(2¢,6¢-Diazido-2¢,6¢-dideoxy-3¢4¢-di-O-acetyl-a-D-man-
nopyranosyl)-1,3-diazido-5,6-di-O-benzyl-2-deoxystreptamine (64).
Yield: 84%; [a]D = +68.9 (c = 0.9, EtOAc); 1H NMR (500 MHz,
CDCl3) d = 7.39–7.26 (m, 10H, Ar), 5.29–5.21(m, 2H, H-3¢, H-4¢),
5.18 (d, 1H, J = 2.5 Hz, H-1¢), 5.02 (d, 1H, J = 11.5 Hz, PhCH2),
4.90 (d, 1H, J = 10.5 Hz, PhCH2), 4.83 (d, 1H, J = 10.5 Hz,
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PhCH2), 4.62 (d, 1H, J = 11.5 Hz, PhCH2), 4.32 (ddd, 1H, J =
3.0, 6.0, 9.0 Hz, H-5¢), 3.53–3.46 (m, 4H, H-2¢, H-4, H-5, H-6),
3.43–3.37 (m, 2H, H-1, H-3), 3.33 (dd, 1H, J = 6.5, 13.5 Hz, H-
6a¢), 3.25 (dd, 1H, J = 3.0, 13.5 Hz, H-6b¢), 2.34 (dt, 1H, J =
4.5, 13.0 Hz, H-2eq), 2.05 (s, 3H, COCH3), 2.04 (s, 3H, COCH3),
1.50 (q, 1H, J = 13.0 Hz, H-2ax); 13C NMR (75 MHz, CDCl3)
d = 169.94 (COCH3), 169.65 (COCH3), 137.35, 137.09, 128.72,
128.52, 128.26, 128.11, 128.05, 127.22, 98.76 (C-1¢), 84.38, 84.10,
79.51, 75.91 (¥2), 70.70, 70.30, 66.76, 61.01, 60.18, 58.79, 51.01,
32.15 (C-2), 20.68 (COCH3), 20.45 (COCH3); HRMS (ESI) m/z
calcd. for C30H34N12O8 (M + Na+) 713.2515, found: 713.2506.
stirred for 18 h under an atmosphere of H2. The mixture was
filtered and concentrated. The residue was purified by ion-
exchange chromatography (Amberlite CG-50, NH4 form) with a
+
linear gradient of aqueous ammonia. Gradient ammonia aqueous
solution (0–10%, 0–15%, 0–20%) was used. The fractions were
collected and concentrated in vacuo. The products were dissolved
in water, and 0.1 N HCl was used to adjust the pH values to
3–4. The final products were obtained after lyophilization. The
preparation of compounds 10–14: H2S gas was introduced into
the solution of pseudodisaccharide (60–62, 64–65) in a mixed
solvent of pyridine/H2O/Et3N (3:2:1) to reduce the azido groups
to amino groups. The solvent was removed and the residue was
purified by column chromatography on silica gel (EtOAc or
CHCl3/methanol/NH4OH as eluents) to give benzyl-protected
pseudodisaccharides. Finally, the benzyl groups were removed
under Pd/C/H2 conditions as described above to provide target
compounds.
4-O-(2¢,6¢-Diazido-2¢,6¢-dideoxy-a-D-galactopyranosyl)-1,3-
diazido-5,6-di-O-benzyl-2-deoxystreptamine (65). Yield: 60%
over two steps; [a]D = +20.7 (c = 0.3, EtOAc); 1H NMR (500 MHz,
CDCl3) d = 7.35–7.25 (m, 10H, Ar), 5.68 (d, 1H, J = 4.0 Hz, H-1¢),
5.02 (d, 1H, J = 11.0 Hz, PhCH2), 4.89–4.86 (m, 2H, PhCH2), 4.82
(d, 1H, J = 10.0 Hz, PhCH2), 4.39 (t, 1H, J = 5.5 Hz, H-3¢), 4.13
(dd, 1H, J = 3.0, 5.5 Hz, H-2¢), 4.03 (d, 1H, J = 2.0 Hz, H-4¢),
3.67–3.57 (m, 3H, H-4, H-5, H-6), 3.53–3.39 (m, 5H, H-1, H-3, H-
5¢, H-6a¢, H-6b¢), 2.52 (br, 2H, OH), 2.31 (dt, 1H, J = 4.5, 13.0 Hz,
H-2eq), 1.50 (q, 1H, J = 12.5 Hz, H-2ax); 13C NMR (75 MHz,
CDCl3) d = 137.75, 137.23, 128.49, 128.13, 128.05, 127.69, 127.06,
97.80 (C-1¢), 84.62, 84.40, 77.19, 75.95, 75.20, 69.65, 69.04, 68.13,
60.24, 59.72, 59.51, 51.22, 32.30 (C-2); HRMS (ESI) m/z calcd.
for C26H30N12O6 (M + Na+) 629.2304, found: 629.2307.
1L-(1,2,4,5/3)-2-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-1,2,3,4,5-cyclohexanepentol (3). 32 mg, yield: 98%;
1
[a]D = +95.0 (c = 0.6, H2O); H NMR (500 MHz, D2O) d =
5.52 (d, 1H, J = 3.5 Hz, H-1¢), 4.22–4.21 (m, 1H, H-1), 4.11–4.05
(m, 3H, H-4, H-5, H-5¢), 3.98 (dd, 1H, J = 9.0, 11.0 Hz, H-3),
3.71 (dd, 1H, J = 3.0, 9.5 Hz, H-2¢), 3.57 (dd, 1H, J = 2.5, 9.0 Hz,
H-2), 3.46–3.41 (m, 3H, H-3¢, H-4¢, H-6a¢), 3.20 (dd, 1H, J =
8.5, 13.5 Hz, H-6b¢), 2.16 (dt, 1H, J = 4.0, 15.5 Hz, H-6eq), 1.78
(dt, 1H, J = 3.0, 15.5 Hz, H-6ax); 13C NMR (125 MHz, D2O)
d = 97.09 (C-1¢), 82.12 (¥2), 74.47, 71.81, 70.53(¥2), 69.84, 69.31,
54.78, 40.88, 32.45 (C-6); HRMS (ESI) m/z calcd. for C12H24N2O8
(M + H+) 325.1605, found: 325.1672.
2-O-(2¢,6¢-Diazido-3¢,4¢-di-O-benzyl-2¢,6¢-dideoxy-a-D-gluco-
pyranosyl)-3-O-benzyl-5-O-methyl-(2R,3S,4R,5R)-7-oxa-bicyclo-
[2.2.1]heptane (59). To a solution of 57 (39 mg, 0.052 mmol)
in CH2Cl2 (2 mL), was added ◦pyridine (42 mL, 0.52 mmol) and
Tf2O (35 mL, 0.21 mmol) at 0 C. After stirring for 40 min, sat.
NaHCO3 was added to quench the reaction. The mixture was
diluted with CH2Cl2 and washed with brine. The organic layer
was collected, dried over Na2SO4, and concentrated. The residue
was purified by column chromatography on silica gel (petroleum
ether–EtOAc 3:1) to give 59 (33 mg, 99%) as a white solid: Rf =
0.23 (petroleum ether–EtOAc 3:1); [a]D = +64.0 (c = 2.9, EtOAc);
1H NMR (500 MHz, CDCl3) d = 7.39–7.24 (m, 15H, Ar), 4.92
(d, 1H, J = 3.5 Hz, H-1¢), 4.90–4.84 (m, 3H, PhCH2), 4.62–4.55
(m, 4H, PhCH2, H-1), 4.51 (d, 1H, J = 5.0 Hz, H-2), 4.05 (dd,
1H, J = 2.5, 7.0 Hz, H-5), 4.02–3.98 (m, 2H, H-3¢, H-5¢), 3.93
(d, 1H, J = 5.5 Hz, H-3), 3.59 (d, 1H, J = 1.5 Hz, H-4), 3.54 (t,
1H, J = 9.5 Hz, H-4¢), 3.50 (dd, 1H, J = 2.5, 13.5 Hz, H-6a¢),
3.35 (dd, 1H, J = 5.0, 13.5 Hz, H-6b¢), 3.31 (dd, 1H, J = 3.5,
10.0 Hz, H-2¢), 3.26 (s, 3H, OCH3), 1.90 (dd, 1H, J = 7.0, 13.5 Hz,
H-6eq), 1.74 (ddt, 1H, J = 1.5, 7.0, 13.5 Hz, H-6ax); 13C NMR
(125 MHz, CDCl3) d = 137.97, 137.88, 137.67, 128.82, 128.78,
128.35, 128.31, 128.23, 128.11, 127.97, 98.30 (C-1¢), 86.91, 84.56,
81.09, 79.99, 79.51, 79.05, 77.56, 75.68, 75.45, 73.23, 71.20, 63.49,
56.76 (OCH3), 51.30, 35.60 (C-6); HRMS (ESI) m/z calcd. for
C34H38N6O7 (M + Na+) 665.2694, found: 665.2697.
1D-(1,3,5/2,4)-2-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-1,2,3,4,5-cyclohexanepentol (4). 25 mg, yield: 98%;
[a]D = +70.0 (c = 0.9, H2O); 1H NMR (500 MHz, D2O) d = 5.54
(d, 1H, J = 4.0 Hz, H-1¢), 4.29 (ddd, 1H, J = 3.0, 8.5, 11.0 Hz,
H-5¢), 3.92 (dd, 1H, J = 9.0, 11.0 Hz, H-3 or H-4), 3.71 (ddd,
1H, J = 5.0, 9.5, 12.5 Hz, H-5), 3.57–3.51 (m, 2H, H-1, H-3¢),
3.48–3.39 (m, 4H, H-2, H-3 or H-4, H-2¢, H-6a¢), 3.31 (t, 1H, J =
9.0 Hz, H-4¢), 3.20 (dd, 1H, J = 8.5, 13.5 Hz, H-6b¢), 2.23 (dt, 1H,
J = 4.5, 12.5 Hz, H-6eq), 1.51 (q, 1H, J = 12.5 Hz, H-6ax); 13C
NMR (125 MHz, D2O) d = 96.67 (C-1¢), 83.93, 77.53, 75.17, 71.69,
69.97, 68.85, 68.75, 67.56, 54.79, 40.84, 37.92 (C-6); HRMS (ESI)
m/z calcd. for C12H24N2O8 (M + H+) 325.1605, found: 325.1615.
1D-(1,2,4/3,5)-4-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-1,2,3,4,5-cyclohexanepentol (5). 17 mg, yield: 99%;
1
[a]D = +169.2 (c = 0.6, H2O); H NMR (500 MHz, D2O) d =
5.56 (d, 1H, J = 3.5 Hz, H-1¢), 4.29 (ddd, 1H, J = 3.0, 9.0 Hz,
H-5), 4.07 (dd, 1H, J = 3.0, 6.0 Hz, H-1), 3.93 (dd, 1H, J = 9.0,
9.5 Hz, H-3¢), 3.88 (ddd, 1H, J = 5.0, 9.0, 12.0 Hz, H-5¢), 3.77 (t,
1H, J = 9.0 Hz, H-4), 3.54–3.39 (m, 5H, H-2, H-3, H-2¢, H-4¢, H-
6a¢), 3.20 (dd, 1H, J = 8.5, 13.5 Hz, H-6b¢), 2.14 (dt, 1H, J = 4.5,
13.5 Hz, H-6eq), 1.62 (ddd, 1H, J = 2.5, 12.0, 13.5 Hz, H-6ax); 13
C
NMR (125 MHz, D2O) d = 96.66 (C-1¢), 84.36, 74.34, 73.85, 71.73,
70.00, 68.76, 68.73, 67.28, 54.84, 40.87, 36.30 (C-6); HRMS (ESI)
m/z calcd. for C12H24N2O8 (M + H+) 325.1605, found: 325.1619.
General procedure for the preparation of compounds 3–14 from
53–62, and 64–65
1L-(1,2,4/3,5)-2-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-1,2,3,4,5-cyclohexanepentol (6). 13 mg, yield: 99%;
The preparation of compounds 3–9: to a solution of the pseu-
dodisaccharide (53–59) in methanol, 10% Pd/C (1.5 times the
weight of the starting material) was added. The mixture was
1
[a]D = +26.7 (c = 0.6, H2O); H NMR (500 MHz, D2O) d =
5.52 (d, 1H, J = 3.5 Hz, H-1¢), 4.21 (dd, 1H, J = 3.0, 5.5 Hz, H-1),
4264 | Org. Biomol. Chem., 2009, 7, 4252–4266
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4.01 (ddd, 1H, J = 3.0, 7.5, 10.5 Hz, H-5¢), 3.95 (dd, 1H, J = 9.5,
10.5 Hz, H-3¢), 3.81–3.76 (m, 2H, H-4, H-5), 3.71 (dd, 1H, J =
3.0, 10.0 Hz, H-2), 3.46–3.39 (m, 3H, H-3, H-2¢, H-6a¢), 3.29 (t,
1H, J = 9.0 Hz, H-4¢), 3.22 (dd, 1H, J = 8.0, 13.5 Hz, H-6b¢), 2.11
(dt, 1H, J = 4.5, 14.5 Hz, H-6eq), 1.58 (ddd, 1H, J = 2.5, 12.0,
13.5 Hz, H-6ax); 13C NMR (125 MHz, D2O) d = 97.56 (C-1¢),
81.68, 77.99, 73.08, 71.66, 69.73, 69.34, 68.65, 68.51, 54.72, 40.86,
35.74 (C-6); HRMS (ESI) m/z calcd. for C12H24N2O8 (M + H+)
325.1605, found: 325.1585.
75.17, 71.46, 70.78, 69.83, 69.25, 69.19, 54.24, 48.71, 47.66, 40.84,
25.68 (C-5); HRMS (ESI) m/z calcd. for C12H26N4O6 (M + H+)
323.1925, found: 323.1954.
1L-(1,3,6/2,4)-1-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-4,6-diamino-1,2,3-cyclohexanetriol (11). 21 mg, yield:
1
90%; [a]D = +68.3 (c = 0.6, H2O); H NMR (500 MHz, D2O)
d = 5.76 (d, 1H, J = 3.5 Hz, H-1¢), 4.20 (dd, 1H, J = 4.5, 10.0 Hz,
H-1), 4.08 (m, 1H, H-6), 4.02 (t, 1H, J = 9.0 Hz, H-3¢), 3.96 (ddd,
1H, J = 3.0, 7.5, 9.0 Hz, H-5¢), 3.86 (t, 1H, J = 9.0 Hz, H-4¢), 3.61
(t, 1H, J = 9.0 Hz, H-3), 3.52–3.42 (m, 4H, H-2, H-4, H-2¢, H-
6¢a), 3.25 (dd, 1H, J = 8.0, 13.5 Hz, H-6b¢), 2.46 (dt, 1H, J = 3.0,
1D-(1,2,4/3,5)-4-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-1-O-methyl-1,2,3,4,5-cyclohexanepentol (7). 18 mg,
1
yield: 96%; [a]D = +93.3 (c = 0.6, H2O); H NMR (500 MHz,
15.5 Hz, H-5eq), 2.16 (ddd, 1H, J = 4.0, 14.0, 16.0 Hz, H-5ax); 13
C
D2O) d = 5.60 (d, 1H, J = 4.0 Hz, H-1¢), 4.32 (ddd, 1H, J = 3.0,
7.5, 10.5 Hz, H-5), 3.97 (dd, 1H, J = 9.5, 10.5 Hz, H-3¢), 3.82
(ddd, 1H, J = 4.5, 9.5, 12.0 Hz, H-5¢), 3.76–3.72 (m, 1H, H-1,
H-4), 3.62 (dd, 1H, J = 3.5, 10.0 Hz, H-2), 3.57–3.42 (m, 7H,
H-3, H-2¢, H-4¢, H-6a¢, OCH3), 3.24 (dd, 1H, J = 8.0, 13.5 Hz,
H-6b¢), 2.42 (dt, 1H, J = 4.5, 14.5 Hz, H-6b), 1.51 (ddd, 1H, J =
2.5, 12.0, 13.5 Hz, H-6a); 13C NMR (125 MHz, D2O) d = 96.67
(C-1¢), 84.24, 78.53, 74.24, 74.08, 71.71, 69.99, 68.76, 67.19, 57.64
(OCH3), 54.82, 40.85, 32.21 (C-6); HRMS (ESI) m/z calcd. for
C13H26N2O8 (M + H+) 339.1767, found: 339.1759.
NMR (125 MHz, D2O) d = 97.55 (C-1¢), 75.24, 73.38, 73.22, 71.60,
69.73, 69.16, 54.34, 50.08, 49.06, 40.90, 27.81 (C-5); HRMS (ESI)
m/z calcd. for C12H26N4O6 (M + H+) 323.1925, found: 323.1924.
1L-(1,3,4/2,6)-1-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-6-amino-4-O-methyl-1,2,3,4-cyclohexanetetrol
(12).
16 mg, yield: 70%; [a]D = +89.2 (c = 0.6, H2O); 1H NMR
(500 MHz, D2O) d = 5.92 (d, 1H, J = 4.0 Hz, H-1¢), 4.02 (ddd,
1H, J = 3.5, 7.0, 10.0 Hz, H-5¢), 3.99 (dd, 1H, J = 9.0, 11.0 Hz,
H-3¢), 3.88 (t, 1H, J = 9.0 Hz, H-4¢), 3.83 (t, 1H, J = 9.0 Hz, H-2
or H-1), 3.79 (dd, 1H, J = 3.5, 5.5 Hz, H-4), 3.63 (dd, 1H, J = 3.0,
9.5 Hz, H-2¢), 3.53–3.45 (m, 4H, H-1 or H-2, H-3, H-6, H-6a¢),
3.41 (s, 3H, OCH3), 3.30 (dd, 1H, J = 7.0, 13.5 Hz, H-6b¢), 2.51
(dt, 1H, J = 4.5, 14.0 Hz, H-5eq), 1.71 (ddd, 1H, J = 2.0, 14.0,
14.5 Hz, H-5ax); 13C NMR (125 MHz, D2O) d = 96.75 (C-1¢),
79.61, 77.34, 74.38, 73.69, 71.41, 69.83, 69.10, 57.76 (OCH3),
54.28, 48.33, 40.84, 27.94 (C-5); HRMS (ESI) m/z calcd. for
C13H27N3O7 (M + H+) 338.1922, found: 338.1914.
1L-(1,2,4,5/3)-2-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-5-O-methyl-1,2,3,4,5-cyclohexanepentol (8). 19 mg,
1
yield: 99%; [a]D = +57.5 (c = 0.6, H2O); H NMR (500 MHz,
D2O) d = 5.51 (d, 1H, J = 3.5 Hz, H-1¢), 4.18–4.17 (m, 1H, H-1),
4.11 (td, 1H, J = 2.5, 9.0 Hz, H-2), 4.06 (t, 1H, J = 9.0 Hz, H-3¢),
3.99 (t, 1H, J = 9.0 Hz, H-4¢), 3.74–4.73 (m, 1H, H-5), 3.68–3.63
(m, 2H, H-2¢, H-5¢), 3.46–3.42 (m, 6H, H-3, H-4, H-6a¢, OCH3),
3.20 (dd, 1H, J = 8.5, 13.5 Hz, H-6b¢), 2.35 (d, 1H, J = 15.0 Hz,
H-6eq), 1.65 (d, 1H, J = 15.0 Hz, H-6ax); 13C NMR (125 MHz,
D2O) d = 97.01 (C-1¢), 81.92, 79.98, 73.83 (¥2), 71.82, 70.61,
69.85, 69.30, 58.11 (OCH3), 54.77, 40.87, 28.72 (C-6); HRMS
(ESI) m/z calcd. for C13H26N2O8 (M + H+) 339.1767, found:
339.1761.
4-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-mannopyranosyl)-2-deo-
xystreptamine (13). 17 mg, yield: 96% over three steps; [a]D
=
+53.3 (c = 0.6, H2O); 1H NMR (500 MHz, D2O) d = 5.67 (d, 1H,
J = 4.0 Hz, H-1¢), 4.26 (dd, 1H, J = 4.0, 7.5 Hz, H-3¢), 4.19 (dt,
1H, J = 5.0, 7.5 Hz, H-5¢), 4.01 (t, 1H, J = 9.5 Hz, H-4 or H-5),
3.84 (t, 1H, J = 4.0 Hz, H-2¢), 3.72 (t, 1H, J = 7.5 Hz, H-4¢),
3.68 (t, 1H, J = 9.0 Hz, H-4 or H-5), 3.61–3.52 (m, 2H, H-1 or
H-3, H-6), 3.47–3.41 (m, 2H, H-6a¢, H-6b¢), 3.35 (dt, 1H, J = 4.0,
12.0 Hz, H-1 or H-3), 2.51 (dt, 1H, J = 4.0, 12.5 Hz, H-2eq), 1.92
(q, 1H, J = 12.5 Hz, H-2ax); 13C NMR (125 MHz, D2O) d =
96.41 (C-1¢), 79.13, 75.50, 73.29, 72.48, 68.40, 67.25, 53.61, 50.45,
49.27, 40.50, 28.82 (C-2); HRMS (ESI) m/z calcd. for C12H26N4O6
(M + H+) 323.1925, found: 323.1921.
2-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopyranosyl)-5-O-
methyl-(2R,3S,4R,5R)-7-oxa-bicyclo[2.2.1]heptane (9). 37 mg,
1
yield: 96%; [a]D = +60.0 (c = 1.0, H2O); H NMR (500 MHz,
D2O) d = 5.36 (d, 1H, J = 3.5 Hz, H-1¢), 4.67 (t, 2H, J = 6.0 Hz,
H-4), 4.18–4.16 (m, 2H, H-5, H-3¢), 3.94 (ddd, 1H, J = 3.0, 8.5,
9.5 Hz, H-5¢), 3.89 (dd, 1H, J = 9.0, 10.5 Hz, H-4¢), 3.76 (d, 1H,
J = 1.0 Hz, H-2), 3.48–3.40 (m, 3H, H-1, H-2¢, H-6a¢), 3.33 (s, 3H,
OCH3), 3.22 (dd, 1H, J = 8.5, 13.5 Hz, H-6b¢), 2.10 (dd, 1H, J =
7.0, 14.0 Hz, H-6ax), 1.76 (ddt, 1H, J = 2.0, 6.5, 14.0 Hz, H-6eq);
13C NMR (125 MHz, D2O) d = 94.30 (C-1¢), 85.14, 82.54, 81.40,
77.82, 76.36, 71.76, 69.88, 69.30, 56.66 (OCH3), 54.21, 40.88, 35.00
(C-6); HRMS (ESI) m/z calcd. for C13H24N2O7 (M + H+) 321.1656,
found: 321.1647.
4-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-galactopyranosyl)-2-deo-
xystreptamine (14). 14 mg, yield: 95% over two steps; [a]D
=
+31.7 (c = 0.6, H2O); 1H NMR (500 MHz, D2O) d = 5.99 (d, 1H,
J = 4.0 Hz, H-1¢), 4.32 (td, 1H, J = 1.0, 5.0 Hz, H-5¢), 4.23 (dd,
1H, J = 3.0, 11.0 Hz, H-3¢), 4.13 (dd, 1H, J = 1.5, 3.0 Hz, H-4¢),
4.00 (dd, 1H, J = 9.0, 10.0 Hz, H-4), 3.71 (t, 1H, J = 9.0 Hz, H-5),
3.67 (dd, 1H, J = 4.0, 11.5 Hz, H-2¢), 3.61 (t, 1H, J = 9.5 Hz, H-6),
3.57 (ddd, 1H, J = 4.0, 10.0, 12.5 Hz, H-1 or H-3), 3.39–3.34 (m,
3H, H-1 or H-3, H-6a¢, H-6b¢), 2.52 (dt, 1H, J = 4.0, 12.5 Hz,
H-2eq), 1.92 (q, 1H, J = 12.5 Hz, H-2ax); 13C NMR (125 MHz,
D2O) d = 96.95 (C-1¢), 78.13, 75.97, 73.25, 70.02, 68.22, 65.81,
50.83, 50.45, 49.27, 41.29, 28.99 (C-2); HRMS (ESI) m/z calcd.
for C12H26N4O6 (M + H+) 323.1925, found: 323.1925.
1L-(1,3,4/2,6)-1-O-(2¢,6¢-Diamino-2¢,6¢-dideoxy-a-D-glucopy-
ranosyl)-4,6-diamino-1,2,3-cyclohexanetriol (10). 18 mg, yield:
1
90%; [a]D = +84.2 (c = 0.6, H2O); H NMR (500 MHz, D2O)
d = 5.80 (d, 1H, J = 3.5 Hz, H-1¢), 4.14–4.12 (m, 3H, H-5¢, H-2,
H-1 or H-3), 4.06–4.01 (m, 2H, H-3¢, H-1 or H-3), 3.94–3.92 (m,
1H, H-4 or H-6), 3.83–3.81 (m, 1H, H-4 or H-6), 3.55–3.51 (m,
3H, H-2¢, H-4¢, H-6a¢), 3.31 (dd, 1H, J = 7.5, 13.5 Hz, H-6b¢), 2.53
(ddd, 1H, J = 4.5, 7.0, 15.0 Hz, H-5eq), 2.22 (ddd, 1H, J = 4.5,
9.0, 15.0 Hz, H-5ax); 13C NMR (125 MHz, D2O) d = 95.68 (C-1¢),
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SPR binding studies
E. E. Swayze, L. Risen and R. H. Griffey, Angew. Chem., Int. Ed., 2003,
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Biotin-labelled RNA fragments were purchased at Bioneer
(Korea). SPR measurements were conducted on a Biocore
3000 system from Biocore AB and performed as described in
the literature.20 Streptavidin-coated sensor-chips (SA-chips) were
obtained from Biocore and loaded with RNA fragments to
591–648 RU. An empty cell was used as reference surface.
Calculation of dissociation constants by fitting the steady-state
responses was performed using the formula R = Rmax[c/(Kd + c)],
where R = response, Rmax = maximum response of one binding
site occupied, and c = concentration.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China, and a “973” grant from the Ministry
of Science and Technology of China.
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