1498
HETEROCYCLES, Vol. 88, No. 2, 2014
1
7
-substituted isomer (13b) (59% yield) as a pale yellow syrup: R
f 3
= 0.53 (1:9 MeOH-CHCl ); H-NMR
(600 MHz) for 13a ! 1.98, 2.05, 2.16 (3H each, 3s, AcO-1’,2’,3’), 2.38 (3H, s, AcN), 4.30 (1H, dd, J3’a,3’b
=
12.3, J2’,3’b = 5.6 Hz, H -3’), 4.42 (1H, dd, J
= 3.2 Hz, H -3’), 5.63 (1H, ddd, H-2’), 6.14 (1H, d,
b
2’,3’a
a
1
J
1’,2’ = 6.5 Hz, H-1’), 8.91 (1H, s, H-7), 10.90 [1H, br s, H-N(3)], 12.50 (1H, br s, AcNH); H-NMR (600
MHz) for 13b ! 2.00, 2.01, 2.20 (3H each, 3s, AcO-1’,2’,3’), 2.37 (3H, s, AcN), 4.26 (1H, dd, J3’a,3’b
=
1
2.3, J2’,3’b = 6.3 Hz, H -3’), 4.38 (1H, dd, J
2’,3’a a 1’,2’
= 3.7 Hz, H -3’), 5.63 (1H, ddd, H-2’), 6.11 (1H, d, J
b
=
C
5.3 Hz, H-1’), 8.72 (1H, s, H-6), 10.90 [1H, br s, H-N(3)], 12.50 (1H, br s, AcNH). Anal. Calcd for
: C, 48.46; H, 4.54. Found: C, 48.33; H, 4.61.
17
19 5 8
H N O
B. From 10. By the same procedures described above, compound 10 gave an inseparable mixture
(17:83) of 13a and 13b in 53% yield.
2
Di-N :3’-O-acetyl-1’,2’-O-isopropylideneneopterin (14a) and its 7-neopterin isomer (14b).
1
3
Compound 9 (124 mg, 0.446 mol) was dissolved in EtOH (2.5 mL) and hydrogenated in the presence of
0% Pd(OH) -C (63.0 mg, 0.089 mmol) at rt under an atmospheric pressure of H . After 20 h, the
catalyst was filtered off and the filtrate was evaporated in vacuo to give 3,4-O-isopropylidene-
D-erythro-pentopyranos-2-ulose (10) (84.0 mg, quant.) in a colorless syrup: R = 0.62–0.50 (AcOEt).
Compound 10 was treated with the same procedures as those described for 11a,b (by condensation at pH
2
2
2
f
8
) to give an inseparable mixture (19:81) of the neopterin derivative (14a) and its 7-substituted isomer
1
(14b) (110 mg, 65% yield from 10) as a pale yellow syrup: R
f
= 0.58 (1:9 MeOH-CHCl
3
); H-NMR (400
MHz) for 14a ! 1.52, 1.71 (3H each, 2s, CMe ), 1.89 (3H, s, AcO-3’), 2.39 (3H, s, AcN), 3.67 (1H, dd,
2
J3’a,3’b = 11.9, J2’,3’b = 5.9 Hz, H
b
-3’), 3.98 (1H, dd, J2’,3’a = 3.9 Hz, H
a
-3’), 4.83 (1H, ddd, H-2’), 5.62 (1H,
1
d, J1’,2’ = 7.4 Hz, H-1’), 9.11 (1H, s, H-7), 10.90 [1H, br s, H-N(3)], 12.50 (1H, br s, AcNH); H-NMR
(
400 MHz) for 14b ! 1.52, 1.70 (3H each, 2s, CMe ), 1.86 (3H, s, AcO-3’), 2.36 (3H, s, AcN), 3.69 (1H,
2
dd, J3’a,3’b = 12.1, J2’,3’b = 5.7 Hz, H
b
-3’), 4.10 (1H, dd, J2’,3’a = 3.3 Hz, H
1H, d, J1’,2’ = 7.6 Hz, H-1’), 8.92 (1H, s, H-6), 10.90 [1H, br s, H-N(3)], 12.50 (1H, br s, AcNH). Anal.
Calcd for C16 : C, 50.93; H, 5.08. Found: C, 50.84; H, 5.10.
a
-3’), 4.82 (1H, ddd, H-2’), 5.46
(
19 5 6
H N O
ACKNOWLEDGEMENTS
We are grateful to the SC-NMR Laboratory of Okayama University for the NMR measurements.
REFERENCES AND NOTES
1
.
(a) W. Pfleiderer, Angew. Chem., Int. Ed. Engl., 1964, 3, 114; (b) H. Rembold and W. L. Gyure,
Angew. Chem., Int. Ed. Engl., 1972, 11, 1061; (c) T. Hama and T. Obika, Nature, 1960, 187, 326;
(d) H. S. Forrest and C. Van Baalen, Ann. Rev. Microbiol., 1970, 24, 91; (e) I. Ziegler and R.