Efficient total syntheses of natural pterin glycosides: limipterin and tepidopterin

Article abstract of DOI:10.1016/j.tet.2007.12.042

The key, versatile precursors N²-(N,N-dimethylaminomethylene)-1′-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (29a) and its ciliapterin analog (29b) were prepared, respectively, from d-xylose (in 14 steps) and l-xylose (in 11 steps). Treatment of 29a and 29b with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl bromide in the presence of silver triflate and tetramethylurea, followed by removal of the protecting groups, led to the first selective syntheses of limipterin (3) and tepidopterin (5), respectively.

Full text of DOI:10.1016/j.tet.2007.12.042

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 2090e2100
www.elsevier.com/locate/tet
Efficient total syntheses of natural pterin glycosides:
limipterin and tepidopterin
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, Okayama 703-8516, Japan
Received 7 November 2007; received in revised form 17 December 2007; accepted 17 December 2007
Available online 23 December 2007
Abstract
The key, versatile precursors N2-(N,N-dimethylaminomethylene)-10-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (29a) and its
ciliapterin analog (29b) were prepared, respectively, from D-xylose (in 14 steps) and L-xylose (in 11 steps). Treatment of 29a and 29b with
3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl bromide in the presence of silver triflate and tetramethylurea, followed by
removal of the protecting groups, led to the first selective syntheses of limipterin (3) and tepidopterin (5), respectively.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Pteridine; Pterin glycoside; Glycosylation; Protecting group
1. Introduction
of the pterin moiety and the anomeric structure of the glyco-
side.8 Tepidopterin (5) was isolated from a green sulfur
photosynthetic bacterium Chlorobium tepidum and was
characterized as the 20-O-(2-acetamido-2-deoxy-b-D-glucopyr-
anosyl) derivative of ciliapterin9 (L-threo-bioptern) (4).10 The
L-threo structure of 4 appears somewhat peculiar in view of
the tendency that biopterin derivatives having an L-erythro
form are common among natural pterin glycosides, and thus
identifying the enzyme from C. tepidum and elucidating the
biosynthetic pathway of 4 have been attempted.11
Pterin glycosides having various kinds of sugars attached to
the side chain at C-6 of the pteridine ring were found to be
produced by certain prokaryotes such as cyanobacteria and an-
aerobic photosynthetic bacteria. As representative examples
for glycosides of biopterin (1), 20-O-(a-D-glucopyranosyl)-
biopterin (2) was isolated from cyanobacterium, Anacystis
nidulans,1 Synechococcus sp.,2 and Spirulina platensis,3
whereas limipterin [20-O-(2-acetamido-2-deoxy-b-D-glucopyr-
anosyl)biopterin] (3) was isolated from a green sulfur photo-
synthetic bacterium, Chlorobium limicola f. thiosulfatophilum
NCIB 8327.4 However, their physiological function5 has re-
mained obscure, in contrast to the detailed study on that of
the parent biopterin, e.g., 1 exhibits enzyme cofactor activity
in aromatic amino acid hydroxylation6 and nitric oxide synthe-
sis7 in the form of its tetrahydro derivative.
O
OH
O
OH
3
HN
6
2'
N
N
N
N
3'
HN
H2N
1'
OR
OR
7
H2N
N
N
2
1 R = H (biopterin)
4 R = H (ciliapterin)
HO
O
HO
O
OH
OH
2 R =
3 R =
5 R =
HO
HO
Various other glycosides consisting of different pterins and
sugar moieties have also been found in nature, although some
of them have remained unclear about the glycosylated position
NHAc
HO
HO
O
OH
HO
NHAc
Despite a considerable interest from the viewpoint of their
biological activities and functions as well as structural proof,
* Corresponding author. Fax: þ81 86 251 7853.
E-mail address: hanaya@cc.okayama-u.ac.jp (T. Hanaya).
0040-4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.12.042

T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
2091
5
3
2. Results and discussion
OR3
O
N
OR3
A retrosynthetic analysis outlined in Scheme 1 suggests
that the biopterin and ciliapterin derivatives (6a and 6b) can
be perceived as the key precursors for 3 and 5, respectively,
to achieve selective 20-O-glycosylation, if the pyrimidine
ring moiety and 10-hydroxy group of the side chain are suit-
ably protected. The pteridine ring formation of 6a would be
obtained by condensation of 2,5,6-triamino-4-hydroxypyrimi-
dine (7) with the L-erythro-pentos-2-ulose (8a), which would
be derived from the 3-O-protected 5-deoxy-L-arabinose (9a).
Compound 9a would be available from D-xylose by inversion
of C-4 configuration and deoxygenation of C-5. Similarly,
compound 6b would be obtainable from the L-threo-pentos-
2-ulose (8b), which would be derived from L-xylose via the
3-O-protected 5-deoxy-L-xylose (9b). Taking into consider-
ation the available conditions to remove the protecting groups
of the glycosides derived from 6a and 6b, we employed p-
methoxybenzyl (PMB) group for protection of 10-hydroxy,
N,N-dimethylaminomethylene group for 2-amino, and 2-(4-
nitrophenyl)ethyl (NPE) group for N(3) of the ring.13
O
N
R2
N
N
R2
N
N
N
N
OH
(R1, R2, R3
OH
R1HN
R1HN
6b
6a
=
protecting groups)
OR3
OR3
O
NH2
NH2
O
O
O
O
HN
+
7
+
OH
H
OH
H2N
N
H
8a
8b
7
CHO
OH
CHO
OH HO
CHO
CHO
HO
HO
HO
R3O
HO
OH
OR3
OH
CH2OH
HO
CH3
CH2OH
CH3
D-xylose
L-xylose
9a
9b
Scheme 1.
1,2-O-Isopropylidene-5-O-tosyl-a-D-xylofuranose(10)(avail-
able from D-xylose in 2 steps) served as the starting material
for preparation of 5-deoxy-3-O-PMB-L-erythro-pentos-2-ulose
(17), the key intermediate for the 10-O-PMB-biopterin deriva-
tive (Scheme 2). Treatment of 10 with 3,4-dihydro-2H-pyran
(DHP) in the presence of pyridinium p-toluenesulfonate
(PPTS) afforded the 3-O-THP derivative (11)15 (in 92% yield),
which was then converted into the 5-deoxy-4-enofuranose (12)
by the action of potassium tert-butoxide in DMF in 68% yield.
Hydrogenation of 12 having the E4 conformation16 proceeded
from the less hindered upper side of the ring, exclusively
affording the 5-deoxy-L-arabinofuranose derivative (13). The
3-O-THP group of 13 was then cleaved with PPTS in methanol
to provide 14. Treatment of 14 with p-methoxybenzyl chloride
and sodium hydride in DMF gave the 3-O-PMB derivative
attempts at preparation of pterin glycosides have so far
scarcely been made. We reported in a previous paper12 that
the glycosylation of a biopterin derivative whose two hydroxy
groups were unprotected did not afford the 20-O-(D-glucopyr-
anosyl)biopterin with high regioselectivity, yielding an appre-
ciable amount of 10-O- and 10,20-di-O-(D-glucopyranosyl)
derivatives as well. These facts prompted us to develop
a more efficient synthetic protocol for pterin 20-O-glycosides
and to prove the proposed structures of the reported natural
products. We give herein a full account of the first, efficient
syntheses of limipterin (3) and tepidopterin (5) by glycosyl-
ation of appropriately protected biopterin and ciliapterin
derivatives.13,14
1) H2/Pd-C
MeOH
1) acetone
TsO
O
O
OTHP
O
O
H2SO4
70% AcOH aq.
O
tert-BuOK
94%
OH
OR
OR
OPMB
OH
OH
DMF, 60 °C
68%
2) PPTS
MeOH
94%
3) PMBCl, NaH
Bu4NI, DMF
97%
2) TsCl, Py
cat. HCl, 40 °C
75%
O
O
O
H3C
H3C
HO
O
O
O
OH
OH
3) DHP, PPTS
92%
16
D-xylose
10 R = H
11 R = THP
12
13 R = THP
14 R = H
15 R = PMB
O
OPMB
OH
O
OPMB
OAc
N
R
N
N
O
1) Me2NCH(OMe)2
DMF, rt, 3 h
2) Ac2O, Py
rt, 12 h
HN
H2N
NH2
NH2
HN
N
O
N
N
N
N
N
N
H2N
N
7
O
OPMB
OH
Cu(OAc)2
19a R =H
18a
+
+
20a R = NPE
H3C
MeOH-H2O
reflux, 1 h
46%
NaHCO3
MeOH-H2O
reflux, 3 h
3) NPEOH, PPh3
DEAD, THF
rt, 12 h
O
(53% from 17)
O
N
N
N
HN
H2N
OH
R
N
N
N
17
N
OAc
4) separation
N
OPMB
OPMB
18b
19b R = H
20b R=NPE (15%)
Scheme 2.

2092
T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
(15), which afforded 5-deoxy-3-O-PMB-L-arabinose (16) by
hydrolysis in 70% acetic acid containing a catalytic amount
of hydrochloric acid. The selective oxidation of 2-hydroxy group
of 16 with cupric acetate17 provided the L-erythro-pentos-2-ulose
derivative (17).
derivative (20a, 53% overall yield from 17) and the 7-bio-
pterin derivative (20b, 15%).
On the other hand, the preparation of ciliapterin derivatives
was started with 1,2-O-isopropylidene-5-O-tosyl-a-L-xylofur-
anose (21), which was easily prepared from L-xylose (Scheme
3). Reduction of 21 with lithium aluminum hydride in ether af-
forded the 5-deoxy derivative (22)19 (in 95% yield), which was
then converted into 5-deoxy-3-O-PMB-L-threo-pentos-2-ulose
(25) via the 3-O-PMB derivatives (23, 24) by employing the
same procedures as those for 17 from 14. The condensation
of 25 with sulfate of 7 was carried out in an aqueous sodium
bicarbonate solution to give an inseparable mixture (75:25) of
the 6-substituted pterin (ciliapterin) derivative (26a) and its
7-substituted isomer (7-ciliapterin)9 (26b). These products were,
as in the cases of 20a,b from 18a,b, converted into the corre-
sponding 20-O-acetyl-N2-(N,N-dimethylaminomethylene)-3-
NPE-10-O-PMB derivatives (28a,b) via 27a,b. Purification
of the crude products on a silica gel column provided the de-
sired ciliapterin derivative (28a) (52% overall yield from 25)
and the 7-ciliapterin derivative (28b) (17%).
The structural assignment of the 6-substituted pterins (20a,
28a) and their 7-substituted isomers (20b, 28b) was made
primarily on the basis of their 1H and 13C NMR spectral
data (Tables 1 and 2). The signals of C-6 and C-7 of 6-alkyl-
pterins generally appear at a similar field, whereas C-7 signals
of 7-alkyl derivatives shift to a lower field (ca. 20 ppm) from
those of C-6.20 Thus, the close values of 20a (C-6: d 150.71,
C-7: d 149.88) and the distant values of 20b (C-6: d 140.92,
C-7: d 159.98) indicate the 6-substituted pterin for the former
and the 7-substituted pterin for the latter. Similarly, the
6-substituted pterin 28a and the 7-substituted pterin 28b
were derived from the corresponding values of 28a (C-6:
d 151.14, C-7: d 149.35) and 28b (C-6: d 140.24, C-7:
d 160.50). These assignments are supported by the fact that
H-7 signals (d 8.96) of 20a and 28a appear at a lower field
than those of H-6 of 20b (d 8.78) and 28b (d 8.77) because
The pteridine ring formation of 17 with monosulfate of
2,5,6-triamino-4-hydroxypyrimidine (7) under neutral condi-
tions afforded an inseparable mixture (24:76) of the C-6
substituted pterin (biopterin) (18a) and its C-7 substituted iso-
mer (7-biopterin)9 (18b), whereas the same condensation in
an aqueous sodium bicarbonate solution resulted in a predomi-
nant formation of the desired 18a in a ratio of 78:22.18 The
difference in the major products (6- vs 7-substituted pterins)
under these conditions could be explained in terms of the
combination of higher electrophilicity of the C-2 carbonyl
carbon (than that of the hemiacetal C-1) of 17 and basicity
of the relevant two amino groups (5- and 6-) of pyrimidine
7; under the basic conditions (pH 9e10), the most nucleo-
philic 5-amino group of 7 would attack the C-2 carbonyl of
17 and the subsequent pteridine ring formation would pre-
dominantly afford the 6-substituted isomer 18a, while under
the neutral conditions an attack of the 6-amino group of 7
(owing to the protonation of the 5-amino group) to the ketone
17 would preferentially take place to yield the 7-substituted
isomer 18b. These products 18a,b were separated and charac-
terized after having been converted into the fully protected
derivatives (20a,b) by the following three steps: treatment
of the mixture (78:22) of 18a,b with N,N-dimethylformamide
dimethyl acetal in DMF, followed by acetylation of a hydroxy
group, afforded 20-O-acetyl-N2-(N,N-dimethylaminomethyl-
ene)-10-O-PMB derivatives (19a,b), whose N(3) position
was then protected with NPE group by Mitsunobu reaction
with 2-(4-nitrophenyl)ethanol in the presence of triphenyl-
phosphine and diethyl azodicarboxylate (DEAD) to give 20a
and 20b. These products were then separated by column chro-
matography over silica gel into the desired biopterin
1) LiAlH4, ether
95%
1) acetone
H2SO4
HO
O
O
O
O
O
O
70% AcOH aq.
HO
OH
O
O
HO
OH
2) TsCl, Py
cat. HCl, 40 °C
83%
2) PMBCl, NaH
Bu4NI, DMF
98%
TsO
H3C
H3C
HO
HO
OR
OPMB
L-xylose
21
22 R = H
23 R = PMB
24
O
OPMB
OAc
O
OPMB
OH
R
N
N
N
O
N
N
1) Me2NCH(OMe)2
HN
NH2
NH2
HN
H2N
DMF, rt, 3 h
N
N
N
N
H2N
N
O
N
2) Ac2O, Py
rt, 12 h
O
Cu(OAc)2
27a R = H
28a R = NPE
(52% from 25)
7
26a
+
OH
+
MeOH-H2O
reflux, 0.5 h
49%
3) NPEOH, PPh3
DEAD, THF
rt, 16 h
NaHCO3
MeOH-H2O
reflux, 3 h
H3C
PMBO
O
N
O
N
N
HN
H2N
OH
R
N
N
OAc
4) separation
25
N
N
N
OPMB
OPMB
26b
27b R = H
28b R = NPE (17%)
Scheme 3.

T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
2093
of the lower electron density of C-7 than that of C-6 due to the
conjugation with the 4-oxo group.21
Methanolysis of 20-O-acetyl-10-O-PMB-biopterin and cilia-
pterin derivatives (20a and 28a) in the presence of sodium
methoxide provided their 10-O-PMB derivatives (29a and
29b), respectively (Scheme 4). These compounds are versatile
precursors for the 20-O-monoglycosylation. Thus, glycosyla-
tion of 29a and 29b was accomplished by the condensation
with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-D-glucopyra-
nosyl bromide22 in the presence of silver triflate and tetrame-
thylurea (TMU) in dichloromethane at room temperature for
3 h, affording the 20-O-(b-D-glucopyranosyl)biopterin deriva-
tive (30a, 82%) and the ciliapterin derivative (30b, 92%),
respectively. The anomeric configurations of these products
were assigned on the evidence of their J1,2 values (8.5 Hz).
Removal of the protecting groups of 30a and 30b was con-
ducted as follows. First, cleavage of the PMB group of 30a
and 30b was performed by use of DDQ to afford 31a (87%)
and 31b (89%), respectively. These were treated with methyl-
amine to remove the phthaloyl, N,N-dimethylaminomethylene,
and acetyl groups and were then acetylated with acetic anhy-
dride in pyridine to give the fully-acetylated derivatives 32a
(91%) and 32b (85%), respectively. Treatment of 32a with
aqueous ammonia (to cleave acetyl groups except for 2-acet-
amido of the sugar moiety) and then with DBU (to cleave
the NPE group) furnished limipterin (3) in 94% overall yield,
while the similar treatment of 32b afforded tepidopterin (5) in
85% yield. The spectral data of the synthetic compounds 3 and
5 were found to be essentially identical with those reported for
the natural product (Table 3).4,10,23
3. Conclusion
The present work demonstrates a novel effective way for
preparation of the pterin 20-O-glycosides via N2-(N,N-dime-
thylaminomethylene)-10-O-PMB-3-NPE-pterin derivatives (29a
and 29b). By employing this synthetic strategy for representa-
tive natural pterin glycosides, the first efficient, total syntheses
of limipterin (3) and tepidopterin (5) were achieved. The 10-O-
PMB-biopterin compound (29a) derived from D-xylose and its
ciliapterin analog (29b) derived from L-xylose are thus re-
garded as highly useful precursors for other pterin glycosides
having various types of sugar moiety.
4. Experimental
4.1. General procedures
All reactions were monitored by TLC (Merck Silica gel 60
254) with an appropriate solvent system [(A) 1:4, (B) 1:2, (C)
F
1:1 AcOEtehexane, (D) AcOEt, (E) 1:9 MeOHeCHCl3, and
(F) 5:3:1 2-PrOHeAcOEteH2O]. Column chromatography
was performed with Daiso Silica Gel IR-60/210w. Compo-
nents were detected by exposing the plates to UV light and/
or 20% H2SO4eEtOH, with subsequent heating. The UV/vis
spectra were taken on a JASCO V-530 spectrophotometer.
Optical rotations were measured with a JASCO P-1020

2094
T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
Table 2
13C NMR (151 MHz) spectral parameters for 6-substituted pterins (20a, 28a) and their 7-substituted isomers (20b, 28b) in CDCl3
Compound
Chemical shifts/d
C-2
C-4
C-4a
C-6
C-7
C-8a
C-10
C-20
C-30
NCH]N
Me2N
COCH3
COCH3
20a
20b
28a
28b
157.55
157.88
157.56
157.83
161.83
161.83
161.78
161.79
128.36
129.29
128.90
129.35
150.71
140.92
151.14
140.24
149.88
159.98
149.35
160.50
153.63
153.17
153.90
153.44
82.21
82.26
82.05
82.33
71.76
71.94
72.11
71.92
15.92
15.61
16.43
16.61
159.31
159.24
159.24
159.19
41.61, 35.51
41.55, 35.51
41.60, 35.49
41.52, 35.49
170.04
169.96
170.15
170.10
21.10
21.11
21.01
20.96
Compound
Chemical shifts/d
NPEeN(3)
PMBOe10
C(ipso)a
C(o)
C(m)
C(p)a
CH2CH2N
CH2N
C(ipso)
C(o)
C(m)
C(p)
CH2O
MeO
20a
20b
28a
28b
a
146.63
146.66
146.66
146.63
129.78
129.79
129.79
129.76
123.71
123.70
123.70
123.67
146.78
146.78
146.73
146.70
34.13
34.15
34.11
34.10
43.26
43.71
43.75
43.66
129.40
129.16
129.11
128.72
129.52
129.64
129.78
130.01
113.84
113.86
113.82
113.82
159.37
159.43
159.43
159.48
71.81
71.98
72.09
71.94
55.26
55.26
55.25
55.22
The assignments may have to be interchanged.
polarimeter in CHCl3. The NMR spectra were measured in
CDCl3 with Varian Unity Inova AS600 (600 MHz for 1H,
crystals; mp 91e93 ꢀC (lit.15 mp 93e94 ꢀC, 68% yield by
use of DHPeTsOH); Rf¼0.43, 0.39 [(B), two diastereomers
with respect to the THP group]. 1H NMR for the faster-eluting
diastereomer d 1.285, 1.435 (3H each, 2s, CMe2), 1.40e1.75
(6H, m, (CH2)3), 2.445 (3H, s, CH3C6eS), 3.51, 3.88 (1H
0
5.6 Hz, H0-5), 4.12 (1H, d, J3,4¼3.2, J2,3¼0 Hz, H-3), 4.26
(1H, dd, J4,5¼7.3 Hz, H-5), 4.34 (1H, ddd, H-4), 4.52 (1H,
m, CHeO-3), 4.73 (1H, d, J1,2¼3.4 Hz, H-2), 5.84 (1H, d,
H-1), 7.35, 7.79 (2H each, 2d, Jo,m¼8.3 Hz, C6H4eS). 1H
NMR for the slower-eluting diastereomer: d 1.29, 1.44 (3H
each, 2s, CMe2), 1.40e1.75 (6H, m, (CH2)3), 2.45 (3H, s,
13
151 MHz for C) at 23 ꢀC, unless otherwise stated. The sol-
vent peak was used as an internal standard for chemical shifts:
in CDCl3, d 7.26 for 1H, 77.00 for 13C; in DMSO-d6, d 2.50 for
1H, 39.70 for 13C. The assignments of 13C signals were made
with the aid of 2D CeH COSY measurements.
each, 2 m, CH2OeCeO-3), 4.12 (1H, dd, J5,5¼9.5, J4,5
¼
4.2. 1,2-O-Isopropylidene-3-O-(tetrahydropyran-2-yl)-5-O-
tosyl-a-D-xylofuranose (11)15
A solution of 10 (1.88 g, 5.46 mmol) and DHP (2.30 g,
27.4 mmol) in dry CH2Cl2 (20 mL) containing PPTS
(140 mg, 0.557 mmol) was stirred at rt for 4 h. The solution
was diluted with CHCl3, washed once with saturated brine,
dried (Na2SO4), and evaporated in vacuo. The residue was pu-
rified by column chromatography with a gradient eluent of 1:4
to 1:2 AcOEtehexane to give 11 (2.15 g, 92%) as colorless
CH3C6eS), 3.51, 3.74 (1H each, 2 m, CH2OeCeO-3), 4.21
0
0
(1H, dd, J5,5¼10.0, J4,5 ¼6.1 Hz, H -5), 4.30 (1H, d,
J3,4¼3.4, J2,3¼0 Hz, H-3), 4.38 (1H, ddd, J4,5¼5.1 Hz, H-4),
4.415 (1H, dd, H-5), 4.775 (1H, d, J1,2¼3.7 Hz, H-2), 4.70
(1H, m, CHeO-3), 5.845 (1H, d, H-1), 7.34, 7.81 (2H each,
2d, Jo,m¼8.3 Hz, C6H4eS).
R2
R1
O
AcO
O
N
Br
O
NPE
N
N
N
OAc
R2 R1
N
O
N
AcO
NPE
N
N
N
NPhth
NaOMe
MeOH, rt, 2 h
DDQ
CH2Cl2, rt, 2 h
20a
28a
N
N
CF3SO3Ag, TMU
CH2Cl2, rt, 3 h
AcO
OH
N
O
OAc
29a R1 = OPMB, R2 = H (98%)
29b R1 = H, R2 = OPMB (98%)
AcO
NPhth
30a R1 = OPMB, R2 = H (82%)
30b R1 = H, R2 = OPMB (92%)
R1
O
R2
O
R2
R2
R1
O
R1
O
O
N
N
N
NPE
NPE
N
N
N
HN
N
N
O
H2N
N
N
N
N
N
AcO
AcNH
1) MeNH2, MeOH
rt, 10 h
1) NH3 aq.
MeOH, rt, 12 h
AcO
HO
O
O
O
2) Ac2O, Py
rt, 12 h
2) DBU, DMF
rt, 12 h
OAc
OAc
OH
AcO
AcO
HO
NPhth
NHAc
NHAc
31a R1 = OH, R2 = H (87%)
31b R1 = H, R2 = OH (89%)
32a R1 = OAc, R2 = H (91%)
3 R1 = OH, R2 = H (94%)
5 R1 = H, R2 = OH (85%)
32b R1 = H, R2 = OAc (85%)
Scheme 4.

T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
2095
4.3. 5-Deoxy-1,2-O-isopropylidene-3-O-(tetrahydropyran-2-
yl)-b-L-threo-pent-4-enofuranose (12)
To a solution of 11 (200 mg, 0.467 mmol) in dry DMF
(4.0 mL) was added potassium tert-butoxide (200 mg,
1.78 mmol) at rt. The mixture was stirred at 60 ꢀC for 8 h. Af-
ter cooling, the mixture was diluted with aqueous NH4Cl and
extracted with CHCl3 several times. The combined organic
layer was washed with water, dried (Na2SO4), and evaporated
in vacuo. The residue was purified by column chromatography
with 1:4 AcOEtehexane to give 12 (81.0 mg, 68%) as a color-
less syrup; Rf¼0.50, 0.46 [(A), two diastereomers with respect
to the THP]. 1H NMR for the faster-eluting diastereomer
d 1.385, 1.47 (3H each, 2s, CMe2), 1.52e1.80 (6H, m,
(CH2)3), 3.55, 3.83 (1H each, 2 m, CH2OeCeO-3), 4.24 (1H,
d, J5E,5Z¼1.7 Hz, H(E)-5), 4.56 (1H, s, J2,3¼0 Hz, H-3), 4.60
(1H, d, H(Z)-5), 4.605 (1H, d, J1,2¼3.2 Hz, H-2), 4.87 (1H, m,
1
CHeO-3), 6.06 (1H, d, H-1); H NMR for the slower-eluting
diastereomer d 1.38, 1.465 (3H each, 2s, CMe2), 1.48e1.80
(6H, m, (CH2)3), 3.53, 3.88 (1H each, 2 m, CH2OeCeO-3),
4.29 (1H, d, J5E,5Z¼1.7 Hz, H(E)-5), 4.53 (1H, d, J1,2¼3.4,
J2,3¼0 Hz, H-2), 4.595 (1H, s, H-3), 4.60 (1H, d, H(Z)-5),
4.82 (1H, m, CHeO-3), 6.055 (1H, d, H-1). Anal. Calcd for
C13H20O5: C, 60.92; H, 7.87. Found: C, 60.79; H, 7.98.
4.4. 5-Deoxy-1,2-O-isopropylidene-3-O-(tetrahydropyran-2-
yl)-b-L-arabinofuranose (13)
Compound 12 (545 mg, 2.13 mmol) dissolved in MeOH
(15 mL) was hydrogenated in the presence of 10% PdeC
(400 mg, 0.38 mmol) at rt under an atmospheric pressure of H2.
After 8 h, the catalyst was filtered off and the filtrate was evapo-
rated invacuo. The residue was purified by column chromatogra-
phy with 1:4 AcOEtehexane to give 13 (516 mg, 94%) as
a colorless syrup; Rf¼0.45 (A). 1H NMR (54:46* diastereomeric
mixture with respect to the THP) d 1.33, 1,335*, 1.54*, 1.545
(6H, 4s, CMe2), 1.405, 1.42* (3H, 2d, J4,5¼6.8, 6.6* Hz, H-5),
1.50e1.82, 1.50e1.82* (6H, m, (CH2)3), 3.54, 3.54*, 3.82*,
3.89 (1H each, 3 m, CH2OeCeO-3), 4.01, 4.04* (1H, 2dd,
J3,4¼2.7, 3.7*, J2,3¼1.0, 1.0*, H-3), 4.14, 4.145* (1H, 2qd, H-
4), 4.52*, 4.70 (1H, 2dd, J1,2¼4.1, 4.1* Hz, H-2), 4.67, 4.75*
(1H, m, CHeO-3), 5.83*, 5.85 (1H, 2d, H-1). Anal. Calcd for
C13H22O5: C, 60.45; H, 8.58. Found: C, 60.29; H, 8.71.
4.5. 5-Deoxy-1,2-O-isopropylidene-b-L-arabinofuranose (14)
A solution of 13 (516 mg, 2.00 mmol) dissolved in MeOH
(20 mL) containing PPTS (110 mg, 0.44 mmol) was refluxed for
1 h. After cooling, the mixture was evaporated in vacuo. The res-
idue was purified by column chromatography with 1:2 AcOEte
hexane to give 14 (329 mg, 94%) as colorless prisms; mp 78e
79 ꢀC (from AcOEtehexane); [a]D18 ꢁ15.2 (c 1.86); Rf¼0.07
1
(A), 0.19 (B); H NMR d 1.33, 1.54 (3H each, 2s, CMe2), 1.42
(3H, d, J4,5¼6.8 Hz, H-5), 1.87 (1H, br s, HO-3), 4.07 (1H, dd,
J3,4¼2.7, J2,3¼0.8 Hz, H-3), 4.09 (1H, qdd, J2,4¼0.8 Hz, H-4),
4.53 (1H, dt, J1,2¼4.1 Hz, H-2), 5.89 (1H, d, H-1); 13C NMR
d 19.76 (C-5), 26.23, 26.85 (Me2C), 80.02 (C-4), 83.63 (C-3),

2096
T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
87.51 (C-2), 105.51 (C-1), 112.61 (Me2C). Anal. Calcd for
C8H14O4: C, 55.16; H, 8.10. Found: C, 55.02; H, 8.19.
and then cupric acetate hydrate (1.02 g, 5.03 mmol) was
added. The mixture was refluxed for 1 h and then precipitates
were filtered off and washed with ethyl acetate. The filtrate
was concentrated in vacuo and the residue was separated by
column chromatography with 1:2 AcOEtehexane to give 17
(110 mg, 46% yield) as a colorless syrup; Rf¼0.24e0.33
(C); from the slower-eluting fraction, compound 16
(58.2 mg, 23%) was recovered.
4.6. 5-Deoxy-1,2-O-isopropylidene-3-O-(4-methoxybenzyl)-
b-L-arabinofuranose (15)
Compound 14 (289 mg, 1.66 mmol), p-methoxybenzyl
chloride (0.450 mL, 3.30 mmol), and tetrabutylammonium io-
dide (180 mg, 0.49 mmol) were dissolved in DMF (10 mL)
and with stirring, sodium hydride (60% in mineral oil,
130 mg, 3.25 mmol) was added at 0 ꢀC under argon. The mix-
ture was stirred at rt for 2 h, diluted with saturated NH4Cl
(5 mL), 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 1:4 AcOEtehexane to give 15 (474 mg, 97%) as a color-
4.9. 20-O-Acetyl-N2-(N,N-dimethylaminomethylene)-10-O-
(4-methoxybenzyl)biopterin (19a) and its 7-biopterin
isomer (19b)
Compound 17 (395 mg, 1.57 mmol) was dissolved in
MeOH (11 mL), and a solution of 2,5,6-triamino-4-hydroxy-
pyrimidine sulfate (450 mg, 1.88 mmol) and NaHCO3
(263 mg, 3.13 mmol) dissolved in water (9 mL) was added.
The mixture was refluxed for 3.5 h and then evaporated in va-
cuo. The residue was dissolved in DMF and sodium sulfate
was filtered off. The filtrate was concentrated in vacuo to
give a mixture of 10-O-(4-methoxybenzyl)biopterin (18a)
and 10-O-(4-methoxybenzyl)-7-biopterin (18b); Rf¼0.15 (E).
The mixture of 18a,b was dissolved in dry DMF (8 mL)
and then N,N-dimethylformamide dimethyl acetal (0.50 mL,
3.75 mmol) was added. The mixture was stirred at rt for 3 h
and concentrated in vacuo. The residue was dissolved in dry
pyridine (15 mL) and acetic anhydride (6.0 mL, 63 mmol)
was added at 0 ꢀC. The mixture was stirred at rt for 12 h
and then concentrated in vacuo. The residue was purified by
column chromatography with 1:19 MeOHeCHCl3 to give an
inseparable mixture (78:22) of the biopterin derivative (19a)
and its 7-biopterin isomer (19b) (554 mg, 78% yield from
1
less syrup. [a]2D1 ꢁ26.1 (c 1.28); Rf¼0.35 (A), 0.58 (B). H
NMR d 1.35, 1.54 (3H each, 2s, CMe2), 1.37 (3H, d,
J4,5¼6.6 Hz, H-5), 3.73 (1H, dd, J3,4¼3.9, J2,3¼1.2 Hz, H-
3), 3.81 (3H, s, MeO), 4.12 (1H, qd, H-4), 4.48, 4.57 (1H
each, 2d, J¼11.5 Hz, CH2O-3), 4.62 (1H, dd, J1,2¼4.2 Hz,
H-2), 5.83 (1H, d, H-1), 6.88, 7.26 (2H each, 2d, Jo,m¼8.7 Hz,
C6H4); 13C NMR d 19.96 (C-5), 26.56, 27.20 (Me2C), 55.26
(MeO), 71.49 (CH2O), 80.32 (C-4), 85.63 (C-3), 86.89
(C-2), 105.33 (C-1), 112.89 (Me2C), 113.87 (C(m) of PMB),
129.39 (C(ipso) of PMB), 129.40 (C(o) of PMB), 159.37
(C(p) of PMB). Anal. Calcd for C16H22O5: C, 65.29; H,
7.53. Found: C, 65.38; H, 7.39.
4.7. 5-Deoxy-3-O-(4-methoxybenzyl)-a,b-L-arabino-
furanoses (16)
1
A solution of 15 (200 mg, 0.679 mmol) in 70% AcOH
(10 mL) containing 0.1 M HCl (0.50 mL) was heated at
40 ꢀC for 12 h. After addition of pyridine (0.20 mL), the mix-
ture was evaporated in vacuo. The residue was purified by col-
umn chromatography to give an inseparable anomeric mixture
(a/b¼39:61) of 16 (129 mg, 75%) as a colorless syrup;
17) as a pale yellow foam; Rf¼0.45 (E). H NMR for 19a
0
0
0
0
d 1.23 (3H, d, J2 ,3 ¼6.4 Hz, H3-3 ), 1.96 (3H, s, AcO-2 ),
3.19, 3.25 (3H each, 2s, Me2N), 3.79 (3H, s, MeO), 4.47,
2
4.50 (1H each, 2d, J¼11.6 Hz, CH2O-10), 4.75 (1H, d,
0
0
0
0
J1 ,2 ¼4.5 Hz, H-1 ), 5.35 (1H, qd, H-2 ), 6.84, 7.21 (2H
each, 2d, Jo,m¼8.7 Hz, C6H4), 8.97 (1H, s, H-7), 9.00 (1H, s,
1
1
0
0
Rf¼0.15 (C), 0.54 (D). H NMR for a-anomer d 1.32 (3H,
CH]N-2); H NMR for 19b d 1.22 (3H, d, J2 ,3 ¼6.4 Hz,
H3-30), 1.97 (3H, s, AcO-20), 3.19, 3.24 (3H each, 2s,
Me2N), 3.79 (3H, s, MeO), 4.45, 4.54 (1H each, 2d,
d, J4,5¼6.4 Hz, H3-5), 1.88, 3.30 (1H each, 2br s, HO-1,2),
3.57 (1H, ddd, J3,4¼3.9, J2,3¼2.0, J1,3¼1.0 Hz, H-3), 3.81
(3H, s, MeO), 4.19 (1H, d, J1,2¼0 Hz, H-2), 4.34 (1H, qd,
2
J¼11.6 Hz, CH2O-10), 4.64 (1H, d, J1 ,2 ¼4.2 Hz, H-1 ),
5.35 (1H, qd, H-20), 6.84, 7.21 (2H each, 2d, Jo,m¼8.7 Hz,
C6H4), 8.76 (1H, s, H-6), 9.00 (1H, s, CH]N-2).
0
0
0
2
H-4), 4.55, 4.56 (1H each, 2d, J¼11.5 Hz, CH2O-3), 5.23
(1H, br d, H-1), 6.89, 7.25 (2H each, 2d, Jo,m¼8.7 Hz,
1
C6H4); H NMR for b-anomer d 1.35 (3H, d, J4,5¼6.6 Hz,
H3-5), 2.54, 3.48 (1H each, 2br s, HO-1,2), 3.67 (1H, dd,
J3,4¼6.0, J2,3¼5.2 Hz, H-3), 3.81 (3H, s, MeO), 3.95 (1H,
quint, H-4), 4.16 (1H, dd, J1,2¼4.4 Hz, H-2), 4.57, 4.68 (1H
each, 2d, 2J¼11.5 Hz, CH2O-3), 5.29 (1H, d, H-1), 6.88,
7.28 (2H, d, Jo,m¼8.7 Hz, C6H4). Anal. Calcd for C13H18O5:
C, 61.41; H, 7.13. Found: C, 61.26; H, 7.02.
4.10. 20-O-Acetyl-N2-(N,N-dimethylaminomethylene)-10-O-
(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin
(20a) and its 7-biopterin isomer (20b)
To a solution of 19a,b (554 mg, 1.22 mmol), 2-(p-nitrophe-
nyl)ethanol (285 mg, 1.70 mmol) and triphenylphosphine
(630 mg, 2.41 mmol) in dry THF (20 mL), was added
DEAD (0.390 mL, 2.12 mmol). The mixture was stirred at rt
for 12 h and then concentrated in vacuo. The residue was
separated by column chromatography with 2:1 AcOEte
hexane to give 20a (502 mg, 53% yield from 17) and 20b
(142 mg, 15% yield).
4.8. 5-Deoxy-3-O-(4-methoxybenzyl)-a,b-L-erythro-pentos-
2-uloses (17)
Compound 16 (242 mg, 0.952 mmol) was dissolved in
MeOH (6 mL) and water (3 mL). The solution was refluxed

T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
2097
Compound 20a: Pale yellow solid; Rf¼0.25 (D); [a]2D9 ꢁ60.6
(c 1.22). 1H and 13C NMR, see Tables 1 and 2. Anal. Calcd for
C30H33N7O7: C, 59.69; H, 5.51. Found: C, 59.51; H, 5.60.
Compound 20b: Pale yellow solid; Rf¼0.35 (D); [a]2D9 ꢁ22.8
(c 1.14). 1H and 13C NMR, see Tables 1 and 2. Anal. Calcd for
C30H33N7O7: C, 59.69; H, 5.51. Found: C, 59.48; H, 5.69.
(3H, s, MeO), 4.24 (1H, d, J1,2¼0 Hz, H-2), 4.39 (1H, qd, H-4),
4.50, 4.61 (1H each, 2d, 2J¼11.5 Hz, CH2O-3), 5.06 (1H, s, H-
1), 6.89, 7.25 (2H, d, Jo,m¼8.8 Hz, C6H4). Anal. Calcd for
C13H18O5: C, 61.41; H, 7.13. Found: C, 61.30; H, 6.98.
4.14. 5-Deoxy-3-O-(4-methoxybenzyl)-L-threo-pentos-2-ulose
(25)
4.11. 5-Deoxy-1,2-O-isopropylidene-a-L-xylofuranose (22)18
By use of same procedures as described for 17 from 16,
compound 24 (361 mg, 1.42 mmol) was treated with cupric
acetate hydrate (1.14 g, 5.71 mmol) in MeOH (10 mL) and
water (5 mL). The products were separated by column chro-
matography to give 25 (177 mg, 49% yield) as a colorless
syrup; Rf¼0.33e0.24 (C); from the slower-eluting fraction,
compound 24 (95.0 mg, 26%) was recovered.
The following modification of the literature procedures17
was made. To a solution of 21 (947 mg, 2.75 mmol) in dry
ether (15 mL), lithium aluminum hydride (210 mg,
5.55 mmol) was added at 0 ꢀC under argon. The mixture
was stirred at rt for 6 h, and then water was added. The pre-
cipitates were filtered off and washed with CHCl3. The fil-
trate was washed with aqueous NaCl, dried (Na2SO4), and
evaporated in vacuo. The residue was purified by column
chromatography with 1:2 AcOEtehexane to give 22 (455 mg,
95%) as colorless needles; mp 68e69 ꢀC (from 1:1 AcOEte
hexane) (lit.18 mp 70e72 ꢀC, 79% yield); Rf¼0.42 (C).
4.15. 20-O-Acetyl-N2-(N,N-dimethylaminomethylene)-10-O-
(4-methoxybenzyl)ciliapterin (27a) and its 7-ciliapterin
isomer (27b)
Compound 25 (174 mg, 0.690 mmol) was dissolved in
MeOH (10 mL), and then a solution of 2,5,6-triamino-4-hy-
droxypyrimidine sulfate (306 mg, 1.28 mmol) and NaHCO3
(358 mg, 4.26 mmol) dissolved in water (10 mL) was added.
The mixture was refluxed for 3 h and then evaporated in va-
cuo. The residue was dissolved in DMF and sodium sulfate
was filtered off. The filtrate was concentrated in vacuo to
give a mixture of 10-O-(4-methoxybenzyl)ciliapterin (26a)
and its 7-ciliapterin isomer (26b); Rf¼0.17 (E).
4.12. 5-Deoxy-1,2-O-isopropylidene-3-O-(4-methoxybenzyl)-
a-L-xylofuranose (23)
By use of same procedures as described for 15 from 14,
compound 22 (455 mg, 2.61 mmol) was treated with p-me-
thoxybenzyl chloride (0.71 mL, 5.2 mmol), tetrabutylammo-
nium iodide (290 mg, 0.79 mmol), and sodium hydride (60%
in mineral oil, 207 mg, 5.2 mmol) in DMF (15 mL) to give
23 (751 mg, 98%) as a colorless syrup; Rf¼0.34 (A), 0.58
The mixture of 26a,b was dissolved in dry DMF (8 mL)
and N,N-dimethylformamide dimethyl acetal (0.34 mL,
2.56 mmol) was added. The mixture was stirred at rt for 3 h
and concentrated in vacuo. The residue was dissolved in dry
pyridine (8 mL) and acetic anhydride (4.0 mL, 42.6 mmol)
was added at 0 ꢀC. The mixture was stirred at rt for 12 h
and then concentrated in vacuo. The residue was purified by
column chromatography with 1:19 MeOHeCHCl3 to give an
inseparable mixture (75:25) of 27a and 27b (257 mg, 82%
(B); [a]2D8 þ50.9 (c 1.26). 1H NMR d 1.29 (3H, d, J4,5
¼
6.6 Hz, H-5), 1.31, 1.48 (3H each, 2s, CMe2), 3.70 (1H, d,
J3,4¼3.2 Hz, J2,3¼0 Hz, H-3), 3.81 (3H, s, MeO), 4.30 (1H,
qd, H-4), 4.44, 4.63 (1H each, 2d, J¼12.0 Hz, CH2O-3),
4.60 (1H, dd, J1,2¼3.9 Hz, H-2), 5.89 (1H, d, H-1), 6.87,
7.25 (2H each, 2d, Jo,m¼8.8 Hz, C6H4); 13C NMR d 13.27
(C-5), 26.16, 26.24 (Me2C), 55.27 (MeO), 71.42 (CH2O),
76.13 (C-4), 82.29 (C-3), 82.79 (C-2), 104.73 (C-1), 111.16
(Me2C), 113.81 (C(m) of PMB), 129.25 (C(o) of PMB),
129.73 (C(ipso) of PMB), 159.31 (C(p) of PMB). Anal. Calcd
for C16H22O5: C, 65.29; H, 7.53. Found: C, 65.38; H, 7.39.
1
from 25) as a pale yellow foam; Rf¼0.44 (E). H NMR for
0
0
0
27a d 1.27 (3H, d, J2 ,3 ¼6.6 Hz, H3-3 ), 1.95 (3H, s,
AcO-20), 3.24, 3.31 (3H each, 2s, Me2N), 3.79 (3H, s,
2
MeO), 4.37, 4.58 (1H each, 2d, J¼11.7 Hz, CH2O-10), 4.77
0
0
0
0
4.13. 5-Deoxy-3-O-(4-methoxybenzyl)-a,b-L-xylofuranoses
(24)
(1H, d, J1 ,2 ¼3.7 Hz, H-1 ), 5.19 (1H, qd, H-2 ), 6.84, 7.21
(2H each, 2d, Jo,m¼8.8 Hz, C6H4), 8.97 (1H, s, H-7), 9.11
(1H, s, CH]N-2); 1H NMR for 27b0 d 1.28 (3H, d,
0
0
0
By use of same procedures as described for 16 from 15,
compound 23 (138 mg, 0.469 mmol) was treated with 70%
AcOH (5.0 mL) containing 0.1 M HCl (0.25 mL) to give an
inseparable anomeric mixture (a/b¼69:31) of 24 (98.6 mg,
J2 ,3 ¼6.6 Hz, H3-3 ), 1.93 (3H, s, AcO-2 ), 3.23, 3.27 (3H
each, 2s, Me2N), 3.79 (3H, s, MeO), 4.36, 4.62 (1H each,
2
2d, J¼11.7 Hz, CH2O-10), 4.60 (1H, d, J1 ,2 ¼3.5 Hz, H-1 ),
5.24 (1H, qd, H-20), 6.84, 7.21 (2H each, 2d, Jo,m¼8.8 Hz,
C6H4), 8.77 (1H, s, H-6), 9.03 (1H, s, CH]N-2).
0
0
0
1
83%) as colorless solid; Rf¼0.15 (C). H NMR for a-anomer
d 1.24 (3H, d, J4,5¼6.4 Hz, H3-5), 2.25 (2H, br s, HO-1,2),
3.80 (1H, ddd, J3,4¼4.9, J2,3¼2.9 Hz, H-3), 3.80 (3H, s,
MeO), 4.20 (1H, dd, J1,2¼4.4 Hz, H-2), 4.41 (1H, qd, H-4),
4.16. 20-O-Acetyl-N2-(N,N-dimethylaminomethylene)-10-O-
(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]ciliapterin
(28a) and its 7-ciliapterin isomer (28b)
2
4.49, 4.62 (1H each, 2d, J¼11.7 Hz, CH2O-3), 5.45 (1H, d,
1
H-1), 6.88, 7.26 (2H each, 2d, Jo,m¼8.8 Hz, C6H4); H NMR
for b-anomer d 1.36 (3H, d, J4,5¼6.6 Hz, H3-5), 2.25 (2H, br
s, HO-1,2), 3.73 (1H, dd, J3,4¼3.9, J2,3¼1.0 Hz, H-3), 3.81
The above mixture of 27a,b (257 mg, 0.605 mmol) was
dissolved in dry THF (10 mL) and then 2-(p-

2098
T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
nitrophenyl)ethanol (143 mg, 0.850 mmol), triphenylphos-
phine (474 mg, 1.81 mmol), and DEAD (1.95 mL,
1.06 mmol) were added. The mixture was stirred at rt for
16 h and then concentrated in vacuo. The residue was sepa-
rated by column chromatography with 1:1 AcOEtehexane to
give 28a (216 mg, 52% yield from 25) and 28b (72.0 mg,
17% yield).
(MeOH) lmax 226 nm (log 3 4.35), 280 (4.38), 309 (4.50),
355 (4.06); 1H NMR d 1.17 (3H, d, J2 ,3 ¼6.4 Hz, H3-3 ),
0
0
0
3
2.78 (3H, s, HO-20), 3.16 (2H, t, J¼7.7 Hz, CH2CH2eN(3)),
3.19, 3.24 (3H each, 2s, Me2N), 3.78 (3H, s, MeO), 4.04 (1H,
0
2
0
0
qd, J1 ,2 ¼5.6 Hz, H-2 ), 4.41, 4.47 (1H each, 2d, J¼11.2 Hz,
2
CH2O-10), 4.59, 4.61 (1H each, 2dt, J¼12.5 Hz, CH2eN(3)),
4.57 (1H, d, H-10), 6.84, 7.21 (2H each, 2d, Jo,m¼8.7 Hz, C6H4
of PMB), 7.40, 8.13 (2H each, 2d, Jo,m¼8.7 Hz, C6H4 of
NPE), 8.88 (1H, s, CH]N-2), 8.92 (1H, s, H-7); 13C NMR
d 18.87 (C-30), 34.07 (CH2CH2N), 35.49, 41.61 (Me2N),
43.77 (CH2N), 55.22 (MeO), 70.36 (C-20), 72.03 (CH2O-10),
84.74 (C-10), 113.86 (C(m) of PMB), 123.68 (C(m) of NPE),
129.94 (C-4a), 129.18 (C(ipso) of PMB), 129.74 (C(o) of
PMB), 129.78 (C(o) of NPE), 146.57, 146.70 (C(ipso, m) of
NPE), 149.24 (C-7), 151.79 (C-6), 153.54 (C-8a), 157.41
(C-2), 159.26 (NCH]N), 159.45 (C(p) of PMB), 161.76
(C-4). Anal. Calcd for C28H31N7O6: C, 59.88; H, 5.56. Found:
C, 59.96; H, 5.69.
4.16.1. Compound 28a
1
Pale yellow solid; Rf¼0.18 (D); [a]2D8 þ28.9 (c 1.91). H
and 13C NMR, see Tables 1 and 2. Anal. Calcd for
C30H33N7O7: C, 59.69; H, 5.51. Found: C, 59.51; H, 5.60.
4.16.2. Compound 28b
1
Pale yellow solid; Rf¼0.30 (D); [a]2D8 þ44.2 (c 1.74). H
and 13C NMR, see Tables 1 and 2. Anal. Calcd for
C30H33N7O7: C, 59.69; H, 5.51. Found: C, 59.39; H, 5.68.
4.17. N2-(N,N-Dimethylaminomethylene)-10-O-(4-methoxy-
benzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (29a)
4.19. N2-(N,N-Dimethylaminomethylene)-10-O-(4-methoxy-
benzyl)-3-[2-(4-nitrophenyl)ethyl]-20-O-(3,4,6-tri-O-
acetyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl)-
biopterin (30a)
Compound 20a (272 mg, 0.451 mmol) was dissolved in
dry MeOH (6.0 mL) and then NaOMe (28% in MeOH,
0.040 mL, 0.21 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 purified by column
chromatography with 1:49 MeOHeCHCl3 to give 29a
(249 mg, 98%) as a pale yellow syrup; Rf¼0.60 (E); [a]D29
ꢁ48.8 (c 1.10); UV (MeOH) lmax 225 nm (log 3 4.32), 279
To a solution of 29a (46.4 mg, 0.0826 mmol), 3,4,6-tri-O-
acetyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl
bromide
(150 mg, 0.302 mmol), and TMU (0.010 mL, 0.083 mmol) in
dry CH2Cl2 (2.0 mL) was added silver triflate (56.0 mg,
0.212 mmol). The mixture was stirred at rt for 2.5 h in the
dark, diluted with CHCl3, and filtered through Celite. The fil-
trate was washed with aqueous NaHCO3, dried (Na2SO4), and
evaporated in vacuo. The residue was purified by column chro-
matography with 1:49 MeOHeCHCl3 to give 30a (66.2 mg,
(4.34), 309 (4.45), 353 (4.02); 1H NMR d 1.12 (3H, d, J2 ,3
¼
0
0
3
6.6 Hz, H3-30), 2.94 (3H, s, HO-20), 3.17 (2H, t, J¼7.8 Hz,
CH2CH2eN(3)), 3.19, 3.25 (3H each, 2s, Me2N), 3.80 (3H,
0
1
82%) as a pale yellow foam; Rf¼0.20 (D), 0.58 (E). H NMR
0
0
s, MeO), 4.26 (1H, qd, J1 ,2 ¼4.4 Hz, H-2 ), 4.46, 4.49 (1H
0
2
each, 2d, J¼11.2 Hz, CH2O-10), 4.60, 4.615 (1H each, 2dt,
0
0
d 1.16 (3H, d, J2 ,3 ¼6.7 Hz, H3-3 ), 1.85, 2.02, 2.08 (3H each,
3s, AcO-3,4,6*), 3.15 (2H, t, 3J¼7.6 Hz, CH2CH2eN(3)),
3.18, 3.24 (3H each, 2s, Me2N), 3.77 (3H, s, MeO), 3.85, 3.98
2J¼12.7 Hz, CH2eN(3)), 4.70 (1H, d, H-10), 6.86, 7.23
(2H each, 2d, Jo,m¼8.7 Hz, C6H4 of PMB), 7.42, 8.14 (2H
each, 2d, Jo,m¼8.7 Hz, C6H4 of NPE), 8.88 (1H, s, CH]
2
(1H each, 2d, J¼11.9 Hz, CH2O-10), 3.91 (1H, ddd,
13
N-2), 8.98 (1H, s, H-7); C NMR d 18.28 (C-30), 34.15
J4,5¼10.1, J5,6a¼5.2, J5,6b¼2.5 Hz, H-5*), 4.14 (1H, dd,
J6a,6b¼12.2 Hz, Hb-6*), 4.21 (1H, qd, J1 ,2 ¼4.0 Hz, H-2 ),
0
0
0
(CH2CH2N), 35.49, 41.60 (Me2N), 43.81 (CH2N), 55.27
(MeO), 69.79 (C-20), 71.95 (CH2O-10), 84.19 (C-10), 113.92
(C(m) of PMB), 123.72 (C(m) of NPE), 128.52 (C-4a),
129.44 (C(ipso) of PMB), 129.66 (C(o) of PMB), 129.78
(C(o) of NPE), 146.66, 146.78 (C(ipso, m) of NPE), 149.88
(C-7), 151.10 (C-6), 153.67 (C-8a), 157.47 (C-2), 159.31
(NCH]N), 159.46 (C(p) of PMB), 161.94 (C-4). Anal.
Calcd for C28H31N7O6: C, 59.88; H, 5.56. Found: C, 59.72;
H, 5.72.
4.29 (1H, dd, Ha-6*), 4.33 (dd, J2,3¼10.7, J1,2¼8.5 Hz, H-2*),
2
4.57, 4.59 (1H each, 2dt, J¼12.2 Hz, CH2eN(3)), 4.45 (1H,
d, H-10), 5.11 (1H, dd, J3,4¼8.9 Hz, H-4*), 5.54 (1H, d, H-1*),
5.82 (1H, dd, H-3*), 6.71, 6.89 (2H each, 2d, Jo,m¼8.7 Hz,
C6H4 of PMB), 7.41, 8.13 (2H each, 2d, Jo,m¼8.6 Hz, C6H4 of
NPE), 7.61, 7.76 (2H each, 2 m, Phth*), 8.54 (1H, s, H-7),
8.84 (1H, s, CH]N-2), *for glycosyl moiety. Anal. Calcd for
C48H50N8O15: C, 58.89; H, 5.15. Found: C, 58.98; H, 5.29.
4.18. N2-(N,N-Dimethylaminomethylene)-10-O-(4-methoxy-
benzyl)-3-[2-(4-nitrophenyl)ethyl]ciliapterin (29b)
4.20. N2-(N,N-Dimethylaminomethylene)-10-O-(4-methoxy-
benzyl)-3-[2-(4-nitrophenyl)ethyl]-20-O-(3,4,6-tri-O-acetyl-
2-deoxy-2-phthalimido-b-D-glucopyranosyl)ciliapterin (30b)
By use of the same procedures as described above, com-
pound 28a (1.05 g, 1.74 mmol) was treated with NaOMe
(28% in MeOH, 0.17 mL, 0.87 mmol) in dry MeOH (20 mL)
to give 29b (963 mg, 98%) as pale yellow crystals; mp
174e176 ꢀC; Rf¼0.66 (E); [a]2D8 þ62.1 (c 1.35); UV
By use of the same procedures as described above, compound
29b (30.0 mg, 0.0534 mmol) was glycosylated with 3,4,6-tri-
O-acetyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl bromide
(80.0 mg, 0.160 mmol) in dry CH2Cl2 (2.0 mL) in the presence

T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
2099
0
0
0
of silver triflate (28.0 mg, 0.106 mmol) and TMU (0.006 mL,
0.054 mmol) giving 30b (48.2 mg, 92%) as a pale yellow foam;
J1 ,2 ¼3.9 Hz, H-2 ), 4.59 (2H, t, CH2eN(3)), 4.65 (1H, d,
H-10), 5.10 (1H, dd, J3,4¼9.0 Hz, H-4*), 5.41 (1H, d, H-1*),
5.69 (1H, dd, H-3*), 7.42, 8.14 (2H each, 2d, Jo,m¼8.7 Hz,
C6H4 of NPE), 7.67, 7.73 (2H each, 2 m, Phth*), 8.64 (1H,
s, H-7), 8.96 (1H, s, CH]N-2), *for glycosyl moiety. Anal.
Calcd for C40H42N8O14: C, 55.94; H, 4.93. Found: C, 56.11;
H, 4.99.
1
0
0
Rf¼0.18 (D), 0.60 (E). H NMR d 1.18 (3H, d, J2 ,3 ¼6.4 Hz,
H3-30), 1.80, 1.99, 2.10 (3H each, 3s, AcO-3,4,6*), 3.15 (2H, t,
3J¼7.3 Hz, CH2CH2eN(3)), 3.23, 3.30 (3H each, 2s, Me2N),
3.76 (3H, s, MeO), 4.12, 4.25 (1H each, 2d, 2J¼11.5 Hz,
CH2O-10), 3.78 (1H, ddd, J4,5¼10.0, J5,6a¼4.9, J5,6b¼2.4 Hz,
H-5*), 4.14 (1H, dd, J6a,6b¼12.2 Hz, Hb-6*), 4.25 (1H, qd,
a
0
0
0
J1 ,2 ¼4.9 Hz, H-2 ), 4.29 (1H, dd, H -6*), 4.26 (dd, J2,3¼10.5,
J1,2¼8.5 Hz, H-2*), 4.56 (2H, t, CH2eN(3)), 4.45 (1H, d, H-10),
5.09 (1H, dd, J3,4¼9.0 Hz, H-4*), 5.40 (1H, d, H-1*), 5.62 (1H,
dd, H-3*), 6.74, 7.03 (2H each, 2d, Jo,m¼8.2 Hz, C6H4 of
PMB), 7.42, 8.16 (2H each, 2d, Jo,m¼8.5 Hz, C6H4 of NPE),
7.63, 7.74 (2H each, 2 m, Phth*), 8.63 (1H, s, H-7), 8.92 (1H, s,
CH]N-2), *for glycosyl moiety. Anal. Calcd for C48H50N8O15:
C, 58.89; H, 5.15. Found: C, 58.78; H, 5.06.
4.23. 20-O-(2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-b-D-
glucopyranosyl)-di-N2:10-O-acetyl-3-[2-(4-
nitrophenyl)ethyl]biopterin (32a)
Compound 31a (80.0 mg, 0.0928 mmol) was dissolved in
MeOH (2.0 mL) and 40% methanolic methylamine (1.5 mL)
was added. The mixture was stirred at rt for 12 h and evapo-
rated in vacuo. The residue was dissolved in pyridine
(2.0 mL) and then acetic anhydride (0.8 mL, 8.8 mmol) was
added at 0 ꢀC. The mixture was stirred at rt for 12 h and evap-
orated in vacuo. The residue was purified by column chroma-
tography with 1:2 AcOEtehexane (to remove impurities) and
then 1:49 MeOHeCHCl3 as an eluent to give 32a (67.8 mg,
91%) as pale yellow crystals; mp 142e144 ꢀC (from
4.21. N2-(N,N-Dimethylaminomethylene)-3-[2-(4-nitro-
phenyl)ethyl]-20-O-(3,4,6-tri-O-acetyl-2-deoxy-2-
phthalimido-b-D-glucopyranosyl)biopterin (31a)
To a solution of 30a (25.2 mg, 0.0257 mmol) in CH2Cl2
(1.0 mL) containing water (0.05 mL) was added DDQ
(17.5 mg, 0.0772 mmol). The mixture was stirred at rt for 2 h
and then diluted with saturated NaCl. The mixture was extracted
with CHCl3 three times. The combined organic layers were dried
(MgSO4) and evaporated in vacuo. The residue was purified by
column chromatography with 1:49 MeOHeCHCl3 to give 31a
AcOEtehexane); Rf¼0.55 (E). 1H NMR d 1.26 (3H, d,
0
0
0
J2 ,3 ¼6.4 Hz, H3-3 ), 1.86, 2.02, 2.02, 2.08, 2.16 (3H each,
5s, AcNH-2*, AcO-3,4,6*, AcO-10), 2.34 (3H, s, AcNH-2),
3.17 (2H, t, 3J¼7.6 Hz, CH2CH2eN(3)), 3.72 (1H, ddd,
J4,5¼10.0, J5,6a¼5.5, J5,6b¼2.4 Hz, H-5*), 3.72 (dt, J2,3
¼
10.6, J1,2¼J2,NH¼8.5 Hz, H-2*), 4.13 (1H, dd, J6a,6b¼12.2 Hz,
(19.2 mg, 87%) as pale yellow crystals; mp 166e167 ꢀC;
Hb-6*), 4.22 (1H, dd, Ha-6*), 4.43, 4.55 (1H each, 2dt,
Rf¼0.50 (E). 1H NMR d 1.22 (3H, d, J2 ,3 ¼6.4 Hz, H3-3 ), 1.82,
2J¼12.4 Hz, CH2eN(3)), 4.44 (1H, qd, J1 ,2 ¼5.2 Hz, H-2 ),
4.82 (1H, d, H-1*), 5.00 (1H, dd, J3,4¼9.4 Hz, H-4*), 5.27
(1H, t, H-3*), 5.83 (1H, br d, NH-2*), 5.91 (1H, d, H-10),
7.50, 8.19 (2H each, 2d, Jo,m¼8.8 Hz, C6H4 of NPE), 8.70
(1H, s, H-7), 13.90 (1H, br s, NH-2), *for glycosyl moiety.
Anal. Calcd for C35H41N7O15: C, 52.56; H, 5.17. Found: C,
52.39; H, 5.29.
0
0
0
0
0
0
3
2.02, 2.11 (3H each, 3s, AcO-3,4,6*), 3.14 (2H, t, J¼7.6 Hz,
CH2CH2eN(3)), 3.20, 3.26 (3H each, 2s, Me2N), 3.91 (1H,
ddd, J4,5¼10.1, J5,6a¼5.2, J5,6b¼2.4 Hz, H-5*), 4.17 (1H, dd,
J6a,6b¼12.0 Hz, Hb-6*), 4.26 (1H, qd, J1 ,2 ¼5.2 Hz, H-2 ), 4.28
(1H, dd, Ha-6*), 4.29 (dd, J2,3¼10.7, J1,2¼8.6 Hz, H-2*), 4.31
(1H, br s, HO-10), 4.55 (2H, t, CH2eN(3)), 4.80 (1H, d, H-10),
5.13 (1H, dd, J3,4¼9.2 Hz, H-4*), 5.53 (1H, d, H-1*), 5.70 (1H,
dd, H-3*), 7.41, 8.14 (2H each, 2d, Jo,m¼8.7 Hz, C6H4 of NPE),
7.65, 7.76 (2H each, 2 m, Phth*), 8.67 (1H, s, H-7), 8.83 (1H, s,
CH]N-2), *for glycosyl moiety. Anal. Calcd for C40H42N8O14:
C, 55.94; H, 4.93. Found: C, 56.02; H, 5.01.
0
0
0
4.24. 20-O-(2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-b-D-
glucopyranosyl)-di-N2:10-O-acetyl-3-[2-(4-
nitrophenyl)ethyl]ciliapterin (32b)
By use of the same procedures as described above, com-
pound 31b (48.0 mg, 0.0559 mmol) gave 32b (38.0 mg,
4.22. N2-(N,N-Dimethylaminomethylene)-3-[2-(4-nitro-
phenyl)ethyl]-20-O-(3,4,6-tri-O-acetyl-2-deoxy-2-
phthalimido-b-D-glucopyranosyl)ciliapterin (31b)
1
85%) as a pale yellow foam; Rf¼0.54 (E). H NMR d 1.29
0
0
0
(3H, d, J2 ,3 ¼6.6 Hz, H3-3 ), 1.82, 2.00, 2.01, 2.08, 2.22 (3H
each, 5s, AcNH-2*, AcO-3,4,6*, AcO-10), 2.35 (3H, s,
AcNH-2), 3.17, 3.19 (1H each, 2dt, 2J¼12.7, 3J¼7.7 Hz,
CH2CH2eN(3)), 3.64 (1H, ddd, J4,5¼10.0, J5,6a¼5.4,
J5,6b¼2.4 Hz, H-5*), 3.61 (dt, J2,3¼10.7, J2,NH¼8.5,
J1,2¼8.3 Hz, H-2*), 4.11 (1H, dd, J6a,6b¼12.2 Hz, Hb-6*),
4.19 (1H, dd, Ha-6*), 4.56 (2H, t, CH2eN(3)), 4.40 (1H, qd,
By use of the same procedures as described above, com-
pound 30b (23.3 mg, 0.0238 mmol) was treated with DDQ
(32.0 mg, 0.141 mmol) in CH2Cl2 (1.0 mL) containing water
(0.05 mL) to give 31b (18.1 mg, 89%) as a pale yellow
1
0
0
foam; Rf¼0.52 (E). H NMR d 1.28 (3H, d, J2 ,3 ¼6.4 Hz,
H3-30), 1.80, 2.01, 2.11 (3H each, 3s, AcO-3,4,6*), 3.16,
3.18 (1H each, 2dt, 2J¼12.7, 3J¼7.6 Hz, CH2CH2eN(3)),
3.23, 3.31 (3H each, 2s, Me2N), 3.30 (1H, br s, HO-10), 3.88
(1H, ddd, J4,5¼10.3, J5,6a¼5.4, J5,6b¼2.5 Hz, H-5*), 4.18
(1H, dd, J6a,6b¼12.2 Hz, Hb-6*), 4.25 (dd, J2,3¼10.7,
J1,2¼8.3 Hz, H-2*), 4.28 (1H, dd, Ha-6*), 4.47 (1H, qd,
J1 ,2 ¼3.4 Hz, H-20), 4.73 (1H, d, H-1*), 4.98 (1H,
dd, J3,4¼9.3 Hz, H-4*), 5.29 (1H, dd, H-3*), 5.82 (1H, br d,
NH-2*), 5.91 (1H, d, H-10), 7.52, 8.20 (2H each, 2d,
Jo,m¼8.7 Hz, C6H4 of NPE), 8.63 (1H, s, H-7), 13.55 (1H,
br s, NH-2), *for glycosyl moiety. Anal. Calcd for
C35H41N7O15: C, 52.56; H, 5.17. Found: C, 52.42; H, 5.11.
0
0

2100
T. Hanaya et al. / Tetrahedron 64 (2008) 2090e2100
4.25. 20-O-(2-Acetamido-2-deoxy-b-D-glucopyranosyl)-
biopterin (limipterin) (3)
3. 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. Biotechnol. 1999, 1, 207.
4. Cha, K. W.; Pfleiderer, W.; Yim, J. J. Helv. Chim. Acta 1995, 78, 600.
5. Some inhibitory activities against tyrosinase were reported for biopterin
D-glucoside (2): Wachi, Y.; Yoshida, S.; Komatsu, K.; Matsunaga, T.
Jpn. Patent 05,286,989, 1993; Chem. Abstr. 1994, 120, 161782t.
6. (a) Kaufman, S.; Fisher, D. B. Molecular Mechanisms of Oxygen Activa-
tion; Hayaishi, O., Ed.; Academic: New York, NY, 1974; pp 285e369; (b)
Kaufman, S.; Kaufman, E. E. Folates and Pterins; Blakley, R., Benkovic,
S. J., Eds.; Wiley and Sons: New York, NY, 1985; Vol. 2, pp 251e352.
7. (a) Kwon, N. S.; Nathan, C. F.; Stuehr, D. J. J. Biol. Chem. 1989, 264,
20496; (b) Marletta, M. A. Cell 1994, 78, 927.
Compound 32a (64.0 mg, 0.0880 mmol) was dissolved in
MeOH (8.0 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
(2.0 mL) and DBU (0.10 mL, 0.64 mmol) was added. The
mixture was stirred at rt for 12 h, diluted with water
(4.0 mL), and neutralized with Amberlite IRC50(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 3 (36.3 mg, 94%) as pale yellow solid;
8. (a) Hatfield, D. L.; Van Baalen, C.; Forrest, H. S. Plant Physiol. 1961, 36,
240; (b) Lin, X.; White, R. H. J. Bacteriol. 1988, 170, 1396; (c) Lee,
H. W.; Oh, C. H.; Geyer, A.; Pfleiderer, W.; Park, Y. S. Biochim. Biophys.
Acta 1999, 1410, 61; (d) Ikawa, M.; Sasner, J. J.; Haney, J. F.; Foxall, T. L.
Phytochemistry 1995, 38, 1229.
1
Rf¼0.28 (F). H NMR, see Table 3; 13C NMR (DMSO-d6)
d 18.00 (C-30), 23.25 (COCH3), 55.87 (C-2*), 61.36 (C-6*),
70.93 (C-4*), 74.55 (C-3*), 745.37 (C-10), 77.06 (C-5*),
78.10 (C-20), 101.88 (C-1*), 127.48 (C-4a), 149.06 (C-7),
150.52 (C-6), 153.93 (C-8a), 156.58 (C-2), 161.88 (C-4),
169.37 (COCH3), *for glycosyl moiety. Anal. Calcd for
C17H24N6O8: C, 46.36; H, 5.49. Found: C, 46.19; H, 5.68.
9. Trivial names of natural pteridines are used according to the pteridine no-
menclature recommended by the International Society of Pteridinology:
Ferre, J.; Jocobson, K. B.; Pfleiderer, W. Pteridines 1990, 2, 129.
10. Cho, S.-H.; Na, J.-U.; Youn, H.; Hwang, C.-S.; Lee, C.-H.; Kang, S.-O.
Biochim. Biophys. Acta 1998, 1379, 53.
11. Supangat, S.; Seo, K. H.; Choi, Y. K.; Park, Y. S.; Son, D.; Han, C.; Lee,
K. H. J. Biol. Chem. 2006, 281, 2249.
12. Hanaya, T.; Soranaka, K.; Harada, K.; Yamaguchi, H.; Suzuki, R.; Endo,
Y.; Yamamoto, H.; Pfleiderer, W. Heterocycles 2006, 67, 299.
13. (a) Hanaya, T.; Torigoe, K.; Soranaka, K.; Yamamoto, H.; Yao, Q.;
Pfleiderer, W. Pteridines 1995, 6, 1; (b) Hanaya, T.; Toyota, H.;
Yamamoto, H. Synlett 2006, 2075.
14. A part of the results concerning tepidopterin synthesis have been reported
as a preliminary communication: Hanaya, T.; Baba, H.; Yamamoto, H.
Carbohydr. Res. 2007, 342, 2159.
4.26. 20-O-(2-Acetamido-2-deoxy-b-D-glucopyranosyl)-
ciliapterin (tepidopterin) (5)
By use of the same procedures as described above, com-
pound 32b (34.0 mg, 0.0425 mol) gave 5 (15.9 mg, 85%) as
1
pale yellow solid; Rf¼0.30 (F). H NMR, see Table 3; 13C
NMR (DMSO-d6) d 18.20 (C-30), 23.31 (COCH3), 56.07
(C-2*), 61.32 (C-6*), 70.83 (C-4*), 74.62 (C-3*), 74.82
(C-10), 77.02 (C-5*), 78.43 (C-20), 101.88 (C-1*), 127.63 (C-
4a), 149.12 (C-7), 150.72 (C-6), 153.91 (C-8a), 156.82
(C-2), 161.27 (C-4), 169.58 (COCH3), *for glycosyl moiety.
Anal. Calcd for C17H24N6O8: C, 46.36; H, 5.49. Found: C,
46.21; H, 5.58.
15. Kiss, J.; D’Souza, R.; Taschner, P. Helv. Chim. Acta 1975, 58, 311.
16. Hall, L. D.; Black, S. A.; Slessor, K. N.; Tracey, A. S. Can. J. Chem. 1972,
50, 1912.
17. (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.
18. The ratio of 18a,b (26a,b) was determined by 1H NMR spectra (based par-
ticularly on the H-10, 6, 7 signals) after having been converted into 20-O-
acetyl-N2-(N,N-dimethylaminomethylene) derivatives 19a,b (27a,b).
19. Jones, N. A.; Nepogodiev, S. A.; MacDonald, C. J.; Hughes, D. L.; Field,
R. A. J. Org. Chem. 2005, 70, 8556.
20. (a)Geerts,J.P.;Nagel,A.;VanderPlas, H. C.Org.Magn.Reson. 1976, 8, 606;
(b) Hanaya, T.; Takayama, D.; Yamamoto, H. Heterocycles 2006, 70, 355.
Acknowledgements
21. (a) Ewers, U.; Gunther, H.; Jaenicke, L. Chem. Ber. 1974, 107, 3275; (b)
¨
We are grateful to the SC-NMR Laboratory of Okayama
University for the NMR measurements.
Tobias, S.; Gunther, H.; Pfleiderer, W. Chem. Ber. 1985, 118, 354.
¨
22. Farkas, J.; Ledvina, M.; Brokes, J.; Jezek, J.; Zajicek, J.; Zaoral, M.
Carbohydr. Res. 1987, 163, 63.
23. The complete assignments of 3 and 5 have been established by the present
work; some ambiguous parameters were included in the previous reports
for the natural compounds. Although 1H and 13C NMR charts for the nat-
ural 5 are shown in Ref. 10 without the assigned parameters, we have
found that the parameters of the synthetic 5 completely agree with the
NMR charts of the natural 5.
References and notes
1. Forrest, H. S.; Van Baalen, C.; Myers, J. Arch. Biochem. Biophys. 1958,
78, 95.
2. Choi, Y. K.; Hwang, Y. K.; Kang, Y. H.; Park, Y. S. Pteridines 2001, 12, 121.