Synthesis of allose-templated hydroxyornithine and hydroxyarginine analogs

Article abstract of DOI:10.1016/j.carres.2010.04.017

Conformationally constrained amino acid analogs are widely used to probe the bioactive conformation of peptides. In this paper we report on the synthesis of hexafunctional allose-templated l- and d-hydroxyornithine and l- and d-hydroxyarginine analogs in which the allose-based polyol scaffold constrains the side chain of hydroxyornithine and hydroxyarginine in an extended conformation. The partially protected building blocks were selected for future use in solid-phase peptide synthesis using the Fmoc-strategy. The synthesis starts from a previously prepared C-glucosyl glycine analog. Multiple chemical protection-deprotection steps and an oxidation are used to prepare 3-keto-C-glucosyl analogs that serve as a precursor to install an amino function via reductive amination. Guanidinylation of the amino group provides access to allose-templated hydroxyarginine analogs. Both hexafunctional building blocks are further chemically modified to provide suitable protection for solid-phase peptide synthesis using the Fmoc-strategy.

Full text of DOI:10.1016/j.carres.2010.04.017

Carbohydrate Research 345 (2010) 1533–1540
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis of allose-templated hydroxyornithine and hydroxyarginine analogs
*
Dhananjoy Mondal, Frank Schweizer
Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 March 2010
Received in revised form 5 April 2010
Accepted 19 April 2010
Available online 22 April 2010
Conformationally constrained amino acid analogs are widely used to probe the bioactive conformation of
peptides. In this paper we report on the synthesis of hexafunctional allose-templated
L- and D-hydroxy-
ornithine and - and -hydroxyarginine analogs in which the allose-based polyol scaffold constrains the
L
D
side chain of hydroxyornithine and hydroxyarginine in an extended conformation. The partially protected
building blocks were selected for future use in solid-phase peptide synthesis using the Fmoc-strategy.
The synthesis starts from a previously prepared C-glucosyl glycine analog. Multiple chemical protec-
tion–deprotection steps and an oxidation are used to prepare 3-keto-C-glucosyl analogs that serve as a
precursor to install an amino function via reductive amination. Guanidinylation of the amino group pro-
vides access to allose-templated hydroxyarginine analogs. Both hexafunctional building blocks are fur-
ther chemically modified to provide suitable protection for solid-phase peptide synthesis using the
Fmoc-strategy.
Keywords:
Sugar-amino acids
Glycosylamino acids
Hydroxyarginine
Hydroxyornithine
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
proteins can undergo post-translational mono- or di-hydroxylation
to hydroxylysines,14 hydroxyarginines,15 and hydroxyprolines.14 In
Conformationally constrained amino acids have found wide
applications as building blocks to probe the bioactive conforma-
tion(s) of peptides when binding to receptors.1–3 Previouswork from
our laboratory has focused on the synthesis and properties of poly-
hydroxylated and conformationally constrained amino acids such as
carbohydrate-templated (hydroxy)proline analogs,4–7 carbohy-
drate-templated lysine analogs,8,9 and carbohydrate-templated
(hydroxy)proline-lysine chimera.10 Carbohydrate-templated amino
acids (CTAAs) form a class of synthetic glycosylamino acids in which
the cyclic polyol scaffold of carbohydrates is part of the side chain of
naturally occurring amino acids. The relative rigidity of the pyran
ring combined with the polyfunctional nature of the carbohydrate
scaffold provides unique opportunities to tune the chemical, physi-
cal and conformational properties of amino acids. In addition, deco-
ration of the polyol scaffold with hydrophobic or hydrophilic
substituents can be used to adjust the pharmacokinetic properties
of CTAAs.
Incorporation of CTAAs into bioactive peptides provides access to
novel peptidomimetics that may overcome the inherent problems of
peptide-based drugs associated with poor pharmacokinetics, bio-
availability and tissue absorption, and proteolytic cleavage of the
peptide bonds.11–13 Furthermore, the incorporation of the carbohy-
drate-based polyol scaffold into the side chain of amino acids may
mimic post-translational hydroxylation in peptides and proteins.
For instance, lysine-, arginine-, and proline-containing peptides/
some cases hydroxylation is followed by glycosylation as in the case
of hydroxylysineand hydroxyproline.14,16 The biological and confor-
mational implications of this ‘double post-translational modifica-
tion’ are currently poorly understood.
In this paper we report on the synthesis of allose-templated
hydroxyornithine (AlloTHyOrn) and allose-templated hydroxargi-
nine analogs (AlloTHyArg) in which the cationic side chain is pre-
sented in an extended conformation (Fig. 1). The glucose-derived
allose scaffold was selected because of the relative stability of the
4C1 chair conformation and expected high reactivity of the equato-
rial hydroxyl groups. Ornithine and arginine were selected due to
their frequent occurrence in many biologically active peptides
including antimicrobial peptides17 and cell penetrating peptides.18
Several approaches to conformationally constrained arginine ana-
logs have been described.19–26 However, none of these described
analogs can be used to incorporate additional diversity and to probe
the effects of single and double post-translational modifications in
peptides.
HO
HO
NH
2
O
HO
HO
NH
2'
OH
2
1'
O
OH
OH
NH
NH
O
1
3
HN
OH
O
NH
2
2
AlloTHyOrn
AlloTHyArg
Figure 1. Structure of hexafunctional allose-templated hydroxyornithine (Allo-
THyOrn) and allose-templated hydroxyarginine (AlloTHyArg) analogs with
extended side-chain conformation.
* Corresponding author. Fax: +1 204 474 7608.
E-mail address: schweize@ms.umanitoba.ca (F. Schweizer).
0008-6215/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2010.04.017

1534
D. Mondal, F. Schweizer / Carbohydrate Research 345 (2010) 1533–1540
access to both gluco- and allo-configurated amines. As a result, we
2. Results and discussion
decided to install the amino function at C-3 via reductive amination.
The unprotected hydroxyl group in 7 and 8 was oxidized using
pyridinium chlorochromate (PCC) in dichloromethane to afford 3-
ulose derivatives 9 and 10 in 93% and 95% yield, respectively
(Scheme 3). Subsequently, 3-ulose derivatives 9 and 10 were reduc-
tively aminated using benzylamine and titanium(IV) isopropoxide
followed by the addition of sodium cyanoborohydride as previously
described by Mattson et al.29 to afford stereoselectively compounds
11 and 12 in 78% and 80% yield, respectively. Using these reductive
amination conditions we were unable to isolate gluco-configurated
benzylamines. During this reaction we also recovered the alcohol
7 and 8 in 12% and 10% yield together with small amounts of (<5%)
of transesterification products containing an isopropyl group. Com-
pounds 11 and 12 were selectively debenzylated by catalytic hydro-
genation on Pd–C in methanol to afford ornithine analogs 13 and 14
(Scheme 3). The stereochemistry of the newly incorporated amino
function was established by 1D and 2D NMR analysis. The coupling
constants JH2,H3 = 2.9 Hz and JH3,H4 = 2.9 Hz for compound 13 and
JH2,H3 = 3.0 Hz and JH3,H4 = 3.0 Hz for 14 are consistent with the axial
position of the amino function.
To modify the polyfunctional ornithine analogs 13 and 14 into
suitable building blocks for solid-phase peptide synthesis we con-
verted them into Fmoc-protected amino acids 23 and 24. CTHyOrn
analogs 23 and 24 are polyfunctional amino acids that fulfill the
requirements for use in solid-phase peptide synthesis using the
Fmoc-strategy. The partially protected hexafunctional building
blocks 23 and 24 were selected with the vision to reduce the num-
ber of steps during global side-chain deprotection in solid-phase
peptide synthesis using acidic conditions.
Previous work from our laboratory has shown that solid-phase
peptide synthesis can be carried out with polyhydroxylated Fmoc-
protected amino acids bearing no secondary hydroxyl protecting
group while protection of the primary hydroxyl groups is usually
required.8 For instance, Fmoc-protected hydroxyproline is fre-
quently used as building block in solid-phase peptide synthesis
without need of protection.30 However, the high reactivity of the pri-
mary hydroxyl group usually interferes with peptide coupling reac-
tion and usually requires protection. As a result, we decided to
protect the primary hydroxyl group in amino acids 13 and 14 with
an acid labile triphenylmethyl group (Trt) and protect the side-chain
amino function as t-butoxycarbonyl group (Boc). This was achieved
via a five-step protection–deprotection sequence (Scheme 4).
Our strategy was to develop a synthetic route to AlloTHyOrn
and AlloTHyArg building blocks suitable for solid-phase peptide
synthesis using the Fmoc-strategy.27 The synthesis started with
the known C-glucopyranosyl glycine derivative 2 easily obtained
in 43% overall yield from commercially available 2,3,4,6-tetra-O-
benzyl-D
-glucono-1,5-lactone 1 in six steps (Scheme 1).28
The C-glucosyl glycine 2 was converted into the benzylidene-
protected derivative 3 in 97% yield by treatment with benzalde-
hyde dimethyl acetal and catalytic amounts of para-toluenesul-
fonic acid (p-TsOH) in N,N-dimethylformamide. Exposure of 3 to
benzoyl chloride in dry pyridine at 0 °C produced benzoate ester
4 and dibenzoate ester 5, respectively. The major isomer 4 was iso-
lated in 87% yield while 5 was isolated in 12% yield. The remaining
hydroxyl group at the C-2 position in 4 was protected as methoxy-
methyl ether (MOM) 6 in moderate yield using MOMCl and Hünig’s
base in dichloromethane. Selective cleavage of the benzoate ester
in 6 was achieved by employing sodium methoxide in methanol
at 0 °C to afford a C-20 epimeric mixture of compounds 7 and 8
(1:3) in combined 96% yield. Both isomers could be conveniently
separated by column chromatography. In order to establish the
absolute stereochemistry at C-20 compounds 7 and 8 were benzoy-
lated separately using benzoyl chloride in dry pyridine at 0 °C to
produce previously synthesized 6 thereby confirming the absolute
C-20 (S) stereochemistry in 8 (Scheme 2).
With both C-20 epimers 7 and 8 in hand, we then explored the
conversion of the C-3 hydroxyl group into an amino function. We
anticipated that the equatorial position of the C-3 hydroxyl group
in both 7 and 8 may complicate nucleophilic substitution reaction
of activated esters at this position. Stereoelectronic considerations
suggest that nucleophilic substitutions bearing axial leaving groups
in conformationally constrained pyranose rings should be preferred
when compared to equatorially positioned leaving groups.32 More-
over, we were interested to develop an approach that would enable
OBn
OH
(6 steps)
NHBoc
OMe
O
BnO
BnO
O
HO
HO
O
OH
OBn
O
2
1
Scheme 1. Previously described synthesis of C-glucosyl glycine 2 from 1.28
H
OH
BzCl, Pyridine
PhCH(OMe)
NHBoc
2
NHBoc
OMe
ο
O
0 C
p-TsOH, DMF
O
Ph
O
HO
HO
O
HO
OMe
4: 87%
5: 12%
97%
OH
2
OH
3
O
O
H
H
MOMCl
CH Cl :DIPEA (1:8)
NHBoc
NHBoc
O
O
2
2
Ph
O
O
Ph
O
O
OMe
OMe
BzO
BzO
85%
OH
4
OBz
5
O
O
7:1
H
H
NaOMe, MeOH
o
NHBoc
O
O
BzO
R
R
2
1
O
Ph
O
0
C to rt
96%
Ph
O
OMe
O
HO
OMe
OMOM
O
OMOM
O
6
7: 8 = 1:3
7: R = NHBoc, R = H
1
2
8: R = H, R =NHBoc
1
2
Scheme 2. Synthesis of suitably protected C-glucosyl glycine analogs 7 and 8.

D. Mondal, F. Schweizer / Carbohydrate Research 345 (2010) 1533–1540
1535
H
H
R
PCC,
R
1
R
O
2
R
1
O
2
Ph
O
Ph
CH Cl
O
O
2
2
O
OMe
OMe
HO
9: 93%
10: 95%
OMOM
O
OMOM
O
O
7: R = NHBoc, R = H
9: R = NHBoc, R = H
10: R = H, R =NHBoc
1
2
1
2
8: R = H, R =NHBoc
1
2
1
2
H
(i) BnNH , Ti(Oi-Pr) , Et O
2
4
2
R
R
1
O
2
(ii) NaCNBH , MeOH
Ph
3
O
O
OMe
11: 78%
12: 80%
OMOM
BnHN
O
11: R = NHBoc, R = H
1
2
12: R = H, R =NHBoc
1
2
H
Pd/C/H
MeOH
R
1
R
2
O
2
Ph
O
O
OMe
13: 90%
14: 93%
OMOM
H N
2
O
13: R = NHBoc, R = H
1
2
14: R = H, R =NHBoc
1
2
Scheme 3. Synthesis of amines 13 and 14 from precursors 7 and 8.
H
(i) HCl, MeOH
(ii) FmocOPfp, NaHCO
H
R
R
1
2
O
3
Ph
O
R
CbzCl, Na CO
2 3
R
O
1
O
2
OMe
acetone:H O (6:1)
Ph
O
2
acetone:H O (10:1)
O
2
OMe
OMOM
CbzHN
O
17: 92%
18: 95%
15: 96%
16: 98%
OMOM
H N
2
O
15: R = NHBoc, R = H
16: R = H, R =NHBoc
1
2
13: R = NHBoc, R = H
14: R = H, R =NHBoc
1
2
1
2
1
2
R
R
1
HO
HO
2
(i) Pd/C/H , EtOAc
2
Ph CCl, pyridine
3
O
R
R
1
2
OMe
HO
HO
(ii) (Boc) O, TEA, MeOH
2
O
21: 91%
22: 90%
OMe
OH
BocHN
O
19: 96%
20: 93%
OH
17: R = NHFmoc, R = H
CbzHN
O
19: R = NHFmoc, R = H
1
2
1
2
20: R = H, R =NHFmoc
1
2
18: R = H, R =NHFmoc
1
2
(i) NaOH, 1,4-dioxane:H O
2
R
Ph CO
HO
R
1
Ph CO
3
HO
R
1
R
3
2
2
(ii) FmocOPfp, NaHCO
3
O
O
OMe
OH
acetone:H O (6:1)
2
OH
OH
BocHN
BocHN
O
O
23: 87%
24: 92%
21: R = NHFmoc, R = H
23: R = NHFmoc, R = H
1
2
1
2
22: R = H, R =NHFmoc
24: R = H, R =NHFmoc
1
2
1
2
Scheme 4. Synthesis of protected allose-templated hydroxyornithine building blocks 23 and 24 for solid-phase peptide synthesis.
At first, the unprotected amino function in the side chain of 13
and 14 was protected as benzylcarbamate (Cbz) by treatment with
benzyloxycarbonyl chloride and sodium carbonate in aqueous ace-
tone to afford N-benzyloxy carbamates 15 and 16 in excellent
yield, respectively. Exposure of compounds 15 and 16 to methano-
lic 6 N HCl at room temperature for 12 h resulted in cleavage of the
benzylidene acetal and N-terminal t-butoxycarbamate group. The
N-terminal amino group was reprotected using 9-fluorenylmethyl
pentafluorophenyl carbonate (FmocOPfp) and sodium bicarbonate
in aqueous acetone to form 9-fluorenylmethyloxy carbamate
derivatives 17 and 18 in 92% and 95% isolated yield over two steps.
The Cbz-group in 17 and 18 was selectively removed in the pres-
ence of 9-fluorenylmethyloxy carbonyl group by catalytic hydroge-
nation using 10% Pd–C in ethyl acetate followed by tert-butyloxy
carbamate (Boc) formation of the resulting 5-amino function to
provide 19 and 20 in 96% and 93% yields, respectively. The primary
hydroxyl group present in 19 and 20 was selectively protected as
triphenylmethyl ether using trityl chloride and dry pyridine to
produce 21 and 22 in 90–91% isolated yield. Finally, ester saponifi-
cation using 1 N NaOH in 1,4-dioxane of compounds 21 and 22
followed by reprotection of the N-terminal amine with FmocOPfp
generated AlloTHyOrn building blocks 23 and 24 (Scheme 4). No
epimerization was observed under this reaction conditions.
In a similar way AlloTHyArg analogs 29 and 30 were prepared
from the hydroxyornithine analogs 17 and 18 in a three-step process
(Scheme 5). At first, the ornithine analog was converted into the
arginine analogs 25 and 26 on treatment with N,N0-di-tert-butoxy-
carbonyl-N00-triflyl-guanidine31 and triethyl amine in dichlorometh-
ane at room temperature. Subsequently, the primary hydroxyl
group in guanidinylated analogs 25 and 26 was protected as triphen-
ylmethyl ethers 27 and 28 and ester saponification followed by
reprotection with FmocOPfp generated AlloTHyArg building blocks
29 and 30 (Scheme 5).
3. Conclusion
We have developed a synthetic method for the synthesis of suit-
ably protected and hexafunctional allose-templated hydroxyorni-

1536
D. Mondal, F. Schweizer / Carbohydrate Research 345 (2010) 1533–1540
R
R
1
2
HO
HO
(i) Pd/C/H , EtOAc
2
R
O
R
1
2
HO
HO
OMe
(i) Ph CCl, dry pyridine
(ii) (BocNH) C=NTf, TEA
2
O
OMe
3
dioxane:H O
2
OH
NH
O
OH
CbzHN
27: 86%
28: 88%
BocN
O
25: 89%
26: 94%
NHBoc
17: R = NHFmoc, R = H
1
2
25: R = NHFmoc, R = H
1
2
18: R = H, R =NHFmoc
1
2
26: R = H, R =NHFmoc
1
2
R
Ph CO
3
HO
R
1
2
(i) NaOH, 1,4-dioxane:H O (1:1)
2
O
Ph CO
3
HO
R
R
1
2
OMe
(ii) FmocOPfp, NaHCO
O
3
OH
acetone:H O (6:1)
2
OH
NH
O
OH
BocN
NH
NHBoc
29: R = NHFmoc, R = H
O
29: 90%
30: 87%
BocN
NHBoc
27: R = NHFmoc, R = H
28: R = H, R =NHFmoc
1
2
1
2
1
2
30: R = H, R =NHFmoc
1
2
Scheme 5. Synthesis of suitably protected allose-templated hydroxyarginine building blocks 29 and 30 for solid-phase peptide synthesis.
thine and hydroxyarginine building blocks. It is envisaged that
conformationally constrained building blocks 23, 24, 29, and 30
will find application in solid-phase peptide synthesis using the
Fmoc-strategy to probe the extended side chain conformation of
ornithine and arginine in bioactive peptides. In addition, the pres-
ence of the polyol scaffold may mimic post-translational modifica-
tions in ornithine- or arginine-containing peptides.
4.3. (20R)-Methyl 20-(t-butoxycarbonylamino)-20-(3-O-benzoyl-
4,6-O-benzylidene-b-
-glucopyranosyl)-acetate (4); (20R)-methyl
20-t-butoxycarbonylamino)-20-(2,3-di-O-benzoyl-4,6-O-
benzylidene-b- -glucopyranosyl)-acetate (5)
D
D
To a stirred solution of the benzylidene compound 3 (0.060 g,
0.17 mmol) in pyridine (1.5 mL) at 0 °C was slowly added benzoyl
chloride (30 lL, 0.26 mmol). The reaction was monitored by TLC.
At the end, the reaction mixture was diluted with EtOAc
(10.0 mL) and washed with a dilute HCl solution, a saturated NaH-
CO3 solution, and then brine. The organic phase was dried over an-
hyd Na2SO4 and evaporated to dryness. The crude product was
subjected to flash column chromatography using hexanes and
EtOAc (4:1, v/v) as an eluant to afford the pure product 4
(0.065 g, 87%) then 5 (0.025 g, 12%) as an amorphous solid. Com-
4. Experimental
4.1. General methods
CH2Cl2 was distilled from calcium hydride. Organic solutions
were concentrated under diminished pressure at <40 °C (bath tem-
perature). NMR spectra were recorded at 300 or 500 MHz for 1H
and at 75 MHz for 13C. Chemical shifts are reported relative to
CHCl3 (dH 7.26, dc (center of triplet) 77.0 ppm) or to CH3OH (dH
3.35, dC (center of septet) 49.0 ppm) or to acetone as an internal
standard (D2O). TLC was performed on E. Merck Silica Gel 60
F254 with detection by charring with 8% H2SO4 acid. Silica gel
(0.040–0.063 mm) was used for column chromatography.
pound 4: Rf = 0.50 (EtOAc–hexane 2:3); ½a D25
ꢂ84.6 (c 0.7, CHCl3);
ꢁ
1H NMR (300 MHz, CDCl3): d 1.47 (s, 9H), 2.02 (br s, 1H), 3.57
(ddd, 1H, J = 4.6, 9.7, 14.3 Hz), 3.72 (t, 2H, J = 9.6 Hz), 3.80 (s, 3H),
3.82 (dd, 1H, J = 2.5, 10.1 Hz), 4.04 (dd, 1H, J = 9.6, 10.2 Hz), 4.37
(dd, 1H, J = 4.6, 10.3 Hz), 4.82 (br d, 1H, J = 8.1 Hz), 5.37 (dd, 1H,
J1 = 9.6 Hz, J2 = 9.6 Hz), 5.48 (d, 1H, J = 9.0 Hz), 5.52 (s, 1H), 7.29–
7.33 (m, 3H), 7.39–7.48 (m, 4H), 7.58 (m, 1H), 8.05–8.11 (m, 2H);
13C NMR (75 MHz, CDCl3): d 28.3, 52.6, 54.0, 68.6, 70.5, 71.0,
76.8, 78.5, 80.6, 81.0, 101.4, 126.1–136.9 (aromatic carbons),
155.5, 167.4, 169.9; MS (ES+): m/z 566.19 [M+Na]+. Anal. Calcd
for C28H33NO10: C, 61.87; H, 6.12; N, 2.58. Found: C, 62.08; H,
6.43; N, 2.39. Compound 5: Rf = 0.60 (EtOAc–hexane 2:3); 1H
NMR (300 MHz, CDCl3): d 1.47 (s, 9H), 3.54 (s, 3H), 3.73 (ddd, 1H,
J = 4.0, 10.0, 14.0 Hz), 3.78 (q, 1H, J = 10.0 Hz), 3.88 (dd, 1H,
J = 9.2, 10.0 Hz), 4.27 (br d, 1H, J = 10.0 Hz), 4.44 (dd, 1H, J = 3.9,
9.8 Hz), 4.8 (br d, 1H, J = 9.6 Hz), 5.5 (s, 1H), 5.57 (d, 1H,
J = 9.8 Hz), 5.65 (d, 1H, J = 9.8 Hz), 5.77 (t, 1H, J = 9.5 Hz), 7.29–
7.43 (m, 6H), 7.44–7.54 (m, 4H), 7.62 (m, 1H), 7.92 (m, 2H),
8.05–8.11 (m, 2H); MS (ES+): m/z 670.21 [M+Na]+. Anal. Calcd for
4.2. (20R)-Methyl 20(t-butoxycarbonylamino)-20-(4,6-O-benzy
lidene-b-D-glucopyranosyl)-acetate (3)
Compound
2
(0.070 g, 0.20 mmol) was dissolved in DMF
L, 1.0 mmol) and a
(2.0 mL). To this mixture, PhCH(OMe)2 (150
l
catalytic amount of toluenesulfonic acid were added. The reaction
mixture was stirred at room temperature for 2 days. After comple-
tion of the reaction, the reaction mixture was poured into a dilute
solution of NaHCO3 (5.0 mL) and extracted with EtOAc
(2 ꢀ 10.0 mL) and then the solvent was removed with a rotovap.
The crude product was subjected to flash column chromatography
using hexanes and EtOAc (3:2, v/v) as an eluant to afford the pure
product 3 (0.085 g, 97%) as a thick liquid. Rf = 0.20 (EtOAc–hexane
C35H37NO11: C, 64.91; H, 5.76; N, 2.16. Found: C, 65.18; H, 6.10;
N, 2.50.
2:3); ½a 2D5
ꢁ
ꢂ44.0 (c 1.0, CHCl3); 1H NMR (300 MHz, MeOH-d4): d
4.4. (20R)-Methyl 20-(t-butoxycarbonylamino)-20-(2-O-methoxy
methyl-3-O-benzoyl-4,6-O-benzylidene-b-D-glucopyranosyl)-
acetate (6)
1.47 (s, 9H), 3.40 (dd, 1H, J = 2.2, 5.6 Hz), 3.46 (dd, 1H, J = 4.6,
9.2 Hz), 3.57–3.67 (m, 2H), 3.67–3.73 (m, 2H), 3.75 (s, 3H), 4.29
(dd, 1H, J = 4.5, 10.1 Hz), 4.68 (br d, 1H, J = 5.6 Hz), 5.56 (s, 1H),
6.91 (d, 1H, J = 9.0 Hz), 7.33–7.38 (m, 3H), 7.48–7.53 (m, 2H); 13C
NMR (75 MHz, CDCl3): d 28.3 (ꢀ3), 52.6, 54.0, 68.6, 70.8, 71.2,
74.8, 80.6 (ꢀ2), 81.1, 101.8, 126.3–137.0 (aromatic carbons),
155.5, 169.9; MS (ES+): m/z 462.26 [M+Na]+. Anal. Calcd for
Methoxymethyl chloride (118.0 lL, 1.55 mmol) was added to a
solution of 4 (0.120 g, 0.22 mmol) in diisopropylethylamine (neat,
3.0 mL). The reaction mixture was stirred at room temperature for
24 h and then water (10.0 mL) was added. The reaction mixture
was extracted with CH2Cl2 (3 ꢀ 10 mL). The combined organic
extracts were washed with saturated NH4Cl solution (5.0 mL) and
C21H29NO9: C, 57.39; H, 6.65; N, 3.19. Found: C, 57.15; H, 6.29;
N, 3.35.

D. Mondal, F. Schweizer / Carbohydrate Research 345 (2010) 1533–1540
1537
evaporated in vacuo. Flash chromatography on silica gel with hex-
2:3); ½a 2D5
ꢁ
ꢂ74.0 (c 0.3, CHCl3); 1H NMR (300 MHz, CDCl3): d 1.47
ane–EtOAc (4:1, v/v) afforded 6 (0.110 g, 85%) as an oil. Rf = 0.50
(2s, 9H), 3.50 (s, 3H), 3.66 (m, 1H), 3.76 (m, 1H), 3.81 (s, 3H),
3.95 (dd, 1H, J = 1.9, 9.7 Hz), 4.24 (dd, 1H, J = 1.9, 9.7 Hz), 4.44
(dd, 1H, J = 4.6, 10.4 Hz), 4.66 (dd, 1H, J = 1.9, 10.4 Hz), 4.76–4.88
(m, 3H), 5.42 (br d, 1H, J = 10.0 Hz), 5.53 (s, 1H), 7.32–7.40 (m,
3H), 7.46–7.52 (m, 2H); 13C NMR (75 MHz, CDCl3): d 28.3 (ꢀ3),
52.7, 54.1, 56.9, 69.0, 73.3, 77.1, 80.3, 82.1, 83.7, 97.0, 101.8,
126.4–136.2 (aromatic carbons), 155.1, 169.2, 197.8; MS (ES+):
m/z 504.22 [M+Na]+. Anal. Calcd for C23H31NO10: C, 57.37; H,
6.49; N, 2.91. Found: C, 57.53; H, 6.72; N, 2.69. Compound 10:
(EtOAc–hexane 2:3);
½
a 2D5
ꢁ
ꢂ60.4 (c 1.0, CHCl3); 1H NMR
(300 MHz, CDCl3): d 1.48 (s, 9H), 3.22 (s, 3H), 3.57–3.72 (m, 3H),
3.81 (dd, 1H, J = 1.9, 9.9 Hz), 3.82 (s, 3H), 4.19 (dd, 1H, J = 9.4,
10.1 Hz), 4.36 (dd, 1H, J = 4.3, 10.0 Hz), 4.76 (s, 2H), 4.80 (br d,
1H, J = 9.6 Hz), 5.40 (s, 1H), 5.50 (br d, 1H, J = 9.6 Hz), 5.57 (t, 1H,
J = 9.0 Hz), 7.26–7.30 (m, 3H), 7.34–7.39 (m, 2H), 7.41–7.48 (m,
2H), 7.55 (m, 1H), 8.07–8.12 (m, 2H); 13C NMR (75 MHz, CDCl3):
d 28.3 (ꢀ3), 52.6, 53.6, 56.5, 68.6, 70.8, 74.9, 76.6, 78.9, 80.3,
81.4, 98.3, 101.4, 126.1–136.9 (aromatic carbons), 155.3, 165.6,
169.6; MS (ES+): m/z 610.17 [M+Na]+. Anal. Calcd for
Rf = 0.45 (EtOAc–hexane 2:3); ½a D25
ꢁ
+16.0 (c 1.8, CHCl3); 1H NMR
(300 MHz, CDCl3): d 1.47 (2s, 9H), 3.46 (s, 3H), 3.48 (br d, 1H,
J = 2.4 Hz), 3.65 (m, 1H), 3.78 (2s, 3H), 3.95 (br d, 1H, J = 9.7 Hz),
4.20–4.40 (m, 2H), 4.65–4.76 (m, 2H), 4.80–4.84 (m, 2H), 5.18
(dd, 1H, J = 10.7, 13.3 Hz), 5.53 (s, 1H), 7.32–7.36 (m, 3H), 7.46–
7.52 (m, 2H); 13C NMR (75 MHz, CDCl3): d 28.2 (ꢀ3), 52.7, 53.1,
56.2, 68.6, 70.1, 73.0, 78.4, 80.3, 81.8, 97.1, 101.8, 126.4–136.2
(aromatic carbons), 155.8, 170.5, 197.8; MS (ES+): m/z 504.11
[M+Na]+. Anal. Calcd for C23H31NO10: C, 57.37; H, 6.49; N, 2.91.
Found: C, 57.01; H, 6.68; N, 3.22.
C30H37NO11: C, 61.32; H, 6.35; N, 2.38. Found: C, 61.07; H, 6.29;
N, 2.70.
4.5. (20R)-Methyl 20-t-butoxycarbonylamino)-20-(2-O-methoxy
methyl-4,6-O-benzylidene-b-
(20S)-methyl 20-(t-butoxycarbonylamino)-20-(2-O-methoxy
methyl-4,6-O-benzylidene-b- -glucopyranosyl)-acetate (8)
D-glucopyranosyl)-acetate (7) and
D
To a solution of 6 (0.050 g, 0.085 mmol) in methanol (1.0 mL)
was added 1.7 mL (2.0 equiv) of a freshly prepared methanol solu-
tion of sodium methoxide (0.1 M). The solution was stirred at room
temperature for 3 h and neutralized with formic acid. After filtra-
tion and concentration, the resulting syrup was purified by flash
chromatography on silica gel, eluting with hexanes–EtOAc 4:1, to
give 7 (30 mg, 72%) and with hexane–EtOAc 3:1, to give 8
(10 mg, 24%) as a colorless liquid. Compound 7: Rf = 0.40 (EtOAc–
4.7. (20R)-Methyl 20-(t-butoxycarbonylamino)-20-(3-amino-3-
deoxy-2-O-methoxymethyl-4,6-O-benzylidene-b-
D-allopyranosyl)-
acetate (13) and (20S)-methyl 20-(t-butoxycarbonylamino)-20-(3-
amino-3-deoxy-2-O-methoxymethyl-4,6-O-benzylidene-b-D-
allopyranosyl)-acetate (14)
A mixture of the ketone 9 or 10 (50 mg, 0.10 mmol), benzyl
amine (11.0 L, 0.10 mmol), and titanium(IV) isopropoxide
(38 L, 0.13 mmol) was stirred at room temperature in a round-
hexane 2:3); ½a 2D5
ꢁ
ꢂ12.0 (c 0.2, CHCl3); 1H NMR (300 MHz, CDCl3):
l
d 1.47 (s, 9H), 3.39 (m, 1H), 3.44 (m, 1H), 3.48 (s, 3H), 3.64–3.76 (m,
4H), 3.78 (s, 3H), 4.32 (dd, 1H, J = 4.4, 10.0 Hz), 4.66 (br s, 1H), 4.74
(br d, 1H, J = 10.1 Hz), 4.82 (s, 1H), 4.87 (m, 1H), 5.43 (br d, 1H,
J = 9.1 Hz), 5.53 (s, 1H), 7.29–7.40 (m, 3H), 7.46–7.52 (m, 2H); 13C
NMR (75 MHz, CDCl3): d 28.3, 52.5, 53.5, 56.3, 68.6, 70.6, 73.5,
77.2, 80.0, 80.3, 82.0, 98.2, 101.9, 126.4, ꢂ136.9 (aromatic carbons),
155.3, 169.6; MS (ES+): m/z 506.21 [M+Na]+. Anal. Calcd for
l
bottomed flask. After 2 h, the viscous solution was diluted with
dry methanol (2.0 mL). Sodium cyanoborohydride (5.0 mg,
0.07 mmol) was added, and the solution was stirred for 20 h. Water
(2.0 mL) was added with stirring, and the resulting inorganic pre-
cipitate was filtered and washed with methanol. The filtrate was
then concentrated in vacuo. The crude product was dissolved in
ethyl acetate, filtered to remove the remaining inorganic solids,
and concentrated in vacuo. The obtained products 11 and 12 (11,
48.0 mg, 78%, 12, 45 mg, 80%) were purified by flash chromatogra-
phy using with hexane–EtOAc 5:1. Both compounds were directly
used for catalytic hydrogenation. Compound 11 or 12 (18.0 mg,
0.032 mmol) was dissolved in MeOH (5.0 mL). Ten percentages of
Pd–C (20 mg) were added and the mixture was hydrogenated for
6 h at atmospheric pressure. The mixture was filtered and concen-
trated. The crude residue was purified with flash silica gel column
chromatography (hexane–EtOAc 1:1) to afford 13 or 14 (13,
14.0 mg, 90%; 14, 18 mg, 93%) as a syrup. Compound 13: Rf = 0.20
C
23H33NO10: C, 57.13; H, 6.88; N, 2.90. Found: C, 57.48; H, 6.67;
N, 3.18. Compound 8: Rf = 0.45 (EtOAc–hexane 2:3); ½a D25
ꢂ12.0
ꢁ
(c 0.2, CHCl3); 1H NMR (300 MHz, CDCl3): d 1.47 (s, 9H), 3.32 (t,
1H, J = 8.7 Hz), 3.46 (s, 3H), 3.48 (m, 2H), 3.66 (t, 1H, J = 9.8 Hz),
3.78 (s, 3H), 3.83 (dd, 1H, J = 8.7, 9.0 Hz), 3.97 (dd, 1H, J = 1.6,
9.7 Hz), 4.26 (dd, 1H, J = 4.4, 10.0 Hz), 4.68 (d, 1H, J = 7.4 Hz), 4.76
(br d, 2H, J = 10.1 Hz), 4.80 (d, 1H, J = 7.6 Hz), 5.17 (br d, 1H,
J = 10.1 Hz), 5.53 (s, 1H), 7.32–7.36 (m, 3H), 7.46–7.52 (m, 2H);
13C NMR (75 MHz, CDCl3): d 28.3, 52.7, 53.1, 56.3, 68.6, 70.1,
73.3, 78.5, 80.3, 80.5, 81.9, 98.7, 101.9, 126.4–136.9 (aromatic car-
bons), 155.8, 171.0; MS (ES+): m/z 506.13 [M+Na]+. Anal. Calcd for
C23H33NO10: C, 57.13; H, 6.88; N, 2.90. Found: C, 57.55; H, 7.11; N,
(EtOAc–hexane 2:3);
½
a 2D5
ꢁ
ꢂ49.0 (c 1.0, CHCl3); 1H NMR
2.65.
(500 MHz, CDCl3): d 1.45 (s, 9H, –C(CH3)3), 3.34 (dd, 1H, J = 2.9,
9.8H-2), 3.43 (s, 3H, –CH2OCH3), 3.48 (dd, 1H, J = 2.9, 9.2 Hz, H-
4), 3.56 (t, 1H, J = 10.0 Hz, H-6a), 3.75 (s, 3H, –CO2Me), 3.90 (m,
1H, H-3), 4.14 (ddd, 1H, J = 5.0, 10.2, 15.2 Hz, H-6b), 4.29 (dd, 1H,
J = 5.1, 10.3 Hz, H-5), 4.65 (d, 1H, J = 9.6 Hz, H-1), 4.76 (ABq, 2H,
J = 7.0 Hz, –OCH2O–), 4.79 (d, 1H, J = 9.6 Hz, CHNHBoc), 5.46 (br
d, 1H, J = 9.6 Hz, NH), 5.48 (s, 1H, CHPh), 7.30–7.39 (m, 3H, Ph),
7.42–7.49 (m, 2H, Ph); 13C NMR (75 MHz, CDCl3): d 28.3 (ꢀ3),
50.0, 52.2, 53.8, 58.2, 64.9, 69.2, 74.3, 75.8, 79.3, 80.0, 96.5, 101.9,
126.2–137.3 (aromatic carbons), 155.3, 170.0; MS (ES+): m/z
483.25 [M+H]+. Anal. Calcd for C23H34N2O9: C, 57.25; H, 7.10; N,
5.81. Found: C, 57.55; H, 7.36; N, 5.94. Compound 14: Rf = 0.25
4.6. (20R)-Methyl 20-(t-butoxycarbonylamino)-20-(2-O-methoxy
methyl-4,6-O-benzylidene-b-
D-gluco-3-ulo-pyranosyl)-acetate (9)
and (20S)-methyl 20-(t-butoxycarbonylamino)-20-(2-O-methoxy
methyl-4,6-O-benzylidene-b-D-gluco-3-ulo-pyranosyl)-acetate
(10)
To a stirred solution of alcohol 7 or 8 (110 mg, 0.23 mmol) and
ground 4 Å molecular sieves (110 mg) in anhyd CH2Cl2 (3.0 mL)
was added PCC (198 mg, 0.92 mmol). The mixture was stirred for
14–16 h (TLC monitoring), diluted with CH2Cl2–EtOAc mixture
(1:1, 10 mL), and poured onto a Celite pad. The solvent was con-
centrated with a rotovap. Elution with the hexane–EtOAc 4:1 sys-
tem gave pure ketone 9 or 10 (9, 102 mg, 93%; 10, 105 mg, 95%) as
a colorless amorphous solid. Compound 9: Rf = 0.40 (EtOAc–hexane
(EtOAc–hexane 2:3); ½a D25
ꢁ
+5.0 (c 0.2, CHCl3); 1H NMR (500 MHz,
CDCl3): d 1.47 (s, 9H, –C(CH3)3), 3.39 (s, 3H, –CH2OCH3), 3.52 (dd,
1H, J = 3.0, 9.2 Hz, H-4), 3.59 (m, 1H, H-6a), 3.65 (dd, 1H, J = 3.0,
9.7 Hz, H-2), 3.77 (s, 3H, –CO2Me), 3.92 (m, 1H, H-3), 4.19 (ddd,
1H, J = 5.1, 10, 14.6 Hz, H-6b), 4.25 (dd, 1H, J = 5.1, 10.0 Hz, H-5),

1538
D. Mondal, F. Schweizer / Carbohydrate Research 345 (2010) 1533–1540
4.46 (br d, 1H, J = 10.3 Hz, H-1), 4.62 (br d, 1H, J = 10.1 Hz,
CHNHBoc), 4.70 (ABq, 2H, J = 7.0 Hz, –OCH2O–), 5.13 (br d, 1H,
J = 10.1 Hz, NH), 5.50 (s, 1H, CHPh), 7.34–7.39 (m, 3H, Ph), 7.46–
7.49 (m, 2H, Ph); 13C NMR (75 MHz, CDCl3): d 28.7 (ꢀ3), 49.9,
52.5, 53.3, 56.2, 64.7, 69.2, 73.7, 73.8, 79.3, 80.2, 96.5, 101.9,
126.2–137.3 (aromatic carbons), 156.0, 171.7; MS (ES+): m/z
483.26 [M+H]+. Anal. Calcd for C23H34N2O9: C, 57.25; H, 7.10; N,
5.81. Found: C, 56.87; H, 6.73; N, 6.13.
flash column chromatography (methanol–EtOAc 1:9) to afford
compound 17/18 (17, 45 mg, 92%; 18, 48 mg, 95%) as a colorless
thick liquid. Compound 17: Rf = 0.20 (EtOAc); ½a D25
ꢂ39.0 (c 0.2,
ꢁ
CHCl3); 1H NMR (300 MHz, MeOH-d4): d 3.40–3.53 (m, 3H), 3.73
(s, 3H), 3.75 (d, 1H, J = 1.9 Hz), 3.86 (d, 1H, J = 9.9 Hz), 3.92 (dd,
1H, J = 3.9, 10.5 Hz), 4.21 (dd, 1H, J = 6.6, 6.8 Hz), 4.34–4.47 (m,
3H), 4.73 (m, 1H), 5.13 (s, 2H), 7.30–7.46 (m, 9H), 7.64–7.70 (d,
2H, J = 7.6 Hz), 7.78 (d, 2H, J = 7.6 Hz); 13C NMR (75 MHz, MeOD):
d 48.4, 52.7, 55.9, 57.0, 63.7, 67.7, 67.9, 68.0, 68.2, 78.2, 78.3,
120.9–145.3 (aromatic carbons), 156.3, 158.7, 171.7; MS (ES+):
m/z 629.10 [M+Na]+. Anal. Calcd for C32H34N2O10: C, 63.36; H,
5.65; N, 4.62. Found: C, 63.70; H, 5.88; N, 4.95. Compound 18:
4.8. (20R)-Methyl 20-(t-butoxycarbonylamino)-20-[3-benzyloxy
carbonylamino-3-deoxy-2-O-methoxymethyl-4,6-O-benzylidene-
D
-allopyranosyl]-acetate (15) and (20S)-methyl 20-(t-butoxycar
Rf = 0.30 (EtOAc); ½a D25
ꢁ
+18.0 (c 0.3, CHCl3); 1H NMR (300 MHz,
b-
bonylamino)-20-[3-benzyloxycarbonylamino-3-deoxy-2-O-meth
oxymethyl-4,6-O-benzylidene-b- -allopyranosyl]-acetate (16)
CDCl3): d 2.15 (br s, 1H), 3.23 (m, 1H), 3.47–3.53 (m, 2H), 3.65
(dd, 1H, J = 3.9, 12.0 Hz), 3.77 (s, 3H), 3.78–3.82 (m, 2H), 4.21 (t,
1H, J = 6.1 Hz), 4.28 (m, 1H), 4.41 (br d, 1H, J = 4.5 Hz), 4.60 (dd,
1H, J = 6.0, 10.9 Hz), 4.63 (dd, 1H, J = 2.2, 8.1 Hz), 4.72 (dd, 1H,
J = 6.2, 10.9 Hz), 5.13 (ABq, 2H, J = 12.0 Hz), 5.17 (br s, 1H), 5.31
(br d, 1H, J = 2.9 Hz), 5.68 (d, 1H, J = 8.1 Hz), 7.30–7.46 (m, 9H),
7.59 (d, 2H, J = 7.6 Hz), 7.78 (d, 2H, J = 7.6 Hz); 13C NMR (75 MHz,
CDCl3): d 47.3, 53.0, 54.2, 55.4, 62.7, 65.4, 67.0, 68.0, 69.5, 75.7,
76.2, 119.9–143.6 (aromatic carbons), 157.7, 160.0, 170.1; MS
(ES+): m/z 629.20 [M+Na]+. Anal. Calcd for C32H34N2O10: C, 63.36;
H, 5.65; N, 4.62. Found: C, 62.98; H, 6.02; N, 4.27.
D
Na2CO3 (44 mg, 0.416 mmol) followed by benzyl chloroformate
(58 L, 0.416 mmol) was added to a solution of 13 or 14 (50 mg,
l
0.104 mmol) in a mixture of acetone and water (3 mL, 10:1). The
reaction mixture was stirred at room temperature for 12 h and
concentrated in vacuo. The crude residue was then extracted with
EtOAc (2 ꢀ 10 mL). The extract was dried over anhyd Na2SO4, fil-
tered, and evaporated. The crude product was purified by flash col-
umn chromatography on silica gel (hexane–EtOAc 3:1) affording
15/16 (15, 62 mg, 96%; 16, 64 mg, 98%) as an oil. Compound 15:
Rf = 0.40 (EtOAc–hexane 2:3); ½a D25
ꢁ
ꢂ26.0 (c 1.1, CHCl3); 1H NMR
(500 MHz, CDCl3): d 1.46 (s, 9H), 3.39 (s, 3H), 3.54–3.65 (m, 3H),
3.70 (dd, 1H, J = 1.8, 10.5 Hz), 3.77 (s, 3H), 4.10 (dd, 1H, J = 4.5,
10.9 Hz), 4.31 (dd, 1H, J = 3.8, 9.5 Hz), 4.64 (d, 1H, J = 6.9 Hz),
4.70–4.80 (m, 2H), 4.83 (d, 1H, J = 7.0 Hz), 5.07 (m, 1H), 5.12
(ABq, 2H, J = 12.0 Hz), 5.47 (br s, 1H), 5.51 (s, 1H), 7.28–7.36 (m,
8H), 7.40–7.44 (m, 2H); 13C NMR (75 MHz, CDCl3): d 28.3 (ꢀ3),
49.9, 52.4, 53.9, 56.5, 67.0 (ꢀ2), 68.9, 70.3, 76.9, 77.5, 80.4, 95.3,
101.4, 126.1–137.0 (aromatic carbons), 155.3, 156.7, 169.5; MS
(ES+): m/z 639.23 [M+Na]+. Anal. Calcd for C31H40N2O11: C, 60.38;
H, 6.54; N, 4.54. Found: C, 60.07; H, 6.76; N, 4.19. Compound 16:
4.10. (20R)-Methyl 20-(9H-fluoren-9-ylmethoxycarbonylamino)-20-
[3-t-butoxycarbonylamino-3-deoxy-b-D-allopyranosyl]-acetate
(19) and (20S)-methyl 20-(9H-fluoren-9-ylmethoxycarbonylamino)-
20-[3-t-butoxycarbonylamino-3-deoxy-b-
D-allopyranosyl]-acetate
(20)
Hydrogenation of 17/18 (1.0 mmol) in 10 mL of EtOAc contain-
ing 0.5 mL of methanol in the presence of Pd–C was accomplished
in 6 h. After removal of the catalyst, the resulting solution was con-
centrated under vacuum. The amine residue was dissolved in
methanol with stirring and reacted with BOC-anhydride
(1.5 equiv) and triethylamine (2.0 equiv). The resulting mixture
was stirred at room temperature for 3 h. Water is then added
and the aqueous layer was extracted with EtOAc (4 ꢀ 10 mL). The
combined organic layers were dried (sodium sulfate) and concen-
trated in vacuo. The resulting residue was purified by flash chro-
matography (methanol–EtOAc 1:8) to provide 19/20 (19 g, 96%;
Rf = 0.45 (EtOAc–hexane 2:3); ½a D25
ꢁ
+20.0 (c 0.4, CHCl3); 1H NMR
(500 MHz, CDCl3): d 1.47 (s, 9H), 3.33 (s, 3H), 3.52–3.62 (m, 3H),
3.77 (s, 3H), 3.82 (dd, 1H, J = 3.9, 10.1 Hz), 4.02 (br d, 1H,
J = 10.1 Hz), 4.24 (dd, 1H, J = 3.9, 10.0 Hz), 4.55 (d, 1H, J = 7.1 Hz),
4.67 (d, 1H, J = 10.1 Hz), 4.77–4.86 (m, 2H), 5.07 (m, 1H), 5.12
(ABq, 2H, J = 12.0 Hz), 5.19 (br s, 1H), 5.51 (s, 1H), 7.18–7.36 (m,
8H), 7.40–7.44 (m, 2H); 13C NMR (75 MHz, CDCl3): d 28.3 (ꢀ3),
49.9, 52.7, 53.3, 56.4, 66.7, 67.0, 68.9, 69.4, 75.3, 76.9, 80.4, 95.3,
101.4, 128.1–137.0 (aromatic carbons), 155.9, 156.7, 171.3; MS
(ES+): m/z 639.19 [M+Na]+. Anal. Calcd for C31H40N2O11: C, 60.38;
H, 6.54; N, 4.54. Found: C, 60.66; H, 6.34; N, 4.87.
20, 93%) as a colorless oil. Compound 19: Rf = 0.15 (EtOAc); ½a D25
ꢁ
ꢂ63.0 (c 0.1, CHCl3); 1H NMR (300 MHz, CDCl3): d 1.47 (s, 9H),
3.10 (m, 1H), 3.50 (m, 1H), 3.72 (m, 2H), 3.76 (s, 3H), 3.80–3.90
(m, 3H), 4.18–4.23 (m, 2H), 4.24 (dd, 1H, J = 3.3, 3.6 Hz, H3),
4.40–4.50 (m, 3H), 4.76 (br d, 1H, J = 7.9 Hz), 5.12 (s, 1H), 5.85
(br d, 1H, J = 7.8 Hz), 7.30–7.46 (m, 4H), 7.59 (m, 2H), 7.75–7.77
(d, 2H, J = 7.6 Hz); 13C NMR (75 MHz, CDCl3): d 28.2 (ꢀ3), 47.3,
52.6, 54.9, 55.2, 62.8, 67.2, 67.3, 67.7, 67.8, 77.2, 81.6, 120.0–
143.6 (aromatic carbons), 157.7, 169.8, 169.8; MS (ES+): m/z
595.21 [M+Na]+. Anal. Calcd for C29H36N2O10: C, 60.83; H, 6.34;
N, 4.89. Found: C, 61.06; H, 5.97; N, 5.21. Compound 20: Rf = 0.25
4.9. (20R)-Methyl 20-(9H-fluoren-9-ylmethoxycarbonylamino)-20-
[3-benzyloxycarbonylamino-3-deoxy-b-D-allopyranosyl]-acetate
(17) and (20S)-methyl 20-(9H-fluoren-9-ylmethoxycarbony
lamino)-20-[3-benzyloxycarbonylamino-3-deoxy-b-
D-
allopyranosyl]-acetate (18)
(EtOAc); ½a 2D5
ꢁ
+30.0 (c 0.15, CHCl3); 1H NMR (300 MHz, CDCl3): d
To a solution of 15 or 16 (0.405 g, 0.62 mmol) in methanol
(10 mL) was added HCl (1 N, 5 drops) and the reaction mixture
was stirred at room temperature for 12 h. The reaction mixture
was diluted with saturated NaHCO3 solution (30 mL) and extracted
with EtOAc (3 ꢀ 30 mL). After removal of solvent, the residue was
dissolved in aqueous acetone (3.0 mL, 1:1) and treated with 9-flu-
orenylmethyl pentafluorophenyl carbonate (91 mg, 0.24 mmol)
and sodium bicarbonate (31 mg, 0.37 mmol) for 4 h at room tem-
perature. Water (10.0 mL) was added and the aqueous layer was
extracted with EtOAc (6 ꢀ 10 mL). Finally, the solvent was dried
(Na2SO4) and concentrated. The crude product was purified by
1.47 (s, 9H), 3.23 (m, 1H), 3.42–3.53 (m, 2H), 3.62 (dd, 1H, J = 4.9,
12.0 Hz), 3.78 (s, 3H), 3.80–3.84 (m, 3H), 4.20 (dd, 1H, J = 3.7,
4.3 Hz, H3), 4.22 (m, 1H), 4.43 (d, 1H, J = 4.8 Hz), 4.47 (dd, 1H,
J = 6.0, 10.9 Hz), 4.62 (dd, 1H, J = 2.2, 8.1 Hz), 4.73 (dd, 1H, J = 6.2,
10.9 Hz), 5.07 (br d, 1H, J = 2.0 Hz), 5.56 (br s, 1H), 5.69 (d, 1H,
J = 8.2 Hz), 7.30–7.46 (m, 4H), 7.59 (d, 2H, J = 7.6 Hz), 7.78 (d, 2H,
J = 7.6 Hz); 13C NMR (75 MHz, CDCl3): d 28.2 (ꢀ3), 47.3, 53.0,
54.2, 55.2, 63.3, 65.2, 67.0, 70.8, 75.7, 76.2, 81.5, 120.0–143.6 (aro-
matic carbons), 157.7, 160.0, 170.0; MS (ES+): m/z 595.16 [M+Na]+.
Anal. Calcd for C29H36N2O10: C, 60.83; H, 6.34; N, 4.89. Found: C,
60.98; H, 6.47; N, 5.21.

D. Mondal, F. Schweizer / Carbohydrate Research 345 (2010) 1533–1540
1539
4.11. (20R)-Methyl 20-(9H-fluoren-9-ylmethoxycarbonylamino)-
20-[3-t-butoxycarbonylamino-3-deoxy-6-O-triphenylmethyl-b-
(75 MHz, MeOH-d4): d 28.9 (ꢀ3), 46.4, 56.4, 56.6, 65.3, 67.7, 68.1,
68.3, 76.8, 77.0, 80.9, 87.9, 121.0–145.7 (aromatic carbons),
159.8, 160.3, 171.8; MS (ES+): m/z 823.41 [M+Na]+. Anal. Calcd
for C47H48N2O10: C, 70.48; H, 6.04; N, 3.50. Found: C, 70.72; H,
6.36; N, 3.17.
D
-allopyranosyl]-acetate (21) and (20S)-methyl 20-(9H-fluoren-9-
ylmethoxycarbonylamino)-20-[3-t-butoxycarbonylamino-3-
deoxy-6-O-triphenylmethyl-b- -allopyranosyl]-acetate (22)
D
A solution of 19/20 (0.1 g) in dry pyridine (3 mL) was cooled to
0 °C under argon. Triphenylmethyl chloride (10 equiv) was added,
and then the mixture was stirred at room temperature overnight.
The reaction mixture was diluted with CH2Cl2 (10 mL), washed
with saturated NaHCO3 solution (5 mL), and dried over MgSO4,
and the solvent was removed in vacuo. The residue was purified
by column chromatography on silica gel (hexane–EtOAc) 1:3 to af-
ford 21/22 (21, 91%; 22, 90%). Compound 21: Rf = 0.40 (EtOAc–hex-
4.13. (20R)-Methyl 20-(9H-fluoren-9-ylmethoxycarbonylamino)-
20-[3-(N,N0-di-tert-butoxycarbonyl-guanidine)-3-deoxy-b-
D-
allopyranosyl]-acetate (25) and (20S)-methyl 20-(9H-fluoren-9-
ylmethoxycarbonylamino)-20-[3-(N,N0-di-tert-butoxycarbonyl-
guanidine)-3-deoxy-b-D-allopyranosyl]-acetate (26)
Hydrogenation of 17/18 (0.607 g, 1.0 mmol) in 10 mL of EtOAc
and few drops of methanol in the presence of Pd–C was accom-
plished in 6 h. After removal of the catalyst, the resulting solution
of amine was concentrated under vacuum. To a solution of amine
(0.095 g, 0.20 mmol) in dioxane and water (3:1, 2 mL) was added
N,N-diBoc-N00-triflylguanidine (157 mg, 0.40 mmol, 2 equiv). After
ane 2:3); ½a 2D5
ꢁ
ꢂ35.0 (c 0.2, CHCl3); 1H NMR (300 MHz, CDCl3): d
1.46 (s, 9H), 3.09–3.20 (m, 2H), 3.32–3.46 (m, 3H), 3.73 (s, 3H),
3.83–3.90 (m, 2H), 4.18–4.28 (m, 2H), 4.32–4.48 (m, 3H), 4.80 (br
d, 1H, J = 8.7 Hz), 5.04 (br s, 1H), 5.73 (br d, 1H, J = 8.2 Hz), 7.28–
7.45 (m, 19H), 7.59 (dd, 2H, J = 7.6, 10.0 Hz), 7.74 (d, 2H,
J = 7.6 Hz); 13C NMR (75 MHz, CDCl3): d 28.2 (ꢀ3), 47.2, 52.1,
54.9, 55.4, 63.1, 64.3, 67.9, 71.0, 75.7, 76.0, 79.3, 86.1, 120.0–
146.9 (aromatic carbons), 154.9, 161.8, 169.9; MS (ES+): m/z
837.39 [M+Na]+. Anal. Calcd for C48H50N2O10: C, 70.74; H, 6.18;
N, 3.44. Found: C, 71.13; H, 6.01; N, 3.78. Compound 22: Rf = 0.50
5 min, NEt3 (56 lL, 0.40 mmol, 2 equiv) was added at room tem-
perature. After 10 h, the dichloromethane was removed under re-
duced pressure. The remaining residue product was purified by
flash column chromatography (hexane–EtOAc 1:9) on silica gel to
give 25/26 (25, 89%; 26, 94%) as an oil. Compound 25: Rf = 0.20
(EtOAc); ½a 2D5
ꢁ
ꢂ49.0 (c 0.4, CHCl3); 1H NMR (300 MHz, CDCl3): d
(EtOAc–hexane 2:3);
½
a 2D5
ꢁ
+15.0 (c 0.2, CHCl3); 1H NMR
1.46 (s, 9H), 1.53 (s, 9H), 2.60 (br s, 2H), 3.54 (m, 1H), 3.75 (m,
1H), 3.77 (s, 3H), 3.83–3.90 (m, 4H), 4.23 (dd, 1H, J = 7.0, 6.9 Hz),
4.01 (br s, 1H), 4.36–4.47 (m, 2H), 4.66 (br s, 1H), 4.80 (br d, 1H,
J = 8.6 Hz), 5.92 (br d, 1H, J = 8.6 Hz), 7.30–7.42 (m, 4H), 7.59 (d,
2H, J = 7.6 Hz), 7.78 (d, 2H, J = 7.6 Hz), 8.96 (br d, 1H, J = 2.8 Hz),
11.4 (s, 1H); 13C NMR (75 MHz, CDCl3): d 28.0 (ꢀ3), 28.1 (ꢀ3),
47.1, 52.6, 54.9, 56.5, 62.6, 67.3, 67.9, 68.5, 75.8, 76.9, 80.1, 84.1,
120.0–143.8 (aromatic carbons), 152.8, 156.2, 159.1, 161.7,
170.1; MS (ES+): m/z 737.14 [M+Na]+. Anal. Calcd for
(300 MHz, CDCl3): d 1.47 (s, 9H), 3.23 (m, 1H), 3.30–3.45 (m, 3H),
3.48–3.62 (m, 2H), 3.76 (s, 3H), 3.85–3.90 (m, 1H), 4.18–4.28 (m,
2H), 4.46 (dd, 2H, J = 6.0, 10.7 Hz), 4.61–4.72 (m, 2H), 5.00 (m,
1H), 5.63 (d, 1H, J = 8.2 Hz), 7.18–7.34 (m, 10H), 7.38–7.45 (m,
9H), 7.59 (dd, 2H, J = 7.6, 10.0 Hz), 7.74 (d, 2H, J = 7.6 Hz); 13C
NMR (75 MHz, CDCl3): d 28.2, 47.3, 53.0, 54.2, 55.2, 63.3, 65.2,
67.0, 71.0, 75.7, 76.0, 81.6, 86.5, 120.0–146.9 (aromatic carbons),
157.7, 163.5, 170.1; MS (ES+): m/z 837.32 [M+Na]+. Anal. Calcd
for C48H50N2O10: C, 70.74; H, 6.18; N, 3.44. Found: C, 70.39; H,
6.56; N, 3.08.
C
35H46N4O12: C, 58.81; H, 6.49; N, 7.84. Found: C, 58.98; H, 6.87;
N, 7.57. Compound 26: Rf = 0.25 (EtOAc); ½a D25
ꢁ
+6.0 (c 0.4, CHCl3);
1H NMR (300 MHz, CDCl3): d 1.47 (s, 9H), 1.53 (s, 9H), 2.40 (br s,
1H), 3.36 (dd, 1H, J = 4.4, 9.9 Hz), 3.49 (m, 1H), 3.58 (dd, 1H,
J = 2.9, 9.9 Hz), 3.68 (br s, 1H), 3.77 (m, 2H), 3.80 (s, 3H), 3.90
(dd, 1H, J = 2.0, 9.9 Hz), 4.00 (br s, 1H), 4.21 (t, 1H, J = 6.5 Hz),
4.47 (dd, 1H, J = 6.0, 10.8 Hz), 4.59 (m, 1H), 4.66 (dd, 1H, J = 6.4,
10.8 Hz), 4.73 (dd, 1H, J = 2.0, 8.3 Hz), 5.70 (br d, 1H, J = 8.3 Hz),
7.30–7.38 (m, 2H), 7.39–7.47 (m, 2H), 7.59 (d, 2H, J = 7.6 Hz),
7.78 (d, 2H, J = 7.6 Hz), 8.91 (br d, 1H, J = 2.8 Hz), 11.45 (s, 1H);
13C NMR (75 MHz, CDCl3): d 28.1 (ꢀ6), 47.3, 53.1, 54.4, 56.4,
63.3, 65.6, 67.1, 71.0, 75.6, 76.6, 80.1, 84.0, 120.0–143.6 (aromatic
carbons), 152.8, 157.7, 159.0, 161.7, 170.0; MS (ES+): m/z 737.37
[M+Na]+. Anal. Calcd for C35H46N4O12: C, 58.81; H, 6.49; N, 7.84.
Found: C, 59.08; H, 6.17; N, 8.22.
4.12. (20R)-20-(9H-Fluoren-9-ylmethoxycarbonylamino)-20-[3-t-
butoxycarbonylamino-3-deoxy-6-O-triphenylmethyl-b-D-allopyr
anosyl]-acetic acid (23) and (20S)-20-(9H-fluoren-9-ylmethoxy
carbonylamino)-20-[3-t-butoxycarbonylamino-3-deoxy-6-O-
triphenylmethyl-b-D-allopyranosyl]-acetic acid (24)
The ester 21/22 (50 mg) was dissolved in aqueous dioxane and
NaOH (4.0 equiv, 1 N) was added at 0 °C. The solution was then
stirred until complete by TLC (usually <1 h). Formic acid was added
until the mixture was neutral and then diluted with EtOAc. The or-
ganic solution was extracted with EtOAc (3 ꢀ 10 mL), dried (so-
dium sulfate), and concentrated in vacuo. The residue was
purified by flash chromatography (methanol–EtOAc 1:19) on SiO2
providing 23/24 (23, 87%; 24, 92%) as a colorless thick oil. Com-
4.14. (20R)-Methyl 20-(9H-fluoren-9-ylmethoxycarbonylamino)-
20-[3-(N,N0-di-tert-butoxycarbonyl-guanidine)-3-deoxy-6-O-
pound 23: Rf = 0.1 (EtOAc); ½a D25
ꢁ
ꢂ56.0 (c 0.5, CHCl3); 1H NMR
(300 MHz, MeOH-d4): d 1.45 (s, 9H), 3.29 (m, 1H), 3.37 (m, 1H),
3.60 (m, 1H), 3.69 (m, 2H, J = 10.1 Hz), 3.70 (m, 1H), 4.12 (m, 1H),
4.21–4.32 (m, 2H), 4.42 (d, 1H, J = 6.9), 4.58 (m, 1H), 7.18–7.26
(m, 5H), 7.32–7.41 (m, 8H), 7.47–7.53 (m, 6H), 7.65 (dd, 2H,
J = 7.8, 10.0 Hz), 7.75 (dd, 2H, J = 4.0, 7.8 Hz); 13C NMR (75 MHz,
CDCl3): d 28.8 (ꢀ3), 46.2, 56.3, 56.7, 65.3, 67.6, 68.2, 68.3, 76.7,
77.3, 80.7, 87.8, 120.9–130.1 (aromatic carbons), 142.5–147.6
(ꢀ7), 159.9, 160.2, 170.9; MS (ES+): m/z 823.29 [M+Na]+. Anal.
Calcd for C47H48N2O10: C, 70.48; H, 6.04; N, 3.50. Found: C,
triphenylmethyl-b-
D
-allopyranosyl]-acetate (27) and (20S)-methyl
20-(9H-fluoren-9-ylmethoxycarbonylamino)-20-[3-(N,N0-di-tert-
butoxycarbonyl-guanidine)-3-deoxy-6-O-triphenylmethyl-b-D-
allopyranosyl]-acetate (28)
A solution of 25 or 26 (50 mg) in pyridine (3 mL) was cooled to
0 °C under argon. Triphenylmethyl chloride (10 equiv) was added,
and then the mixture was stirred at room temperature overnight.
The reaction mixture was diluted with CH2Cl2 (15 mL), washed
with saturated NaHCO3 solution (5 mL), and dried over MgSO4,
and the solvent was removed in vacuo. The residue was purified
by column chromatography on silica gel (EtOAc–hexane 1:1) to af-
ford 27/28 (27, 86%; 28, 88%) as an oil. Compound 27: Rf = 0.45
70.20; H, 6.25; N, 3.85. Compound 24: Rf = 0.10 (EtOAc); ½a D25
ꢁ
+36.0 (c 0.1, CHCl3); 1H NMR (300 MHz, MeOH-d4): d 1.48 (s, 9H),
3.23 (m, 1H), 3.35 (m, 1H), 3.56 (m, 1H), 3.65 (m, 2H), 3.70 (m,
1H), 4.10 (m, 1H), 4.21–4.32 (m, 2H), 4.42 (d, 1H, J = 6.8 Hz), 4.56
(m, 1H), 7.20–7.27 (m, 5H), 7.29–7.38 (m, 8H), 7.45–7.50 (m,
6H), 7.63 (dd, 2H, J = 7.6, 10.6 Hz), 7.76 (t, 2H, J = 7.6); 13C NMR
(EtOAc–hexane 2:3);
(300 MHz, CDCl3): d 1.45 (s, 9H), 1.52 (s, 9H), 2.00 (br s, 2H), 3.06
½
a 2D5
ꢁ
ꢂ42.0 (c 0.5, CHCl3); 1H NMR

1540
D. Mondal, F. Schweizer / Carbohydrate Research 345 (2010) 1533–1540
(s, 1H), 3.38 (d, 2H, J = 4.6 Hz), 3.60 (m, 1H), 3.74 (s, 3H), 3.80 (dd,
1H, J = 2.4, 9.9 Hz), 3.98 (m, 2H), 4.22 (dd, 1H, J = 7.8, 7.9 Hz), 4.34
(dd, 1H, J = 7.6, 10.8 Hz), 4.43 (dd, 1H, J = 7.5, 10.6 Hz), 4.70 (s, 1H),
4.88 (dd, 1H, J = 2.6, 10.0 Hz), 5.80 (br d, 1H, J = 8.9 Hz), 7.20–7.49
(m, 19H), 7.59 (d, 1H, J = 7.9 Hz), 7.74 (d, 2H, J = 7.6 Hz), 8.9 (s, 1H),
11.4 (s 1H); 13C NMR (75 MHz, CDCl3): d 28.0, 28.1, 47.2, 52.1, 52.6,
56.2, 64.0, 67.4, 68.5, 69.9, 74.7, 76.8, 80.3, 84.1, 87.2, 120.0–144.0
(aromatic carbons), 152.9, 156.3, 158.9, 161.9, 170.0; MS (ES+): m/
z 979.38 [M+Na]+. Anal. Calcd for C54H60N4O12: C, 67.77; H, 6.32; N,
5.85. Found: C, 67.93; H, 6.00; N, 6.20. Compound 28: Rf = 0.50
68.3, 71.4, 77.3, 80.7, 85.1, 87.8, 120.9–130.1 (aromatic), 142.5–
147.6 (aromatic), 154.3, 159.0, 160.0, 163.6, 170.1; MS (ES+): m/z
965.36 [M+Na]+. Anal. Calcd for C53H58N4O12: C, 67.50; H, 6.20;
N, 5.94. Found: C, 67.18; H, 6.53; N, 6.32.
Acknowledgments
This work was supported by Natural Sciences and Engineering
Research Council (NSERC) of Canada in the form of a Discovery
Grant and the University of Manitoba.
(EtOAc–hexane 2:3);
½
a 2D5 +28.0 (c 0.4, CHCl3); 1H NMR
ꢁ
(300 MHz, CDCl3): d 1.43 (s, 9H), 1.55 (s, 9H), 3.16–3.28 (m, 2H),
3.36 (br d, 1H, J = 10.1 Hz), 3.48 (dd, 1H, J = 3.9, 10.1 Hz), 3.54 (m,
1H), 3.74 (m, 2H), 3.77 (s, 3H), 3.96 (dd, 1H, J = 2.0, 9.9 Hz), 4.24
(m, 1H), 4.48 (dd, 1H, J = 6.6, 10.8 Hz), 4.56 (dd, 1H, J = 7.0,
10.6 Hz), 4.62 (m, 1H), 4.80 (dd, 1H, J = 2.0, 8.3 Hz), 5.64 (br d,
1H, J = 8.3 Hz), 7.20–7.34 (m, 10H), 7.37–7.48 (m, 9H), 7.59 (m,
2H), 7.76 (d, 2H, J = 7.6 Hz), 8.87 (br s, 1H), 11.50 (s, 1H); 13C
NMR (75 MHz, CDCl3): d 28.1 (ꢀ6), 47.3, 53.1, 54.4, 56.4, 64.1,
65.9, 67.4, 68.2, 69.8, 76.0, 80.0, 84.0, 86.5, 120.0–144.0 (aromatic
carbons), 152.8, 157.7, 159.2, 161.9, 170.0; MS (ES+): m/z 979.41
[M+Na]+. Anal. Calcd for C54H60N4O12: C, 67.77; H, 6.32; N, 5.85.
Found: C, 67.36; H, 6.69; N, 6.16.
Supplementary data
Supplementary data (1H NMR and 13C NMR spectra for com-
pounds 3–10 and 13–24) associated with this article can be found,
in the online version, at doi:10.1016/j.carres.2010.04.017.
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Ester 27 or 28 (50 mg, 0.05 mmol) was dissolved in aqueous
dioxane and NaOH (4.0 equiv, 1 N) was added at 0 °C. The solution
was then stirred until complete by TLC (usually <1 h). Formic acid
was added until the mixture is neutral and then diluted with
EtOAc. The organic solution was extracted with EtOAc
(3 ꢀ 10 mL), dried (sodium sulfate), and concentrated in vacuo.
The residue was purified by flash chromatography (methanol–
EtOAc 1:19) on SiO2 providing 29/30 (29, 90%; 30, 87%) as a color-
less thick oil. Compound 29: Rf = 0.15 (EtOAc); ½a D25
ꢂ32.0 (c 0.1,
ꢁ
CHCl3); 1H NMR (300 MHz, MeOH-d4): d 1.37 (s, 9H), 1.45 (s, 9H),
3.23 (m, 1H), 3.35–3.46 (m, 3H), 3.65 (m, 2H), 3.97 (m, 1H), 4.14
(m, 1H), 4.21–4.32 (m, 2H), 4.56 (m, 1H), 4.72 (dd, 1H, J = 2.8,
3.2 Hz, H-3), 7.09–7.17 (m, 5H), 7.19–7.28 (m, 8H), 7.34–7.40 (m,
6H), 7.57 (dd, 2H, J = 7.6, 10.6 Hz), 7.76 (t, 2H, J = 7.6); 13C NMR
(75 MHz, CDCl3): d 28.4, 28.6, 47.3, 57.5, 64.3, 65.1, 67.7, 68.1,
68.3, 71.1, 77.4, 80.9, 85.1, 87.9, 121.0–145.7 (aromatic carbons),
155.0, 159.2, 160.3, 163.8, 171.8; MS (ES+): m/z 965.27 [M+Na]+.
Anal. Calcd for C53H58N4O12: C, 67.50; H, 6.20; N, 5.94. Found: C,
27. Carpino, L. A. Acc. Chem. Res. 1987, 20, 401–407.
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67.88; H, 5.93; N, 6.17. Compound 30: Rf = 0.15 (EtOAc); ½a D25
ꢁ
+16.0 (c 0.1, CHCl3); 1H NMR (300 MHz, MeOH-d4): d 1.35 (s, 9H),
1.46 (s, 9H), 3.29 (m, 1H), 3.37–3.45 (m, 3H), 3.60–3.70 (m, 2H),
3.96 (br d, 1H, J = 10.0 Hz), 4.13 (dd, 1H, J = 6.5, 7.4 Hz), 4.24–
4.36 (m, 2H), 4.56 (m, 1H), 4.70 (dd, 1H, J = 2.9, 3.3 Hz, H-3),
7.08–7.16 (m, 5H), 7.17–7.29 (m, 8H), 7.32–7.41 (m, 6H), 7.55
(dd, 2H, J = 7.8, 10.0 Hz), 7.65 (dd, 2H, J = 4.0, 7.8 Hz); 13C NMR
(75 MHz, MeOH-d4): d 28.3, 28.5, 47.2, 57.3, 64.2, 65.0, 67.5, 68.2,