Synthesis of racemic 9-methyl-10-hexadecenoic acid

Fatty Acids from a Glass Sponge Aulosaccus sp. Occurrence of New Cyclopropane‐Containing and Methyl‐Branched Acids

“…The 1 H-or/ and 13 C-NMR spectra of the FA fractions showed cis-double bonds of major unsaturated compounds (according to the chemical shifts of their allylic protons or/and carbons [7][8][9]) and some other structural characteristics as described below. For example, the signals of allylic (δ H 2.08-2.10, m; δ C 20.5, CH 2 -19 of 20:5; δ C 26.5, CH 2 -4 of 20:4 and 20:5; δ C 27.3, CH 2 -16 of 20:4) and bis-allylic CH 2 (δ H 2.81-2.85, m; δ C 25.6) were observed in the 1 H-, 13 C-NMR, 1 H-1 H-COSY, HSQC and HMBC spectra of the fraction containing major cis-polyenes, 20:4Δ5Z,8Z,11Z,14Z and 20:5Δ5Z,8Z,11Z,14 Z,17Z [8,9].…”

“…The 1 H-NMR data of these monoenes with an allylic methyl groups were analyzed using the correlations in the 1 H-1 H-COSY spectrum: the mid-chain CH 3 [2,7] are known to be characteristics of a trans-or E-double bond. Previously, to investigate the configuration of the double bond of natural 9-methyl-hexadec-10-enoic acid, its synthesis was accomplished but the NMR data of a major cis-monoene only were reported; the E double bond configuration of the naturally occurring FA was confirmed by gas chromatographic co-elution experiments [13].…”