13C magnetic resonance studies. 119. Tricyclo[3.3.0.0] and [3.2.1.0]octanones from substituted norbornenones via cyclopropanation and homoketonization

Simmons–Smith cyclopropanation of the trimethylsilyi enoi ethers of 7-isopropylidene- and two 7-spirocyclopropyl-norbomenones leads directly to the 8-substituted 2-trimethylsilyl ethers of homoquadricyclene. Homoketonization of the unsaturated ether proceeds regiospecifically to the corresponding tricyclo[3.3.0.02.8]octan-4-one while the others give the tricyclo[3.2.1.02.6]octan-4-ones exclusively, all with high stereoselectivity favoring inversion of configuration. This difference in the regiochemistry of homoketonization can be attributed to a directive effect of β-functionalization overcoming thermodynamic control of cleavage.

The enzymic conversion of linoleic acid into 9-(nona-1′,3′-dienoxy)non-8-enoic acid, a novel unsaturated ether derivative isolated from homogenates of Solanum tuberosum tubers

1. A major component of the lipids in aqueous (pH7.5) homogenates of tuber tissue from Solanum tuberosum was isolated and characterized as 9-(nona-1′,3′-dienoxy)non-8-enoic acid. 2. This novel unsaturated ether fatty acid derivative, which contains a butadienylvinyl ether function, has the structure: [Formula: see text] and is formed from linoleic acid by a sequence of enzymic reactions. 3. A precursor of the unsaturated ether derivative is 9-d-hydroperoxyoctadeca-10,12-dienoic acid, formed by the action of S. tuberosum lipoxygenase on linoleic acid. 4. An enzyme that converts the fatty acid hydroperoxide into the unsaturated ether derivative was isolated from S. tuberosum. The pH optimum of this enzyme is approx. 9, although the overall conversion of linoleic acid into the ether derivative is maximal at pH7.5. 5. An unusual feature of this pathway is the insertion of an oxygen atom into the alkyl chain of a fatty acid. 6. This novel mechanism may play a role in the breakdown of polyunsaturated fatty acids to volatile products in plants.