Cyclopropanecarboxylic acids structure

Structural parameters of some cyclopropanecarboxylic acids are compiled in Table 5. 

S. Abele, P. Seiler, D. Seebach, Synthesis, Crystal Structures, and Modelling of P-Oligopeptides Consisting of l-(Aminomethyl)cyclopropanecarboxylic Acid Ribbon-Type Arrangement of Eight-Membered H-Bonded Rings , Helv. Chim. Acta 1999, 82, 1559 - 1571. 

Figure 26. Nearest-neighbor H-bonds observed in ( peptides synthesized from l-(aminomethyl)cyclopropanecarboxylic acids.226 This S(8) pattern is an example of residue-induced turn formation, resulting from the dihedral and bond angle constraints introduced into the ft2-2 backbone by the cyclopropyl substituents. The crystal structures show a dipeptide and tripeptide in which the S(8) H-bond segments are rendered in thick cylinders. For the dipeptide, Newman projections are shown looking down the Ca—Cp bond and the C(O)—Ca bond.

The etiolate of cyclopropanecarboxylic acid and its derivatives is an important building block for organic synthesis.However, the strained methylenecyclopropane structure of the enolate renders this species not only difficult to prepare, but also unstable. A rather simple method for the preparation of substituted 2-cyclopropylidene-5,5-dimethyl-l,3-dioxanes 15 is the thermolysis of the corresponding 2-alkylidenecyclopropanone acetals 14 which rearrange at 150 °C to the hydrolytically unstable ketene acetals. 

Permethrinic acid,3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxyl-ic acid, is another kind of cyclopropanecarboxylic acid producing insecticides of higher performance and stability [5]. The structure of permethrin, a totally synthetic pyrethroid, is shown in Fig. 2. The most effective isomer of permethrinic acid is shown to be the d-cis isomer rather than the d-trans isomer [6]. 

In comparative structure-activity relationship studies, (5)-a-cyano-3-phenoxy-benzyl esters of dihalovinyl-cyclopropanecarboxylic acids were much more active while the (R)-a-isomers were generally much less active than the unsubstituted esters lacking the cyano group (Elliott et al.. 1978). 

The first example of such a methylenecyclopropane rearrangement was the isomerization of dimethyl rraM -3-methylenecyclopropane-l,2-dicarboxylate (the dimethyl ester of Feist s acid, 1) which occurred upon heating to about 200°C. It was not until 1952 that this reaction was formulated in proper structural terms. Thus, 1 rearranged to a 1 1 mixture of methyl (Z)- and ( )-2-(methoxycarbonylmethylene)cyclopropanecarboxylate (2). ... 

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