Fatty acids alkynoic

The natural occurrence of fatty acids with cyclopropane and cyclopropene systems led to an interest in the synthesis of such acids from appropriate alkenoic and alkynoic acids. 

Fatty adds with one or more triple bonds (alkynoic, ethynoic or acetylenic acids), or fatty acids containing both double and triple bonds, occur rarely in nature. Examples are stearoHc (octadec-9-ynoic) add (3-17) and isanic (octadec-17-en-9,ll-diynoic) acid, also known as boledc add (3-18), in short 9a-18 l (or 18 1,9a) and 17,9a,la-18 3 (18 3,17 ,9a,l la). The positional isomer of stearolic add is tariric (octadec-6-ynoic) add. 

Alkynoic, branched-chain and cyclic fatty acids... 

A full report has been published on the preparation and synthetic applications of the acetylenic dianions (35) of note here is their use in the preparation of allene-l,3-dicarboxylic acids (36). Kolbe co-electrolysis of 5-alkynoic adds, RC=C(CH2)3C02H, with half-esters of diadds Me02C(CH2) C02H followed by saponification gives the coupled product (37) in 45—50% yield. Alternative conditions have been reported for the preparation of oi-acetylenic acids from o>-iodoacids (esp. from fatty acids) using the lithium acetylide-ethylenediamine complex in HMPA. ... 

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