Synthesis and structure of 2: 1 adduct of myrcene and 1,4-benzoquinone

Abstract

Natural meroterpenoids often exhibit high and diverse biological activity [1] which is obviously related to their amphiphilicity. Well known examples are tocopherols, tocotrienols [2, 3], cannabinoids [4], prenylflavonoids, etc. [5, 6]. Synthesis of such compounds extends their structural diversity and hence the spectrum of their biological activity. As a rule, synthetic meroterpenoids are more accessible than natural ones whose concentration in natural sources is generally very low. We have studied the Diels–Alder reaction of myrcene as lipophilic diene with 1,4-benzoquinone as hydrophilic dienophile under the conditions allowing both electrophilic double bonds of the dienophile to be involved. Apart from the synthesis of a new meroterpenoid, 2 : 1 adduct of myrcene with benzoquinone, we have determined the regioselectivity of the addition of the second myrcene molecule to initially formed 1 : 1 adduct I which was reported in [7]. By heating benzoquinone with excess myrcene in boiling toluene for 8 h we obtained a crystalline product in ~75% yield. According to the GC/MS data, the crude product was a mixture of four isomers at a ratio of 10 : 15 : 70 : 5 (M 380) with very close retention times ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 12, pp. 1842–1844. © Pleiades Publishing, Ltd., 2014. Original Russian Text © A.V. Chuiko, O.A. Lodochnikova, S.A. Appolonova, V.V. Plemenkov, 2014, published in Zhurnal Organicheskoi Khimii, 2014, Vol. 50, No. 12, pp. 1859–1860.