Synthetic studies on pterin glycosides: the first synthesis of 2′-O-(α-d-glucopyranosyl)biopterin

Article abstract of DOI:10.1016/j.tet.2009.07.043

l-Rhamnose was led, in a 14-step-sequence, to N²-(N,N-dimethylaminomethylene)-1′-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (23), an appropriately protected precursor for 2′-O-glycosylation, while 4,6-di-O-acetyl-2,3-di-O-(4-methox

Full text of DOI:10.1016/j.tet.2009.07.043

Tetrahedron 65 (2009) 7989–7997
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthetic studies on pterin glycosides: the first synthesis
of 20-O-(
a- -glucopyranosyl)biopterin
D
,
a
a
b
Tadashi Hanaya a , Hiroki Baba , Hiroki Toyota , Hiroshi Yamamoto
*
a Department of Chemistry, Faculty of Science, Okayama University, Tsushima-naka, Okayama 700-8530, Japan
b School of Pharmacy, Shujitsu University, Nishigawara, Okayama 703-8516, Japan
a r t i c l e i n f o
a b s t r a c t
-Rhamnose was led, in a 14-step-sequence, to N2-(N,N-dimethylaminomethylene)-10-O-(4-methoxy-
benzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (23), an appropriately protected precursor for 20-O-glyco-
sylation, while 4,6-di-O-acetyl-2,3-di-O-(4-methoxybenzyl)- -glucopyranosyl bromide (32), a novel
glycosyl donor, was efficiently prepared from -glu-
-glucose in 8 steps. The first synthesis of 20-O-(
Article history:
Received 30 June 2009
Received in revised form 21 July 2009
Accepted 21 July 2009
Available online 24 July 2009
L
a-D
D
a-D
copyranosyl)biopterin (2a) was achieved by treatment of the key intermediate 23 with 32 in the pres-
ence of silver triflate and tetramethylurea, followed by successive removal of the protecting groups.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Pterin glycoside
Pteridine
Glycosylation
Protecting group
Total synthesis
1. Introduction
been isolated from cyanobacteria, anaerobic photosynthetic bac-
teria, and chemoautotrophic archaebacteria, although the glyco-
A variety of pterin derivatives having a hydroxyalkyl side chain
at C-6, a representative example being biopterin (1), have been
found in nature. Some of them isolated from certain prokaryotes
possessed a glycosidic form having a sugar attached to the side
sidic linkages of some derivatives remain unclear. Among these
pterin glycosides, biopterin -glucoside (2a) is the most note-
worthy because of its abundant occurrence in various kinds of
cyanobacteria, Anacystis nidulans,1 Oscillatoria sp.,2 Synechococcus
sp.,3 and Spirulina platensis,4 but there has been no report for
synthesis of 2a since its first discovery in 1958.
The physiological function of the parent pterins has been
studied in detail: for example, 1 plays, in the form of its tetrahydro
derivative, an important role as an enzyme cofactor in aromatic
amino acid hydroxylation9 and nitric oxide synthesis.10 By contrast,
the functional roles of pterin glycosides have remained obscure,
although some inhibitory activities against tyrosinase11 and
photostabilization of photosynthetic pigments4,12 were reported
for 2a. Despite a considerable interest from the viewpoint of their
biological activities and functions, as well as structural proof of
hitherto reported natural products, attempts at preparation of
pterin glycosides have so far scarcely been made, except for our
synthetic studies on limipterin (3) and ciliapterin glycosides.13,14
We reported in a previous paper13 that the glycosylation of a bio-
pterin derivative whose two hydroxy groups were unprotected did
a-D
chain (Fig. 1); for example, 20-O-(
(2a)1–4 and limipterin [20-O-(2-acetamido-2-deoxy-
a-
D-glucopyranosyl)biopterin
b-D-glucopyr-
anosyl)biopterin] (3)5 were isolated from cyanobacteria and a green
sulfur photosynthetic bacterium, respectively. Various other gly-
cosides consisting of different pterins (such as ciliapterin,6 neo-
pterin,7 and 6-hydroxymethylpterin8) and sugar moieties (such as
D-ribose, D-mannose, D-galactose, and D-glucuronic acid) have also
not yield the 20-O-(
for example, treatment of N2-(N,N-dimethylaminomethylene)-3-[2-
(4-nitrophenyl)ethyl]biopterin (4) with tetra-O-benzoyl- -gluco-
pyranosyl bromide (5)15 (3 mol equiv) in the presence of tin(IV)
chloride afforded 20-O-(
-glucopyranosyl)biopterin (6) (41% yield),
D-glucopyranosyl)biopterins withhigh selectivity:
Figure 1. Structures of biopterin and its glycosides.
a-D
* Corresponding author. Tel.: þ81 86 2517838; fax: þ81 86 2517853.
E-mail address: hanaya@cc.okayama-u.ac.jp (T. Hanaya).
b-D
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.07.043

7990
T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
hydrochloric acid, followed by acetalization with 2,2-dimethoxy-
propane, providing allyl 2,3-O-isopropylidene- -rhamnopyrano-
side (13)19 (80%) along with the corresponding
-anomer (8%)
a-L
b
(Scheme 3). Treatment of 13 with p-methoxybenzyl chloride and
sodium hydride in DMF gave the 4-O-PMB derivative 14, which was
then converted into the 1-propenyl glycoside 15 with potassium
tert-butoxide in DMSO. Hydrolysis of 15 in 70% acetic acid20 affor-
ded 4-O-PMB-L-rhamnopyranose (16).
The cleavage of C-1 of 16 was accomplished by application of
Hough and Taylor’s procedures21 with a slight modification.
Namely, treatment of 16 with ethanethiol in the presence of
p-toluenesulfonic acid in acetic acid gave the dithioacetal 17, which
was then oxidized with m-chloroperbenzoic acid (mCPBA) to the
corresponding sulfone 18. Degradation of 18 with dilute aqueous
ammonia afforded 5-deoxy-3-O-PMB-
selective oxidation for 2-hydroxy group of 19 with cupric acetate22
provided the -erythro-pentos-3-ulose derivative 20.
L-arbinofuranose (19). The
L
The pteridine ring formation of 20 with 2,5,6-triamino-4-
hydroxypyrimidine sulfate was carried out in aqueous sodium bi-
carbonate solution to give an inseparable mixture of the biopterin
derivative 21a and its C-7 substituted isomer 21b in a ratio of 78:22.
These products were separated by column chromatography after
having been subjected to the three-step procedures for in-
troduction of N,N-dimethylaminomethylene, acetyl, and NPE
groups, thus providing 20-O-acetyl-N2-(N,N-dimethylamino-
methylene)-10-O-PMB-3-NPE-biopterin (22a) (53% overall yield
from 20) and its C-7 substituted congener 22b (17%).14
Scheme 1.
together with 10-O-glycosyl isomer 7 (15%) and 10,20-di-O-glycosyl
derivative 8 (14%) (Scheme 1). These results prompted us to develop
a more efficient protocol for selective 20-O-monoglycosylation. In
addition, we undertook preparation of an effective glycosyl donor
Methanolysis of 20-O-acetyl-10-O-PMB-biopterin derivative 22a
in the presence of sodium methoxide provided the 10-O-PMB de-
leading to preponderant production of pterin a-glycosides instead of
b
-glycosides. We give herein a full account of the first, efficient syn-
thesis of the representative, natural pterin glycoside, 20-O-(
copyranosyl)biopterin (2a).16
a
versatile precursor for 20-O-monoglycosylation
a-D-glu-
rivative 23,
(Scheme 4). Glycosylation of 23 was then examined by use of tetra-
O-benzoyl- -glucopyranosyl bromide (5) as a glycosyl donor in
a-D
the presence of various activators. While treatment of 23 with 5 in
dichloromethane at rt in the presence of tetrabutylammonium
bromide and N-ethyldiisopropylamine23 did not proceed, the same
reaction in the presence of tin(IV) chloride13 as an activator resulted
in the formation of diol 4, instead of glycosylation, by cleavage of
PMB group. Efficient glycosylation of 23, however, was attained by
the condensation with 3.0 mol equiv of 5 in the presence of silver
triflate (2.0 mol equiv) and tetramethylurea (TMU)24 (1.0 mol equiv)
2. Results and discussion
A retrosynthetic analysis for 2a is outlined in Scheme 2. The
biopterin derivative 9, whose pyrimidine ring moiety and 10-hy-
droxy group of the side chain are protected, can be perceived as the
key precursor to accomplish complete 20-O-glycosylation, while the
pteridine ring formation of 9 would be achieved by condensation of
2,5,6-triamino-4-hydroxypyrimidine with the pentos-2-ulose 10,
in dichloromethane at rt for 3 h, giving the 20-O-(
b-D-gluco-
which would be derived from the 4-O-protected
the 3-O-protected 5-deoxy-
L-rhamnose 12 via
L
-arabinose 11.17 A rational consider-
pyranosyl)biopterin derivative 24 as a sole product in 75% yield.
Removal of the protecting groups of 24 was performed by the
following four-step procedures: first, cleavage of PMB by the use of
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to afford 6 in
88%, then the three successive treatment with sodium methoxide
(to cleave benzoyl groups), aqueous ammonia (to cleave the N,N-
dimethylaminomethylene group), and DBU (to cleave the NPE
ation of the available conditions to remove the protecting groups of
the glycoside derived from 9 led us to employ p-methoxybenzyl
(PMB) group for protection of 10-hydroxy, N,N-dimethylamino-
methylene group for 2-amino, and 2-(4-nitrophenyl)ethyl (NPE)
group for N-3 of the ring.18
group)18 furnished 20-O-(
b-D-glucopyranosyl)biopterin (2b), the
anomeric isomer of the natural product, in 89% overall yield from 6.
Structure of 2b was unambiguously established as the corre-
sponding hexaacetyl derivative 25b obtained by usual acetylation.
Treatment of 25b with aqueous ammonia regenerated 2b quanti-
tatively. The precise 1H NMR parameters of 25b and 2b are sum-
marized in Tables 1 and 2.
This successful synthesis of biopterin 20-O-
led us to execute preparation of the natural product, biopterin
20-O-
-glucoside (2a). The stereoselective formation of the -gly-
b-D-glucoside (2b)
a-D
b
coside 24 from 23 was mainly caused by participation of the 2-O-
benzoyl group of the glycosyl donor 5 through the formation of an
acyloxonium ion intermediate.25 Accordingly, in order to avoid
such a neighboring group participation, we sought to introduce an
ether substituent for protection of 2-OH of a glycosyl donor. Tak-
ing into consideration the available combination of protecting
groups employed for the synthetic pathway, PMB and acetyl
groups were, respectively, chosen for protection of 2,3-OH and
Scheme 2.
L
-Rhamnose, which served as the starting material to obtain the
key intermediate 5-deoxy-3-O-PMB- -arabinose (19), was sub-
jected to glycosidation with allyl alcohol in the presence of
L

T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
7991
Scheme 3.
Scheme 4.
4,6-OH. We thus undertook the preparation of methyl 4,6-di-
O-acetyl-2,3-di-O-PMB-1-thio- -glucopyranose (31) and its
-glucopyranosyl bromide derivative 32, the potential glycosyl
donors for the pterin -glycosides, starting with penta-O-acetyl-
-glucopyranose (26),26 which is readily available from
-glucose
(Scheme 5).
subsequent acetalization with 2,2-dimethoxypropane in the
presence of p-toluenesulfonic acid provided the 4,6-O-iso-
propylidene derivative 28. Treatment of 28 with p-methoxybenzyl
chloride and sodium hydride in DMF gave the 2,3-di-O-PMB
derivative 29. Hydrolysis of 29 in 70% acetic acid provided methyl
b-D
a-D
a
b-
D
D
2,3-di-O-PMB-1-thio-b-D-glucopyranoside (30), which was then
Treatment of 26 with thiourea and boron trifluoride etherate,
acetylated to give the desired 4,6-di-O-acetyl derivative 31. Then
the thioglycoside 31 was transformed to the corresponding
followed by the action of methyl iodide and triethylamine, gave
rise to the methyl 1-thio-
b
-
D
-glucopyranose derivative 27.27
D
-glucopyranosyl bromide 32 by the action of bromine in
Methanolysis of 27 in the presence of sodium methoxide and the
dichloromethane in the presence of 2,6-lutidine.

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T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
Table 1
1H NMR (600 MHz) spectral parameters for biopterin
a
-D
-glycosides (25a, 33a, 34a) and
Me2NCH]N-2
b-
D
-glucosides (24, 25b, 34b) in CDCl3
Compound
Chemical shifts/
d
(coupling constants/Hz)
Pterin moiety
NPE-N(3)
Other signals
H-7
H-10 (J1 ,2
)
H-20 (J2 ,3
)
0
H3-30
1.23
Me2N
CH]N
H(o) (Jo,m
7.42 (8.6)
)
H(m)
CH2CH2N (3JH,H
)
CH2N (2JH,H
)
0
0
0
24
8.78
4.67 (3.7)
6.01 (4.8)
5.95 (5.4)
4.77 (3.9)
6.06 (4.6)
5.94 (5.9)
4.37 (6.6)
4.43 (6.4)
4.47 (6.4)
4.25 (6.4)
4.45 (6.4)
4.54 (6.4)
3.23, 3.18
8.82
8.14
3.16 (7.8)
4.59, 4.57
(12.7)
3.77
(MeO of PMBa)
2.19
25a
25b
33a
34a
34b
9.00
8.87
9.08
8.90
8.75
1.20
1.30
1.16
1.18
1.31
12.56 (NH-2),
2.45 (AcNH-2)
12.59 (NH-2),
2.45 (AcNH-2)
3.24, 3.20
10.58 [H–N(3)]
10.35 [H–N(3)]
(AcO-10)b
2.15
(AcO-10)b
3.77
8.88
8.86
8.84
7.43 (8.8)
7.42 (8.8)
7.43 (8.6)
8.15
3.18 (7.8)
3.16 (7.8)
3.18 (7.6)
4.62, 4.60
(12.2)
4.60, 4.58
(12.0)
4.63, 4.61
(12.4)
(MeO of PMBc)
2.19
3.24, 3.19
3.24, 3.19
8.14
8.15
(AcO-10)b
2.13
(AcO-10)b
Compound
Glycosyl moiety
H-1 (J1,2 H-2 (J2,3
)
)
H-3 (J3,4
)
H-4 (J4,5
)
H-5 (J5,6a
)
Ha-6 (J6a,6b
)
Hb-6 (J5,6b
)
Other signals
24
5.17 (7.8)
5.21 (3.8)
4.62 (8.1)
4.82 (3.7)
5.22 (3.9)
4.66 (8.1)
5.55 (9.8)
4.79 (10.3)
4.86 (9.5)
3.49 (9.8)
4.80 (10.3)
4.87 (9.5)
5.91 (9.5)
5.22 (9.6)
5.10 (9.5)
3.77 (9.3)
5.33 (9.5)
5.06 (9.5)
5.63 (10.0)
4.98 (10.2)
5.00 (10.0)
4.92 (10.3)
5.00 (10.3)
5.01 (10.0)
4.18 (3.2)
4.63 (12.2)
4.22 (12.5)
4.21 (12.2)
3.96 (12.7)
4.19 (12.5)
4.23 (12.2)
4.47 (5.6)
4.00 (2.2)
4.12 (2.4)
3.68 (2.2)
3.94 (2.2)
4.13 (2.4)
8.00, 7.91, 7.89, 7.80 [Bz(o)], 7.51–7.25 [Bz(m,p)]
2.09, 2.01, 1.98, 1.97 (AcO-2,3,4,6)b
25a
25b
33a
34a
34b
3.90 (4.2)
3.68 (5.4)
3.79 (3.9)
3.83 (4.2)
3.70 (5.1)
2.08, 2.01, 1.96, 1.94 (AcO-2,3,4,6)b
2.02, 1.89 (AcO-4,6), 3.79, 3.78 (MeO of PMBc)
2.08, 1.99, 1.99, 1.98 (AcO-2,3,4,6)b
2.09, 2.01, 1.95, 1.88 (AcO-2,3,4,6)b
7.00 [H(o), Jo,m¼8.8 Hz], 6.73 [H(m)], 4.28, 4.13 (CH2, 2J¼11.7 Hz).
a
b
c
The assignments of acetyl groups may have to be interchanged.
7.20, 7.18, 7.15 [H(o), Jo,m¼8.8 Hz], 6.84, 6.83, 6.78 [H(m)], 4.75, 4.53 (CH2, 2J¼11.0 Hz), 4.59, 4.46 (CH2, 2J¼11.0 Hz), 4.45,4.45 (CH2).
Table 2
600 MHz 1H and 151 MHz 13C NMR spectral parameters for biopterin
a-D-glucoside (2a) and b-D-glucoside (2b) in D2O
Compound
Chemical shifts/
Pterin moiety
d
(coupling constants/Hz)
Glycosyl moiety
H-1 (J1,2 H-2 (J2,3
H-7
H-10 (J1 ,2
)
H-20 (J2 ,3
)
0
H-30
)
)
H-3 (J3,4
)
H-4 (J4,5
)
H-5 (J5,6a
)
Ha-6 (J6a,6b
)
Hb-6 (J5,6b
)
0
0
0
Synthetic 2aa
Natural 2ab
2ba
8.79
8.79
8.83
4.83 (7.1)
4.82 (7.3)
4.98 (4.9)
4.07 (6.1)
4.06 (5.9)
4.37 (6.6)
1.30
1.29
1.24
5.00 (3.9)
4.99 (3.3)
4.56 (8.2)
3.41 (10.0)
3.40 (9.2)
3.18 (9.3)
3.32 (9.0)
3.30 (9.2)
3.40 (9.0)
3.22 (10.0)
3.21 (9.2)
3.33 (9.8)
2.40 (3.6)
2.38 (3.4)
3.43 (2.2)
3.43 d
3.43 (3.6)
c
c
3.88 (12.5)
3.68 (5.9)
Pterin moiety
Glycosyl moiety
C-2
C-4
C-4a
C-6
C-7
C-8a
C-10
C-20
C-30
C-1
95.83
96.39
97.73
96.3
C-2
C-3
C-4
C-5
C-6
Synthetic 2ad
Synthetic 2af
Natural 2ab
Natural 2ag
2bd
155.72
156.63
157.45
155.7
156.32
156.46
165.37
128.31
127.50
130.24
128.6
128.22
127.51
152.24
149.59
149.01
151.57
150.1
149.68
149.08
155.23
154.51
154.21
155.4
154.97
154.49
75.53e
74.92
77.43e
76.0
75.05
74.61
75.58e
75.23
77.48e
76.0
79.75
78.13
14.94
71.64
71.87
73.55
72.1
73.81
73.97
73.36
73.24
75.27
73.9
69.48
69.65
71.41
70.1
70.23
70.26
72.49
72.54
74.41
72.9
60.53
60.32
62.44
61.2
61.31
61.30
162.09
151.16
14.71
c
c
c
165.4
166.29
162.02
152.8
151.07
150.56
15.2
16.73
16.66
103.10
103.14
76.49e
77.11e
76.31e
76.54e
2bf
a
The solvent peak (d 4.79) was used as an internal standard.
b
c
d
e
f
Ref. 4 (at 270 MHz for 1H, 67.5 MHz for 13C). The internal or external standard is not shown.
Not reported.
1,4-Dioxane (
The assignments may have to be interchanged.
In DMSO-d6. The solvent peak ( 39.70) was used as an internal standard.
Ref. 11 (at 100 MHz). The internal or external standard is not shown.
d 67.20) was used as an internal standard.
d
g
Scheme 5.

T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
7993
Scheme 6.
Glycosylation of the 10-O-PMB-biopterin derivative 23 with
glycosyl donors (31, 32) was examined under various conditions in
the presence of activators (Scheme 6). Treatment of 23 with the
thioglycoside 31 in dichloromethane at rt in the presence of methyl
triflate28 or N-iodosuccinimide-silver triflate29 as activators resul-
ted in the formation of unidentified, decomposed compounds in-
stead of the desired glycoside.30 Glycosylation of 23 with
4.0 mol equiv of the glycosyl bromide 32 in dichloromethane in the
presence of tetrabutylammonium bromide and N-ethyl-
diisopropylamine did not proceed, whereas the same reaction in
the presence of silver triflate (2.0 mol equiv) and tetramethylurea
(TMU) (1.0 mol equiv) afforded an inseparable anomeric mixture
Figure 2. The optimized structures A (for 2a) and B (for 2b) based on MOPAC PM3
methods.
(85:15) of the 20-O-(
and its -anomer 33b in 66% yield, along with the recovery of 23
a-D-glucopyranosyl)biopterin derivative 33a
b
(24%). Separation of these isomers was achieved by removal of PMB
groups and the subsequent acetylation. Thus, the mixture of 33a,b
was treated with DDQ in dichloromethane, followed by acetylation
with acetic anhydride in pyridine, afforded the 20-O-(2,3,4,6-tetra-
Figure 2, the optimized structure (A) for 2a has anti H–C-10–C-20–H
conformation, whereas that for 2b (B) has the gauche conformation.
Moreover, an extraordinary upfield shift observed for the H-5 signal
(
d
2.40) of the
D
-glucopyranosyl moiety of 2a in comparison with the
O-acetyl-
yield from 23) and its
structure of 34a was derived from its J1,2 value (3.9 Hz) of 1H NMR,
while the larger J1,2 value (8.1 Hz) confirmed the b-form of 34b
(Table 1).
a
-
D
-glucopyranosyl)biopterin derivative 34a in 51% (total
relatively normal value (
d
3.43) of the corresponding -glucoside
b
b
-anomer 34b in 9%. The -anomeric
a
(2b) could be explained in terms of such a conformation as H-5 of the
sugar moiety locating above the pterin ring where an appreciable
shielding effect is exerted, as visualized in its optimized structure (A).
Removal of the protecting groups of 34a was accomplished in
the following manner: 34a was treated with aqueous ammonia to
cleave the N,N-dimethylaminomethylene and acetyl groups and
then with DBU to cleave NPE group, furnishing the desired 20-O-
3. Conclusion
We have developed a novel, effective way for selective prepa-
ration of both pterin 20-O-
b
- and 20-O-
a
-glycosides. By use of the
key intermediate 10-O-PMB-biopterin derivative 23 and the novel
glycosyl donor 32 the first synthesis of biopterin -glucoside (2a)
(a
-D
-glucopyranosyl)biopterin (2a) in 90% overall yield. For the
purpose of structural confirmation and further purification, as in
the case of the -isomer 2b, the -isomer 2a was converted into the
a-D
b
a
was achieved. This synthetic strategy has proved a useful method
applicable to a series of other natural pterin glycosides and their
analogs.
hexaacetyl derivative 25a, which regenerated 2a upon ammonol-
ysis. The precise parameters obtained on 1H and 13C NMR spectra
for 2a and 25a are listed in Tables 1 and 2. The spectral data of the
synthetic
a-glucoside 2a were found to be essentially identical with
those reported for natural product4,11 (Table 2).
4. Experimental
0
0
The considerable difference between the J1 ,2 values of 2a (7.1 Hz)
and 2b (4.9 Hz) indicates that these isomers are likely to exist in
different rotamers along C-10-C-20 of the pterin side chain. Accord-
ingly we have calculated the most favorable conformations of 2a,b
using semi-empirical (MOPAC PM3)31 methods. As depicted in
4.1. General procedures
All reactions were monitored by TLC (Merck Silica gel 60 F254
with an appropriate solvent system. Column chromatography was
)

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T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
b
0
0
0
0
0
0
performed with Daiso Silica Gel IR-60/210w. Components were
detected by exposing the plates to UV light and/or 20% H2SO4–
EtOH, with subsequent heating. The NMR spectra were measured in
CDCl3 with Varian Unity Inova AS600 (600 MHz for 1H, 151 MHz for
J1b ,2 ¼6.3, J1 b,3 E¼J1b ,3 Z¼1.3 Hz, H -10 of allyl), 4.16 (1H, ddt,
a
J1 a,2 ¼5.3, J1 a,3 E¼J1a ,3 Z¼1.5 Hz, H -10 of allyl), 4.16 (1H, dd, J2,3¼5.8,
0
0
0
0
0
0
J1,2¼0.7 Hz, H-2), 4.27 (1H, dd, H-3), 4.56, 4.84 (1H each, 2d,
2J¼11.2 Hz, CH2O-4), 5.01 (1H, d, H-1), 5.20 (1H, dq, J2 ,3 E¼10.4,
0
0
1
E
Z
13C) or Mercury300 (300 MHz for H) at 23 ꢀC. Chemical shifts are
J3 E,3 Z¼1.8 Hz, H -30 of allyl), 5.29 (1H, dq, J2 ,3 Z¼17.2 Hz, H -30 of
allyl), 5.89 (1H, dddd, H-20 of allyl), 6.89, 7.29 (2H each, 2d,
Jo,m¼8.8 Hz, C6H4). Anal. Calcd for C20H28O6: C, 65.91; H, 7.74.
Found: C, 66.11; H, 7.59.
0
0
0
0
reported as
d
values relative to CHCl3 (7.26 ppm) for 1H and CDCl3
(77.00 ppm) for 13C as an internal standard, unless otherwise
stated. Optical rotations were measured with a JASCO P-1020 po-
larimeter in CHCl3.
4.4. (Z)-1-Propenyl 2,3-O-isopropylidene-4-O-(4-
methoxybenzyl)-a-L-rhamnopyranoside (15)
4.2. Allyl 2,3-O-isopropylidene-
a
-L
-rhamnopyranoside (13)19
and its -anomer
b
Compound 14 (880 mg, 2.41 mmol) was dissolved in dry
DMSO (10 mL) and potassium tert-butoxide (770 mg, 6.85 mmol)
was added in small portions. The mixture was stirred at 100 ꢀC
for 20 min and then saturated NH4Cl was added at 0 ꢀC. The
mixture was diluted with aqueous NaHCO3 and evaporated in
vacuo. The residue was dissolved in water and extracted with
CHCl3 three times. The combined organic layers were dried
(MgSO4) and evaporated in vacuo. The residue was purified by
column chromatography with 1:9 AcOEt–hexane to give 15
(837 mg, 95%) as a colorless syrup: Rf¼0.33 (1:9 AcOEt–hexane);
The following modification of the literature procedures was
made. To solution of -rhamnose monohydrate (3.56 g,
a
L
19.5 mmol) in allyl alcohol (28 mL) was added 4 M HCl in dioxane
(6.0 mL, 24 mmol). The mixture was refluxed for 2 h, neutralized
with TEA (10 mL), and concentrated in vacuo. The residue was
dissolved in toluene (20 mL) and evaporated in vacuo to remove
allyl alcohol three times. The residual syrup was dissolved in dry
acetone (12 mL) and 2,2-dimethoxypropane (9.6 mL, 78 mmol) and
then p-toluenesulfonic acid monohydrate (30 mg, 0.16 mmol) was
added. The mixture was stirred at rt for 10 h and then TEA (5 mL)
was added. The mixture was concentrated in vacuo and the residue
was purified by column chromatography with 1:4 AcOEt–hexane to
give 13 (3.83 g, 80%) (lit.19 68% yield on acetalization with acetone
1H NMR (300 MHz, CDCl3)
d
1.24 (3H, d, J5,6¼6.3 Hz, H3-6), 1.39,
1.53 (3H each, 2s, CMe2), 1.56 (3H, dd, J2 ,3 ¼6.9, J1 ,3 ¼1.8 Hz, H-30
of propenyl), 3.21 (1H, dd, J4,5¼9.9, J3,4¼6.9 Hz, H-4), 3.68 (1H, dq,
H-5), 3.80 (3H, s, MeO), 4.25 (1H, dd, J2,3¼5.8, J1,2¼0.7 Hz, H-2),
0
0
0
0
0
0
0
alone) and its
Compound 13. Colorless syrup; Rf¼0.67 (1:1 AcOEt–hexane);
1H NMR (600 MHz, CDCl3)
b
-anomer (372 mg, 7.8%).
4.32 (1H, dd, H-3), 4.57 (1H, quint, J1 ,2 ¼6.3 Hz, H-2 of propenyl),
4.57, 4.84 (1H each, 2d, 2J¼11.2 Hz, CH2O-4), 5.18 (1H, d, H-1), 6.14
(1H, dq, H-10 of propenyl), 6.88, 7.29 (2H each, 2d, Jo,m¼8.7 Hz,
C6H4). Anal. Calcd for C20H28O6: C, 65.91; H, 7.74. Found: C, 66.16;
H, 7.63.
d
1.29 (3H, d, J5,6¼6.3 Hz, H3-6), 1.35,
1.52 (3H each, 2s, CMe2), 2.45 (1H, br s, HO-4), 3.40 (1H, dd,
J4,5¼9.4, J3,4¼7.2 Hz, H-4), 3.68 (1H, dq, H-5), 4.00 (1H, ddt,
b
J1 a,1 b¼12.7, J1 b,2 ¼6.4, J1 b,3 Z¼J1 b,3 E¼1.3 Hz, H -10 of allyl), 4.09
0
0
0
0
0
0
0
0
(1H, dd, J2,3¼5.7 Hz, H-3), 4.16 (1H, dd, J1,2¼0.7 Hz, H-2), 4.19 (1H,
4.5. 4-O-(4-Methoxybenzyl)-a,b-L-rhamnopyranoses (16)
a
ddt, J1a ,2 ¼5.3, J1 a,3 E¼J1 a,3 Z¼1.6 Hz, H -10 of allyl), 5.00 (1H, br s,
0
0
0
0
0
0
E
H-1), 5.21 (1H, dq, J2 ,3 E¼10.5, J3 E,3 Z¼2.0 Hz, H -30 of allyl), 5.30
Compound 15 (830 mg, 2.28 mol) was dissolved in 70% aqueous
AcOH (10 mL) and the mixture was stirred at 35 ꢀC for 24 h. The
mixture was concentrated in vacuo and the residue was purified by
column chromatography with 1:1 AcOEt–hexane to give an in-
0
0
0
0
Z
(1H, dq, J2 ,3 Z¼17.1 Hz, H -30 of allyl), 5.90 (1H, dddd, H-20 of
0
0
allyl).
b
-Anomer of 13. Pale yellow prisms; mp 52–53 ꢀC (from AcOEt–
27
hexane); [
a
]
þ80.1ꢀ (c 2.50, CHCl3); Rf¼0.38 (1:1 AcOEt–hexane);
separable anomeric mixture (
a
:
b
¼ca. 1:1) of 16 (515 mg, 79%) as
D
1H NMR (600 MHz, CDCl3)
d
1.34 (3H, d, J5,6¼6.1 Hz, H3-6), 1.39,
a colorless foam: Rf¼0.21 (AcOEt); 1H NMR [300 MHz, CDCl3 (D2O
1.57 (3H each, 2s, CMe2), 2.25 (1H, br s, HO-4), 3.29 (1H, dq,
exchange)]
d
1.19
*
, 1.24 (3H each, 2d, J5,6¼6.3
*
, 5.6 Hz, H3-6 of
a
*
,
b
),
), 3.56
, 3.68 (3H, 2s, MeO of
and H-2 of ), 4.465, 4.47, 4.68,
), 4.62, 5.11 (1H, 2d,
J4,5¼9.8 Hz, H-5), 3.53 (1H, dd, J3,4¼7.3 Hz, H-4), 4.02 (1H, dd,
3.25 (2H, m, H-4,5 of
b
), 3.32 (1H, t, J3,4¼J4,5¼9.1 Hz, H-4 of
a
0
0
0
0
J2,3¼5.6 Hz, H-3), 4.18 (1H, ddt, J1 a,1 b¼12.9, J1 b,2 ¼6.8,
(1H, dd, J3,4¼8.7, J2,3¼3.5 Hz, H-3 of
b
), 3.65
*
b
J1 b,3 Z¼J1 b,3 E¼1.2 Hz, H -10 of allyl), 4.24 (1H, dd, J1,2¼2.2 Hz, H-2),
a
*
,b
), 3.83–3.95 (4H, m, H-2,3,5 of
a
b
0
0
0
0
a
4.43 (1H, ddt, J1 a,2 ¼4.9, J1 a,3 E¼J1 a,3 Z¼1.6 Hz, H -10 of allyl), 4.78
4.69 (1H each, 4d, 2J¼10.7 Hz, CH2O-4 of
a
,
b
*
0
0
0
0
0
0
E
(1H, d, H-1), 5.23 (1H, dddd, J2 ,3 E¼10.5, J3 E,3 Z¼2.0 Hz, H -30 of
J1,2¼1.0, 1.2
*
Hz, H-1 of
a ,b), 6.77, 6.75, 7.18, 7.19 (2H each, 4d,
*
0
0
0
0
Z
allyl), 5.31 (1H, dddd, J2 ,3 Z¼17.3 Hz, H -30 of allyl), 5.94 (1H, dddd,
H-20 of allyl). Anal. Calcd for C12H20O5: C, 59.00; H, 8.25. Found: C,
58.89; H, 8.45.
Jo,m¼8.7 Hz, C6H4 of
a,b). Anal. Calcd for C14H20O6: C, 59.14; H, 7.09.
0
0
Found: C, 59.02; H, 7.26.
4.6. 4-O-(4-Methoxybenzyl)-L-rhamnose diethyl
4.3. Allyl 2,3-O-isopropylidene-4-O-(4-methoxybenzyl)-
a
-L-
dithioacetal (17)
rhamnopyranoside (14)
To a solution of 16 (95.4 mg, 0.336 mmol) in ethanethiol
(3.6 mL) and AcOH (1.2 mL), p-toluenesulfonic acid monohydrate
(6.4 mg, 0.034 mmol) was added at 0 ꢀC. The mixture was stirred
at ca. 10 ꢀC for 40 min, diluted with saturated NaHCO3, and con-
centrated in vacuo. The residue was dissolved in CHCl3, washed
with water, dried (MgSO4), and evaporated in vacuo. The residue
was purified by column chromatography with 1:2 AcOEt–hexane
To a solution of 13 (620 mg, 2.54 mmol) and p-methoxybenzyl
chloride (0.69 mL, 5.09 mmol) in dry DMF (6.0 mL) was added
tetrabutylammonium iodide (281 mg, 0.726 mmol) and then so-
dium hydride (60% in oil, 305 mg, 7.26 mmol) at 0 ꢀC. The mixture
was stirred at rt for 2 h and then saturated NH4Cl was added slowly
at 0 ꢀC. The mixture was diluted with aqueous NaHCO3 and evap-
orated in vacuo. The residue was dissolved in CHCl3, washed with
water, dried (MgSO4), and evaporated in vacuo. The residue was
purified by column chromatography with 1:9 AcOEt–hexane to give
14 (880 mg, 95%) as a colorless syrup: Rf¼0.24 (1:9 AcOEt–hexane);
to give 17 (95.4 mg, 73%) as colorless prisms: mp 47–48 ꢀC (from
26
AcOEt–hexane); [
a
]
ꢁ20.5ꢀ (c 2.95, CHCl3); Rf¼0.41 (1:1 AcOEt–
D
hexane); 1H NMR (600 MHz, CDCl3)
d 1.27, 1.28 (3H each, 2 t,
3J¼7.4 Hz, CH3CH2S), 1.29 (3H, d, J5,6¼6.6 Hz, H3-6), 2.48 (3H, br s,
HO-2,3,5), 2.61, 2.72 (2H each, 2q, CH2S), 3.63 (1H, dd, J4,5¼4.4,
J3,4¼1.5 Hz, H-4), 3.80 (3H, s, MeO), 3.86 (1H, dd, J2,3¼8.8,
J1,2¼2.4 Hz, H-2), 4.07 (1H, dd, H-3), 4.14 (1H, qd, H-5), 4.25 (1H,
1H NMR (300 MHz, CDCl3)
d
1.26 (3H, d, J5,6¼6.3 Hz, H3-6), 1.38, 1.52
(3H each, 2s, CMe2), 3.20 (1H, dd, J4,5¼9.9, J3,4¼7.1 Hz, H-4), 3.69
0
0
(1H, dq, H-5), 3.81 (3H, s, MeO), 3.98 (1H, ddt, J1 a,1 b¼13.1,

T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
7995
d, H-1), 4.59, 4.67 (1H each, 2d, 2J¼11.2 Hz, CH2O-4), 6.88, 7.28
4.11. N2-(N,N-Dimethylaminomethylene)-10-O-(4-methoxy-
benzyl)-3-[2-(4-nitrophenyl)ethyl]-20-O-(2,3,4,6-tetra-O-
benzoyl-b-D-glucopyranosyl)biopterin (24)
(2H each, 2d, Jo,m¼8.8 Hz, C6H4). 13C NMR (151 MHz, CDCl3)
d
14.60 (CH3CH2S), 14.71 (CH3CH2S), 19.22 (C-6), 25.73 (CH2S),
26.16 (CH2S), 54.56 (C-1), 55.27 (MeO), 68.59 (C-5), 70.75 (C-3),
72.90 (CH2O), 72.91 (C-2), 79.16 (C-4), 113.90 (C(m) of PMB),
129.87 (C(o) of PMB), 129.96 (C(ipso) of PMB), 159.49 (C(p) of
PMB). Anal. Calcd for C18H30O5S2: C, 55.36; H, 7.42. Found: C,
55.48; H, 7.48.
To a solution of 23 (56.0 mg, 0.100 mmol), glycosyl bromide 5
(200 mg, 0.303 mmol) and TMU (0.012 mL, 0.10 mmol) in dry
CH2Cl2 (1.0 mL) was added silver triflate (56.0 mg, 0.218 mmol). The
mixture was stirred at rt for 3 h in the dark, diluted with CHCl3, and
filtered through Celite. The filtrate was washed with aqueous
NaHCO3, dried (Na2SO4), and evaporated in vacuo. The residue was
purified by column chromatography with 2:1 AcOEt–hexane to give
24 (85.6 mg, 75%) as a pale yellow foam: Rf¼0.38 (AcOEt); 1H NMR
(600 MHz, CDCl3), see Table 1. Anal. Calcd for C62H57N7O15: C, 65.31;
H, 5.04. Found: C, 65.18; H, 4.96.
4.7. 1,6-Dideoxy-1,1-bis(ethylsulfonyl)-4-O-(4-
methoxybenzyl)-L-mannitol (18)
To a solution of 17 (199 mg, 0.510 mmol) in dry dioxane (4 mL)
was added mCPBA (572 mg, 2.55 mmol). The mixture was stirred at
rt for 1 h and then evaporated in vacuo. The residue was diluted
with CHCl3, washed with cold saturated NaHCO3, dried (MgSO4),
and evaporated in vacuo. The residue was purified by column
4.12. N2-(N,N-Dimethylaminomethylene)-3-[2-(4-
nitrophenyl)ethyl]-20-O-(2,3,4,6-tetra-O-benzoyl-
b-D-
glucopyranosyl)biopterin (6)13
chromatography with 1:1 AcOEt–hexane to give 18 (179 mg, 77%)
27
as colorless needles: mp 115–116 ꢀC (from AcOEt–hexane); [
a]
D
ꢁ5.43ꢀ (c 2.30, CHCl3); Rf¼0.20 (1:1 AcOEt–hexane); 1H NMR
To a solution of 22 (54.4 mg, 0.0477 mmol) in CH2Cl2 (1.0 mL)
containing water (0.10 mL) was added DDQ (16.2 mg,
0.0716 mmol). The mixture was stirred at rt for 2 h and then
evaporated in vacuo. The residue was purified by column chro-
(600 MHz CDCl3):
d
¼1.31 (3H, d, J5,6¼6.4 Hz, H3-6), 1.42, 1.44 (3H
each, 2 t, 3J¼7.6 Hz, CH3CH2S), 2.37 (3H, br s, HO-2,3,5), 3.38, 3.57
(1H each, 2dq, 2J¼14.0 Hz, CH2S), 3.39, 3.62 (1H each, 2dq,
2J¼14.0 Hz, CH’2S), 3.53 (1H, dd, J4,5¼5.1, J3,4¼1.7 Hz, H-4), 3.81 (3H,
s, MeO), 4.19 (1H, qd, H-5), 4.32 (1H, dd, J2,3¼9.5 Hz, H-3), 4.53, 4.68
(1H each, 2d, 2J¼11.2 Hz, CH2O-4), 4.66 (1H, dd, J1,2¼1.0 Hz, H-2),
4.83 (1H, d, H-1), 6.90, 7.30 (2H each, 2d, Jo,m¼8.6 Hz, C6H4). 13C
matography with 1:99 MeOH–CHCl3 to give 6 (40.6 mg, 83%) as
20
a pale yellow syrup: Rf¼0.63 (1:9 MeOH–CHCl3); [
a
]
þ37.1ꢀ (c
D
2.17, CHCl3). 1H NMR spectra were in accord with previously pub-
lished data.13 Anal. Calcd for C54H49N7O14: C, 63.59; H, 4.84. Found:
C, 63.44; H, 4.99.
NMR (151 MHz, CDCl3):
d
¼5.33 (CH3CH2S), 5.59 (CH3CH2S), 19.60
(C-6), 48.34 (CH3CH2S), 51.18 (CH3CH2S), 55.30 (MeO), 68.19 (C-5),
69.92 (C-3), 70.22 (C-2), 72.80 (CH2O), 77.70 (C-1), 77.96 (C-4),
114.10 (C(m) of PMB), 129.22 (C(o) of PMB), 130.29 (C(ipso) of PMB),
159.71 (C(p) of PMB). Anal. Calcd for C18H30O9S2: C, 47.56; H, 6.65.
Found: C, 47.68; H, 6.72.
4.13. 20-O-(
b-D-Glucopyranosyl)biopterin (2b)
4.13.1. From 6. Compound 6 (54.1 mg, 0.0530 mmol) was dissolved
in MeOH (2.0 mL) and 28% methanolic NaOMe (0.03 mL,
a
0.15 mmol) was added at 0 ꢀC. The mixture was stirred at rt for 1 h
and neutralized with Amberlite IR-120(Hþ). The resin was filtered
off and the filtrate was evaporated in vacuo. The residue was dis-
solved in MeOH (3.0 mL) and 28% aqueous ammonia solution
(3.0 mL) was added. The mixture was stirred at rt for 12 h and
evaporated in vacuo. The residue was dissolved in DMF (1.0 mL) and
DBU (0.050 mL, 0.32 mmol) was added. The mixture was stirred at
rt for 12 h, diluted with water (3.0 mL), and neutralized with
Amberlite FPC3500(Hþ). The resin was filtered off and the filtrate
was evaporated in vacuo. The residue was washed with CHCl3 and
dried under reduced pressure to give 2b (18.7 mg, 89% from 6) as
a yellow powder.
4.8. 5-Deoxy-3-O-(4-methoxybenzyl)-a,b-L-
arabinofuranoses (19)14
Compound 18 (153 mg, 0.337 mmol) was dissolved in 10%
aqueous ammonia (3 mL). The mixture was stirred at rt for 10 h and
then concentrated in vacuo. The residue was purified by column
chromatography with 1:2 AcOEt–hexane to give an inseparable
mixture (40:60) of a- and b-anomers of 19 (70.1 mg, 82%) as a col-
orless syrup: Rf¼0.15 (1:1 AcOEt–hexane), 0.54 (AcOEt). 1H NMR
spectra were in accord with previously published data.14
4.9. 5-Deoxy-3-O-(4-methoxybenzyl)-a,b-L-erythro-pentos-2-
4.13.2. From 25b. Compound 25b (26.0 mg, 0.0399 mmol) was
dissolved in MeOH (2.0 mL) and 28% aqueous ammonia solution
(1.0 mL) was added. The mixture was stirred at rt for 12 h and
evaporated in vacuo. The residue was washed with CHCl3 to give 2b
(15.6 mg, 98%): Rf¼0.23 (5:3:1 i-PrOH–AcOEt–H2O); 1H NMR
(600 MHz, D2O) and 13C NMR (151 MHz, D2O and DMSO-d6), see
Table 2. Anal. Calcd for C15H21N5O8: C, 45.11; H, 5.30. Found: C,
44.89; H, 5.53.
uloses (20)14
Compound 19 (282 mg, 1.11 mmol) was dissolved in MeOH
(6 mL) and water (3 mL). The solution was refluxed and then cupric
acetate hydrate (1.44 g, 7.23 mmol) was added. The mixture was
refluxed for 1 h and then precipitates were filtered off and washed
with ethyl acetate. The filtrate was evaporated in vacuo and the
residue was separated by column chromatography with 1:3 AcOEt–
hexane to give 20 (142 mg, 51% yield, lit.14 46%) as a colorless syrup:
Rf¼0.25ꢁ0.33 (1:1 AcOEt–hexane). From the slower-eluting frac-
tion, compound 17 (55.2 mg, 20%) was recovered.
4.14. Di-N2:10-O-acetyl-20-O-(2,3,4,6-tetra-O-acetyl-
b-D-
glucopyranosyl)biopterin (25b)
Compound 1b (18.7 mg, 0.0468 mmol) was dissolved in pyri-
dine (2.0 mL) and then acetic anhydride (1.0 mL) was added at 0 ꢀC.
The mixture was stirred at rt for 12 h and evaporated in vacuo. The
residue was purified by column chromatography with AcOEt to give
25b (28.0 mg, 92%) as a pale yellow syrup: Rf¼0.52 (1:9 MeOH–
CHCl3); 1H NMR (600 MHz, CDCl3), see Table 1. Anal. Calcd for
C27H33N5O14: C, 49.77; H, 5.10. Found: C, 49.92; H, 5.02.
4.10. N2-(N,N-Dimethylaminomethylene)-10-O-(4-methoxy-
benzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (23)14
By use of the same procedures described in the literature,14
compound 20 was converted into 23 in five steps: Rf¼0.60 (1:9
MeOH–CHCl3).

7996
T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
4.15. Methyl 2,3,4,6-tetra-O-acetyl-1-thio-
b-D
-
4.18. Methyl 2,3-di-O-(4-methoxybenzyl)-1-thio-
glucopyranoside (30)
b-D-
glucopyranoside (27)27
The following modification of the literature procedures was
made.27 To a solution of 26 (5.41 g, 13.9 mmol) in dry acetonitrile
(28 mL), were added thiourea (1.17 g, 15.4 mmol) and BF3-etherate
(3.7 mL, 29.1 mmol). The mixture was refluxed for 20 min and then
TEA (23.2 mL, 166 mmol) and methyl iodide (8.6 mL, 139 mmol)
were slowly added at 0 ꢀC. The reaction mixture was stirred at rt for
2 h and concentrated in vacuo. The residue was dissolved in CHCl3
and then the mixture was washed with brine, dried (Na2SO4), and
evaporated in vacuo. The residue was purified by column chro-
matography with 1:5 AcOEt–hexane to give 27 [4.66 g, 89% (lit.27
57% yield)] as colorless crystals: mp 89–90 ꢀC (from AcOEt–hex-
ane); Rf¼0.26 (1:2 AcOEt–hexane); 1H NMR (600 MHz, CDCl3)
To a solution of 29 (240 mg, 0.489 mmol) in MeOH (1.5 mL) was
added 70% aqueous AcOH (3.0 mL). The mixture was stirred at rt for
10 h and evaporated in vacuo. The residue was purified by column
chromatography with 1:1 AcOEt–hexane to give 30 (213 mg, 97%
yield) as colorless needles: mp 45–46 ꢀC (from AcOEt–hexane);
26
[a
]
ꢁ16.2ꢀ (c 1.81, CHCl3); Rf¼0.14 (1:1 AcOEt–hexane); 1H NMR
D
(600 MHz, CDCl3)
d 1.97 (2H, br s, HO-4,6), 2.24 (3H, s, SMe), 3.33
(1H, ddd, J4,5¼9.4, J5,6b¼5.2, J5,6a¼3.4 Hz, H-5), 3.38 (1H, t, J1,2¼9.5,
J2,3¼8.8 Hz, H-2), 3.45 (1H, t, J3,4¼8.9 Hz, H-3), 3.53 (1H, t, H-4), 3.74
(1H, dd, J6a,6b¼11.9 Hz, Hb-6), 3.80 (6H, s, MeO), 3.87 (1H, dd, Ha-6),
4.39 (1H, d, H-1), 4.64, 4.70
9.8
*
, 4.86
*
, 4.91 (1H each, 4d, 2J¼11.3,
*
Hz, CH2O-2,3), 6.88, 6.89 (2H each, 2d, Jo,m¼8.5 Hz, m of PMB),
d
2.01, 2.03, 2.07, 2.09 (3H each, 4s, AcO-2,3,4,6), 2.17 (3H, s, SMe),
7.26, 7.36 (2H each, 2d, o of PMB). Anal. Calcd for C23H30O7S: C,
3.73 (1H, ddd, J4,5¼10.0, J5,6a¼4.9, J5,6b¼2.4 Hz, H-5), 4.15 (1H, dd,
J6a,6b¼12.5 Hz, Hb-6), 4.25 (1H, dd, Ha-6), 4.39 (1H, d, J1,2¼10.0 Hz,
H-1), 5.07 (1H, dd, J3,4¼9.5 Hz, H-4), 5.08 (1H, dd, J2,3¼9.5 Hz, H-2),
5.23 (1H, t, H-3).
61.31; H, 6.71. Found: C, 61.10; H, 6.93.
4.19. Methyl 4,6-di-O-acetyl-2,3-di-O-(4-methoxybenzyl)-1-
thio-b-D-glucopyranoside (31)
Compound 30 (295 mg, 0.655 mmol) was dissolved in pyridine
(3.0 mL) and then acetic anhydride (0.62 mL, 6.56 mmol) was
added at 0 ꢀC. The mixture was stirred at rt for 12 h and evaporated
in vacuo. The residue was purified by column chromatography with
4.16. Methyl 4,6-O-isopropylidene-1-thio-b-D-
glucopyranoside (28)
Compound 27 (607 mg, 1.60 mmol) was dissolved in dry MeOH
(3.5 mL) and then a 28% methanolic sodium methoxide (0.87 mL,
4.33 mmol) was added at 0 ꢀC. The mixture was stirred at rt for 2 h
and neutralized with Amberlite IR-120(Hþ). The resin was filtered
off and the filtrate was evaporated in vacuo. The residue was dis-
solved in dry DMF (5.0 mL) and then 2,2-dimethoxypropane
(0.79 mL, 6.42 mmol) and p-toluenesulfonic acid monohydrate
(24 mg, 0.13 mmol) were added. The mixture was stirred at rt for
12 h and then pyridine (0.5 mL) was added. The mixture was con-
centrated in vacuo and the residue was purified by column chro-
matography with 1:2 AcOEt–hexane to give 28 (364 mg, 90%) as
a colorless syrup: Rf¼0.16 (1:1 AcOEt–hexane); 1H NMR (600 MHz,
1:3 AcOEt–hexane to give 31 (342 mg, 98% yield) as colorless
26
needles: mp 82–83 ꢀC (from AcOEt–hexane); [
a
]
D
ꢁ0.69ꢀ (c 1.21,
CHCl3); Rf¼0.22 (1:2 AcOEt–hexane); 1H NMR (600 MHz, CDCl3)
d
1.94, 2.06 (3H each, 2s, AcO-4,6), 2.22 (1H, s, SMe), 3.48 (1H, t,
J1,2¼9.8, J2,3¼8.8 Hz, H-2), 3.54 (1H, ddd, J4,5¼9.8, J5,6a¼5.2,
J5,6b¼2.4 Hz, H-5), 3.61 (1H, t, J3,4¼9.5 Hz, H-3), 3.80 (6H, s, MeO),
4.08 (1H, dd, J6a,6b¼12.2 Hz, Hb-6), 4.20 (1H, dd, Ha-6), 4.35 (1H, d,
H-1), 4.59, 4.67
*
, 4.77, 4.81
*
(1H each, 4d, 2J¼11.0, 10.1
*
Hz, CH2O-
2,3), 5.02 (1H, t, H-4), 6.855, 6.86 (2H each, 2d, Jo,m¼8.8 Hz, m of
PMB), 7.18, 7.30 (2H each, 2d, o of PMB). Anal. Calcd for C27H34O9S:
C, 60.66; H, 6.41. Found: C, 60.58; H, 6.55.
CDCl3)
d 1.43, 1.50 (3H each, 2s, Me2C), 2.21 (3H, s, SMe), 3.00, 3.25
4.20. 4,6-Di-O-acetyl-2,3-di-O-(4-methoxybenzyl)-a-D-
glucopyranosyl bromide (32)
(1H each, 2br s, HO-2,3), 3.32 (1H, ddd, J5,6b¼10.3, J4,5¼9.6,
J5,6a¼5.4 Hz, H-5), 3.47 (1H, dd, J1,2¼9.8, J2,3¼8.3 Hz, H-2), 3.57 (1H,
t, J3,4¼9.3 Hz, H-4), 3.67 (1H, dd, H-3), 3.75 (1H, t, J6a,6b¼10.9 Hz,
Hb-6), 3.93 (1H, dd, Ha-6), 4.32 (1H, d, H-1). Anal. Calcd for
C10H18O5S: C, 47.98; H, 7.25. Found: C, 48.11; H, 7.02.
Compound 31 (650 mg, 1.22 mmol) and 2,6-lutidine (0.40 mL,
3.41 mmol) were dissolved in dry CH2Cl2 (4.0 mL) and then bro-
mine (0.15 mL, 2.92 mmol) was added with stirring at 0 ꢀC. The
mixture was stirred at rt for 2 h and then cyclohexene (0.30 mL,
2.96 mmol) was added. The mixture was concentrated in vacuo and
the residue was dissolved in AcOEt. The insoluble matter was fil-
tered off and the filtrate was evaporated in vacuo. The residue was
purified by column chromatography with 1:4 AcOEt–hexane to give
32 (623 mg, 90%) as a colorless syrup: Rf¼0.42 (1:2 AcOEt–hexane);
4.17. Methyl 4,6-O-isopropylidene-2,3-di-O-(4-methoxy-
benzyl)-1-thio-b-D-glucopyranoside (29)
Compound 28 (778 mg, 3.11 mmol), p-methoxybenzyl chloride
(2.10 mL, 15.5 mmol) and tetrabutylammonium iodide (344 mg,
0.93 mmol) were dissolved in dry DMF (30 mL) and then sodium
hydride (60% in oil, 621 mg, 15.5 mmol) was added with stirring at
0 ꢀC. The mixture was stirred at rt for 10 h, diluted with saturated
NH4Cl, and evaporated in vacuo. The residue was dissolved in
CHCl3, washed with water, dried (Na2SO4), and evaporated in
vacuo. The residue was purified by column chromatography with
1H NMR (600 MHz, CDCl3)
d 1.95, 2.05 (3H each, 2s, AcO-4,6), 3.53
(1H, dd, J2,3¼9.2, J1,2¼3.9 Hz, H-2), 3.80, 3.81 (3H each, 2s, MeO),
3.92 (1H, t, J3,4¼9.5 Hz, H-3), 4.02 (1H, dd, J6a,6b¼12.5, J5,6b¼2.1 Hz,
Hb-6), 4.14 (1H, ddd, J4,5¼10.4, J5,6a¼4.6 Hz, H-5), 4.26 (1H, dd, Ha-
6), 4.58
*
, 4.62, 4.67, 4.80
*
(1H each, 4d, 2J¼11.6, 11.3
*
Hz, CH2O-2,3),
5.05 (1H, dd, H-4), 6.26 (1H, d, H-1), 6.86, 6.88 (2H each, 2d,
Jo,m¼8.6 Hz, m of PMB), 7.19, 7.29 (2H each, 2d, o of PMB). Anal.
Calcd for C26H31BrO9: C, 55.03; H, 5.51. Found: C, 54.91; H, 5.74.
1:6 AcOEt–hexane to give 29 (1.25 g, 82% yield) as colorless prisms:
26
mp 80–81 ꢀC (from AcOEt–hexane); [
a
]
þ4.25ꢀ (c 1.44, CHCl3);
D
Rf¼0.34 (1:4 AcOEt–hexane); 1H NMR (600 MHz, CDCl3)
d 1.43, 1.51
(3H each, 2s, Me2C), 2.20 (3H, s, SMe), 3.26 (1H, dt, J5,6b¼10.2,
J4,5¼9.7, J5,6a¼5.4 Hz, H-5), 3.38 (1H, dd, J1,2¼9.8, J2,3¼8.5 Hz, H-2),
3.60 (1H, t, J3,4¼9.1 Hz, H-3), 3.69 (1H, t, H-4), 3.75 (1H, t,
J6a,6b¼11.0 Hz, Hb-6), 3.80 (6H, s, MeO), 3.93 (1H, dd, Ha-6), 4.37
4.21. N2-(N,N-Dimethylaminomethylene)-10-O-(4-
methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]-20-O-[4,6-di-O-
acetyl-2,3-di-O-(4-methoxybenzyl)-a-D-glucopyranosyl]-
biopterin (33a) and its -anomer 33b
b
(1H, d, H-1), 4.69, 4.72
*
, 4.74
*
, 4.80 (1H each, 4d, 2J¼11.0, 10.0
*
Hz,
CH2O-2,3), 6.855, 6.86 (1H each, 2d, Jo,m¼8.6 Hz, m of PMB), 7.28,
7.30 (2H each, 2d, o of PMB). Anal. Calcd for C26H34O7S: C, 63.65; H,
6.99. Found: C, 63.81; H, 7.01.
To
0.0534 mmol), the
0.21 mmol) and TMU (0.0064 mL, 0.054 mmol) in dry CH2Cl2
a
solution of the biopterin derivative (23) (30.0 mg,
D-glucopyranosyl bromide (32) (122 mg,

T. Hanaya et al. / Tetrahedron 65 (2009) 7989–7997
7997
(2.0 mL), was added silver triflate (28.0 mg, 0.109 mmol). The mix-
ture was stirred at rt for 3 h and the suspension was filtered through
Celite. The residue was washed with CHCl3 and the filtrate was
treated with saturated NaHCO3. The mixture was extracted with
CHCl3 three times. The combined organic layers were dried (Na2SO4)
and evaporated in vacuo. The residue was purified by column chro-
matography with 1:1 AcOEt–hexane to give an inseparable anomeric
mixture (85:15) of 33a and 33b (37.0 mg, 66%) as a pale yellow syrup:
Rf¼0.50 (AcOEt). From the slower-eluting fraction, compound 23
(7.2 mg, 24% recovery) was recovered: Rf¼0.12 (AcOEt).
(19.6 mg, 90%) as a yellow syrup: Rf¼0.29 (AcOEt); 1H NMR
(600 MHz, CDCl3), see Table 1. Anal. Calcd for C27H33N5O14: C,
49.77; H, 5.10. Found: C, 49.99; H, 5.29.
Acknowledgements
We are grateful to the SC-NMR Laboratory of Okayama Univer-
sity for the NMR measurements and to WESCO Scientific Promotion
Foundation (to T.H.), which partially supported this work.
Compound 33a. 1H NMR (600 MHz, CDCl3), see Table 1.
References and notes
4.22. 10-O-Acetyl-N2-(N,N-dimethylaminomethylene)-3-[2-(4-
nitrophenyl)ethyl]-20-O-(2,3,4,6-tetra-O-acetyl-
a-D-gluco-
1. Forrest, H. S.; Van Baalen, C.; Myers, J. Arch. Biochem. Biophys. 1958, 78, 95.
2. Matsunaga, T.; Burgess, J. G.; Yamada, N.; Komatsu, K.; Yoshida, S.; Wachi, Y.
Appl. Microbiol. Biotechnol. 1993, 39, 250.
pyranosyl)biopterin (34a) and its b-anomer 34b
3. Choi, Y. K.; Hwang, Y. K.; Kang, Y. H.; Park, Y. S. Pteridines 2001, 12, 121.
4. Noguchi, Y.; Ishii, A.; Matsushima, A.; Haishi, D.; Yasumuro, K.; Moriguchi, T.;
Wada, T.; Kodera, Y.; Hiroto, M.; Nishihara, H.; Sekine, M.; Inada, Y. Mar. Bio-
technol. 1999, 1, 207.
5. Cha, K. W.; Pfleiderer, W.; Yim, J. J. Helv. Chim. Acta 1995, 78, 600.
6. (a) Ikawa, M.; Sasner, J. J.; Haney, J. F.; Foxall, T. L. Phytochemistry 1995, 38, 1229;
(b) Cho, S.-H.; Na, J.-U.; Youn, H.; Hwang, C. S.; Lee, C. H.; Kang, S. O. Biochim.
Biophys. Acta 1998, 1379, 53.
7. (a) Suzuki, A.; Goto, M. J. Biochem. 1968, 63, 798; (b) Lin, X.; White, R. H.
J. Bacteriol. 1988, 170, 1396.
8. (a) Lee, H. W.; Oh, C. H.; Geyer, A.; Pfleiderer, W.; Park, Y. S. Biochim. Biophys.
Acta 1999, 1410, 61; (b) Hatfield, D. J.; Van Baalen, C.; Forrest, H. S. Plant Physiol.
1961, 36, 240.
9. (a) Kaufman, S.; Fisher, D. B. In Molecular Mechanisms of Oxygen Activation;
Hayaishi, O., Ed.; Academic: New York, NY, 1974; pp 285–369; (b) Kaufman, S.;
Kaufman, E. E. In Folates and Pterins; Blakley, R., Benkovic, S. J., Eds.; John Wiley
& Sons: New York, NY, 1985; Vol. 2, pp 251–352; (c) Fitzpatrick, P. F. Annu. Rev.
Biochem. 1999, 68, 355.
10. (a) Crane, B. R.; Arvai, A. S.; Ghosh, D. K.; Wu, C. Q.; Getzoff, E. D.; Stuehr, D. J.;
Tainer, J. A. Science 1998, 5359, 2121; (b) Kwon, N. S.; Nathan, C. F.; Stuehr, D. J.
J. Biol. Chem. 1989, 264, 20496; (c) Marletta, M. A. Cell 1994, 78, 927.
11. Wachi, Y.; Yoshida, S.; Komatsu, K.; Matsunaga, T. Jpn. Patent 05,286,989, 1993;
Chem. Abstr. 1994, 120, 161782t.
To a solution of 33a,b (59.0 mg, 0.0563 mmol) in CH2Cl2 (2.0 mL)
containing water (0.2 mL) was added DDQ (154 mg, 0.68 mmol).
The mixture was stirred at rt for 2 h and then diluted with CHCl3.
The mixture was washed with aqueous NaHCO3, dried (Na2SO4),
and evaporated in vacuo. The residue was dissolved in dry pyridine
(2.0 mL) and then acetic anhydride (0.27 mL, 2.82 mmol) was
added at 0 ꢀC. The mixture was stirred at rt for 12 h and then
evaporated in vacuo. The residue was purified by column chro-
matography with 2:1 AcOEt–hexane to give 34a (35.2 mg, 51% from
23) and 34b (6.2 mg, 9%).
Compound 34a. Pale yellow syrup; Rf¼0.27 (AcOEt); 1H NMR
(600 MHz, CDCl3), see Table 1. Anal. Calcd for C36H43N7O15: C, 53.13;
H, 5.33. Found: C, 53.01; H, 5.49.
Compound 34b. Pale yellow syrup; Rf¼0.30 (AcOEt); 1H NMR
(600 MHz, CDCl3), see Table 1.
4.23. 20-O-(
a-D-Glucopyranosyl)biopterin (2a)
12. Saito, T.; Ishikawa, H.; Hada, Y.; Fukui, K.; Kodera, Y.; Matsushima, A.; Inada, Y.
Dyes Pigments 2003, 56, 203.
4.23.1. From 34a. Compound 34a (30.2 mg, 0.0371 mmol) was
dissolved in MeOH (2.0 mL) and 28% aqueous ammonia solution
(2.0 mL) was added. The mixture was stirred at rt for 12 h and then
evaporated in vacuo. The residue was dissolved in DMF (2.0 mL)
and DBU (0.027 mL, 0.18 mmol) was added. The mixture was stirred
at rt for 12 h and neutralized with Amberlite FPC3500(Hþ). The
resin was filtered off and the filtrate was evaporated in vacuo. The
residue was washed with CHCl3 and dried under reduced pressure
to give 2a (13.4 mg, 90%).
13. Hanaya, T.; Soranaka, K.; Harada, K.; Yamaguchi, H.; Suzuki, R.; Endo, Y.;
Yamamoto, H.; Pfleiderer, W. Heterocycles 2006, 67, 299.
14. Hanaya, T.; Baba, H.; Toyota, H.; Yamamoto, H. Tetrahedron 2008, 64, 2090.
15. Ness, R. K.; Fletcher, H. G., Jr.; Hudson, C. S. J. Am. Chem. Soc. 1950, 72, 2200.
16. A part of the results have been reported as preliminary communications:
(a) Hanaya, T.; Toyota, H.; Yamamoto, H. Synlett 2006, 2075; (b) Hanaya, T.;
Baba, H.; Yamamoto, H. Heterocycles 2009, 77, 747.
17. For an alternative route of preparation of biopterin derivative (9) from D-xylose,
see Ref. 14.
18. Hanaya, T.; Torigoe, K.; Soranaka, K.; Yamamoto, H.; Yao, Q.; Pfleiderer, W.
Pteridines 1995, 6, 1.
19. Gigg, R.; Payne, S.; Conant, R. J. Carbohydr. Res. 1983, 2, 207.
20. Acidic hydrolysis of methyl 2,3-O-isopropylidene-4-O-PMB-
a-L-rhamnopyr-
4.23.2. From 25a. Compound 25a (18.0 mg, 0.0276 mmol) was
dissolved in MeOH (1.0 mL) and 28% aqueous ammonia solution
(1.0 mL) was added. The mixture was stirred at rt for 12 h and then
evaporated in vacuo. The residue was washed with CHCl3 and dried
under reduced pressure to give 2a (10.4 mg, 94%) as a pale yellow
solid: Rf¼0.11 (5:3:1 2-PrOH–AcOEt–H2O); 1H NMR (600 MHz, D2O)
and 13C NMR (151 MHz, D2O and DMSO-d6), see Table 2. Anal. Calcd
for C15H21N5O8: C, 45.11; H, 5.30. Found: C, 45.01; H, 5.50.
anoside in an attempt to obtain 4-O-PMB- -rhamnose (16) resulted in a pref-
L
erential removal of the PMB group rather than hydrolysis of methyl glycoside.
Therefore we employed 1-propenyl glycoside, which is cleavable under weaker
acidic conditions.
21. Hough, L.; Taylor, T. J. J. Chem. Soc. 1955, 3544.
22. (a) Weinstock, J. U.S. Patent 3,505,329, 1970; Chem. Abstr. 1970, 72, 132787h;
(b) Taylor, E. C.; Jacobi, P. A. J. Am. Chem. Soc. 1976, 98, 2301–2307.
23. Lemieux, R. U.; Hendriks, K. B.; Stick, R. V.; James, K. J. Am. Chem. Soc. 1975,
97, 4056.
24. Hanessian, S.; Banoub, J. Methods Carbohydr. Chem. 1980, 8, 247.
25. Wulff, G.; Ro¨hle, G. Angew. Chem., Int. Ed. Engl. 1974, 13, 157 and references cited
therein.
26. Wolfrom, M. L.; Thompson, A. Methods Carbohydr. Chem. 1963, 2, 211.
27. Ibatullin, F. M.; Shabalin, K. A.; Ja¨nis, J. V.; Shavva, A. G. Tetrahedron Lett. 2003,
44, 7961.
4.24. Di-N2:10-O-acetyl-20-O-(2,3,4,6-tetra-O-acetyl-
a-D-
glucopyranosyl)biopterin (25a)
28. Lo¨nn, H. Carbohydr. Res. 1985, 139, 105.
29. Yin, H.; D’Souza, F. W.; Lowary, T. L. J. Org. Chem. 2002, 67, 892.
30. In model experiments using thioglycoside 31 with 2-propanol in CH2Cl2, the
corresponding glycosides were obtained in good yields: 95% (
use of MeOTf; 91% (56:44) by use of NIS-AgOTf.
31. (a) Stewart, J. J. P. J. Comput.-Aided Mol. Des. 1990, 4, 1; (b) Coolidge, M. B.;
Marlin, J. E.; Stewart, J. J. P. J. Comput. Chem. 1991, 12, 948.
Compound 2a (13.4 mg, 0.0336 mmol) was dissolved in dry
DMF (1.0 mL) and dry pyridine (1.0 mL) and then acetic anhydride
(0.17 mL, 1.84 mmol) was added at 0 ꢀC. The mixture was stirred at
rt for 12 h and then evaporated in vacuo. The residue was purified
by column chromatography with 4:1 AcOEt–hexane to give 25a
a
:b
¼60:40) by