Synthesis of δ‐eicosanolactone and δ‐docosanolactone directly from meadowfoam oil

Abstract

δ-Eicosanolactone and δ-docosanolactone were synthesized directly from the triacylglycerides of meadowfoam (Limnanthes) oil. Perchloric and sulfuric acids were used in stoichiometric quantities (0.5-4.0 mol equiv) to cyclize triglyceride to δ-lactone. When the reactions were run in the absence of solvent at 40°C, δ-lactone yields ranged from 17-75% where δ/γ ratios ranged from 6:1 to 10.4:1. Sulfuric and perchloric acids gave similar yields for their individually optimized reactions. Perchloric acid-catalyzed reactions required less acid to produce similar amounts of δ-lactone (HClO 4 at 2.0 mol equiv gave 73% yield vs. H 2 SO 4 , which gave 75% yield at 2.5 mol equiv). The use of polar nonparticipating solvents during the reaction had little impact on δ-lactone formation or δ/γ ratio. Higher perchloric acid concentrations provided higher δ-lactone yields with δ/γ ratios remaining nearly constant. The effect of sulfuric acid on δ-lactone yield and δ/γ ratio was more direct; higher acid concentration improved both. Both crystallization and short path distillation improved δ-lactone quality, but short path distillation gave higher recovered yields. The δ-lactones were converted to their corresponding 5-hydroxy acids in the same reaction vessel, separated, and cyclized back to δ-lactones upon heating under vacuum. This provided a convenient method for δ-lactone purification.

Fats and oils as renewable feedstock for chemistry

“…Cyclizations of 6 to cyclopentane [24] and to cyclohexanone derivatives [25] have been reported. The dlactone of fatty acid 7 can be obtained directly from meadowfoam oil [26]. The seed oil of Calendula officinalis contains up to 60% of calendic acid [(8E,10E,12Z)-octadecatrienoic acid] 8 with a conjugated and stereochemically well-defined hexatriene system [27,28].…”

Fatty Acid Estolides: A Review

“…Hydrochloric acid, phosphoric acid, and nitric acid gave a lower yield of estolides due to the hydrolysis of estolides caused by a large proportion of water in these catalysts. Due to its excellent performance, perchloric acid was widely applied with other fatty acids from new crop oils such as pennycress (Cermak et al, 2015b), coriander (Cermak et al, ), cuphea (Cermak and Isbell 2004b), and meadowfoam, from which 71% yield was obtained (Isbell and Kleiman, ). It was observed that temperature plays a critical role in these esterification reactions.…”

“…It was observed that temperature plays a critical role in these esterification reactions. The reaction rate is low at lower temperatures, while the yield decreased above an optimum temperature due to the production of lactone byproducts (Isbell et al, ; Isbell and Kleiman, ). The concentration of catalyst also influenced the reaction significantly.…”