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Herbicides and plant growth regulators are widely used in crop production to improve productivity.1) Repeated use of the same herbicide or herbicides with the same mechanism of action, however, can lead to the appearance of weed species with tolerance to the applied agrochemicals, such as sulfonylurea-resistant paddy weeds or triazine-resistant weeds.2) Therefore, the continued development of novel herbicides and plant growth regulators is essential to supplement the current limited treatment options for resistant weeds. 1)We are interested in furan-containing structures, since it has been reported that L-3-(2-furyl)alanine (1) 3) used as a 500 mg/l spray on tomatoes completely prevented infection by Phytophthora infestansa, 3a) and L-3-(3-furyl)alanine (2) has fungicidal activity.4) These compounds (1, 2) were prepared from 2-(2-furylmethyl)-and 2-(3-furylmethyl)-2-acetylaminopropanedioic acid diethyl esters (3a, 4), respectively.In addition, 3-(2-furyl)propionic acid (5) was proven to be a weak growth accelerator by Tamari. 5) On the basis of this report, Kato et al. examined the phytogrowth-inhibitory activity of 3-(2-furyl)propionates (6) and 3-(2-furyl)propionamides (7). However, they did not show a remarkable herbicidal activity. 6)In this study, we examined the possibility that 2-acetylamino-2-ethoxycarbonyl-3-(2-furyl)propanamides (8) 7) having one ester group and two amide groups at the same carbon, might have plant growth-regulatory activity. We report herein the preparation of the diamides (8), and their testing in germination assays using rape and leek seeds.Preparation of N-substituted 2-acetylamino-2-ethoxycarbonyl-3-(2-furyl)propanamides (8) The synthetic route reported here was designed to prepare a series of test diamides (8) from the half acid (3b) obtained via the diester (3a), 8) as shown in Chart 2. Compound 3a has been synthesized from the reaction of diethyl acetamidomalonate with 2-(chloromethyl)furan (10a), itself obtained from the reaction of 2-furylmethanol (9) with thionyl chloride in the presence of pyridine. 9) However, 10a is extremely unstable and decomposes during purification by distillation to give hydrogen chloride, which catalyzes polymerization of the furan ring with explosive violence.10) To avoid this difficulty, we used 3-(bromomethyl)furan (10b) 11) as an equivalent of 10a. An important consideration is that the procedure for the preparation of 10b does not require a base such as pyridine as a scavenger of hydrogen chloride. 11a)First, 2-furylmethanol (9) in THF was allowed to react with phosphorus tribromide at 0°C for 1.5 h to yield the corresponding bromo compound (10b), which could be extracted from the reaction mixture with ether, and used without further purification. Then, 10b was directly treated with diethyl acetamidomalonate at 70°C in the presence of sodium ethoxide as a base to afford the corresponding diethyl ester (3a) in 81% yield. The success of this reaction using the bromo compound (10b) in place of the chloro compound (10a) allowed us to develop a con...

An Improved Method for the Synthesis of DL-3-(2-Furyl)alanine (IV). --(KITAGAWA, T.; AKIYAMA, N.; Chem.

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