Chiral cruciferous phytoalexins: Preparation, absolute configuration, and biological activity

• Published in: Bioorganic & medicinal chemistry Vol. 13; no. 17; pp. 5206 - 5212
• Main Authors: Monde, Kenji, Taniguchi, Tohru, Miura, Nobuaki, Kutschy, Peter, Čurillová, Zuzana, Pilátová, Martina, Mojžiš, Ján
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2005
• Subjects: Antiproliferative activity; Brassicaceae - chemistry; Cell Line, Tumor; Chiral HPLC; Chromatography, High Pressure Liquid; Circular Dichroism; Drug Screening Assays, Antitumor; ECD; Humans; Molecular Structure; Optics and Photonics; Phytoalexins; Plant Extracts - chemistry; Plant Extracts - pharmacology; Sesquiterpenes; Spirocyclization; Stereoisomerism; Terpenes; VCD; Phytoalexins; Chiral HPLC; Spirocyclization; Antiproliferative activity; VCD; ECD
• ISSN: 0968-0896; 1464-3391
• DOI: 10.1016/j.bmc.2005.06.001

[Display omitted] Synthesized by an efficient one-pot spirocyclization method, two chiral cruciferous phytoalexins, 1-methoxyspirobrassinin ( 2) and 1-methoxyspirobrassinol methyl ether ( 4a), were prepared through optical resolution using the chiral HPLC method of corresponding racemates. The absolute configuration of natural (+)- 2 was elucidated as R by using the direct comparison of ECD and VCD spectra with those of known ( S)-(−)-spirobrassinin ( 1). Another chiral phytoalexin, (−)- 4a, had its absolute configuration 2 R,3 R elucidated through the comparison of observed and calculated VCD. Interestingly, the absolute configurations of natural ( S)-(−)-spirobrassinin ( 1) and ( R)-(+)-1-methoxyspirobrassinin ( 2) were opposite of each other, even though their structures are almost similar, with the exception of an N-methoxy group. A significant difference in the antiproliferative activity between (2 R,3 R)-(−) and (2 S,3 S)-(+)- 4a was observed.