Org. Lett., 2013, 15 (17), pp 4320–4323  /    , DOI: 10.1021/ol401741z ,

Structures of Spiroindicumides A and B, Unprecedented Carbon Skeletal Spirolactones, and Determination of the Absolute Configuration by Vibrational Circular Dichroism Exciton Approach

Teigo Asai§*, Tohru Taniguchi§, Takashi Yamamoto, Kenji Monde and Yoshiteru Oshima*

Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-yama, Aoba-ku, Sendai 980-8578, Japan. Faculty of Advanc-ed Life Science, Frontier Research Center for Post-Genome Science and Technology, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan,

Spiroindicumides A (1) and B (2), novel spirolactone polyketides, were isolated from a filamentous fungus, Chaetomium indicum, cultivated in the presence of an HDAC inhibitor. Their structures including relative configurations were determined by spectroscopic analyses. Their absolute configurations were unambiguously assigned by the VCD exciton chirality method using only ca. 0.3 mg of each sample. This study presents the first application of the VCD exciton approach to novel natural products. A possible biosynthetic pathway of the new compounds was also proposed.