Retipolides - Unusual Spiromacrolactones from the Mushrooms Retiboletus retipes and R. ornatipes

• Published in: European Journal of Organic Chemistry Vol. 2007; no. 33; pp. 5560 - 5572
• Main Authors: Justus, Karl, Herrmann, Rupert, Klamann, Jörg-Dieter, Gruber, Gertraud, Hellwig, Veronika, Ingerl, Andrea, Polborn, Kurt, Steffan, Bert, Steglich, Wolfgang
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.11.2007; WILEY‐VCH Verlag; Wiley
• Subjects: Basidiomycetes; Chemistry; Chemistry, Organic; Macrolactones; Natural products; Oxepinones; Physical Sciences; Retipolides; Science & Technology; Spiro compounds; basidiomycetes; natural products; macrolactones; METABOLIC PRODUCTS; PIPERAZINOMYCIN; ASPERGILLUS-TERREUS; retipolides; spiro compounds; oxepinones; DISTANNOXANE; DERIVATIVES; TRANSESTERIFICATION
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.200700579

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)