- A practical synthesis of long-chain iso-fatty acids (iso-C 12-C19) and related natural products
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A gram-scale synthesis of terminally-branched iso-fatty acids (iso-C 12-C19) was developed commencing with methyl undec-10-enoate (methyl undecylenate) (for iso-C12-C14) or the C15 and C16 lactones pentadecanolide (for iso-C 15-C17) and hexadecanolide (for iso-C18-C 19). Central to the approaches outlined is the two-step construction of the terminal isopropyl group through addition of methylmagnesium bromide to the ester/lactones and selective reduction of the resulting tertiary alcohols. Thus, the C12, C17 and C18 iso-fatty acids were obtained in three steps from commercially-available starting materials, and the remaining C13-C16 and C19 iso-fatty acids were prepared by homologation or recursive dehomologations of these fatty acids or through intercepting appropriate intermediates. Highlighting the synthetic potential of the iso-fatty acids and various intermediates prepared herein, we describe the synthesis of the natural products (S)-2,15-dimethylpalmitic acid, (S)-2-hydroxy-15-methylpalmitic acid, and 2-oxo-14-methylpentadecane.
- Richardson, Mark B.,Williams, Spencer J.
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p. 1807 - 1812
(2013/10/22)
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- Alkylation of alkenes: Ethylaluminum sesquichloride-mediated hydro-alkyl additions with alkyl chloroformates and di-tert-butylpyrocarbonate
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A general method for the hydro-alkyl addition to the nonactivated C=C double bond of alkenes using alkyl chloroformates (primary, secondary), 12, and di-tert-butylpyrocarbonate, 52, mediated by ethylaluminum sesquichloride (Et3Al2Cl3) has been developed. Reaction of 12 and 52, respectively, with Et3Al2Cl3 gives an alkyl cation which is added to the alkene; hydride transfer to the adduct carbenium ion or, if applicable, 1,2-H shift followed by hydride transfer from Et3Al2Cl3 to the rearranged adduct carbenium ion gives the saturated addition product. The reaction has been applied to 1-alkenes, 2-methyl-1-alkenes, internal double bonds, and to three cyclic alkenes. Special interest has been focused on alkylations of unsaturated fatty compounds, such as oleic acid (2), which are important renewable feedstocks. 2-Methylalkanes, 3-methylalkanes, 2,4-dimethylalkanes, 2,3-dimethylalkanes, 2,2,4-trimethylalkanes, cyclohexylalkanes, and carboxylic acids and esters with the respective branched alkyl chain have been synthesized with good to moderate yields.
- Biermann, Ursula,Metzger, Juergen O.
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p. 10319 - 10330
(2007/10/03)
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- Synthesis and Absolute Configuration of 2-Hydroxy-12-methyl Tridecanoic Acid
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The synthesis of racemic 2-hydroxy-12-methyl tridecanoic acid is described.The absolute configuration of the two enantiomers has been determined by the method of Dale and Mosher. - Keywords: 2-Hydroxy-12-methyl Tridecanoic Acid, Absolute COnfiguration
- Balzer, Th.,Budzikiewicz, H.
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p. 1367 - 1368
(2007/10/02)
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- Biosynthetic Studies of Marine Lipids. 5. The Biosynthesis of Long-Chain Branched Fatty Acids in Marine Sponges
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The very long chain branched fatty acids 25-methyl-5,9-hexacosadienoic (Δ5,9-iso-27:2)-and 24-methyl-5,9-hexacosadienoic (Δ5,9-anteiso-27:2) acids as well as the straight-chain 5,9-hexacosadienoic (Δ5,9-26:2) acid were shown to originate from the short-chain precursors 13-methyltetradecanoic (iso-15:0), 12-methyltetradecanoic (anteiso-15:0), and palmitic (n-16:0) acids, respectively, by means of 14C incorporation experiments in the marine sponge Jaspis stellifera.These results confirm that methyl branching does not occur after chain elongation.The unusual Δ5,9 unsaturation probably takes place after chain elongation of short branched or straight-chain fatty acids.
- Carballeira, Nestor,Thompson, Janice E.,Ayanoglu, Eser,Djerassi, Carl
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p. 2751 - 2756
(2007/10/02)
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