1. SYNTHESIS OF ALPHA-ESTERS OF 1,2,3-PROPANETRICARBOXYLIC ACID. 2. GCMS ANALYSIS OF ISOMERIC OLEFINS. 3. AN OXIRANYLPHENYL ANGELATE FROM PIMPINELLA DIVERSIFOLIA (ALTERNARIA ALTERNATA, FATTY ACIDS)

Methods are described for preparation of -mono-esters of 1,2,3-propanetricarboxylic acid. Oxidation of methyl cyclopent-3-ene-1-carboxylate with RuO(,4) gives 3-(methoxycarbonyl)-pentanedioic acid, which is converted readily to the corresponding anhydride, 3-(methoxycarbonyl)-pentanedioic acid anhydride. Reactions of the anhydride with alcohols give the (beta)-methyl-(alpha)-alkyl diesters of 1,2,3-propanetricarboxylic acid. The desired (alpha)-monoesters are then obtained by selective de-methylation with benzyl thiolate. Relevance of this work to the synthesis of the AA1 host-specific phytotoxins is discussed. A reasonably rapid method for locating multiple bonds in long chain compounds, such as 9-octadecenoic acid and 10-tetradecenol, has been developed. Derivatization of olefins followed by multiple scanning gas chromatography/mass spectrometry allowed the location of double bonds and the detection of > 0.5% double bond isomers. Several functionalized olefins were oxidized with OsO(,4) or performic acid to the corresponding diols, and these were converted on successive treatment with dimethyl sulfinyl carbanion and methyl iodide or deuteriomethyl iodide to the diethers. Use of both methyl and deuteriomethyl ethers removed ambiguities in assigning elemental compositions to the fragments. Multiple scanning mass spectrometry allowed analysis of mixtures with isomers that co-elute on gas chromatography. KH was found to be much more reliable than NaH for preparation of dimethyl sulfinyl carbanion. Reduction of fatty acids to the alcohols followed by etherification of the primary hydroxyl was found to increase the relative abundance of fragments from the "carboxyl" end of the derivatized double bond. The GCMS method provided estimates of the extent of isomerization on synthesis of long carbon chains containing a multiple bond. Commercial "99%" oleic acid (by GC) was found to contain > 4% double bond isomers. The major component of the essential oil from the roots of Pimpinella diversifolia, gathered in the Kumaun region of India, was found to be (+)-4-methoxy-2-(E-3-methyl-2-oxiranyl)phenyl Z-2-methyl-2-butenoate (3.3b). Aromatic ('13)C NMR resonances of 3.3b and its synthetic acetate as well as those of 2-methoxy-4-(E-3-methyl-2-oxiranyl)phenyl acetate (3.1d) prepared from isoeugenol, were found to be in excellent agreement with calculated values.