2-Methylcyclopentanecarboxylic acid

A special case of diastereoselective alkylation reaction via azaenolates is the intramolecular cyclization of metalated 4,5-dihydro-2-(5-iodohexyl)-4,4-dimethyloxazole which furnishes the thermodynamically less favored cri-2-methylcyclopentanecarboxylic acid derivative 8 preferentially32. 

These investigators found that the normal acids occurred in much greater abundance than the branched acids. The cyclic acids isolated by Lochte and coworkers (31) include cyclopentanecarboxylic acid, 2-methylcyclopentanecarboxylic acid, 3-methylcyclopentane-carboxylic acid, cyclopentaneacetic acid, 3-methylcyclopentaneacetic acid, 2,3-dimethyl-cyclopentaneacetic acid, 1,2,2-trimethylcyclopentanecarboxylic acid, cyclohexanecarbox-ylic acid, p-methylcyclohexanecarboxylic acid, and the cis and trans forms of 2,2,6-tri-methylcyclohexanecarboxylic acid. In addition, Lochte and coworkers (31) isolated dimethylmaleic anhydride, which has also been isolated by Nenitzescu and coworkers (42). 

The 1,2-dipolar cycloaddition of chlorosulfonyl isocyanate to different cycloalkenes has become a well-known route for the synthesis of cycloalkane-fused p-lactams, and for alicyclic P-amino acids, after hydrochloric acid treatment. The addition takes places regio- and stereospecifically, in accordance with the Markovnikov orientation rule [51-55]. In this manner, a number of homologue and analogue alicyclic P amino acids have been prepared, such as czs-2-amino-2-methylcyclopentanecarboxylic acid [56], m-2-amino-2-methylcyclo-hexanecarboxylic acid [56], (l/ , 2S, 4S )2-amino-4-terMnitylcyclopenta-necarboxylic acid [55, 58], 3-exo-aminobicyclo[2.2.1]heptane-2-exo-carboxylic acid [59, 60] and 3-exo-aminobicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid [61]. 

Methylation of nickelacycle 30, obtained in the reaction between Ni(COD)(py)2 and 2-cyclopentencarboxylic acid, unexpectedly leads to the formation of cw-2-methylcyclopentanecarboxylic acid (Scheme 29) 33(0 pjijs product probably arises by methylation of isomeric nickelacycle 56, formed by 3-hydride elimination and insertion with the opposite regiochemistry. When the same reaction is carried out with a large excess of iodomethane, d.y-3-methylcyclopentanecarboxylic acid is obtained. Methylation reactions of related azanickelacycles have also been reported. ... 

A listing of compounds evaluated in the laboratory as cockroach repellents summarizes 872 synthetic compounds out of 901 bioassayed from 1953 to 1974 (43). Fencholic acid [512-77-6] (3-isopropyl-l-methylcyclopentanecarboxylic acid) has been used as a standard repellent in tests conducted by placing 20 cockroaches in a glass crystallizing dish without food and water and offering them a choice of two cardboard shelters, one of which was treated with 1 or 2 ml, of a 1% solution of the candidate in acetone. Counts were made daily for seven days. 

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