[structure: see text] The structures recently assigned to the mushroom metabolites boletunones A (1) and B (2) are revised to those of 15-methoxycyclocalopin A (5) and isocyclocalopin A (6), respectively.

Boletus calopus and closely related mushrooms of the Boletus section Calopodes are characterized by their bitter taste, which is caused mainly by O-acetylcyclocalopin A (6a), a member of a series of unique delta-lactone derivatives. Besides the simple lactone calopin (1b) and its O-acetyl derivative la, the more complex cyclocalopins 6-12 have been isolated and their structures elucidated. Cyclocalopin D (10a) is an unprecedented a-glucoside in which the sugar residue is bound to an enolic hydroxy group, The chemical conversion of 6b into la established the same stereochemistry for the calopin and cyclocalopin types of metabolites. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.

More like an industrial fungicide than a natural product is the title compound, which occurs as the potassium salt in the carrot truffle, Stephanospora caroticolor, and is responsible for its orange color (see picture). On injury of the fruit body, 1 is transformed into the toxic 2-chloro-4-nitrophenolate (2) by loss of the side chain.

The antifungal and cytostatic compound strobilurin M (1) is a new variant of the strobilurins produced by Mycena sp. 96097, a tropical basidiomycete. The same fungus was found to produce tetrachloropyrocatechol (3a) and tetrachloropyrocatechol methyl ether (3b), new natural products, which exhibit antifungal, antibacterial and cytotoxic activities.

The new antifungal strobilurins I (1) and K (19) are 3,4-dihydro-2H-benzo[b][1,4]dioxepin derivatives. Their structure and stereochemistry was determined by degradation to aldehyde 3. Both enantiomers of 3 were synthesised and the absolute configurations assigned by the high-field 1H NMR variant of Mosher's method. (S)-3 is identical with the compound derived from the natural products. In the course of these investigations the epoxide structures 15, 16 and 17 previously assigned to strobilurin D, hydroxystrobilurin D and 9-methoxystrobilurin K have to be changed in 18, 21 and 20, respectively. All these compounds possess the same benzodioxepin core structure and (S)-configuration as strobilurin I (1).

A new antifungal (E)-β-methoxyacrylate, noroudemansin A (1), was isolated from cultures of Pterula sp. 82168. Its biological activities were investigated and compared with oudemansin A. The structure was elucidated by spectroscopic methods. Three semisynthetic noroudemansin A derivatives were synthesized from the natural product.

Arthrosporone (1) and eight new triquinane-type sesquiterpenoids have been isolated from mycelial cultures of the agaric Macrecystidia cucumis. The cucumins A-D (2, 4-6) are highly unsaturated hirsutane derivatives, whereas the cucumins E-G (7-9) represent a new type of linear triquinanes. Cucumin H (10) is a new member of the ceratopicane group. The absolute configuration of cucumin F (8) was assigned by H-1-NMR analysis of the corresponding Mosher esters. Two further metabolites were identified as cycle(phenylalanylprolyl) (12) and cyclo(leucylprolyl) (13). Cucumin A (2) exhibits antibacterial and cytotoxic activities.

Root bark of Millettia griffoniana yielded two new O-geranylated isoflavones and a new 3-phenylcoumarin. Their structures were determined on the basis of spectral evidence as 4′-methoxy-7-O-[(E)-3-methyl-7-hydroxymethyl-2,6-octadienyl]isoflavone, 3′,4′-dihydroxy-7-O-[(E)-3,7-dimethyl-2,6-octadienyl]isoflavone and 4-hydroxy-5,6,7-trimethoxy-3-(3′,4′-methylenedioxy)phenylcoumarin.

5-Hydroxyaloin A and a new anthrone, named as microstigmin A, were isolated from the leaf exudate of Aloe microstigma. The structure of microstigmin A was determined by spectroscopic techniques as well as by conversion into 5-hydroxyaloin A.