Christopher D. Donner

Antibacterial metabolites from Australian macrofungi from the genus Cortinarius

In this study, ethyl acetate and aqueous fractions from 117 collections of Australian macrofungi belonging to the mushroom genus Cortinarius were screened for antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Overall, the lipophilic fractions were more active than the aqueous fractions. The ethyl acetate fractions of most or all collections of 13 species, namely Cortinarius ardesiacus, C. archeri, C. austrosaginus, C. austrovenetus, C. austroviolaceus, C. coelopus, C. [Dermocybe canaria](2), C. clelandii, C. [D. kula], C. memoria-annae, C. persplendidus, C. sinapicolor, C. vinosipes and forty seven collections of un-described Cortinarius species exhibited IC(50) values of 0.09 mg/mL against S. aureus. In contrast, most or all collections of only four species, namely C. abnormis, C. austroalbidus, C. [D. kula], C. persplendidus, and eleven un-described Cortinarius collections exhibited similar effects against P. aeruginosa (IC(50) <or= 0.09 mg/mL). Anthraquinonoid pigments isolated from C. basirubescens together with emodin physcion and erythrogluacin were assessed for their antimicrobial activity. The fungal octaketides austrocortilutein, austrocortirubin, torosachrysone, physcion and emodin were found to strongly inhibit the growth of S. aureus (IC(50) 0.7-12 microg/mL) whereas only physcion and emodin exhibited potency against P. aeruginosa (IC(50) 1.5 and 2.0 microg/mL, respectively).

SYNTHESIS AND ABSOLUTE STEREOCHEMISTRY OF THYSANONE

Abstract The structure and absolute stereochemistry of thysanone 3 , a fungal benzoisochromanquinone with potent human rhinovirus 3C-protease inhibitory activity, is established by the total synthesis of its antipode 1 from ( S )-propylene oxide.

Total synthesis of enantiopure 1,3-dimethylpyranonaphthoquinones including ventiloquinones E, G, L and eleutherin.

A new synthetic approach to enantiopure pyranonaphthoquinones is described. (S)-Mellein 10, prepared in 6 steps from (S)-propylene oxide 16, is converted stereospecifically to the (1R,3S)-dimethylpyran 15. The pyran 15 is then converted to the benzoquinone 14, which undergoes regiospecific Diels-Alder reactions with a variety of oxygenated butadienes to give pyranonaphthoquinones including ventiloquinones E, G, L, eleutherin and ent-deoxyquinone A.

Synthetic and Computational Studies of Acyl Radical Cyclizations with β-Alkoxyacrylates: Formal Synthesis of (±)-Longianone

An investigation into the cyclization of acyl radicals with mono- and disubstituted β-alkoxyacrylates is described. Ether-tethered acyl radicals, generated directly from the corresponding aldehyde, undergo cyclization to form dioxaspiro heterocyclic systems including 1,7-dioxaspiro[4,4]nonane-4,8-dione and 1,8-dioxaspiro[5,4]decane-5,9-dione. This strategy is applied to a concise formal synthesis of the fungal metabolite longianone. Density functional theory calculations provide insight into the chemistry of the acyl radicals in this study.

Pigments of fungi. Part 68. Synthesis and absolute configuration of thysanone

The (1R,3S)-absolute stereochemistry of thysanone 1, a fungal benzoisochromanquinone with potent human rhinovirus 3C-protease inhibitory activity, is established for the first time by total synthesis of the natural product from ethyl (S)-lactate and CD comparison with authentic material.

Pigments of Fungi. Part 70.* Total Synthesis of (R)-Semixanthomegnin and the X-Ray Crystal Structure of (±)-7-Chloro-10-methoxy-3-methyl-3, 4-dihydro-1 H-naphtho[2,3-c]pyran-1,6,9-trione

(R)-Semixanthomegnin (8), which has been converted by others to the mould metabolite (3R,3′ R)-xanthomegnin (9), is prepared in seven steps from (R)-propylene oxide (16). A single-crystal X-ray structure analysis of (±)-7-chloro-10-methoxy-3-methyl-3,4-dihydro-1H-naphtho[2,3-c]pyran-1,6,9-trione (25) confirms the regiochemistry of the cycloaddition reaction between 2,5-dichloro-1,4-benzoquinone and the new, highly oxygenated, chiral butadiene derivative (2).

Pigments of Fungi. LXIX. Total Synthesis of (R)-Ochratoxin α and the Formal Total Synthesis of Ochratoxin

(R)-Ochratoxin α, the monochiral carboxylic acid component of the biologically active dipeptide ochratoxin A, is synthesized for the first time over nine steps from (R)-propylene oxide. The method constitutes a versatile and general route to functionalized dihydroisocoumarins.

Synthesis and X-Ray Crystal Structure of Cynandione B Analogues

The synthesis of analogues of cynandione B, a phenolic acetophenone from Cynanchum taiwanianum, is described. The one-step conversion of benzochromenones to the heptacyclic spiroacetal core of cynandione B using methylmagnesium bromide is investigated and structural requirements for this novel transformation established. X-ray crystal structure analysis has established the relative configuration in these unusual heterocycles.

A Serendipitous Synthesis of the Novel Spiroacetal Core of Cynandione B

The novel spiroacetal core of cynandione B 2 is prepared from the isochromenone (S)-mellein 4 by treatment with methylmagnesium bromide. The expected lactol product undergoes spontaneous dimerization to form the spiroacetal system 8 as a single diastereoisomer, the stereochemistry of which is established from a single crystal X-ray structure analysis of a methanol solvate.