Illudanes

Humulane, Caryophyllane, Protoilludane, Illudane, Marasmane, Hirsutane... 

A protoilludane intermediate (225) (c/. Vol. 4, p. 113) has been implicated in the biosynthesis of protoilludane, illudane, illudalane, and marasmane sesquiterpenoids... 

Since the discovery of the illudane-type sesquiterpenoids, a number of related compounds have been isolated, viz., illudalic acid (167), illudinine (168), and dihydroilludin S (169, R = a-OH). The absolute stereochemistry of illudin S (169, R = =0) has been determined. A sequel to the successful stereospecific synthesis of illudin M (170) has been reported by Matsumoto et in which the diacetate (171, R = Ac), which had previously been prepared in the first synthesis, was selectively hydrolysed to the monoacetate (171, R = H). This compound was converted in three steps to the diacetate (172), which, after another selective hydrolysis, Jones oxidation, and acetate hydrolysis, yielded illudin M (170). 

Full details of the previously reported (Vol. 6, p. 73) synthesis of the seco-illudane sequiterpenoid hypacrone (346) have been published. An interesting feature of the synthetic route is the use of a directed crossed aldol condensation between the diketone (344) and the trimethylsilyl enol-ether (343) to produce the trans-isomer (345) of hypacrone (346). The absolute configuration of fomannosin (347) has finally been established by X-ray analysis of the camphanate ester derivative (348). Full details of the biosynthesis of fomannosin (347) from [l,2- C2]acetate (c/. Vol. 7, pp. 82, 196) have been published. The labelling pattern and couplings in fomannosin (347) are consistent with a biosyn-... 

In spite of this powerful battery of chemical weaponry, it is the illudanes which impart the greatest hostility to bracken s defense mechanisms. 

On the other hand, doses as low as 4.5 pg/ml of ptaquiloside at pH 7.4 (no dienone present) elicited chromatid exchange-type chromosomal aberrations in hamster lung fibroblast cells [246]. The illudane-dienone... 

Ptaquiloside is not the only illudane present in PteridiumThe clear chemical connection between ptaquiloside and pterosin B, carries within the suggestion that at least some of the myriad indanones that bracken synthesizes is the result of the biosynthetic progress from ptaquiloside-like precursors. Supporting evidence was drawn from the fact that ptaquiloside and pterosin B concentrations vary simultaneously with aging of the fronds [124,218], With this idea in mind, Castillo and coworkers pursued the search of additional illudanes in this fern. 

Fig. (12). Structure of other illudanes found in neotropical Pteridium aquilinum var. caudatum and other ferns of the...

Table 2 1H RMN data (400 MHz) of bracken illudanes in C5D5N (ppm) (Castillo et al., 1997,1998). Coupling constants are given in Hz.

Ptaquiloside-like illudanes are not unique to Pteridium sp. On the one hand, ptaquiloside itself was discovered in the rock fern Cheilanthes sieberi from the southwestern Pacific [265]. This fem was investigated in view that it thrived in bracken-free farms in parts of Australia that had a history of bovine or ovine enzootic hematuria. The content of ptaquiloside was highest in the crozier and amounted to 0.034% of the fem biomass, only a fraction of the ptaquiloside found in Pteridium but still high... 

The single adduct (67a) is obtained by photoaddition of 1,1-dimethoxyethylene to the ester (66a). Adducts (67b) and (68) were also obtained by the photoaddition of the same olefin to the enone (66b). The molecules obtained by this process were chemically elaborated to yield compounds with the proto-illudane skeleton (69). ... 

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