Weed analogy

Horst Prinzbach and Eberhard Futterer Diquinolylmethane and Its Analogs G. Scheibe and E. Daltrozzo Recent Advances in 1,3,4-Oxadiazole Chemistry A. Hetzheim and K. Mockel The Literature of Heterocyclic Chemistry A. R. Katritzky and S. M. Weeds Mass Spectrometry of Heterocyclic Compounds G. Spiteller... 

The naming of a new product is not as simple as it may appear at first glance. The name must be unique in the field in which it is to be used. Because of the many thousands of names now registered, it is not too easy to find a name that is suitable for the product and yet does not bear too close a resemblance to a trademark already in use. Generally, a preliminary list of names is drawn up and is then weeded out until only a very few names are left. Even these names, however, may have to be discarded because conscious or subconscious analogies are drawn from existing names. 

A similar situation occurred when the (2-chlorophenyl)methyl was replaced with related structures. For example, the l-(2-chloro-phenyl)ethyl and the 2-(2-chlorophenyl)ethyl analogs not only were ineffective in weed control, but the typical bleaching response was also absent. 

As can be seen from Table IV, the nitrophenyl analogs of the nicotinamides are inactive. Interestingly, the 2-(3-trifluoromethylphenyl ) benzamides (compound IV minus the nitro group) were moderate herbicides (less than 50% weed control at 1 lb). These compounds are also bleaching herbicides as are the well known 3-phenoxybenzamides. The 3-phenoxybenzamides are also known to be inhibitors of phytoene desaturase (11). 

With the discovery that the 3,5-dichloro analog was very active (10), a variety of 3,5-disubstituted compounds were prepared and tested. The 3,5-dimethyl epoxide 10 exhibited good activity in the greenhouse but under field conditions did not give season-long weed control while the 3-chloro-5-fluoro derivative 11 was somewhat more active than tridiphane. 

Synthetic peptide analogs derived from the phytotoxin tentoxin, have been examined for their phytotoxicity and herbicidal potential to a variety of plants and agronomically significant weeds. Structurally modified analogs included both cyclic and acyclic derivatives. 

Because of the lengthy periods of viability of the seeds of Stri ga and Orobanche (broomrape) in the soil, effective control of these parasitic weeds is extremely difficult. An attractive method of control would involve treatment of an infected field with a biosynthetic product (such as strigol) or synthetic analog to induce suicidal germination of the weed seed in the absence of a host plant. The results of field tests with ethylene (11) and synthetic strigol analogs (12) offer evidence of the utility of this method of control. 

The synthesis of strigol and its derivatives and the possibility of using these compounds for weed control and eradication has stimulated interest for their use in other parasitic and dormant weed seeds. A number of strigol analogs and precursors have been prepared and evaluated, permitting the proposal of structure-activity correlations. In this paper, we review these results and discuss the implications of these investigations. 

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