9136 J. Agric. Food Chem., Vol. 54, No. 24, 2006
Li et al.
Chart 1. Structures of Some Commercial Herbicides Related to the Present Study
2
by suction, and the solvent was evaporated to give crude, white
ment based on F2 using the weight of 1/[σ2(Fo ) + (0.0742P)2
+ 0.059P] gave final values of R ) 0.0481, ωR ) 0.1388, and
GOF(F) ) 1.066 for 332 variables and 2237 contributing
reflections; maximum shift/error ) 0.024(3), max/min residual
electron density ) 0.217/-0.189 e Å-3. Hydrogen atoms were
observed and refined with a fixed value of their isotropic
displacement parameter.
crystals of 7a that could be purified by recrystallization from
1
toluene. Yield 88%. mp 225-227 °C. H NMR (CDCl3): δ
2.58 (s, 3H, CH3), 3.77 (s, 6H, 2 × OCH3), 5.75 (s, 1H, PyHet-
H), 7.53 (d, J ) 8.0 Hz, 1H, 7′-ArH), 7.67 (d, J ) 8.0 Hz, 1H,
5′-ArH), 7.86 (t, J ) 8.0 Hz, 1H, 6′-ArH), 9.56 (s, 1H, N-H).
EI MS: m/z (%) 314 (M+, 100), 299 (40), 283 (75), 256 (16),
226 (45), 173 (21), 144 (12), 101 (13). Anal. Calcd for
C15H14N4O4: C, 57.32; H, 4.49; N, 17.83. Found: C, 57.06;
H, 4.32; N, 17.62.
Biological Assay. AHAS Inhibition ActiVity. The Ki values
of compounds 7a-7w against wild-type A. thaliana aceto-
hydroxyacid synthase (AHAS, EC 4.1.3.18) were deter-
mined according to the methods reported previously (13, 14);
KIH-6127 was used as a control, and the results were listed in
Table 1.
General Procedure for the Synthesis of Target Com-
pounds 7b-7w. A solution of 7a (1 mmol) and NaH (60%,
dispersion in mineral oil) (1.2 mmol) in N,N-dimethylformamide
(DMF) (10 mL) was stirred at room temperature for 0.5 h, and
halogenated compound (1.1 mmol) was then added. The reaction
was continued for 9-24 h at room temperature. The mixture
was poured into 200 mL of water, extracted with ethyl acetate
(50 mL × 3), dried with anhydrous magnesium sulfate, and
filtered off by suction, and the solvent was evaporated to give
the crude product, which was then purified by chromatography
on silica using petroleum ether/ethyl acetate as the eluent to
give the target compounds. Example data for 7b are included
here, and data for 7c-7w can be found in the Supporting
Information.
Herbicidal ActiVities on Weeds. The herbicidal activities of
compounds 7a-7w against Echinochloa crusgalli (EC), Digi-
taria sanguinalis (DS), Setaria Viridis (SV), Brassica juncea
(BJ), Amaranthus retroflexus (AR), and Chenopodium album
(CA) were evaluated according to a previously reported pro-
cedure (15). All test compounds were formulated as 100 g/L
emulsified concentrates using DMF as the solvent and TW-80
as an emulsification reagent. The concentrates were diluted with
water to the required concentration and applied to pot-grown
plants in a greenhouse. The soil used was a clay soil with pH
6.5, 1.6% organic matter, 37.3% clay particles, and a CEC of
12.1 cmol/kg. The rate of application (g ai/ha) was calculated
by the total amount of active ingredient in the formulation
divided by the surface area of the pot. Plastic pots with a diam-
eter of 9.5 cm were filled with soil to a depth of 8 cm. Approx-
imately 20 seeds of Echinochloa crusgalli (EC), Digitaria
sanguinalis (DS), Setaria Viridis (SV), Brassica juncea (BJ),
Amaranthus retroflexus (AR), and Chenopodium album (CA)
were sown in the soil at a depth of 1-33 cm and grown at 15-
30 °C in a greenhouse. The diluted formulation solutions were
applied for pre-emergence treatment 24 h after the weeds were
sown. For postemergence treatment, dicotyledon weeds were
treated at the two-leaf stage, and monocotyledon weeds were
treated at the one-leaf stage. The pre- and postemergence
application rates were estimated as 150 g ai/ha. Untreated
seedlings were used as the control group, and solvent- (DMF-)
treated seedlings were used as the solvent control group.
Herbicidal activity was evaluated visually 15 days posttreatment.
Biological activity was rated on the basis of the percentage of
weed growth inhibition using the following rating system: ++
for >80%, + for 50-80%, and - for <50%. The DMF control
displayed no herbicidal activity, and the results are reported in
Table 1.
1
Data for 7b. Yield 93%. mp 106-108 °C. H NMR (400
MHz, CDCl3): δ 2.61 (s, 3H, CH3), 3.77 (s, 6H, 2 × OCH3),
4.68 (d, J ) 6.0 Hz, 2H, CH2), 5.14-5.18 (m, 2H, dCH2),
5.75 (s, 1H, PyHet-H), 5.93-5.70 (m, 1H, dCH), 7.50 (d, J )
8.0 Hz, 1H, 7′-ArH), 7.65 (d, J ) 8.0 Hz, 1H, 5′-ArH), 7.83 (t,
J ) 8.0 Hz, 1H, 6′-ArH). EI MS: m/z (%) 356 ([M + 2]+, 28),
354 (M+, 69), 339 (33), 284 (45), 258 (26), 256 (48), 229 (20),
138 (36), 88 (65), 69 (39), 40.8 (100). Anal. Calcd for
C18H18N4O4: C, 61.01; H, 5.12; N, 15.81. Found: C, 61.33;
H, 5.39; N, 15.65.
X-ray Diffraction. Colorless blocks of 7m (0.50 mm × 0.25
mm × 0.20 mm) were coated on a quartz fiber with protection
oil. Cell dimensions and intensities were measured at 293 K on
a Bruker SMART CCD area detector diffractometer with
graphite-monochromated Mo KR radiation (λ ) 0.71073 Å); θmax
) 27.00; 20552 measured reflections; 4578 independent reflec-
tions (Rint ) 0.0615), of which 4477 had |Fo| > 2|Fo|. Data
were corrected for Lorentz and polarization effects and for
absorption (Tmin ) 0.9704; Tmax ) 0.9869). The structure was
solved by direct methods using SHELXS-97 (11); all other
calculations were performed with Bruker SAINT System and
Bruker SMART programs (12). Full-matrix least-squares refine-
RESULTS AND DISCUSSION
Scheme 1. Design of the Title Compounds
Synthesis and Structure Characterization. As shown in
Scheme 2, intermediates 2-6 were prepared readily using
3-hydroxyacetophenone as the starting material according to the
reported methods (7, 8). The deprotection of intermediate 6
afforded compound 8 successfully in our hands (Scheme 3);
however, according to the reported methods (16-18), the
Li, Yuan-Xiang
