Cyclic unsaturated compounds Communication 51. direction of lactonization of bicyclo[2.2.1]-2-heptene-5,6-dicarboxylic acids

Abstract

1. A study was made of the NMR spectra of some methyl-substituted lacto esters that are derivatives of the acids that are formed in the spontaneous lactonization of the correspondingbicyclo[2.2.1]-2-heptene-5.6-dicarboxylic acids. 2. In the mentioned acids with a monosubstituted double bond the closure of the γ-lactone ring is accomplished at the C2-center (containing the substituent). In the acids with a disubstituted double bond the substituent at C3 in the formed lactones assumes an exo-configuration. 3. Additional proof was obtained for the endo-configuration of the anhydride ring in the adducts of substituted cyclopentadienes with maleic anhydride, and in the case of the 5-substituted cyclopentadienes, for the syn-configuration of the substituent at the C7-center (at the bridge) in the adducts that predominate in the corresponding mixtures of the stereoisomers.