Australasian fungi : a natural product study. (1998)
AuthorsNicholas, Gillian Mayshow all
A number of Australasian fungi were investigated in a search for novel biologically active natural products.
Extracts of the fungus Favolaschia calocera were investigated, and resulted in the isolation of four compounds. These compounds were structurally assigned using mass spectrometry and NMR spectroscopy as the 5-stearate (30a) and 5-palmitate (30b) esters of (2E,6£)-1-(2-hydroxy-4-methoxyphenyl)-5-hydroxy-3,7,11-trimethyldodeca- 2,6,10-triene, (E)-6-phenylhex-5-en-2-ol (32) and as methyl (4E,6E)-3-hydroxy-7- phenylhepta-4,6-dienoate (28b). The absolute stereochemistry of the previously isolated and characterised methyl (4E, 6£)-3-benzoyloxy-7-phenylhepta-4,6-dienoate (28a) was determined using Masher's method.
To unambiguously assign the structure of the Favolaschia calocera metabolite 9- methoxystrobilurin K as structure 16, appropriate model compounds (33-40) were synthesised. The previously reported epoxyprenyl structure for 9-methoxystrobilurin K (17) and the dioxan structure for 9-methoxystrobilurin L (20) are now both revised to the prenyldioxepin structure 16.
A blue-violet compound was isolated from an extract of Entoloma hochstetteri. This compound was identified as 7-acetyl-1,4-dimethylazulene (56) and is thought to be an artefact of the extraction and isolation process.
The chemistry of a Cortinarius species collected from the Catlins (New Zealand) was investigated because crude extracts showed significant biological activity. Three disulfide compounds (59-61) were isolated and identified using a combination of NMR spectroscopy, mass spectrometry and synthesis. Two of these compounds (59 and 61) were assigned as symmetrical disulfides that arise from the third unsymmetrical disulfide, cortamidine oxide (61), through disulfide exchange. All three compounds were assigned as also containing N-oxide functionality.
Extracts of the Australian mushroom Cortinarius rotundisporus were investigated due to the cytotoxicity observed against the P388 murine leukaemia cell line during a screening programme. Two triterpenes of the malabaricane class were isolated and identified, using NMR techniques and mass spectrometry, as rotundisine A (94) and B (95).