The Synthesis of cis-4-Alkenoic Acids Isolated from the Seed Oil of Litsea glauca Sieb

Abstract

cis-4-Decenoic, cis-4-dodecenoic and cis-4-tetradecenoic acids were synthesized by the condensation of the corresponding alkanals (C6, C3 and C10) with phosphorane [6] which were prepared from the reaction of phosphonium iodide [5] with sodium methoxide in dimethylformamide, as shown in the flow diagram of the reaction sequence (Fig. 1). The position of the double bond at Δ4 was unambiguous from the fact, that the resulting acids were succinic and the corresponding saturated C6-, C8- and C10-acids when methyl alkenoates were oxidized with KMnO4 according to Armstrong and Hilditch, and also from their NMR spectra which showed an apparent strong doublet at τ 7.65 and a multiplet centered at τ 4.65. Presence of the broad absorptions centered at 720 cm–1 and absence of the absorptions at 965~970cm–1 in the IR spectra of the title acids showed that their double bonds take the cis-configuration. The physical constants of the title acids, their methyl esters, p-bromophenacyl esters and p-phenylphenacyl esters were compared with those of the cis-4-alkenoic acids of the same carbon atoms which were previously separated from the seed oil of Litsea glauca Sieb. © 1973, The Chemical Society of Japan. All rights reserved.