Abstract
(+)-epi-Epoformin (1), is a fungal cyclohexene epoxide isolated together with diplopimarane and sphaeropsidins A and C, a nor-ent-pimarane and two pimaranes, from the culture filtrates of Diplodia quercivora, a fungal pathogen for cork oak in Sardinia, Italy. Compound 1 possesses a plethora of biological activities, including antifungal, zootoxic and phytotoxic activity. The last activity and the peculiar structural feature of 1 suggested to carry out a structure activity relationship study, preparing eight key hemisynthetic derivatives and the phytotoxicity was assayed. The complete spectroscopic characterization and the activity in the etiolated wheat coleoptile bioassay of all the compounds is reported. Most of the compounds inhibited growth and some of them had comparable or higher activity than the natural product and the reference herbicide Logran. As regards the structure-activity relationship, the carbonyl proved to be essential for their activity of 1, as well as the conjugated double bond, while the epoxide could be altered with no significant loss.
Highlights
Introduction(+)-epi-Epoformin (1, Figure 1) is a cyclohexene epoxide, isolated together with some nor-ent-pimaranes and pimarane diterpenes, namely diplopimarane and sphaeropsidins A and C, from culture filtrates of the fungus Diplodia quercivora, isolated from declining Quercus canariensis trees in Tunisia as a canker-causing agent [1]
Its total enantioselective and asymmetric synthesis [4,5,6,7] was developed and the assignment of its absolute configuration was determined by time-dependent density together with that of other close naturally occurring cyclohexene oxides [8]
In leaf-puncture tests on holm oak (Quercus ilex L.), cork oak (Quercus suber L.), and tomato (Lycopersicum esculentum Mill.) leaves, 1 caused necrotic lesions on holm and cork oak
Summary
(+)-epi-Epoformin (1, Figure 1) is a cyclohexene epoxide, isolated together with some nor-ent-pimaranes and pimarane diterpenes, namely diplopimarane and sphaeropsidins A and C, from culture filtrates of the fungus Diplodia quercivora, isolated from declining Quercus canariensis trees in Tunisia as a canker-causing agent [1]. The fungi belonging to Diplodia genus are well known as pathogens of forest plants and as producers of several bioactive metabolites belonging to different classes of natural compounds [2]. When isolated from D. quercivora, 1 was tested for its phytotoxic activity using different bioassays. In leaf-puncture tests on holm oak (Quercus ilex L.), cork oak (Quercus suber L.), and tomato (Lycopersicum esculentum Mill.) leaves, 1 caused necrotic lesions on holm and cork oak In a tomato cutting bioassay, 1 caused, to different extents, stewing on stem at 0.2 and 0.1. 1 showed significant inhibition of all the species tested importantcrops cropsincluding including legumes. 1 showed significant inhibition of all the species exhibiting an effective penetration [9]. In order to Inthis thismanuscript, manuscript,11was wasisolated isolatedand andtested tested with eight hemisynthetic derivatives in order obtain clues about the structure-activity (SAR).
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