New sesquiterpenic phytotoxins establish unprecedented relationship between different groups of blackleg fungal isolates

Phytotoxins, Elicitors and Other Secondary Metabolites from Phytopathogenic “Blackleg” Fungi: Structure, Phytotoxicity and Biosynthesis

“…Plant leaves of brown mustard treated with depsilairdin (27) showed strong necrotic and chlorotic lesions, but such symptoms were not observed in canola in a wide range from 1 µM to 1 mM. Ten sesquiterpenes have been reported from extracts of cultures of L. maculans [42,43]. Phomalairdenones A note that lairdinol A (36), a eudesmene type sesquiterpene, is a structural moiety of the hostselective phytotoxin depsilairdin (27).…”

“…(iii) Leptosphaeria species / unknown asexual (Polish and Canadian isolates Laird 2 and Mayfair 2, virulent on brown mustard) producing as characteristic metabolites various polanrazines (17)(18)(19)(20)(21)(22), phomapyrones (49)(50)(51)(52)(53)(54)(55) and phomalairdenones (28)(29)(30)(31) in MM ( Figure 21 It is worthy to note that so far only an Australian isolate of L. maculans (IBCN 18) was found to produce substantial amounts of sirodesmin PL (1) (and related metabolites), together with phomalairdenones A (28), B (29) and C (30) [43]. Isolate IBCN 18 was reported to be virulent on both canola and brown mustard.…”

Total Synthesis of Depsilairdin

“…19 Compound 51 indicated the presence of three distinct methyl singlets, an olefinic methylene and three methine protons which were determined by using 1 H, 13 C NMR and HSQC. The spin systems were determined with the help of COSY and further correlations were deduced by using HMBC.…”

“…The absolute configuration for lairdinol A (51) was assigned based on its relationship with depsilairdin (55) and on the fact that they were isolated from the same fungal cultures. 19 The absolute configuration for 55 was assigned indirectly via a 2,5-morpholinedione degradation product. 25 The enantiomer of 51, cyperusol C (ent-51), has been isolated from the plants Cyperous longus 42 and Erigeron annus.…”

“…19 Lairdinol A (51) belongs to the eudesmane family of sesquiterpenes. This class of natural products has attracted considerable attention from synthetic chemists because of the challenge to construct the trans decalin ring junction.…”