Looplure synthesis

Of interest is the fact that one of the coupling partners in the looplure synthesis was the half acid-half ester (59). Since the ester was untouched in the coelectrolysis, it could potentially function as a site for a second Kolbe oxidation and subsequent coupling. This strategy was utilized in the synthesis of disparlure (67 Scheme 16) [36]. A mixed coupling between the half-acid ester (62) and nonanoic acid (63) (1 10 ratio) proceeded smoothly to afford (64). Saponification... 

Of interest is the fact that one of the coupling partners in the looplure synthesis was the half acid, half ester 27. Since the ester unit is untouched in the coelectrolysis, it could potentially function as a site for a second Kolbe oxidation and subsequent coupling... 

The radicals may dimerize, participate in mixed coupling between two different radicals, or undergo cyclization. Each of these avenues is illustrated by the examples discussed next. Simple dimerization allows retrosynthetic disconnections to be made at any symmetrical carbon-carbon bond in a target molecule, and has been used in, for example, the synthesis of onocerin (13) [5], a- and )6-oconceradiene (14 and 15) [6], and pentacyclosqualene (16) [6,7]. The use of a mixed Kolbe oxidation allows disconnections to be made at nonsymmetrically substituted sites. A host of natural products have been generated using the latter protocol including, for example, brevicomin (21) [8], looplure (29) [9], and disparlure (35) [10] [note Scheme 2, Eq. (6), and Scheme 3]. 

Heterocoupling has been used for the extension of the carbon chain in fatty acids [83]. The method has recently been applied to the synthesis of pheromones [16]. For example, muscalure (24) has been synthesized in 80% yield [84, 85]. Furthermore, the antagonist of muscalure (Z)-l 1-heneicosene [86], looplure (25) [87], brevicomin... 

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