As-Dimethylsuccinic acid

The preparation of as-dimethylsuccinic acid according to the following scheme has a number of points of interest ... 

The second model compound, 2,5 dimethyltetrahydrofuran-3,4-dicarboxylic acid, was found to consist of three isomers (plus a partially hydrogenated material). We were unable to assign the stereochemistry of this model unequivocally. We also used as a model 2,3-dimethylsuccinic acid which was a mixture of the racemic and meso forms. On this basis, one can show that the resonances of the carbons al a to the anhydride or acid group along the backbone occur at 44.6 ppm and are approximately equal to that found in the copolymer. 

In contradistinction to NMR spectra 130), mass spectra 120) are insensitive to the stereochemistry of the substituents of tetrahydro-furanoid neolignans. The absolute configurations of galbacin (1.7a) and calopiptin (1.8b) were determined [basic evidence ozonolysis leads to (25,3 -2,3-dimethylsuccinic acid (705)]. Conversions of 1.8b into 1.7b and 1.8c (705), as well as of 1.8a into 1.8b (772) proved, consequently, of stereochemical significance. An X-ray analysis of grandinsin (1.7c) and ORD/CD correlations with other neolignans of the series were planned 82). 

Type iii-b This reaction leads to products (67). The electrochemical oxidation of the sodium salts of acetic, propionic, and isovaleric acids in the presence of ethylenic compounds bearing electron-withdrawing substituents gives 1,2-dialkylated adducts as the main products. A methyl radical generated from an acetate ion reacts with diethyl fumarate to give diethyl 2,3-dimethylsuccinate in 80% yield [106]. 

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