Pyridine-2,6-Dicarboxamide Systems

Many other compounds are presendy in use a 1993 database search showed 27 active ingredients in 212 products registered by the U.S. EPA for human use as repellents or feeding depressants, including octyl bicycloheptene dicarboxamide (A/-2-ethylhexylbicyclo[2.2.1]-5-hepten-2,3-dicarboxamide), dipropyl isocinchomeronate (2,5-pyridine dicarboxyhc acid, dipropyl ester), dimethyl phthalate, oil of citroneUa, cedarwood oil, pyrethrins, and pine tar oil (2). Repellent—toxicant or biting depressant systems are available which are reasonably comfortable for the user and can protect completely against a number of pests for an extended period of time (2). 

Recently, dyes based on the dicarboxamide pyridine as acceptor have been designed to obtain a high two-photon excited fluorescence and second harmonic signals for potential membrane measurement (Table 2) [66]. These systems have been foimd to present axpA values close to those of the most ef-... 

A partially rigid foldamer system was recently reported by Parquette et al. [79]. The oligomers were derived from alternating sequences of pyridine-2,6-dicarboxamides and raeta-(phenylazo)azobenzenes. The helical conformations were revealed by crystal structures. In solution, the folded conformations and their corresponding dynamics were probed by NMR. 

More recently the same authors have studied the anion binding ability of similar macrocyclic systems based on isophthalamides [21]. The isophthala-mide moieties were introduced as previous studies have shown isophthala-mide derivatives bind anions more strongly than the analogous pyridine-2,6-dicarboxamides [22],... 

Stability constants were obtained for receptors 13a, 13b and 13c using analogous conditions to those employed for receptors 12a, 12b and 12c. As with the pyridine-2,6-dicarboxamide macrocydes, the stability constants for the isophthalamide macrocydes appear to be influenced by the size and flexi-bihty of the system with the higher constants observed in the 20-membered receptor 13a with notable decreases in the assodation constants with the 22-and 24-membered receptors 13b and 13c. The greatest decreases where observed in the stability constants obtained with the carboxylate anions. In the case of acetate the constants decreased from 3130 M for 13a to 552 M and 205 M for 13b and 13c, respedively. hi the case of benzoate a constant of 601 M was calculated for 13a decreasing to 302 M and 82 M for 13b and 13c, respectively. Unexpectedly lower binding constants were obtained for the isophthalamide macrocydes (13a-13c) compared to the pyridine-... 

Recently Katayev, Sessler and co-workers have further developed the hybrid macrocycle systems by replacing the pyridine-2,6-dicarboxamide moieties used in receptors 43 and 44 with bipyrrole and dipyrromethane subunits... 

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