The Diels-Alder Reaction of Levopimaric Acid and Its Use in Quantitative Determinations²

The Stereochemistry of Maleopimaric Acid and the Long Range Shielding Effect of the Olefinic Bond

“…Levopimaric acid (I) reacts quantitatively with maleic anhydride in benzene a t room temperature (1) to yield an adduct, maleopimaric acid, which has recently been assigned the-stereochemistry shown in I1 (R = H) (2). This assignment was based mainly on CH3 COOH 15 studies of nlolecular models coupled with the observation that a single isomer is formed in the reaction (2).…”

“…This assignment was based mainly on CH3 COOH 15 studies of nlolecular models coupled with the observation that a single isomer is formed in the reaction (2). At that time the configuration a t C-13 in levopimaric acid had not been definitely established and, in fact, Klyne (3), using the method of molecular rotation differences, had assigned the @-configuration.…”

Rosin Product Review

“…However, they also possess anti-aromatic characteristics which make them conducive to reaction under mild conditions. Rosin acids can undergo isomerisation at elevated temperatures and interchange the form of levopimaric acid (Figure 4) that is subjected to Diels-Alder addition ( Figure 5) [10] which can be used as a rigid building block in the main chain of aliphatic polyesters to manipulate their mechanical properties and crystallisation behaviours. The modified rosin provides different softening points and acid values that is used for various applications (Table 1).…”

Etudes stereochimiques. VIII. Sur la serie exo-maleopimarique

“…The following may be given as examples. Coumarin undergoes dimerization affording cyclobutane isomers, the geometry of which is solvent and sensitizer dependent (1,2). Ethyl trans-cinnamate, ethyl trans-a-methylcinnamate and analogous lactones 'Acknowledgement is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society for support of this work.…”

“…Parmi les quatre isomkres susceptibles de se former dans la reaction, seul l'adduit 3a, de configuration endo bien Ctablie (1-3) a Ct C dtcrit dans la IittCrature. Cette synth2se diCnique Ctait donc considCrCe jusqu'a prtsent comme tout B fait st6rCospCciiique et utilisable par exemple pour la dttermination quantitative de l'acide 1Cvopi-marique dans les rCsines (1). On doit signaler, cependant, que Sandermann (4), en titrant par acidimktrie l'adduit formi, a envisage la formation possible dans la rCaction d'un deuxieme isomkre; cette hypothkse n'a pas Ct C prise jusqu'h prksent en considkration.…”