Azaheterocyclic derivatives of α-pyrono[2,3-f]isoflavones

Article abstract of DOI:10.1007/s10600-006-0248-6

9-Azahetaryl-3-arylpyrano[2,3-f]chromen-4,8-diones were synthesized by condensation of 7-hydroxy-8-formylisoflavones with 2-azahetarylacetonitriles followed by acid hydrolysis.

Full text of DOI:10.1007/s10600-006-0248-6

Chemistry of Natural Compounds, Vol. 42, No. 6, 2006
AZAHETEROCYCLIC DERIVATIVES OF
α-PYRONO[2,3-f]ISOFLAVONES
T. V. Shokol, V. A. Turov, V. V. Semenyuchenko, and V. P. Khilya
UDC 547.814.5
9-Azahetaryl-3-arylpyrano[2,3-f]chromen-4,8-diones were synthesized by condensation of 7-hydroxy-8-
formylisoflavones with 2-azahetarylacetonitriles followed by acid hydrolysis.
Key words: isoflavones, 2-azahetarylacetonitriles, condensation, α-pyrono[2,3-f]isoflavones.
The broad class ofnatural complicated flavonoids contains compounds with α-andγ-pyrone cores in a single molecule,
in particular, derivatives of pyrano[2,3-f]chromen-4,8-dione (1). Roots of Clausena heptaphylla afforded clausenidine (2) [1,
2]; the powdery film from the leaf surface of the fern Pityrogramma calomelanos, calomelanol D (3) [3-7], which are partially
hydrogenated derivatives of 1.
9
O
O
O
OH
1
O
O
O
Me
Me
7 O
O
O
O
O
Me
Me
3
5
OH
O
CH
2
1
2
3
Synthetic derivatives ofα-pyrono[2,3-f]chromones have been proposed as monofunctional photoreagents for DNA [8].
α-Pyrono[2,3-f]flavones, their heteroanalogs, and isoflavones exhibit bactericidal activity [9, 10].
The pyrano[2,3-f]chromen-4,8-dione system can be synthesized via annellation of the γ-pyrone core to the coumarin
core [9-13] or, on the other hand, by annellation of the α-pyrone ring to the chromone ring [9, 14-18]. α-Pyrono[2,3-
f]isoflavones were prepared through both pathways, by acylation of 5-hydroxy-6-arylacetylcoumarin using the Kostanetsky
reaction [11] and starting with 7-hydroxy-8-formylchromones under forcing Perkin reaction conditions [9, 15]. Derivatives of
this system with heterocyclic substituents in the α-pyrone ring are known. Therefore, it seemed interesting to modify
α-pyrono[2,3-f]isoflavones by adding pharmacophoric azaheterocyclic groups.
Thus, we investigated the reaction of 7-hydroxy-8-formylisoflavones 4-7 with 2-azahetarylacetonitriles. The starting
materials for synthesizing the formyl derivatives were the natural isoflavone formononetin (8) and its synthetic analogs 9-11
that are unsubstituted and substituted at the 2- and 6-positions. 8-Formylformononetin (4) was synthesized previously from 8
using the Duff reaction [19, 20]. We used this method to synthesize 7-hydroxy-8-formylisoflavones 4-7. Reaction of 8-11
with an excess of hexamethylenetetramine in acetic acid with subsequent work up with dilute HCl produced in good yields (60-
73%) 4-7.
PMR spectra of 4-7 in DMSO-d contained a singlet at 6.8 ppm that was characteristic of H-8 in starting isoflavones
6
8-11. The formyl proton resonated at 10-53-10.59 ppm. A broad singlet for the 7-OH was shifted to weak field by almost
2 ppm as a result of the formation of an intramolecular H-bond with the O atom of the 8-CHO group. The chelate structure of
the products was also confirmed bytheir characteristic red-brown color in alcohol solution with FeCl [14, 19] and the presence
3
-1
of a broad band at 3070-3100 cm in the IR spectra. Formyl C=O and isoflavone carbonyl stretching vibrations were observed
-1
as a strong broad band at 1640-1650 cm .
Taras Shevchenko Kiev National University, 01033, Kiev, ul. Vladimirskaya, 64, e-mail: vkhilya@mail.univ.kiev.ua.
Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 544-547, November-December, 2006. Original article submitted
July 3, 2006.
0009-3130/06/4206-0668 ©2006 Springer Science+Business Media, Inc.
668

O
N
O
N Me
N
HN
N
O
O
O
R
2
O
R
O
O
O
O
O
O
2
R
3
O
R
1
R
NO
R
1
2
12 - 14
15
16, 17
CHO
HO
R
2
O
O
HO
O
O
2
(CH ) N
R
3
2 6
4
R
3
AcOH
R
1
R
1
8 - 11
4 - 7
Me
N
S
N
S
N
N
S
O
O
O
R
O
O
R
O
O
O
2
2
O
O
R
3
O
R
1
R
1
O
R
1
18 - 20
21, 22
23 - 25
4:
8:
5:
6:
7:
R1 = OMe, R2 = R3 = H; R1 = NO2, R2 = R3 = H; R1 = Cl, R2 = Me, R3 = H; R1 = F, R2 = Me, R3 = Et;
9:
R1 = OMe, R2 = R3 = H; R1 = NO2, R2 = R3 = H;
10:
11:
R1 = Cl, R2 = Me, R3 = H;
R1 = F, R2 = Me, R3 = Et;
12:
18:
24:
13:
19:
14:
20:
16:
17:
R1 = NO2, R2 = R3 = H;
R1 = OMe, R2 = H;
R1 = OMe, R2 = H;
R1 = NO2, R2 = H;
R1 = Cl, R2 = Me;
R1 = Cl, R2 = Me;
R1 = F, R2 = Me, R3 = Et;
23:
R1 = OMe, R2 = R3 = H;
21:
22:
R1 =NO2, R2 = H;
R1 = OMe;
R1 = NO2;
25:
R1 = NO2, R2 = R3 = H;
R1 = F, R2 = Me, R3 = Et
4 7
7-Hydroxy-8-formylisoflavones - underwent a Knoevenagel reaction with 2-cyanomethyl derivatives of azines
(pyridine and quinazolin-4-one) and azoles (1-methylbenzimidazole, 4-methylthiazole, 5-phenyl-1,3,4-thiadiazole, and
benzothiazole) in DMF in the presence of catalytic amounts of piperidine at room temperature. Hydrolysis of the condensation
12 14 16 20 24
,
products by H SO (3%) for 5 h isolated in high yields 9-azahetaryl-3-arylpyrano[2,3-f]chromen-4,8-diones
-
,
-
,
2
4
25
and . Longer boiling in H SO (30%) was required to form
15
21 23 12 25
. Compounds - are high melting and poorly
and
-
2
4
soluble in organic solvents.
12 25
in CF CO D contained signals characteristic of the isoflavone protons and the azaheterocyclic
3 2
PMR spectra of
-
part of the molecules in addition to a weak-field singlet at 9.43-10.15 ppm for H-10 ofpyrano[2,3-f]chromen-4,8-dione that was
deshielded by the azaheterocycle N atom. Formation of the α-pyrone ring was confirmed by the appearance in IR spectra of
-1
12 25
-
of a strong band for C=O stretches of a lactone carbonyl at 1710-1750 cm . The chromone C=O was located at 1640-
-1
1660 cm , which agreed with previous results for α-pyronochromones [10, 17].
Thus, reaction of 7-hydroxy-8-formylisoflavones with 2-azahetarylacetonitriles under mild conditions produced new
derivatives of α-pyrono[2,3-f]isoflavone with an azaheterocyclic substituent in the α-pyrone ring.
669

EXPERIMENTAL
The purity of the products was monitored by TLC on Silufol UV-254 plates using CHCl :CH OH (9:1). PMR spectra
3
3
were recorded in DMSO-d and CF CO D on a Varian Mercury 400 spectrometer relative to TMS (internal standard). IR
6
3
2
spectra were recorded on a UR-20 instrument in KBr disks. Elemental analyses of all compounds agreed with those calculated.
General Method for Synthesizing 7-Hydroxy-8-formylisoflavones 4-7. A solution of 8-11 (5 mmol) and
hexamethylenetetramine (7 g, 50 mmol) in acetic acid (20 mL) was heated on a water bath for 6-8 h, poured into HCl:H O (1:1,
2
24 mL), boiled for 10 min, and diluted with water (40 mL). After several hours the resulting precipitate was filtered off and
recrystallized from EtOH.
7-Hydroxy-8-formyl-4′-methoxyisoflavone (4). Yield 60%, mp 178°C (lit. [19] mp 166°C, [20] 165-185°C),
C H O . PMR spectrum (400 MHz, DMSO-d , δ, ppm, J/Hz): 3.82 (3H, s, CH O-4′), 6.97 (2H, d, J = 8.8, H -2′, H -6′),
17 12
5
6
3
Ar
Ar
7.07 (1H, d, J = 8.8, H-6), 7.52 (2H, d, J = 8.8, H -3′, H -5′), 8.28 (1H, d, J = 8.8, H-5), 8.37 (1H, s, H-2), 10.55 (1H, s,
Ar
Ar
-1
CHO-8), 12.25 (1H, s, OH-7). IR spectrum (KBr, ν, cm ): 3080 (CHO...HO), 1640 (C=O).
7-Hydroxy-8-formyl-4′-nitroisoflavone (5). Yield 70%, mp 182°C, C H NO . PMR spectrum (400 MHz,
16
9
6
DMSO-d , δ, ppm, J/Hz): 7.12 (1H, d, J = 8.8, H-6), 7.92 (2H, d, J = 8.8, H -2′, H -6′), 8.27 (3H, d, J = 8.8, H-5, H -3′,
6
Ar
Ar
Ar
-1
H -5′), 8.68 (1H, s, H-2), 10.53 (1H, s, CHO-8), 12.26 (1H, s, OH-7). IR spectrum (KBr, ν, cm ): 3080 (CHO...HO), 1650
Ar
(C=O).
7-Hydroxy-2-methyl-8-formyl-4′-chloroisoflavone (6). Yield 72%, mp 165°C, C H ClO . PMR spectrum
17 11
4
(400 MHz, DMSO-d , δ, ppm, J/Hz): 2.36 (3H, s, CH -2), 7.04 (1H, d, J = 8.8, H-6), 7.28 (2H, d, J = 8.4, H -2′, H -6′), 7.44
6
3
Ar
Ar
(2H, d, J = 8.4, H -3′, H -5′), 8.17 (1H, d, J = 8.8, H-5), 10.56 (1H, s, CHO-8), 12.22 (1H, s, OH-7). IR spectrum (KBr, ν,
Ar
Ar
-1
cm ): 3100 (CHO...HO), 1640 (C=O).
7-Hydroxy-2-methyl-8-formyl-6-ethyl-4′-fluoroisoflavone (7). Yield 73%, mp 183°C, C H FO . PMR spectrum
19 15
4
(400 MHz, DMSO-d , δ, ppm, J/Hz): 1.27 (3H, t, J = 7.6, CH CH -6), 2.35 (3H, s, CH -2), 2.73 (2H, q, J = 7.6, CH CH -6),
6
3
2
3
3
2
7.20 (2H, t, J
= J
= 8.4, H -3′, H -5′), 7.30 (2H, dd, J
= 8.4, J
= 5.6, H -2′, H -6′), 8.05 (1H, s,
H-3′,H-2′
H-3′,F
Ar
Ar
H-2′,H-3′
-1
H-2′,F Ar Ar
H-5), 10.59 (1H, s, CHO-8), 12.80 (1H, s, OH-7). IR spectrum (KBr, ν, cm ): 3070 (CHO...HO), 1640 (C=O).
General Method for Synthesizing 9-Azahetaryl-3-arylpyrano[2,3-f]chromen-4,8-diones 12-25. A solution of 4-7
(1 mmol) in DMF (2 mL) was treated with the appropriate 2-azahetarylacetonitrile (1 mmol) and piperidine (3 drops), heated
for 5 min, held at room temperature for 12 h, treated with H SO (10 mL, 3%), boiled for 5 h (for 15 and 21-23, for 15 h in 30%
2
4
H SO ), and cooled. The precipitate was filtered off and recrystallized from DMF.
2
4
3-(4-Methoxyphenyl)-9-(pyridin-2-yl)pyrano[2,3-f]chromen-4,8-dione (12). Yield 79%, mp 217°C, C H NO .
24 15
5
PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 3.85 (3H, s, OCH -4′), 6.98 (2H, d, J = 8.8, H -2′, H -6′), 7.28 (2H, d,
3
2
3
Ar
Ar
J = 8.8, H -3′, H -5′), 7.53 (1H, d, J = 9.2, H-6), 7.97 (1H, t, J = 6.8, H -4″), 8.22 (1H, s, H-2), 8.61-8.66 (3H, m, H-5,
Ar
Ar
Py
-1
H -3″, H -5″), 8.77 (1H, d, J = 5.6, H -6″), 9.44 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1740 (C=Oα), 1660 (C=Oγ).
Py
Py
Py
3-(4-Nitrophenyl)-9-(pyridin-2-yl)pyrano[2,3-f]chromen-4,8-dione (13). Yield 51%, mp >300°C, C H N O .
23 12
2 6
PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 7.79 (1H, d, J = 9.2, H-6), 7.84 (2H, d, J = 8.8, H -2′, H -6′), 8.21 (1H,
3
2
Ar
Ar
t, J = 6.8, H -4″), 8.47 (2H, d, J = 8.8, H -3′, H -5′), 8.57 (1H, s, H-2), 8.83-8.90 (3H, m, H-5, H -3″, H -5″), 9.01 (1H,
Py
Ar
Ar
Py
Py
-1
d, J = 5.6, H -6″), 9.68 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1750 (C=Oα), 1645 (C=Oγ).
Py
2-Methyl-9-(pyridin-2-yl)-3-(4-chlorophenyl)pyrano[2,3-f]chromen-4,8-dione (14). Yield 75%, mp 267°C,
C H ClNO . PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 2.61 (3H, s, CH -2), 7.30 (2H, d, J = 8.4, H -2′, H -6′),
24 14
4
3
2
3
Ar
Ar
7.55 (2H, d, J = 8.4, H -3′, H -5′), 7.76 (1H, d, J = 8.8, H-6), 8.21 (1H, m, H -4′), 8.81-8.84 (3H, m, H-5, H -3″, H -5″),
Ar
Ar
Py
Py
Py
-1
9.01 (1H, d, J = 5.6, H -6″), 9.67 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1730 (C=Oα), 1650 (C=Oγ).
Py
3-(4-Nitrophenyl)-9-(4-oxo-3,4-dihydroquinazolin-2-yl)pyrano[2,3-f]chromen-4,8-dione (15).
Yield 83%,
mp >300°C, C H N O . PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 7.79 (1H, d, J = 9.2, H-6), 7.83 (2H, d,
26 13
3
7
3
2
J = 8.8, H -2′, H -6′), 8.01 (1H, t, J = 7.6, H-7″), 8.17 (1H, d, J = 8.0, H-8″), 8.26 (1H, t, J = 7.6, H-6″), 8.47 (2H, d, J = 8.8,
Ar
Ar
H -3′, H -5′), 8.51 (1H, s, H-2), 8.61 (1H, d, J = 8.0, H-5″), 8.97 (1H, d, J = 9.2, H-5), 10.15 (1H, s, H-10). IR spectrum (KBr,
Ar
Ar
-1
ν, cm ): 1710 (C=Oα), 1670 (C=O ), 1645 (C=Oγ).
q
9-(1-Methylbenzimidazol-2-yl)-3-(4-nitrophenyl)pyrano[2,3-f]chromen-4,8-dione (16). Yield 82%, mp 291°C,
C H N O . PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 4.32 (3H, s, N–CH ), 7.79 (1H, d, J = 9.2, H-6), 7.86 (5H,
26 15
3
6
3
2
3
m, H -2′, H -6′, H -5″, H -6″, H -7″), 8.00 (1H, d, J = 8.0, H -4″), 8.48 (2H, d, J = 8.0, H -3′, H -5′), 8.56 (1H, s,
Ar
Ar
Bzi
Bzi
Bzi
Bzi
Ar
Ar
-1
H-2), 8.90 (1H, d, J = 9.2, H-5), 9.43 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1735 (C=Oα), 1660 (C=Oγ).
670

2-Methyl-9-(1-methylbenzimidazol-2-yl)-3-(4-fluorophenyl)-6-ethylpyrano[2,3-f]chromen-4,8-dione (17). Yield
83%, mp >300°C, C H FN O . PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 1.52 (3H, t, J = 7.6, CH CH -6), 2.58
29 21
2
4
3
2
3
2
(3H, s, CH -2), 3.17 (2H, q, J = 7.6, CH CH -6), 4.32 (3H, s, N–CH ), 7.27 (2H, t, J
= J
= 8.4, H -3′, H -5′),
3
3
2
3
H-3′,H-2′
H-3′,F Ar Ar
7.37 (2H, dd, J
= 8.4, J
= 5.6, H -2′, H -6′), 7.87-8.01 (4H, m, H -4″, H -5″, H -6″, H -7″), 8.70 (1H,
H-2′,H-3′
H-2′,F
Ar
Ar
-1
Bzi
Bzi
Bzi
Bzi
s, H-5), 9.44 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1720 (C=Oα), 1630 (C=Oγ).
9-(4-Methylthiazol-2-yl)-3-(4-methoxyphenyl)pyrano[2,3-f]chromen-4,8-dione (18). Yield 78%, mp 271°C,
C H NO S. PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 2.58 (3H, s, CH -4″), 3.85 (3H, s, OCH -4′), 6.98 (2H, d,
23 15
5
3
2
3
3
J = 8.8, H -2′, H -6′), 7.28 (2H, d, J = 8.8, H -3′, H -5′), 7.51 (1H, d, J = 9.2, H-6), 7.56 (1H, s, H-5″), 8.21 (1H, s, H-2),
Ar
Ar
Ar
Ar
-1
8.64 (1H, d, J = 9.2, H-5), 9.43 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1735 (C=Oα), 1650 (C=Oγ).
9-(4-Methylthiazol-2-yl)-3-(4-nitrophenyl)pyrano[2,3-f]chromen-4,8-dione (19).
Yield 74%, mp 292°C,
C H N O S. PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 2.82 (3H, s, CH -4″), 7.78 (1H, d, J = 9.2, H-6), 7.79 (1H,
22 12
2
6
3
2
3
s, H-5″), 7.84 (2H, d, J = 8.4, H -2′, H -6′), 8.46 (2H, d, J = 8.4, H -3′, H -5′), 8.58 (1H, s, H-2), 8.87 (1H, d, J = 9.2, H-5),
Ar
Ar
Ar
Ar
-1
9.75 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1740 (C=Oα), 1660 (C=Oγ).
2-Methyl-9-(4-methylthiazol-2-yl)-3-(4-chlorophenyl)pyrano[2,3-f]chromen-4,8-dione(20). Yield76%, mp275°C,
C H ClNO S. PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 2.60 (3H, s, CH -2), 2.80 (3H, s, CH -4″), 7.29 (2H, d,
23 14
4
3
2
3
3
J = 8.4, H -2′, H -6′), 7.54 (2H, d, J = 8.4, H -3′, H -5′), 7.73 (1H, d, J = 8.8, H-6), 7.78 (1H, s, H-5″), 8.81 (1H, d, J = 8.8,
Ar
Ar
Ar
Ar
-1
H-5), 9.73 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1725 (C=Oα), 1660 (C=Oγ).
3-(4-Methoxyphenyl)-9-(5-phenyl-[1,3,4]thiadiazol-2-yl)pyrano[2,3-f]chromen-4,8-dione (21). Yield 87%,
mp >300°C, C H N O S. PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 3.85 (3H, s, OCH -4′), 6.99 (2H, d, J = 8.8,
27 16
2
5
3
2
3
H -2′, H -6′), 7.30 (2H, d, J = 8.8, H -3′, H -5′), 7.54-7.59 (3H, m, H-6, H -3″, H -5″), 7.73 (1H, t, J = 7.6, H -4″), 7.93
Ar
Ar
Ar
Ar
Ph
Ph
Ph
-1
(2H, d, J = 7.6, H -2″, H -6″), 8.26 (1H, s, H-2), 8.65 (1H, d, J = 9.2, H-5), 9.65 (1H, s, H-10). IR spectrum (KBr, ν, cm ):
Ph
Ph
1725 (C=Oα), 1640 (C=Oγ).
3-(4-Nitrophenyl)-9-(5-phenyl-[1,3,4]thiadiazol-2-yl)pyrano[2,3-f]chromen-4,8-dione (22). Yield88%, mp>300°C,
C H N O S. PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 7.79 (3H, m, H-6, H -3″, H -5″), 7.84 (2H, d, J = 8.8,
26 13
3
6
3
2
Ph
Ph
H -2′, H -6′), 7.94 (1H, t, J = 7.6, H -4″), 8.16 (2H, d, J = 7.6, H -2″, H -6″), 8.47 (2H, d, J = 8.8, H -3′, H -5′), 8.60
Ar
Ar
Ph
Ph
Ph
Ar
Ar
-1
(1H, s, H-2), 8.87 (1H, d, J = 9.2, H-5), 9.90 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1725 (C=Oα), 1660 (C=Oγ).
9-Benzothiazol-2-yl-3-(4-methoxyphenyl)pyrano[2,3-f]chromen-4,8-dione (23). Yield 89%, mp >300°C,
C H NO S. PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 4.09 (3H, s, OCH -4′), 7.23 (2H, d, J = 8.4, H -2′, H -6′),
26 15
5
3
2
3
Ar
Ar
7.53 (2H, d, J = 8.4, H -3′, H -5′), 7.66 (1H, d, J = 8.8, H-6), 7.95 (1H, t, J = 8.4, H-6″), 8.03 (1H, t, J = 8.4, H-5″), 8.31 (1H,
Ar
Ar
d, J = 8.4, H-7″), 8.40 (1H, d, J = 8.4, H-4″), 8.49 (1H, s, H-2), 8.94 (1H, d, J = 8.8, H-5), 9.89 (1H, s, H-10). IR spectrum (KBr,
-1
ν, cm ): 1735 (C=Oα), 1645 (C=Oγ).
9-Benzothiazol-2-yl-3-(4-nitrophenyl)pyrano[2,3-f]chromen-4,8-dione (24). Yield 78%, mp>300°C, C H N O S.
25 12
2 6
PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 7.81 (1H, d, J = 8.8, H-6), 7.86 (2H, d, J = 8.8, H -2′, H -6′), 7.96 (1H,
3
2
Ar
Ar
t, J = 8.4, H-6″), 8.04 (1H, t, J = 8.4, H-5″), 8.32 (1H, d, J = 8.4, H-7″), 8.40 (1H, d, J = 8.4, H-4″), 8.48 (2H, d, J = 8.8, H -3′,
Ar
-1
H -5′), 8.62 (1H, s, H-2), 8.94 (1H, d, J = 8.8, H-5), 9.90 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1725 (C=Oα), 1650
Ar
(C=Oγ).
9-Benzothiazol-2-yl-2-methyl-3-(4-fluorophenyl)-6-ethylpyrano[2,3-f]chromen-4,8-dione (25). Yield 85%,
mp >300°C, C H FNO S. PMR spectrum (400 MHz, CF CO D, δ, ppm, J/Hz): 1.49 (3H, t, J = 7.6, CH CH -6), 2.61 (3H,
28 18
4
3
2
3
2
s, CH -2), 3.16 (2H, q, J = 7.6, CH CH -6), 7.24 (2H, t, J
= J
= 8.4, H -3′, H -5′), 7.34 (2H, dd, J
= 8.4,
3
3
2
H-3′,H-2′
H-3′,F
Ar
Ar
H-2′,H-3′
J
= 5.6, H -2′, H -6′), 7.93 (1H, t, J = 8.4, H-6′), 8.00 (1H, t, J = 8.4, H-5″), 8.29 (1H, d, J = 8.4, H-7″), 8.35 (1H, d,
Ar Ar
H-2′,F
-1
J = 8.4, H-4″), 8.72 (1H, s, H-5), 9.87 (1H, s, H-10). IR spectrum (KBr, ν, cm ): 1725 (C=Oα), 1645 (C=Oγ).
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