NMR characterization of dihydrosterculic acid and its methyl ester

Abstract

Cyclopropane FA occur in nature in the phosphoplipids of bacterial membranes, in oils containing cyclopropene FA, and in Litchi sinensis oil. Dihydrosterculic acid (2-octyl cyclopropaneoctanoic acid) and its methyl ester were selected for 1H and 13C NMR analysis as compounds representative of cyclopropane FA. The 500 MHz 1H NMR spectra acquired with CDCl3 as solvent show two individual peaks at -0.30 and 0.60 ppm for the methylene protons of the cyclopropane ring. Assignments were made with the aid of 2D correlations. In accordance with previous literature, the upfield signal is assigned to the cis proton and the downfield signal to the trans proton. This signal of the trans proton is resolved from the peak of the two methine protons of the cyclopropane ring, which is located at 0.68 ppm. The four protons attached to the two methylene carbons alpha to the cyclopropane ring also show a split signal. Two of these protons, one from each methylene moiety, display a distinct shift at 1.17 ppm, and the signal of the other two protons is observed at 1.40 ppm, within the broad methylene peak. The characteristic peaks in the 13C spectra are also assigned.

Structural diversity and possible functional roles of free fatty acids of the novel soil isolate Streptomyces sp. NP10

“…Three high-field signals in the 1 H NMR spectrum, mutually coupled in homonuclear 2D spectra, were indicative of the presence of a cis 1,2-disubstituted cyclopropane ring in the detected cyclopropane FAs (Macmillan and Molinski 2005;Knothe 2006). For compounds eluting at RI 2002 and 2202, it was assumed, based on comparisons of retention indices with literature values, that these are normal chain homologues 17:0cy9-10 and 19:0cy9-10, respectively (Zouari et al 2011).…”

Challenging cyclopropanation reactions on non-activated double bonds of fatty esters

“…Cyclopropanation of methyl fatty esters with EDA catalysed by Rh 2 (OAc) 4 Rhodium is the most commonly used catalyst for cyclopropanation reactions, 29,30 and hence Rh 2 (OAc) 4 was tested as catalyst in the three reactions described above. The results are summarized in Table 3.…”

“…3 Cyclopropane fatty acids are present in nature, 4 and their synthesis has been usually tackled by construction of the alkyl chains from the pre-formed cyclopropane ring. 5,6 The Simmons-Smith reaction has been also described for this purpose, 7 but surprisingly, the catalytic cyclopropanation of carbon-carbon double bonds has been scarcely explored.…”

“…Organic layers were combined and washed with water (2 Â 10 mL) and brine (10 mL). Then, the organic solution was dried with anhydrous MgSO 4 and concentrated under vacuum. 8-((1S*,2S*,3R*)-2-(Hydroxymethyl)-3-octylcyclopropyl)-octan-1-ol (12).…”

“…The resulting solution was extracted with diethyl ether (3 Â 10 mL). Organic layers were combined, dried with anhydrous MgSO 4 and concentrated under vacuum.…”