Roseic Acid and Roseolactones A and B, Furan‐Cucurbitane Triterpenes from Russula aurora and R. minutula (Basidiomycota). Issue 25 (18th July 2014)

• Record Type: Journal Article
• Authors: Clericuzio, Marco; Vidari, Giovanni; Cassino, Claudio; Legnani, Laura; Toma, Lucio
• Is Part Of: European journal of organic chemistry. Issue 25(2014)
• Page Start: 5462
• Page End: 5468
• Publication Date: 2014-07-18
• Subjects: Natural products -- Terpenoids -- Structure elucidation -- Conformation analysis -- Ab initio calculations; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201402208
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract: Three new seco‐cucurbitane triterpenes, viz. roseic acid (1 ) and roseolactones A (2 ) and B (3 ), all bearing a furan moiety condensed to the B‐ring, were isolated from Russula aurora and R. minutula . Their structures were elucidated using 1D and 2D NMR spectroscopy, and ESI HRMS. Compounds2 and3 were found to be epimers at C‐23. A detailed ab initio theoretical investigation was carried out to assess their relative stereochemistries. The conformations and NMR spectra of the two isomers were calculated, and the results were compared to the experimental data. The new compounds show a bright pink reaction with sulfo‐vanillin at room temperature, and they are therefore responsible for the systematically significant reaction performed by mycologists on R. aurora and R. minutula fruiting bodies. A mixture of compounds2 and3 was found to be weakly active against HepG2, WISH, and CAKI‐1 human tumour cells. Abstract : The fruiting bodies of the gilled fungi Russula aurora and R. minutula give a coral pink colour with sulfo‐vanillin (SV). We found that they synthesize a few triterpenes, belonging to the seco‐cucurbitane series, a rare skeleton type. These compounds show the above reaction with SV on TLC. Assignment of the configurations of2 and3 required a thorough ab initio theoretical investigation.