“…Winkler and co-workers found that regiochemical control of the dioxenone photocycloaddition can be greatly improved using the intramolecular version of this reaction. 26 a tethered dioxenone 66 produced photoadduct 67 which on retro-aldol fragmentation provided six-, seven-and eightmembered ring esters 68 in excellent yield with exceedingly high ( > 50 : 1) levels of regiochemical control.…”
Section: Construction Of the Tricyclic Nucleus Of The Ingenane Diterp...mentioning
“…Winkler and co-workers found that regiochemical control of the dioxenone photocycloaddition can be greatly improved using the intramolecular version of this reaction. 26 a tethered dioxenone 66 produced photoadduct 67 which on retro-aldol fragmentation provided six-, seven-and eightmembered ring esters 68 in excellent yield with exceedingly high ( > 50 : 1) levels of regiochemical control.…”
Section: Construction Of the Tricyclic Nucleus Of The Ingenane Diterp...mentioning
“…1 Like that of ingenol (2), 2 the structure of eurifoloid A contains several synthetically challenging features that are found in numerous oxygenated terpenoid natural products. 3 These include a congested stereogenic cis-triol segment located on the upper face from C3 to C5, two adjacent quaternary stereocenters at C4 and C10, a functionalized cyclopropane, and an unusual and highly strained bicyclo [4.4.1]undecane ring system with trans-bridgehead, which is known as in/out intrabridgehead stereochemistry 4 of the BC ring system. Slightly different from ingenol, however, eurifoloid A contains an allcarbon quaternary stereocenter at C15, an angeloyloxy group at C5, and a tigloyloxy group at C17, which also pose considerable synthetic challenges.…”
Construction of the [5-7-7] tricyclic core of eurifoloid A, which contains an unusual and highly strained bicyclo[4.4.1]undecane ring system with trans-bridgehead, was attempted using a type II intramolecular [5 + 2] cycloaddition reaction and a Meinwald rearrangement reaction of the epoxide as key synthetic steps. The reported chemistry illustrates the feasibility of constructing the 8-epi-eurifoloid A framework by type II intramolecular [5 + 2] cycloaddition.
“…While we have shown that irradiation of 12 leads to the formation of 13 in good yield (Scheme ), irradiation of a 1:1 mixture of 10 and 12 led to the formation of none of the desired photoadduct 13 , a result that is consistent with quenching of the dioxenone triplet (of both 10 and 12 ) by the diene moiety present in 10 . 3 …”
[reaction: see text] Pauson-Khand cyclization of dioxanone photoadduct 21 leads to the formation of a single product in good yield. However, retro-aldol fragmentation of the pentacyclic cyclopentenone 22 leads to the formation of 23, with cis C-8/C-10 intrabridgehead stereochemistry, unlike the target compound ingenol 1, which possesses C-8/C-10 trans intrabridgehead stereochemistry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
