Simple, stereospecific syntheses of 14C-labelled (f) -trans-chrysanthemum mono-and di-carboxylic acids, required for biosynthetic and toxicological work, are described. The methyl esters of the acids are obtained by Wittig condensation between the (+) -trans-cyclopropane aldehyde (2) and the appropriate 14C-labelled phosphoranes. Aldehyde (2) is obtained in high yield by osmium tetroxide-sodium periodate oxidation of methyl trans-chrysanthemate. The conversion of methyl chrysanthemate into chrysanthemum dicarboxylic acid via aldehyde (2) proceeds in an overall yield of 39%.Methyl nor-( 9) and bisnor-(8) (*) -trans-chrysanthemates are synthesised from (2) by condensation with a p p ro p r i at e a I ky I i den e p hos p h o ra n es.

Thermal decomposition of chrysanthemumdicarboxylic acid (1 b) produces a mixture of acidic and neutral products and liberates ca. 0.7 mol. equiv. of carbon dioxide. Separation and identification of the methyl esters of the six acidic products has shown that the acids are cis(Z)and trans(€)-norchrysanthemic acid [(2a) and (9)], trans(€)-2,6-dimethylhepta-4,6-dienoic acid (5). cis(Z)-and trans(€)-2,6-dimethylhepta-3,5-dienoic acid [(6) and (7)], and 2,6-dimethylhept-3-(or 4)-enoic acid (8) ; the acids ( 6) and ( 7) together constitute ca. 65% of the total acidic product. Thermal decarboxylation of the 14C-side-chain-carboxy-labelled diacid (1 8) liberates carbon dioxide containing 13% of the initial activity. The mechanism of formation of the ring cleavage products ( 5) and ( 6) is discussed, and the bearing these results have on the stereochemistry of biosynthesis of chrysanthemummono-and di-carboxylic acids (1 a and b) is considered.(+)-tY6i?nS-CHRYSANTHEMUM-MONO-AND -DI-CARBOXYLIC ACIDS (la and b) are the acidic degradation products of the naturally occurring insecticidal esters (pyrethrins) found in Chrysanthemum cinerariaefo1ium.l Thermal decarboxylation of the diacid (lb) is reported in the early literature to produce a high yield of the acid (2a) and little or none of the alternative acidic product (3), and this observation has been used recently to determine some stereochemical details of the biosynthesis of the acids (la and b) (see ref. 3 and later discussion).

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Durch oxidative Spaltung des trans‐Chrysanthemats (I) [(+)‐Form bzw. Racemat] wird der Aldehyd (II) [(+)‐Form bzw. Racemat] dargestellt.

Bei der thermischen Zersetzung der Säure (I) unter Stickstoff entstehen außer Neutralstoffen und 0,7 Val Kohlendioxid sechs Säuren, die als Methylester identifiziert werden: cis‐ und trans‐(II), (III), cis‐ und trans‐(IV) (65% der Gesamt‐ 91 ausbeute der sauren Produkte) und die 3‐ und 4‐ungesättigte Säure (V).