Synthesis and quantitative structure-activity relationships of oxanilates as chemical hybridizing agents for wheat (Triticum aestivum L.)

Article abstract of DOI:10.1021/jf025870+

Chemical hybridizing agents (CHAs) can facilitate two-line breeding in heterosis programs of crops. Twenty-seven oxanilates having different aromatic substitutions were synthesized and screened as CHAs on two genotypes of wheat, PBW 343 and HD 2733, during two Rabi (winter) seasons, 2000-01 and 2001-02. The oxanilates prepared by thermal condensation of anilines with diethyl oxalate or by acylation with ethoxycarbonyl methanoyl chloride were sprayed at 1000 and 1500 ppm at the premeiotic stage of wheat, when the length of the emerging spike of the first node was 7-8 mm. Pollen sterility and spikelet sterility were measured in each treatment. Ethyl oxanilates 5, 6, and 25, containing 4-F, 4-Br, and 4-CF₃ aromatic substituents, respectively, induced greater than 98% spikelet sterility, the desired level, at 1500 ppm. Quantitative structure-activity relationship analysis revealed a direct relationship between F_p and molecular mass but an inverse relationship between MR, E_s, and R in influencing the bioactivity. Several F₁ hybrids were developed using 5, and at least one showed heterosis.

Full text of DOI:10.1021/jf025870+

992 J. Agric. Food Chem. 2003, 51, 992−998
Synthesis and Quantitative Structure−Activity Relationships of
Oxanilates as Chemical Hybridizing Agents for Wheat (Triticum
aestivum L.)‡
KAJAL CHAKRABORTY, CHAKRAVARTHI DEVAKUMAR,* SHIV M. S. TOMAR,† AND
RAJENDRA KUMAR
Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi-110012, India
Chemical hybridizing agents (CHAs) can facilitate two-line breeding in heterosis programs of crops.
Twenty-seven oxanilates having different aromatic substitutions were synthesized and screened as
CHAs on two genotypes of wheat, PBW 343 and HD 2733, during two Rabi (winter) seasons, 2000-
01 and 2001-02. The oxanilates prepared by thermal condensation of anilines with diethyl oxalate
or by acylation with ethoxycarbonyl methanoyl chloride were sprayed at 1000 and 1500 ppm at the
premeiotic stage of wheat, when the length of the emerging spike of the first node was 7-8 mm.
Pollen sterility and spikelet sterility were measured in each treatment. Ethyl oxanilates 5, 6, and 25,
containing 4-F, 4-Br, and 4-CF3 aromatic substituents, respectively, induced greater than 98% spikelet
sterility, the desired level, at 1500 ppm. Quantitative structure-activity relationship analysis revealed
a direct relationship between Fp and molecular mass but an inverse relationship between MR, ES,
and R in influencing the bioactivity. Several F1 hybrids were developed using 5, and at least one
showed heterosis.
KEYWORDS: Chemical hybridizing agents (CHAs); Triticum aestivum L. wheat; male sterility; oxanilates;
ethyl N-aryl carbamoyl methanoate; QSAR
INTRODUCTION
dihydro-5-oxo-4-pyridazinecarboxylic acid potassium salt] has
been registered as a CHA for wheat (3). Oxanilates and related
thio and thiono analogues have been reported to induce male
sterility in maize and barley (4), but their effect on wheat, rice,
and chickpea is not known. Furthermore, there is a need to
develop very potent analogue(s) by a proper structure optimiza-
tion.
In a program of design and development of potential CHAs,
we have undertaken the synthesis of several N-acylanilines,
amino acid analogues, and pyridones at the Indian Agricultural
Research Institute, New Delhi, India. Encouraging results have
been obtained with the field trials of a few N-acylanilines on
rice (5, 6) wheat (7, 8), and chickpea (9). Quantitative structure-
activity relationship (QSAR) analysis is a powerful tool for
unraveling the essential structural features governing bioactivity.
To the best of our knowledge, QSAR has not been applied in
the design of CHAs. We now report the synthesis, spectroscopic
data, and QSAR analysis of 27 oxanilates, including 15 new
compounds, as potential CHAs for wheat.
The production of hybrid wheat (Triticum aestiVum L.) offers
an exciting opportunity for overcoming the stagnating yield
plateau of wheat in India. Exploitation of heterosis at the
commercial level depends on the availability of stable male
sterile lines. A viable and stable cytoplasmic-genetic male sterile
system, along with perfect restorer lines in wheat, is not in place,
although considerable research efforts are underway. In view
of this, the other option of using chemical hybridizing agents
(CHAs) involving two-line hybrid breeding needs to be pursued
intensively. The aim is to induce physiological male sterility
by spraying the plant with chemicals to induce stamen sterility
without harming the pistil.
CHAs facilitate cross-breeding in plant species with perfect
flowers by selectively sterilizing male sex cells or by interrupting
microsporogenesis to prevent self-pollination and to promote
fertilization by an outside pollen source. Unlike the cytoplasmic-
genetic male sterile system, the CHAs have unique advantages
of saving time and labor (1), since no restorer-maintainer lines
are required (2), and any profitable heterotic combination is
significant. Recently, Clofencet [2-(4-chlorophenyl)-3-ethyl-2,5-
MATERIALS AND METHODS
Chemicals and Reagents. Substituted anilines and diethyl oxalate
were procured from Aldrich Chemical Co. Inc. Isoproturon [3-(4-
isopropylphenyl)-1,1-dimethylurea] was isolated from a formulation (50
WP) obtained from the Division of Agronomy of this institute. Xylene
used in this study was of rectified grade.
‡ Contribution no. 771 from the Division of Agricultural Chemicals.
* To whom correspondence should be addressed. Tel.: 91-11-5783272.
Fax: 91-11-5783272. E-mail: cdevakumar@yahoo.com or devakumarc@
hotmail.com.
† Current address: Division of Genetics, IARI, New Delhi-110 012, India.
10.1021/jf025870+ CCC: $25.00 © 2003 American Chemical Society
Published on Web 01/07/2003

Synthesis and QSAR of Oxanilates as CHAs for Wheat
J. Agric. Food Chem., Vol. 51, No. 4, 2003 993
Ethyl 3′-Chloro-4′-fluorooxanilate (4). A white crystalline solid was
obtained from the reaction for 2 h; yield 4.78 g (89%); mp 130-131
°C (lit. mp 130-131 °C) (4); TLC Rf 0.49; GC tR 13.63 min; 1H NMR
(CDCl3) δ 1.50 (t, J ) 6 Hz, 3H, -CH3), 4.50 (q, J ) 6 Hz, 2H,
-OCH2), 7.80 (m, 1H, Ha-aromatic), 7.20 (m, 2H, Hb, Hb′-aromatic),
9.01 (s, 1H, NH); EI-MS m/z (relative intensity) 245 (M+, 12), 171
(22), 173 (10), 174 (6), 172 (20), 147 (6), 146 (33), 145 (22), 144
(100), 129 (16), 131 (5), 119 (15), 117 (45), 109 (49), 108 (45), 93
(15), 92 (15), 91 (11), 83 (7), 82 (16), 81 (15), 63 (10), 57 (23), 56
(15).
Ethyl 4′-Fluorooxanilate (5). A white crystalline solid was obtained
from the reaction for 30 min; yield 4.75 g (90%); mp 118-119 °C (lit.
1
mp 118.5 °C) (4); TLC Rf 0.50; GC tR 7.82 min; H NMR (CDCl3) δ
1.65 (t, J ) 6 Hz, 3H, -CH3), 4.70 (q, J ) 6 Hz, 2H, -OCH2), 7.40
(t, J ) 6 Hz, 2H, Hb, Hb′-aromatic), 7.95 (d, J ) 6 Hz, 1H, Ha-aromatic),
8.10 (d, J ) 6 Hz, 1H, Ha′-aromatic), 9.44 (s, 1H, NH); IR 3333 (as.
NH str), 1698 (CdO ester str.), 1640 (amide-I band, CdO str.), 1400
(CF str.), 1295 (aromatic secondary δCH); EI-MS m/z (relative intensity)
211 (M+, 100), 139 (18), 138 (93), 137 (72), 110 (92), 75 (12), 83
(32), 63 (5).
Figure 1. General synthesis of meta- and para-substituted oxanilates.
Chromatography and Spectroscopy. IR spectra (νmax in cm-1) were
recorded on a Nicolet Impact 400 FT-IR spectrometer using a potassium
bromide (KBr) disk, scanning from 625 to 4000 cm-1. NMR spectra
were recorded on a Varian EM-360, 60-MHz spectrometer using
tetramethylsilane (TMS) as an internal reference; chemical shifts are
reported in δ (parts per million) values relative to TMS, and J values
are expressed in hertz (Hz). Mass spectra were recorded under electron
impact (70 eV) conditions using a Fisons GC-MS (GC-8000 coupled
with an EI mass detector MD-800) with a 30-m × 0.32-mm-i.d., OV-
17 capillary column, helium (He) as the carrier gas, at a flow rate of
2 mL/min. Thin-layer chromatography (TLC) was performed on 250-
µm silica gel G plates, preactivated at 100 °C for 2 h, using hexane-
ethyl acetate (4:1) as the developing medium. GC data were recorded
on a HP Series-II GC using a FID detector and a 10-m × 0.53-mm-
i.d., 0.25-µm, OV-1 megabore column with the injector temperature
maintained at 250 °C and the oven temperature programmed from 80
to 250 °C at 9.9 °C/min. The carrier gas used was N2, at a flow rate of
30 mL/min.
Ethyl 4′-Bromooxanilate (6). A white crystalline solid was obtained
from the reaction between 4-bromoaniline and diethyl oxalate for 2 h;
yield 5.11 g (75%); mp 152-153 °C (lit. mp 152-153 °C) (4); TLC
1
Rf 0.50; GC tR 15.64 min; H NMR (CDCl3) δ 1.45 (t, J ) 6 Hz, 3H,
-CH3), 4.45 (q, J ) 6 Hz, 2H, -OCH2), 7.65 (m, 4H, aromatic), 9.12
(s, 1H, NH); IR 3332 (as. NH str), 1702 (CdO ester str.), 1695 (amide-I
band, CdO str.), 560 (-C Br str.); EI-MS m/z (relative intensity) 273
(M+, 81), 271 (84), 200 (76), 199 (100), 198 (82), 197 (89), 172 (82),
170 (82), 92 (24), 91 (66), 90 (28), 76 (27), 75 (25), 64 (38), 63 (52).
Ethyl 3′-Chlorooxanilate (8). White crystals were obtained from the
reaction of diethyl oxalate with m-chloroaniline for 2 h; yield 3.61 g
1
(78%); mp 110 °C; TLC Rf 0.52; GC tR 9.67 min; H NMR (CDCl3)
δ 1.50 (t, J ) 6 Hz, 3H, -CH3), 4.45 (q, J ) 6 Hz, 2H, -OCH2), 7.30
(m, 1H, Hc-aromatic), 7.35 (t, J ) 6 Hz, 1H, Hb-aromatic), 7.55 (t,
J ) 6 Hz, 1H, Ha-aromatic), 7.75 (t, 1H, Ha′-aromatic), 9.10 (s, 1H,
NH); IR 3331 (as. sec. NH str), 1710 (CdO ester str), 1709 (amide-I
band, CdO str), 1295 (aromatic sec. CNδ), 707 (C-Cl str); EI-MS
m/z (relative intensity) 227 (M+, 73), 156 (33), 154 (100), 153 (37),
129 (12), 128 (18), 126 (50), 125 (6), 113 (12), 111 (36), 101 (5), 100
(7), 99 (17), 91 (8), 90 (10), 76 (7), 75 (21), 64 (8), 63 (14). Elemental
analysis, found C, 52.9; H, 4.5; N, 6.2 (C10H10 Cl NO3 requires C,
52.76; H, 4.43; N, 6.15).
Melting points (mp) were determined by using a sulfuric acid bath
and are uncorrected. Elemental analysis of the synthesized compounds
was carried out using a Euro Vector elemental analyzer (model no.
EA3011).
Ethyl 2′,6′-Dichlorooxanilate (9). A white crystalline solid was
obtained from the reaction of 2,6-dichloroaniline with diethyl oxalate
for 3 h; yield 4.85 g (82%); mp 86-88 °C; TLC Rf 0.45; GC tR 4.05
General Procedure for the Synthesis of Oxanilates (1, 3-6, 8-14,
16-19, 21, 22, 24-27). The following method illustrates the general
scheme of synthesis of the title compounds using different substituted
anilines and diethyl oxalate.
1
min; H NMR (CDCl3) δ 1.40 (t, J ) 6 Hz, 3H, -CH3), 4.15 (q, J )
6 Hz, 2H, -OCH2), 7.10 (m, 2H, Hb, Hb′-aromatic), 7.00 (m, 1H, Hc-
aromatic), 9.40 (s, 1H, NH); EI-MS m/z (relative intensity) 262 (M+,
95), 161 (59), 90 (26), 75 (23), 73 (42), 72 (24), 65 (29), 63 (100), 62
(68), 61 (55), 60 (28), 52 (75). Elemental analysis, found C, 45.9; H,
3.5; N, 5.4 (C10H9Cl2 NO3 requires C, 45.83; H, 3.46; N, 5.34).
Ethyl 4′-Chlorooxanilate (10). White flakes were obtained from the
reaction for 2 h; yield 4.89 g (86%); mp 152-153 °C (lit. mp 151-
Aniline (0.025 mol, 2.3 mL), diethyl oxalate (0.03 mol, 4.06 mL),
and toluene (50 mL) were mixed together in a 100-mL round-bottomed
flask fitted with a Dean-Stark apparatus. The mixture was refluxed
for 45 min, and ethanol was collected as an azeotrope. The reaction
was cooled to 90 °C to let the product solidify, triturated with boiling
ethanol, and refrigerated to allow for recrystallization of 1. TLC and
GC were used to monitor the course of the reaction shown in Figure
1. The duration of the reaction, yield, and physicochemical character-
istics of the products thus prepared were as follows:
1
154 °C) (4); TLC Rf 0.45; GC tR 9.27 min; H NMR (CDCl3) δ 1.52
(t, J ) 6 Hz, 3H, -CH3), 4.60 (q, J ) 6 Hz, 2H, -OCH2), 7.65 (d,
J ) 6 Hz, 2H, Hb, Hb′-aromatic), 7.95 (d, J ) 6 Hz, 2H, Ha, Ha′-
aromatic), 9.36 (s, 1H, NH); IR 3332 (as. NH str.), 1703 (CdO ester
str), 1702 (amide-I band, CdO str), 1296 (aromatic sec. CNδ), 713
(C-Cl str); EI-MS m/z (relative intensity) 229 (31), 227 (M+, 95), 156
(27), 155 (44), 154 (83), 153 (87), 149 (20), 140 (16), 129 (14), 128
(34), 127 (48), 126 (100), 125 (12), 113 (8), 111 (24), 101 (10), 99
(32), 75 (27), 73 (13), 64 (11), 63 (21).
Ethyl Oxanilate (1). White crystalline solid; yield 4.2 g (87%); mp
1
71-72 °C; TLC Rf 0.56; GC tR 11.32 min; H NMR (CDCl3) δ 1.35
(t, J ) 6 Hz, 3H, -OCH2CH3), 4.35 (q, J ) 6 Hz, 2H, -OCH2), 7.50
(m, 2H, Ha, Ha′-aromatic), 7.20 (m, 3H, Hb, Hb′, and Hc-aromatic), 8.85
(s, 1H, NH); EI-MS m/z (relative intensity) 193 (M+, 7), 120 (53), 106
(24), 92 (25), 77 (23), 59 (16), 58 (100). Elemental analysis, found C,
62.3; H, 5.8; N, 7.3 (C10H11 NO3 requires C, 62.17; H, 5.74; N, 7.25).
Ethyl 3′-Fluorooxanilate (3). A white crystalline solid was obtained
from the reaction between 3-fluoroaniline and diethyl oxalate for 3 h;
yield 4.28 g (81%); mp 86-88 °C (lit. mp 83-88 °C) (4); TLC Rf
Ethyl 2′-Methoxyoxanilate (11). 2-Anisidine and diethyl oxalate were
refluxed in xylene for 3 h to furnish light brown crystals; yield 4.34 g
1
(86%); mp 96 °C, TLC Rf 0.52; GC tR 9.92 min; H NMR (CDCl3) δ
1
0.54; GC tR 10.66 min; H NMR (CDCl3) δ 1.45 (t, J ) 6 Hz, 3H,
1.43 (t, J ) 3 Hz, 3H, -CH3), 3.88 (s, 3H, -OCH3), 4.32 (q, J ) 6
Hz, 2H, -OCH2), 6.85 (m, 3H, Hb, Hb′, Hc-aromatic), 8.25 (dd, 1H,
Ha′-aromatic), 9.23 (s, 1H, NH); IR 3346 (as. sec. NH str.), 2836
(methyl CH str.), 1716 (CdO ester str), 1702 (amide-I band, CdO
str), 1302 (aromatic sec. CNδ), 763 (aromatic CNδ due to ortho
substitution); EI-MS m/z (relative intensity) 224 (M+, 10), 223 (8), 151
-OCH2CH3), 4.40 (q, J ) 6 Hz, 2H, -OCH2), 6.80 (m, 1H,
Hc-aromatic), 6.90 (m, 1H, Hb-aromatic), 7.40 (m, 1H, Ha-aromatic),
7.70 (m, 1H, Ha′-aromatic), 9.20 (s, 1H, NH); EI-MS m/z (relative
intensity) 211 (M+, 15), 138 (52), 137 (27), 124 (12), 111 (37), 110
(100), 109 (21), 95 (48), 83 (85), 82 (17), 75 (27), 63 (16), 57 (47).

994 J. Agric. Food Chem., Vol. 51, No. 4, 2003
Chakraborty et al.
(10), 150 (100), 149 (42), 136 (7), 135 (44), 123 (8), 122 (31), 120
(11), 108 (13), 94 (24), 92 (19), 79 (10), 77 (12), 65 (18). Elemental
analysis, found C, 59.2; H, 5.9; N, 6.3 (C11H13 NO4 requires C, 59.19;
H, 5.87; N, 6.27).
3.92 g (75%); mp 58-59 °C (lit. mp 58.5 °C) (4); TLC Rf 0.28; GC tR
1
6.20 min; H NMR (CDCl3) δ 1.38 (t, J ) 6 Hz, 3H, CH3), 2.25 (s,
3H, ArCH3), 4.28 (q, J ) 6 Hz, 2H, OCH2), 6.80 (m, 1H, Hc-aromatic),
7.10 (m, 1H, Hb′-aromatic), 7.30 (m, 2H, Ha, H′a-aromatic), 9.38 (s,
1H, NH); IR 3360 (as. sec. NH str), 2870 (methyl CHstr), 1719 (CdO
ester str), 1700 (amide-I band), 1306 (aromatic sec. δCH); EI-MS m/z
(relative intensity) 207 (M+, 69), 134 (100), 106 (41), 91 (53), 77 (17),
65 (17).
Ethyl 3′-Cyanooxanilate (21). A grayish-white crystalline solid was
obtained from the reaction between 3-aminobenzonitrile and diethyl
oxalate for 3 h; yield 3.81 g (71%); mp 144 °C (lit. mp 144 °C) (4);
TLC Rf 0.48; GC tR 14.22 min; 1H NMR (CDCl3) δ 1.45 (t, J ) 6 Hz,
3H, CH3), 4.35 (q, J ) 6 Hz, 2H, OCH2), 7.45 (m, 2H, Hc,
Hb′-aromatic), 7.95 (m, 2H, Ha, H′a-aromatic), 9.00 (s, 1H, NH); EI-
MS m/z (relative intensity) 218 (M+, 18), 145 (73), 144 (19), 118 (70),
117 (100), 102 (46), 90 (82), 65 (11), 64 (42), 62 (12).
Ethyl 4′-Cyanooxanilate (22). A white crystalline solid was obtained
from the reaction between 4-aminobenzonitrile and diethyl oxalate for
2.5 h; yield 4.19 g (78%); mp 189 °C; TLC Rf 0.72; GC tR 14.45 min;
1H NMR (CDCl3) δ 1.40 (t, J ) 6 Hz, 3H, CH3), 4.40 (q, J ) 6 Hz,
2H, OCH2), 7.25 (m, 2H, Hb, Hb′-aromatic), 7.70 (m, 2H, Ha, H′a-
aromatic), 9.00 (s, 1H, NH); EI-MS m/z (relative intensity) 218 (M+,
19), 145 (71), 144 (24), 118 (70), 117 (100), 116 (21), 102 (55), 91
(29), 90 (79), 89 (16), 76 (21), 75 (27), 65 (13), 64 (32), 63 (49), 62
(18), 51 (20). Elemental analysis, found C, 60.6; H, 4.7; N, 12.9 (C11H10
N2O5 requires C, 60.55; H, 4.62; N, 12.84).
Ethyl 3′-(Trifluoromethyl)oxanilate (24). Grayish-white crystals of
24 were obtained from the reaction between 3-(trifluoromethyl)aniline
and diethyl oxalate for 2.5 h; yield 4.70 g (73%); mp 122 °C (lit. mp
122 °C) (4); TLC Rf 0.66; GC tR 11.03 min; 1H NMR (CDCl3) δ 1.50
(t, J ) 6 Hz, 3H, CH3), 4.40 (q, J ) 6 Hz, 2H, OCH2), 7.45 (m, 2H,
Hc, Hb′-aromatic), 8.15 (m, 2H, Ha, H′a-aromatic), 10.30 (s, 1H, NH);
EI-MS m/z (relative intensity) 261 (M+, 27), 249 (7), 207 (12), 189
(100), 188 (36), 187 (12), 161 (77), 145 (22), 141 (52), 140 (31), 105
(13), 101 (16), 91 (75), 83 (85), 75 (86), 73 (13), 65 (31), 59 (51), 54
(27).
Ethyl 4′-(Trifluoromethyl)oxanilate (25). A white crystalline solid
of 25 was obtained from the reaction between 4-(trifluoromethyl)aniline
and diethyl oxalate for 2 h; yield 5.22 g (81%); mp 139-141 °C (lit.
mp 137-142 °C) (4); TLC Rf 0.66; GC tR 10.78 min; 1H NMR (CDCl3)
δ 1.35 (t, J ) 6 Hz, 3H, CH3), 4.35 (q, J ) 6 Hz, 2H, OCH2), 7.35 (m,
2H, Hb, Hb′-aromatic), 7.85 (m, 2H, Ha, H′a-aromatic), 8.85 (s, 1H,
NH); EI-MS m/z (relative intensity) 261 (M+, 5), 207 (4), 188 (9), 145
(7), 59 (12), 58 (100).
Ethyl 4′-Ethyloxanilate (26). White crystals were obtained from the
reaction between 4-ethyl aniline and diethyl oxalate for 2.5 h; yield
3.97 g (73%); mp 56-57 °C (lit. mp 55-58 °C) (4); TLC Rf 0.67; GC
tR 4.56 min; 1H NMR (CDCl3) δ 1.22 (t, J ) 6 Hz, 3H, CH2CH3), 1.40
(t, J ) 6 Hz, 3H, OCH2CH3), 2.60 (q, J ) 6 Hz, 2H, CH2), 4.32 (q,
J ) 6 Hz, 2H, OCH2), 7.08 (dd, 2H, Hb, Hb′-aromatic), 7.45 (dd, 2H,
Ha, H′a-aromatic), 9.15 (s, 1H, NH); EI-MS m/z (relative intensity) 221
(M+, 26), 145 (71), 148 (26), 118 (70), 147 (45), 132 (75), 120 (99),
106 (28), 103 (21), 93 (44), 91 (62), 79 (25), 78 (48), 77 (72), 65 (25),
58 (100), 52 (49), 51 (60).
Ethyl 3′-Methoxyoxanilate (12). 3-Anisidine and diethyl oxalate were
refluxed in xylene to furnish creamy white powders of 12; yield 4.01
g (86%); mp 98 °C; TLC Rf 0.43; GC tR 10.13 min; 1H NMR (CDCl3)
δ 1.45 (t, J ) 3 Hz, 3H, -CH3), 3.91 (s, 3H, -OCH3), 4.60 (q, J ) 6
Hz, 2H, -OCH2), 7.00 (dd, 1H, Hc-aromatic), 7.48 (m, 1H, Hb′-
aromatic), 7.55 (m, 1H, Ha′-aromatic), 7.60 (m, 1H, Ha-aromatic), 9.22
(s, 1H, NH); IR 3346 (as. sec. NH str.), 2837 (methyl CH str.), 1703
(CdO ester str.), 1700 (amide-I band, CdO str), 1302 (aromatic sec.
CNδ), two bands, i.e., 862 and 762 (aromatic CNδ due to meta
substitution); EI-MS m/z (relative intensity) 223 (M+, 89), 151 (11),
150 (100), 149 (66), 136 (8), 123 (19), 122 (39), 107 (60), 95 (15), 94
(7), 93 (6), 92 (18), 77 (29), 65 (8), 64 (15). Elemental analysis, found
C, 59.3; H, 5.9; N, 6.3 (C11H13 NO4 requires C, 59.19; H, 5.87; N,
6.27).
Ethyl 4′-Methoxyoxanilate (13). 4-Anisidine and diethyl oxalate were
refluxed for 1.5 h to provide creamy white powders of 13; yield 3.96
g (84.93%); mp 112-113 °C (lit. mp 112-113 °C) (4); TLC Rf 0.34;
1
GC tR 13.06 min; H NMR (CDCl3) δ 1.40 (t, J ) 6 Hz, 3H, -CH3),
4.35 (q, J ) 6 Hz, 2H, -OCH2), 3.75 (s, 3H, -OCH3), 6.85 (dd, J )
6 Hz, 2H, Hb, Hb′-aromatic), 7.50 (dd, J ) 6 Hz, 2H, Ha, Ha′-aromatic),
8.90 (s, 1H, NH); EI-MS m/z (relative intensity) 223 (M+, 16), 150
(7), 149 (100), 136 (99.9), 135 (26), 134 (22), 123 (7), 122 (82), 108
(19), 106 (15), 95 (41), 80 (34), 79 (23), 77 (20), 65 (15), 53 (16), 52
(22).
Ethyl 2′,4′-Dimethoxyoxanilate (14). Grayish-white crystals were
obtained from the reaction of 2,4-dimethoxyaniline with diethyl oxalate
for 3 h in xylene; yield 4.27 g (76%); mp 86-88 °C; TLC Rf 0.46; GC
1
tR 11.30 min; H NMR (CDCl3) δ 1.45 (t, J ) 6 Hz, 3H, CH3), 3.80
(ds, 6H, OCH3), 4.40 (q, J ) 6 Hz, 2H, OCH2), 6.70 (m, 2H, Hb, H′b-
aromatic), 8.10 (m, 1H, Ha-aromatic), 9.40 (s, 1H, NH); EI-MS m/z
(relative intensity) 253 (M+, 65), 179 (94), 165 (91), 164 (100), 138
(32), 110 (36), 107 (34), 95 (33), 79 (54), 53 (33), 52 (35). Elemental
analysis, found C, 57.0; H, 6.0; N, 5.6 (C12H15 NO5 requires C, 56.91;
H, 5.97; N, 5.53).
Ethyl 3′-Nitrooxanilate (16). 3-Nitroaniline and diethyl oxalate were
refluxed for 3 h in xylene to furnish deep yellow crystals; yield 3.33
1
g (56%); mp 96-98 °C; TLC Rf 0.65; GC tR 12.22 min; H NMR
(CDCl3) δ 1.30 (t, J ) 6 Hz, 3H, CH3), 4.30 (q, J ) 6 Hz, 2H, OCH2),
7.50 (m, 2H, Hc, Hb′-aromatic), 7.95 (m, 1H, Ha′-aromatic), 8.40 (t,
1H, Ha-aromatic), 9.10 (s, 1H, NH); IR 3335 (as. sec. NH str), 2994
(methyl CH str), 1703 (CdO ester str), 1728 (amide-I band), 1532 (sym.
ArNO2 str), 784 (aromatic δCH due to meta substitution); EI-MS m/z
(relative intensity) 238 (M+, 58), 166 (41), 165 (100), 164 (15), 159
(17), 149 (29), 148 (15), 138 (35), 137 (36), 91 (37), 77 (15), 76 (38),
75 (26), 65 (20), 64 (31), 63 (30). Elemental analysis, found C, 50.5;
H, 4.4; N, 11.9 (C10H10 N2O5 requires C, 50.42; H, 4.23; N, 11.76).
Ethyl 4′-Nitrooxanilate (17). 4-Nitroaniline and diethyl oxalate were
refluxed for 2 h in xylene to furnish yellow crystals; yield 4.98 g (84%);
mp 144-145 °C; TLC Rf 0.45; GC tR 11.35 min; 1H NMR (CDCl3) δ
1.50 (t, J ) 6 Hz, 3H, CH3), 4.45 (q, J ) 6 Hz, 2H, OCH2), 8.10 (m,
4H, aromatic), 10.80 (s, 1H, NH); EI-MS m/z (relative intensity) 238
(M+, 53), 166 (64), 165 (100), 149 (33), 138 (45), 137 (39), 108 (24),
92 (37), 80 (19), 76 (44), 75 (30), 65 (15). Elemental analysis, found
C, 50.5; H, 4.3; N, 11.8 (C10H10 N2O5 requires C, 50.42; H, 4.23; N,
11.76).
Ethyl 4′-Isopropyloxanilate (27). A white powder was obtained from
the reaction between 4-isopropylaniline and diethyl oxalate for 3 h (as
shown in Figure 1); yield 3.65 g (63%); mp 103-104 °C; TLC Rf
1
0.35; GC tR 5.09 min; H NMR (CDCl3) δ 1.30 (m, 7H, CH(CH3)2),
2.55 (t, J ) 6 Hz, 3H, OCH2CH3), 4.30 (q, J ) 6 Hz, 2H, OCH2), 7.15
(m, 2H, Hb, Hb′-aromatic), 7.55 (m, 2H, Ha, H′a-aromatic), 9.25 (s, 1H,
NH). Elemental analysis, found C, 66.4; H, 7.3; N, 6.0 (C13H17 NO5
requires C, 66.36; H, 7.28; N, 5.95).
General Procedure for the Synthesis of Ortho-Substituted
Anilates (2, 7, 15, 20, and 23). The following example illustrates the
general scheme of synthesis of the title compounds using ortho-
substituted anilines and the corresponding esters.
To 2-fluoroaniline (0.25 mol, 2.78 mL), ethoxycarbonyl methanoyl
chloride (0.25 mol) in CHCl3 (10 mL) was dispensed drop by drop
under stirring at e10 °C. After the addition of acid chloride, the aliquot
was left overnight at room temperature for completion of reaction. It
was poured into ice-cold water (100 mL), and then the CHCl3 layer
Ethyl 2′,4′-Dinitrooxanilate (18). 2,4-Dinitroaniline and diethyl
oxalate were refluxed together in xylene for 3 h (as shown in Figure
1) to furnish deep yellow crystals; yield 4.62 g (72%); mp 140 °C dec;
TLC Rf 0.42; GC tR 16.15 min; 1H NMR (CDCl3) δ 1.60 (t, J ) 6 Hz,
3H, CH3), 4.50 (q, J ) 6 Hz, 2H, OCH2), 8.10 (m, 2H, Hb,
Hb′-aromatic), 9.00 (m, 1H, Ha-aromatic), 10.90 (s, 1H, NH); EI-MS
m/z (relative intensity) 285 (M+, 1), 183 (26), 153 (50), 79 (24), 65
(25), 64 (48), 63 (62), 62 (33), 53 (18), 52 (100). Elemental analysis,
found C, 42.5; H, 3.3; N, 14.9 (C10H9N3O7 requires C, 42.41; H, 3.20;
N, 14.84).
Ethyl 3′-Methyloxanilate (19). 3-Toluidine and diethyl oxalate were
refluxed in toluene for 3 h to furnish a grayish-white powder; yield

Synthesis and QSAR of Oxanilates as CHAs for Wheat
J. Agric. Food Chem., Vol. 51, No. 4, 2003 995
OCH2), 7.20 (m, 1H, Hc-aromatic), 7.60 (m, 3H, Ha′, Hb, and Hb′-
aromatic), 8.85 (s, 1H, NH); EI-MS m/z (relative intensity) 261 (M+,
31), 188 (77), 168 (22), 161 (30), 160 (100), 117 (100), 145 (87), 140
(76), 133 (32), 125 (31), 114 (61), 113 (71), 109 (26), 95 (37), 91
(30), 83 (36), 75 (36), 69 (48), 63 (46), 51 (27). Elemental analysis,
found C, 50.6; H, 3.9; N, 5.4 (C11H10 F3NO3 requires C, 50.58; H,
3.86; N, 5.36).
Field Trials. Variety. Two high-yielding varieties of bread wheat
(Triticum aestiVum L.), PBW 343 and HD 2733, recommended for
timely sowing in the North Western Plain Zone of India, were chosen
for the evaluation of chemical induction of male sterility.
Experimental Layout. The field trials were conducted in two Rabi
(winter) seasons, November 2000-April 2001 and November 2001-
April 2002. The experiment was laid out in randomized block design
in three replicates. Randomization was done independently for the
subplots in each of the three replicates. Seeds of both of the wheat
varieties were sown using a seed drill in November, using 100 kg of
N, 60 kg of P2O5, and 40 kg of K2O following a 100 kg/ha seed rate
at IARI. The row-to-row distance was kept at 23 cm. Four rows of 2
m length were taken as a plot. Other optimum agronomic practices
were also followed which included recommended fertilizer schedule,
timely weeding, and other cultural operations. Five irrigations were
done at different stages of crop growth, viz., crown root initiation, late
tillering, late jointing, flowering, and dough stage.
Figure 2. General synthesis of ortho-substituted oxanilates (2, 7, 15, 20,
and 23).
was washed with NaHCO3 solution once followed by water and dried
over anhydrous Na2SO4. On evaporation of CHCl3, the product was
obtained as a white solid which was recrystallized from ethanol to
furnish milky white crystals of ethyl 2′-fluorooxanilate (Figure 2).
Ethyl 2′-Fluorooxanilate (2). Yield 4.91 g (93%); mp 103 °C; TLC
1
Rf 0.63; GC tR 4.79 min; H NMR (CDCl3) δ 1.35 (t, J ) 6 Hz, 3H,
CH3), 4.35 (q, J ) 6 Hz, 2H, OCH2), 7.20 (m, 3H, Hb, Hb′, and Hc-
aromatic), 7.50 (m, 1H, Ha-aromatic), 9.15 (s, 1H, NH); EI-MS m/z
(relative intensity) 211 (M+, 14), 139 (40), 111 (100), 91 (18), 84 (45),
83 (63), 64 (41), 63 (36), 57 (59), 52 (23), 50 (16). Elemental analysis,
found C, 56.9; H, 4.8; N, 6.6 (C10H10 FNO3 requires C, 56.87; H, 4.77;
N, 6.63).
Field Applications. The test chemicals were sprayed at both 1000
and 1500 ppm as an oil-in-water emulsion containing cyclohexanone
(1%) and polyoxyethylene sorbitan monooleate (FW ≈ 1200) (Tween-
80) as emulsifier (0.02%) at the premeiotic stage (60 days after sowing),
when the length of the spike emerging out from the first node was
7-8 mm (10). The spraying was carried out on three replicate plots of
about 2-m lengths of two lines containing about 400 tillers, keeping
the outermost two lines as pollinator lines. During spraying, the
innermost two lines were covered by polyethylene to ensure that
chemicals did not fall on the plants of the pollinator lines. As the degree
of synchrony of flowering varied with the variety, care was taken to
tag the treated tillers at the appropriate stage. Ten spikes of each treated
plot were covered with rainproof paper bags to prevent out-crossing at
the pre-emergent stage, when awns were just emerging. The remaining
ear heads were left uncovered.
Observations Made. Pollen Sterility. Anthers from three or four
florets were smeared together over a drop of acetocarmine (1%) or KI
(2%) in iodine and examined under a light microscope (6). From the
stain test, it was seen that the sterile grains were transparent, thereby
confirming the disintegration of cytoplasm and nucleus in the sterile
pollen. In contrast, fertile pollen from control plots was stained uniform
deep red or blue, depending on the stain, confirming the induction of
male sterility in various treatments.
Ethyl 2′-Chlorooxanilate (7). Compound 7 was obtained from
2-chloroaniline (as shown in Figure 2) as a white crystalline solid;
1
yield 5.17 g (91%); mp 108 °C; TLC Rf 0.52; GC tR 8.63 min; H
NMR (CDCl3) δ 1.40 (t, J ) 6 Hz, 3H, CH3), 4.45 (q, J ) 6 Hz, 2H,
OCH2), 7.25 (m, 3H, Hb, Hb′, and Hc-aromatic), 8.65 (d, J ) 6 Hz,
1H, Ha-aromatic), 9.60 (s, 1H, NH); IR 3368 (as. sec. NH str), 1719
(CdO ester str), 1718 (amide-I band), 1308 (aromatic sec. CNδ), 755
(aromatic δCH due to ortho substitution), 749 (C-Cl str.); EI-MS m/z
(relative intensity) 229 (22), 227 (M+, 70), 193 (10), 192 (91), 156
(33), 154 (100), 153 (32), 140 (18), 129 (14), 128 (30), 127 (47), 126
(86), 120 (12), 99 (32), 90 (30), 75 (17), 73 (10), 65 (7), 64 (12), 63
(18). Elemental analysis, found C, 52.8; H, 4.5; N, 6.2 (C10H10 ClNO3
requires C, 52.76; H, 4.43; N, 6.15).
Ethyl 2′-Nitrooxanilate (15). Reaction of 2-nitroaniline and ethoxy-
carbonyl methanoyl chloride gave a deep yellow crystalline solid; yield
1
5.36 g (90%); mp 116 °C; TLC Rf 0.56, GC tR 10.53 min; H NMR
(CDCl3) δ 1.58 (t, J ) 6 Hz, 3H, CH3), 4.60 (q, J ) 6 Hz, 2H, OCH2),
7.50 (m, 1H, Hc-aromatic), 7.90 (m, 1H, Hb′-aromatic), 8.55 (t, 1H,
Hb-aromatic), 9.11 (t, 1H, Ha′-aromatic), 10.36 (s, 1H, NH); IR 3309
(as. sec. NH str), 1741 (CdO ester str.), 1728 (amide-I band), 1515
(as. ArNO2 (N-O)2 str.), 1340 to 1278 (sym. ArNO2 (N-O)2 str), 1302
(aromatic sec. CNδ), 860 (CN str for ArNO2), 739 (aromatic δCH due
to ortho substitution); EI-MS m/z (relative intensity) 238 (M+, 74), 192
(24), 165 (100), 164 (18), 149 (13), 148 (57), 138 (17), 122 (18), 121
(86), 118 (21), 105 (17), 103 (18), 93 (10), 92 (75), 91 (92), 90 (92),
64 (38), 63 (40), 80 (25), 78 (30), 77 (16), 76 (12), 66 (20), 65 (37).
Elemental analysis, found C, 50.5; H, 4.3; N, 11.8 (C10H10 N2O5 requires
C, 50.42; H, 4.23; N, 11.76).
Spikelet Sterility. Ten each of bagged and unbagged spikes including
one control were harvested at maturity. To study the floret sterility,
the number of fertile (filled) and sterile (unfilled) grains was counted,
and the percent male sterility was computed as percent inhibition of
seed set in bagged spikes of treated plants. Percent sterility is calculated
from the following formula:
% sterility ) (Sc - Sf)/Sc × 100
where Sc is the number of seeds per spikelet in bagged spikes of control
plants and Sf is the number of seeds per spikelet in bagged spikes of
treated plants.
Ethyl 2′-Cyanooxanilate (20). 2-Aminobenzonitrile, following the
reaction shown in Figure 2, gave 20 as a white buff solid; yield 4.62
1
g (86%); mp 143-144 °C; TLC Rf 0.45, GC tR 13.78 min; H NMR
Quantitative Structure-Activity Relationship Study (QSAR):
Descriptor Variables. The following descriptor variables were used
for aromatic substituents: electronic parameters, Swain-Lupton field
constant (F) (11), Hammett constant (σm, σp), σ+, R (12, 13), Taft steric
parameter (Es), molecular weight (MW), Verloop-Hoogenstraaten
multidimensional steric parameters L and B4 (14, 15), hydrophobic
parameters π and π2, and other parameters such as molar refractivity
(MR), δ 13C, chemical shift values of C atoms containing NH moiety
with reference to various substituents (17, 18), and index variable. The
steric parameters Es, MR, L, and B4 were designated according to their
position on the phenyl ring with a subscript indicating ortho, meta, or
(CDCl3) δ 1.45 (t, J ) 6 Hz, 3H, CH3), 4.40 (q, J ) 6 Hz, 2H, OCH2),
7.40 (m, 2H, Hc, Hb′-aromatic), 8.15 (m, 2H, Ha and Hb-aromatic), 9.75
(s, 1H, NH); EI-MS m/z (relative intensity) 218 (M+, 26), 146 (14),
145 (73), 144 (22), 118 (14), 117 (100), 116 (21), 102 (59), 91 (31),
90 (78), 89 (18), 76 (18), 75 (26), 64 (36), 63 (46), 62 (19), 51 (22).
Elemental analysis, found C, 60.6; H, 4.7; N, 12.8 (C11H10 N2O5 requires
C, 60.55; H, 4.62; N, 12.84).
Ethyl 2′-(Trifluoromethyl)oxanilate (23). White crystalline solid; yield
1
5.28 g (82%); mp 132-134 °C; TLC Rf 0.67; GC tR 6.35 min; H
NMR (CDCl3) δ 1.50 (t, J ) 6 Hz, 3H, CH3), 4.40 (q, J ) 6 Hz, 2H,

996 J. Agric. Food Chem., Vol. 51, No. 4, 2003
Chakraborty et al.
HD 2733
Table 1. Percent Spikelet Sterility of CHAs Tested in Rabi (Winter) 2000−01 and 2001−02
spikelet sterility (%) in genotypes at 1000 and 1500 ppm spray concentrations
2000−01 2001−02
PBW 343
HD2733
PBW 343
aromatic
oxanilates
substituents
1000
1500
1000
1500
1000
1500
1000
1500
1
2
3
4
5
6
7
8
H
2-F
3-F
3-Cl, 4-F
4-F
4-Br
2-Cl
3-Cl
2,6-Cl2
4-Cl
2-OMe
3-OMe
4-OMe
2,4-(OMe)2
2-NO
3-NO
79.91
48.85
27.91
64.85
89.90
86.34
23.95
15.77
20.23
44.00
55.91
14.16
70.74
51.78
34.26
11.28
63.09
72.48
1.92
63.04
52.75
82.49
69.52
78.91
88.69
12.86
9.70
90.11
59.77
37.16
72.00
97.86
97.04
37.43
29.93
26.56
64.73
68.87
23.45
79.06
58.65
50.86
14.77
69.55
77.58
3.73
80.39
47.6
27.71
64.21
90.53
86.1
90.76
59.12
37.75
67.75
97.3
95.54
38.54
29.66
28.13
64.7
67.67
23.73
76.52
58.78
48.78
21.59
70.99
77.62
3.77
75.32
63.01
95.20
88.41
93.13
97.10
2.66
77.99
54.76
32.78
71.56
99.54
98.76
28.62
20.03
24.71
49.67
66.39
18.34
77.69
55.34
39.44
15.31
70.41
79.57
5.49
84.18
68.13
50.04
77.91
99.97
99.96
50.25
44.25
41.56
72.09
78.02
39.07
84.39
63.43
61.00
32.13
79.06
82.37
23.29
81.43
71.74
96.63
84.59
94.86
99.57
18.48
9.41
79.92
56.58
37.48
72.52
99.59
99.12
34.17
24.48
31.24
52.44
69.21
22.35
78.38
56.49
41.66
22.12
70.85
79.94
13.07
69.45
62.28
92.65
77.19
91.72
99.47
12.89
8.77
86.35
70.99
55.81
77.11
99.99
99.97
56.37
50.07
48.98
74.95
78.75
45.86
85.76
68.49
63.64
44.34
81.57
84.12
31.69
82.56
72.71
98.46
93.03
96.81
99.98
20.18
10.09
24.26
14.17
21.21
43.29
54.94
11.95
70.10
49.92
32.06
11.71
62.99
71.94
2.28
61.48
54.74
83.29
68.76
82.42
89.70
8.32
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
2
2
4-NO
2,4-(NO )
2
2 2
3-Me
2-CN
3-CN
4-CN
2-CF3
3-CF3
4-CF3
4-Et
76.82
65.97
93.85
80.36
91.86
97.14
6.32
68.95
57.13
91.31
76.4
87.2
98.44
11.28
7.64
i
4-Pr
3.84
4.44
5.27
control (without spray)
emulsion control
CD (P ) 0.05)
0.04
0.25
2.03
0.04
0.34
0.02
0.33
1.78
0.02
0.46
0.02
0.26
0.59
0.02
0.46
0.02
0.34
0.54
0.02
0.49
para, as the case may be. Thus, Es(o) denotes Taft’s steric parameter
for the ortho substituents, Es(m) that for the meta substituents, and Es(p)
that for the para substituents. Thirty-two independent variables were
used in constructing the correlation matrix. The independent variables,
which were found orthogonal to each other, were minimized. In cases
containing two substituents, additive nature of MR and Es was
presumed. The mean percent spikelet sterility caused by test oxanilates
tested at 1500 ppm on wheat variety PBW 343 in Rabi (winter) 2001-
02 was transformed into sin arc and used as the dependent variable
(Ms %).
Multiple Linear Regression (MLR) Analysis. The independent
variables were used in generating MLR equations by autocorrelation
using the computer software package SPSSPC (Version 9.1). None of
the independent variables appearing in the equations was restrained to
be orthogonal.
broad singlet ranging from δ 8.85 ppm in simple oxanilates to
δ 10.90 ppm in ethyl 2′,4′-dinitrooxanilate. The substituents at
ortho and para positions caused deshielding, the highest effect
of δ 10.80 ppm by the 2,4-dinitro group, followed by the para
nitro group having the chemical shift of δ 10.36 ppm.
Spikelet Sterility. The results of induction of spikelet sterility
on bread wheat caused by test chemicals at two test concentra-
tions on two genotypes for two winter seasons are given in
Table 1. All the test chemicals showed significant induction of
spikelet sterility at both of the test concentrations on both of
the genotypes tested. The results, which were dose-dependent,
were consistent in a two-year field trial. There was no marked
variation in the response of two genotypes. The para-substituted
oxanilates, 5, 6, 25, and 22, containing F, Br, CF3, and CN,
respectively, were found to be the best in that order when
considered across two test concentrations, two genotypes, and
two-year trial data. The other substituents at the para position
influenced the activity in the order OMe > NO2 > Cl. The
disubstituted analogues 4, 9, 14, and 18 were found to be inferior
to their respective mono(para)substituted ones generally. The
ortho analogues performed next best in all cases except in CF3
substitution, wherein meta (24) was found to be better than ortho
(23). Alkyl substitution in oxanilates 19, 26, and 27 gave the
least effect. It can be inferred that para substitution with highly
electronegative groups such as F, CN, or CF3 can give rise to
analogues having high levels of activity. From a practical point
of view, the percent spikelet sterility induced must not be less
than 98%. Three compounds, 5, 6, and 25, containing fluoro,
bromo, and trifluoromethyl substituents in the para position,
respectively, met the above criterion at the 1500 ppm test
concentration.
RESULTS AND DISCUSSION
Synthesis. The various N-acylanilines were prepared by the
thermal condensation of respective anilines with diethyl oxalate.
In the case of some ortho-substituted anilines, the yield obtained
by this method was low, and therefore the N-acylanilines of
this type were prepared by N-acylation using ethoxycarbonyl
methanoyl chloride.
Spectral Analysis. IR spectra showed characteristic peaks
for symmetrical NH stretching vibrations at 3339 ( 16 cm-1
for oxanilates. The CdO stretching vibration of ester was
centered at 1711 ( 12 cm-1. The characteristic features of
proton magnetic resonance spectra were the presence of a triplet
around δ 1.30 ppm (in ethyl 3′-nitrooxanilate) to as high as δ
1.65 ppm (in ethyl 4′-fluorooxanilate) and a quartet centered at
δ 4.15 ppm in ethyl 2′,6′-dichlorooxanilate to δ 4.70 ppm in
ethyl 4′-fluorooxanilate. The anilide NH proton appeared as a

Synthesis and QSAR of Oxanilates as CHAs for Wheat
J. Agric. Food Chem., Vol. 51, No. 4, 2003 997
Table 2. Chemical Descriptors for Aromatic Substituents in Ethyl Oxanilates
R
π
σm
σp
δ
13C
σ+
MR
ES
F
R
L
B
4
p
H
2-F
3-F
4-F
4-Br
2-Cl
3-Cl
4-Cl
2-OMe
3-OMe
4-OMe
2-NO
3-NO
0.00
0.12
0.13
0.12
1.01
0.71
0.76
0.71
−0.02
0.11
−0.02
−0.28
0.10
−0.28
0.56
−0.30
−0.32
−0.21
0.88
1.09
0.88
1.08
1.64
0.00
0.00
0.34
0.00
0.00
0.00
0.37
0.00
0.00
0.12
0.00
0.00
0.71
0.00
−0.07
0.00
0.56
0.00
0.00
0.43
0.00
0.00
0.00
0.00
0.06
0.00
0.06
0.23
0.23
0.00
0.23
−0. 27
0.00
−0.27
0.78
0.00
0.78
0.00
0.66
0.00
0.66
0.54
0.00
0.54
−0.15
−0.15
128.5
114.2
129.4
124.1
127.0
128.7
129.5
126.5
114.1
129.5
120.7
124.2
129.8
134.7
129.2
132.6
129.9
133.5
125.2
128.8
131.7
125.2
125.9
0.00
0.00
0.00
−0.07
0.15
0.00
0.00
0.11
0.00
0.00
−0.78
0.00
0.00
0.79
0.00
0.00
0.00
0.66
0.00
0.00
0.61
−0.30
−0.28
3.09
0.92
0.92
0.92
8.88
6.03
6.03
6.03
7.87
7.87
7.87
7.36
7.36
7.36
5.65
6.33
6.33
6.33
5.02
5.02
5.02
10.3
14.96
0.00
−0.46
−0.46
−0.46
−1.16
−0.99
−0.97
−0.97
−0.55
−0.55
−0.55
−2.52
−2.52
−2.52
−1.24
−0.51
−0.51
−0.51
−2.40
−2.40
−2.40
−1.31
−1.71
0.00
0.43
0.43
0.43
0.44
0.41
0.41
0.41
0.26
0.26
0.26
0.67
0.67
0.67
−0.04
0.51
0.51
0.51
0.38
0.38
0.38
−0.05
−0.05
0.00
0.39
0.39
7.18
2.65
2.65
2.65
3.83
3.52
3.52
3.52
3.98
3.98
3.98
3.44
3.44
3.44
3.00
4.23
4.23
4.23
3.30
3.30
3.30
4.11
4.11
3.00
1.35
1.35
1.35
1.95
1.80
1.80
1.80
2.87
2.87
2.87
2.44
2.44
2.44
2.04
1.60
1.60
1.60
2.41
2.41
2.41
2.97
3.16
0.39
−0.22
−0.19
−0.19
−0.19
−0.56
−0.56
−0.56
8.39
8.39
8.39
−0.18
0.15
0.15
0.15
0.16
0.16
0.16
−0.15
−0.19
2
2
4-NO
2
3-Me
2-CN
3-CN
4-CN
2-CF3
3-CF3
4-CF3
4-Et
i
4-Pr
Quantitative structure-activity relationship analysis was
carried out using sin arc-transformed spikelet sterility percent
as the dependent variable and the physicochemical parameters
of the substituents listed in Table 2 as independent variables.
Six multiple regression equations were obtained with multiple
R-values of 0.7 and above. Only the best equation is given
below:
and high percent of germination. One of them was found to
out-yield its parents in a preliminary agronomic evaluation.
ACKNOWLEDGMENT
The authors are thankful to the Director, I.A.R.I., for providing
facilities and Dr. Eugene S. J. Nidiry of IIHR, Bangalore, India,
for some information on descriptor variables.
Ms (sin arc %) ) 39.59F - 2.86 MR +
∑
p
LITERATURE CITED
0.67MW - 5.11D -2.57 R -16.91 π -64.28
∑
∑
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Received for review August 5, 2002. Revised manuscript received
November 25, 2002. Accepted November 25, 2002. K.C. is the recipient
of the ICAR award of a senior research fellowship.
JF025870+