SYNTHESIS OF NEW HETEROCYCLIC DERIVATIVES OF 1A,4A-DEHYDROQUINOPYMARIC ACID
One of the most intensively developing areas of organic chemistry is the chemistry of heterocyclic compounds, the increasing interest in which is due to their increased biological activity. Thus, among heterocyclic diterpene derivatives, compounds that inhibit the cholesterol acyltransferase activity, as well as compounds with antioxidant, antiviral, antibacterial and fungicidal activity, were identified. In the present work, 1а,4а-dehydroquinopimaric acid, an available derivative of the levopimaric acid diene adduct (the main component of pine resin Pinus Silvestris) and p-benzoquinone, was used as the starting compound for heterocyclization. The reaction of 1а,4а-dehydroquinopimaric acid with ethylenediamine in methylene chloride in the presence of a catalytic amount of acetic acid resulted in the synthesis of a quinoxaline derivative. As a result of the interaction of 1а,4а-dehydroquinopimaric acid with 1H-pyrazole-carboxamidine hydrochloride in methylene chloride in the presence of triethylamine, a diterpene derivative with a benzimidazole fragment was obtained. The reaction of 1а,4а-dehydroquinopimaric acid with potassium thiocyanate in ethanol leads to the formation of a benzoxathiolone derivative. All heterocyclic derivatives are obtained as single regioisomers. The high regioselectivity during ring closure at the C3-C4 bond is apparently associated with steric factors caused by the bulky isopropylethene group, which makes it difficult for the reagent to approach position 2 of the E ring of 1a,4a-dehydroquinopimaric acid.