Synthetic Photochemistry. XXXIV. Synthetic Strategy of 5-8-5-Membered Tricyclic Higher Terpenoids Based on the Condensation of Two Optically-Active Iridoids, C10-Synthons Obtained from Photo-Cycloadduct of Methyl 2,4-Dioxopentanoate–Isoprene, and Its Application to a Synthesis of the Basic Carbon Skeleton of Fusicoccane
For the total synthesis of protopanaxadiol: (1) an optically active trienic epoxide was submitted to Ti‐(III)‐mediated radical cascade to afford an original 6/6/8/5 tetracyclic structure; (2) using a “ring‐by‐ring” synthesis gave access to 12‐epi‐protopanaxadiol. 20‐Hydroxydammar‐24‐ene‐3,12‐dione was also synthesized, which represents a formal synthesis of chikusetsusaponin‐LT8, isolated from Panax
Zinc or indium-mediated Barbier-type allylation of aldehydes with 3-bromomethyl-5H-furan-2-one in aqueous media: an efficient synthesis method for α-methylene-γ-butyrolactone
A zinc or indium-mediated Barbier-typeallylation of aldehydes with 3-bromomethyl-5H-furan-2-one in aqueous solvents was developed to provide an efficient route to α-methylene-γ-butyrolactone, which is synthetically very useful. The desired products were obtained in moderate to high yields in aqueous solvents. Excellent drs were achieved, among which the best diastereomeric ratios of products were
Asymmetric Synthesis and Structure Revision of Guignardone H and I: Development of a Chiral 1,3-Diketone Possessing <i>C</i><sub>2</sub> Symmetry
作者:Toyoharu Kobayashi、Iori Takizawa、Ayumu Shinobe、Yuichiro Kawamoto、Hideki Abe、Hisanaka Ito
DOI:10.1021/acs.orglett.9b00486
日期:2019.5.3
A novel chiral 1,3-diketone possessing C2symmetry was synthesized and utilized in the asymmetric synthesis of guignardone H and I by employing sequential condensation–6π-electrocyclization reactions with the novel 1,3-diketone followed by stereoselective hydrogenation as key steps. Although the synthetic compounds differed from natural guignardone H and I, we realized that the C4-epimers of the proposed
Total synthesis of albolic acid and ceroplastol II, 5–8–5-membered tricyclic insect sesterterpenoids, via a lactol-regulated silyloxy–Cope rearrangement
Optically active albolicacid and ceroplastolII, 5–8–5-memberedtricyclicsesterterpenoids, were stereoselectively synthesised from two C10 synthons (iridoids)via CrCl2-condensation, lactol-regulatedsilyloxy–Coperearrangement with a normally disfavoured boat transition geometry, TiCl2-ring closure, and C5-homologation.