Mushrooms of the genus Retiboletus contain the retipolides A–D (1, 6–8), unusual 14‐membered spiromacrolides with a biphenyl ether linkage. The structures of these metabolites suggested a biogenetic sequence starting from retipolide E (16), which could furnish the unique 2(3H)‐oxepinone unit of retipolide C (7) via an oxidative enlargement of the 4‐hydroxyphenyl ring. A subsequent O/C‐acyl shift would then lead to the cyclopenta[c]pyran system of retipolide A (1). The proposed precursor 16 was synthesized and subsequently detected in the fungal extract in addition to the probable biosynthetic intermediates butyrolactone II (13), tyrosol (14), and secoretipolide E (15). The structural elucidation of retipolide A (1) was accomplished after transformation into a methoxyfulvene derivative 2a, and the absolute (R) configuration of 1 was assigned by a single‐crystal X‐ray analysis of the corresponding (S)‐sec‐butoxyfulvene analogue 2b. Some samples of R. retipes/ornatipes contained isoretipolide A (9), an isomer of 1 with a highly strained 12‐membered lactone ring incorporating two C,C‐coupled 4‐hydroxyphenyl units. A comparison of the CD spectrum of retipolide A (1) with those of the other retipolides and isoretipolide A (9) indicates that all of these macrolides possess R configuration. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The North American stalked puffball Calostoma cinnabarinum (Boletales) owes its red-orange colour to the heptaene pigment calostomal. Its structure has been determined by 1 H and 13 C NMR spectroscopy of the corresponding methyl ester as all-trans-16-oxohexadeca-2,4,6,8,10,12,14-heptaenoic acid (1). Neither pulvinic acids nor other typical Boletales pigments could be detected in this fungus. The structural relationship of 1 to other polyene pigments from fungi is discussed.

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The close genetic relationship of the mushrooms Retiboletus griseus and R. nigerrimus is supported by the occurrence of the orange-yellow retiboletic acid, resp. its methyl ester, in both species. The structures of these highly substituted pulvinic acid derivatives have been elucidated by spectroscopic investigations. R. nigerrimus also contains two N-protocatechuyl-L-phenylalaninol derivatives, nigerrimin A and B, the first reported occurrence of such compounds in nature. Their configuration was established by the synthesis of nigerrimin B.

The synthesis and accumulation of lychnose and isolychnose in leaves of Cerastium arvense during late fall and winter were shown to be controlled mainly by the temperature regime, while the photoperiodic regime had only a quantitative effect. Labelled lychnose and isolychnose were formed from [(14)C]raffinose in a cell-free enzyme preparation of leaves of Cerastium arvense in accordance with the equation: raffinose+raffinose →(iso-)lychnose+sucrose.