Teigo Asai†*, Dan Luo†, Kouwa Yamashita‡ and Yoshiteru Oshima†*
†Graduate School of Pharmaceutical Sciences, ‡Tohoku University, Aoba-yama, Aoba-ku, Sendai 980-8578, Japan
‡Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan
Novel polyketides, citreoviripyrone A (1) and B (2), known citreomontanin (3), and (−)-citreoviridin (4) were isolated from the mycelium of the endophytic fungus. The endophytic fungus, which belongs to the genus Penicillium, was separated from surface-sterilized healthy leaves of Catharanthus roseus. The structures of 1 and 2 were determined on the basis of NMR data, and 1 was characterized as an α-pyrone polyketide featuring bicyclo[4.2.0]octadiene. The biomimetic synthesis of 1 and 2 from 3 elucidated a plausible biosynthetic pathway. Both Zn(II)-type and NAD+-dependent histone deacetylase inhibitors significantly enhanced the production of 1 and 3.