Molecules 2018, 23, 2271
13 of 18
4.5. 8,9-Difluoronaphtho[2,3-g]pteridine-2,4(1H,3H)-dione (3)
Compound
3 was synthesized according to the General Procedure, Approach A. Reaction of
diamine
C
(0.499 g, 3.47 mmol) with alloxan monohydrate (0.561 g, 3.47 mmol) and boric acid (0.211
◦
g, 3.47 mmol) provided compound
(lit. 310–312 C) [46]. H-NMR (DMSO-d6, TMS):
3
as a light purple solid (yield 0.504 g, 58%). M.p. 310–311 C
◦
1
δ 12.01 (s, 1H), 11.78 (s, 1H), 8.29 (dd, J = 10.9, 8.6 Hz,
1H), 8.00 (dd, J = 11.4, 8.2 Hz, 1H). Elemental analysis calcd (%) for C10H4F2N4O2: C 48.01, H 1.61, N
22.04; found: C 48.07, H 1.68, N 22.09.
4.6. 2,4-Dioxo-1,2,3,4-tetrahydropteridine-6,7-dicarbonitrile (4)
Compound
diamine (0.500 g, 4.63 mmol) with alloxan monohydrate (0.740 g, 4.63 mmol) and boric acid (0.291 g,
4.63 mmol) provided compound
as a light grey solid (yield 0.319 g, 32%). M.p. > 330 ◦C. 1H-NMR
(DMSO-d6, TMS): 158.55, 149.98, 149.35,
12.87 (br s, 1H), 12.17 (s, 1H). 13C-NMR (DMSO-d6, TMS):
4 was synthesized according to the General Procedure, Approach A. Reaction of
D
4
δ
δ
134.72, 131.41, 125.39, 114.09, 113.55. Elemental analysis calcd (%) for C8H2N6O2: C 44.87, H 0.94, N
39.25; found: C 48.84, H 1.02, N 39.21.
4.7. Pyreno[4,5-g]pteridine-11,13(10H,12H)-dione (5)
Compound
diamine (0.270 g, 1.16 mmol) with alloxan monohydrate (0.186 g, 1.16 mmol) and boric acid (0.072 g,
1.16 mmol) provided compound
(DMSO-d6, TMS): 12.19 (s, 1H), 11.82 (s, 1H), 9.22–9.14 (m, 2H), 8.48 (d, J = 7.5 Hz, 1H), 8.39
5 was synthesized according to the General Procedure, Approach A. Reaction of
E
◦
as a yellow solid (yield 0.293 g, 75%). M.p. > 330 C. 1H-NMR
5
δ
(d, J = 7.5 Hz, 1H), 8.26–8.12 (m, 4H). Elemental analysis calcd (%) for C20H10N4O2: C 71.00, H 2.98, N
16.50; found: C 71.08, H 2.95, N 16.44. EI/MS (m/z): 338.080. Found 338.081 (100). IR (neat, cm−1):
3182, 3064, 2937, 2825, 1720, 1689, 1570, 1555, 1447, 1422, 1385, 1364, 1304, 1279, 1234, 1176, 1163, 1033,
928, 859, 829, 812, 752, 718, 653, 617, 590, 525, 487, 459, 445, 434.
4.8. Pteridino[6,7-b]phenazine-2,4(1H,3H)-dione (6)
Compound
6 was synthesized according to the General Procedure, Approach A. Reaction of
diamine
F
(0.101 g, 0.480 mmol) with alloxan monohydrate (0.077 g, 0.480 mmol) and boric acid
◦
(0.030 g, 0.480 mmol) provided compound
6
as a dark purple solid (yield 0.080 g, 57%). M.p. > 330 C.
Elemental analysis calcd (%) for C16H8N6O2: C 60.76, H 2.55, N 26.57; found: C 60.74, H 2.52, N 26.50.
4.9. General Procedure for the Preparation of the Non-Fused Flavins 7–11 by Approach B
5,6-Diaminouracil sulphate (1.31 mmol, 1 eq.) was suspended in water (35 mL). The mixture was
made alkaline using a methanolic solution of NaOH (0.65M, 3 eq.) and heated to 90 ◦C for 15 min.
A solution of diketone (1.96 mmol, 1.5 eq.) in a mixture of THF (40 mL) and water (15 mL) was added
and the mixture was stirred at 90 ◦C for 45 min. The reaction mixture was acidified glacial acetic acid
(15 mL) and heated at 90 ◦C for another 20 h. The reaction mixture was subsequently concentrated to
approximately 1/3 of the volume, cooled in the freezer and the as-obtained suspension was filtered
and the solid fraction was washed with cold water (30 mL) and cold ethanol (20 mL) to yield the crude
flavin derivative. The crude product was purified by digestion in boiling methanol. The digested
flavin derivative was further subjected to vacuum sublimation to yield the final target compound.
4.10. Phenanthro[9,10-g]pteridine-11,13(10H,12H)-dione (7)
Compound
diketone (0.817 g, 3.92 mmol) with 5,6-diaminouracil sulphate (1.00 g, 2.62 mmol) provided
compound
12.21 (s, 1H), 11.84 (s, 1H), 9.09–8.99 (m, 2H), 8.91–8.81 (m, 2H), 7.98–7.90 (m, 1H), 7.89–7.80 (m, 3H).
Elemental analysis calcd (%) for C8H2N6O2: C 68.79, H 3.21, N 17.83; found: C 68.66, H 3.11, N 17.75.
7 was synthesized according to the General Procedure, Approach B. Reaction of
G
◦
1
7
as a yellow solid (yield 0.304 g, 37%). M.p. > 330 C. H-NMR (DMSO-d6, TMS):
δ