Synthesis and Activity of Novel Acylthiourea with Hydantoin

The 41 novel acylthiourea derivatives with hydantoin were synthesized in moderate to excellent yields by using 5-(4-aminophenyl)- and 5-(4-aminobenzyl)- hydantoin or 5-(4-aminobenzyl)-thiohydantoin as raw materials and characterized by IR, 1H NMR spectra and elementary analysis. The preliminary bioassay showed that these compounds exhibit certain selectively herbicidal activities with the 91%, 94% and 87% inhibition rates of 7l, 8o and 8p against B. campestris, 100%, 100% and 95% efficacy against B. campestris in a greenhouse test, respectively. 7a, 7b, 7c and 7d exhibited 74%, 79%, 79% and 71% inhibition rates against F. oxysporum, respectively.

The data in Table 1 showed that some of these compounds, such as 7l, 8o and 8p exhibit 91%, 94% and 87% inhibition rates against B. campestris, respectively, while they only have less than 25% inhibition rates against E. crus-galli at the concentration of 100 µg/mL. Further tests in a greenhouse were performed and the results in Table 2 showed that 7l, 8o and 8p inhibit the growth of B. campestris with 100%, 100% and 95% efficacy after the post-emergence treatments, and only 23%, 46% and 31% efficacy after the pre-emergence treatments at the dosage of 1000 g/ha. However they exhibited less than 15% efficacy against E. crus-galli after the post-emergence or pre-emergence treatments. These results indicated that these compounds exhibit certain selectively herbicidal activities.
The data in Table 3 showed that only 7a, 7b, 7c, 7d and 7h exhibit more than 70% inhibition rates against Fusarium oxysporum, and the others including 8 and 9 (data not shown in Table 3) have less than 55% inhibition rates against Alternaria solani, Botryospuaeria berengeriana, Cercospora arachidcola and Fusahum graminearum at the concentration of 100 µg/mL. The inhibition rates of 7a, 7b, 7c, 7d and 7h against F. oxysporum were 74%, 79%, 79%, 71% and 71%, respectively. They are weaker when compared to carbendazin (the positive control) against F. oxysporum and need further structure modification to increase the fungicidal activity.

General Information
All reactions were performed under room temperature with magnetic stirring. Unless otherwise stated, all reagents were purchased from commercial suppliers and used without further purification. Organic solutions were concentrated under reduced pressure using a rotary evaporator or oil pump. Melting points were measured on a Yanagimoto apparatus (Yanagimoto MFG Co., Kyoto, Japan) and uncorrected. Infrared spectra were recorded using a Shimadzu IR-435 instrument with KBr plates. 1 H NMR spectra were obtained on Bruker DPX 300 spectrometer (Bruker Biospin Co., Stuttgart, Germany) with DMSO-d 6 as a solvent and TMS as an internal standard. Elemental analysis was performed on a Vario EL instrument (Elementar Vario Micro Cube, Hanau, Germany).

5-(4-Aminobenzyl)-Thiohydantoin (6) and Acyl Isothiocyanate Derivatives
The synthesis of the intermediates 4, 5 and 6 were carried out according to the protocols in our previous paper and their spectral data were identical with that in the reference [37]. To a suspension of benzoic acid derivative (20 mmol) in 25 mL of CH 2 Cl 2 in a 50 mL three-necked flask, 8 mL SOCl 2 and a drop of N,N-dimethylformamide (DMF) were added. After stirring at room temperature for 3 h, the solution was evaporated. The resulting acyl chloride was dissolved in 15 mL of anhydrous acetonitrile and added to a solution of 20 mmol potassium thiocyanate in 25 mL of acetonitrile with two drops of polyethylene glycol-400 (PEG-400). After stirring at room temperature for 2 h, the mixture was filtered to give the acyl isothiocyanate derivatives, which were used without further purification [14,15].

Bioassay of Herbicidal and Fungicidal Activity
The preliminary herbicidal activities of compounds 7-9 against B. campestris and E. crus-galli were assayed using the protocols in the references [11][12][13]. The preliminary fungicidal activities of compounds 7-9 against F. oxysporurm, A. solani, B. berengeriana, C. arachidcola and F. graminearum were evaluated using methods in the references [7,10] by the mycelium growth rate test [38]. The culture was incubated at 25 ± 0.5 °C. Three replicates were performed and the mean measurements were calculated from the three replicates.
The greenhouse test was performed using the procedures in reference [39] according to the pre-emergence and post-emergence applications. The formulations were sprayed before the seedlings were planted in a pot or the formulations were sprayed during one to two-leaf appeared after the seedlings were planted in a pot. Then they were kept in the greenhouse to observe the root and stem growth of the plants in three weeks, and the inhibition rates of compounds were obtained comparison the fresh plant weights with the blank control. Three replicates were performed and the mean measurements were calculated from the three replicates.