title: Total syntheses of lyconadins A-C.
abstract: The total synthesis of the  Lycopodium  alkaloid lyconadin A was accomplished and it was applied to the total syntheses of the related congeners, lyconadins B and C. Lyconadin A has attracted attention as a challenging target for total synthesis due to the unprecedented pentacyclic skeleton. Our synthesis of lyconadin A features a facile construction of the highly fused tetracyclic skeleton through a combination of an aza-Prins reaction and an electrocyclic ring opening, followed by formation of a C-N bond. Transformation of the bromoalkene moiety of the tetracycle to a key enone intermediate was extensively investigated, and three methods via sulfide, oxime, or azide intermediates were established. A pyridone ring was constructed from the key enone intermediate to complete the synthesis of lyconadin A. A dihydropyridone ring could also be formed from the same enone intermediate, leading to a synthesis of lyconadin B. Establishment of the conditions for an electrocyclic ring opening without formation of the C-N bond resulted in completion of the total synthesis of lyconadin C.
authors: Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Takuya
authors: T
authors: Nishimura
authors: Aditya K
authors: AK
authors: Unni
authors: Satoshi
authors: S
authors: Yokoshima
authors: Tohru
authors: T
authors: Fukuyama
mesh_terms: D003500:Cyclization; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D011083:Polycyclic Compounds; C435307:lyconadin A; C514204:lyconadin B; C582718:lyconadin C