SYNTHESIS AND CHARACTERIZATION OF ENANTIOMERS OF 5-METHYLOCTANOIC AND 6-METHYLOCTANOIC ACIDS

Enantiomers of 5- and 6-methyloctanoic acids were synthesized in high configurational purity from 1,4-butanediol and 1,5-pentanediol, respectively. Each diol was alkylated with para-methylbenzyl bromide to form a monoether alcohol. The residual alcohol group was converted to a bromide that was then alykalated with valeric or butyric acid dianions, respectively, leading to α-branched acids that were resolved by fractional crystallization of diastereomeric α-phenylethylamides. Subsequently, the diastereomerically pure amides were reductively cleaved, the hydroxymethyl groups were reduced to methyl substituents, the para-methylbenzyl group was hydrogenolyzed, and the resulting alcohol was oxidized to the acid. Configurational assignments are described. © 1990.