Abstract:Synthetic studies towards the insect antifeedant jodrellin A l a are reported. This work delineates a synthetic strategy that affords a polycyclic epoxy diacetate model compound 2 which contains most of the structural features found in the natural product. This material was also shown to possess mild insect antifeedant activity against Spodoptera littoralis.
“…The behavior of 4 , 8 , 13 , and 16 under reduction or esterification reactions (Schemes and ) may be a consequence of the steric hindrance around the C-6α and C-19β positions, and this was corroborated by reactions such as the reduction of some neoclerodan-19,2α-olides. Although these derivatives have not been isolated from Scutellaria plants, synthetic analogues have been used as model intermediates in an approach to the total synthesis of 1 , , where diisobutylaluminum hydride (DIBAH) reduction of 19,2α-lactone derivatives without substituents at C-9 gives rise to the corresponding 19,2α-lactol group. For this reason, we treated the 19,2α-lactones 9 and 10 (Schemes and , respectively) with DIBAH in toluene.…”
Section: Resultsmentioning
confidence: 99%
“…The different biological action of 1 and 2 3 with respect to 4 , together with the uncertain knowledge available on the structure−activity relationships of these compounds, − , prompted us to undertake some chemical transformations of 4 in order to establish how the nature of the C-9 side chain and the functionality of the decalin part modulate feeding behavior of S. littoralis larvae. Furthermore, 4 is a suitable substrate for obtaining analogues of some intermediates involved in an approach to the total synthesis of 1 and 2 , , and knowledge of its chemical reactivity would be useful for the synthesis of these and other structurally related compounds. …”
Scutegalin B (4), a natural neoclerodane diterpenoid possessing phagostimulant activity against larvae of the lepidopteran Spodoptera littoralis, has been subjected to a series of chemical transformations obtaining several derivatives. The activity of some of these changes to antifeedant (10, 12, 16, and 17), although other derivatives are inactive (6, 7, and 15) or maintain phagostimulant activity (8 and 9) of the starting material (4). The most potent antifeedant was 16, which possesses 16,15-lactone and a (19S)-19, 2alpha-hemiacetal groups instead of the 16,15-lactol and (19R)-(19-O-tigloyl)19,2alpha-hemiacetal of the phagostimulant precursor 4. These and other structure-activity relationships are discussed, establishing that the biological action is strongly modulated by minimal structural variations.
“…The behavior of 4 , 8 , 13 , and 16 under reduction or esterification reactions (Schemes and ) may be a consequence of the steric hindrance around the C-6α and C-19β positions, and this was corroborated by reactions such as the reduction of some neoclerodan-19,2α-olides. Although these derivatives have not been isolated from Scutellaria plants, synthetic analogues have been used as model intermediates in an approach to the total synthesis of 1 , , where diisobutylaluminum hydride (DIBAH) reduction of 19,2α-lactone derivatives without substituents at C-9 gives rise to the corresponding 19,2α-lactol group. For this reason, we treated the 19,2α-lactones 9 and 10 (Schemes and , respectively) with DIBAH in toluene.…”
Section: Resultsmentioning
confidence: 99%
“…The different biological action of 1 and 2 3 with respect to 4 , together with the uncertain knowledge available on the structure−activity relationships of these compounds, − , prompted us to undertake some chemical transformations of 4 in order to establish how the nature of the C-9 side chain and the functionality of the decalin part modulate feeding behavior of S. littoralis larvae. Furthermore, 4 is a suitable substrate for obtaining analogues of some intermediates involved in an approach to the total synthesis of 1 and 2 , , and knowledge of its chemical reactivity would be useful for the synthesis of these and other structurally related compounds. …”
Scutegalin B (4), a natural neoclerodane diterpenoid possessing phagostimulant activity against larvae of the lepidopteran Spodoptera littoralis, has been subjected to a series of chemical transformations obtaining several derivatives. The activity of some of these changes to antifeedant (10, 12, 16, and 17), although other derivatives are inactive (6, 7, and 15) or maintain phagostimulant activity (8 and 9) of the starting material (4). The most potent antifeedant was 16, which possesses 16,15-lactone and a (19S)-19, 2alpha-hemiacetal groups instead of the 16,15-lactol and (19R)-(19-O-tigloyl)19,2alpha-hemiacetal of the phagostimulant precursor 4. These and other structure-activity relationships are discussed, establishing that the biological action is strongly modulated by minimal structural variations.
“…A large number of neoclerodane diterpenoids have been isolated from plants and microorganisms in the past few years. − These compounds have attracted interest because of their biological activities, especially as antifeedants against some economically important lepidopterous pests, , and as antifungal, antitumor, antimicrobial, and molluscicidal agents . The species of the genus Scutellaria (family Labiatae) are the source of the most potent neoclerodane insect antifeedants known so far. − In continuation of our studies on Scutellaria plants − we report here on the isolation and structure elucidation of nine new neoclerodane derivatives isolated from Scutellaria polyodon Juz.…”
Nine new neoclerodane diterpenoids, scupolins A−I,
have been isolated from an Me2CO extract
of the aerial parts of Scutellaria polyodon
(3−11), together with the known
neoclerodanes
jodrellin B (1) and scutecolumnin A (2).
Structures 3−11 were established by
spectroscopic
means and by comparison with closely related compounds.
“…This behavior makes them potentially useful as ecologically acceptable agents for pest control. Species of the genus Scutellaria (family Labiatae) are the source of the most potent neoclerodane insect antifeedants known so far, , and efforts toward the total synthesis of such compounds have been made recently. , …”
Treatment of scutebaicalin (1) with K-t-BuO yielded both the (13S)- and (13R)-8beta,13-epoxyclerodanes 2 and 3, respectively, by a Michael-type heterocyclization reaction. Identical treatment of scutalpin B (4) gave the corresponding (11E)-11-deacetoxy-12-dehydro derivative 5 by an elimination reaction. Side chains at C-9, such as those of compounds 1-5, are frequent among the neoclerodanes found in Scutellaria species, and these transformations suggest a plausible biogenetic pathway for these diterpenoids.
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.
