Insect Feeding Inhibitors in Plants

Wada, Kojiro; Enomoto, Yuji; Munakata, Katsura

doi:10.1271/bbb1961.34.946

Cited by 11 publications

(6 citation statements)

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“…(À)-4-Hydroxyallohedycaryol (12) was obtained in a four-step sequence from (+)-1 by: 1) directed epoxidation with VO-(acac) 2 to give bis-epoxide 9 (77 % yield); 2) chemoselective reduction of the less-hindered epoxide to diol (+)-10 with LiAlH 4 ; 3) mesylation of the secondary alcohol providing (+)-11 (44 % over 2 steps); and 4) reductive elimination of the epoxy mesylate (+)-11 with lithium naphthalenide to afford (À)-12 in 65 % yield, together with recovered diol 10 in 23 % yield. Chemoselective hydrogenation of the isopropylidene side chain in (+)-1 using Crabtrees catalyst [17] afforded (+)-shiromool [18] (13) in good yield (65-84 %). It was found that the addition of 2,6-di-tert-butylpyridine was crucial to suppress side-product formation.…”

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“…Reaction of (+)-16 with WCl 6 and nBuLi [21] effected the removal of the 4,5-epoxide, followed by saponification of the acetate group with K 2 CO 3 /MeOH at 50 8C gave (À)-(1E,4E)-7aH-germacra-1(10),4-dien-6b-ol [22] (17) in 82 % yield over two steps. Oxidation of this natural product (À)-17 with IBX [23] gave (+)-acoragermacrone [24] (18) in 90% yield.…”

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“…Depending on the acid used with (AE)-12, trichotomol [25] (19) and its C10-epimer 20, d-cadinene-11-ol [26] (21) and g-cadinene- 11-ol (22) were obtained in varying ratios (Scheme 4). [27] The elemene skeleton can be accessed by a Cope rearrangement of acoragermacrone (18), giving a 21:4 mixture of shyobunone [28] (23) and its epimer 24, respectively. [24a] Alternatively, treating 18 with acid would afford selinane-type sesquiterpenes, acolamone [29] (25; 55 % yield) and isoacolamone (26; 23 % yield).…”

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Scalable, Enantioselective Synthesis of Germacrenes and Related Sesquiterpenes Inspired by Terpene Cyclase Phase Logic

et al. 2012

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Our laboratory has a longstanding interest in harvesting new chemical knowledge by learning from terpene biosynthesis. The straightforward construction of carbocyclic terpene backbones such as epoxy-germacrenol (1, Scheme 1A) in a low oxidation state (cyclase phase) followed by regio-, chemo-, and stereoselective oxidative modifications (oxidase phase) allow Nature to access a wide variety of related family members in a divergent manner. [1] Earlier this year, we reported our initial forays into the redox-economic synthesis of terpenes that resemble 1 by oligomerization of unfunctionalized isoprene (Scheme 1B, path a). [2] These studies ultimately led us to a new approach that utilizes the more advanced, yet readily available, C 15 building block farnesol (2, Scheme 1A) as a starting point. In this communication, a short, efficient, scalable, and enantioselective synthesis of 1 is described. Furthermore, we demonstrate how the key intermediate 1 can be processed not only to germacrane-type natural products by chemo-and stereoselective oxidations, but also to a variety of polycyclic sesquiterpene frameworks (like selinanes, guaianes, or elemenes) by acid-mediated transannular cyclization reactions.For the goal of establishing a scalable, divergent, and broadly applicable entry to a variety of related sesquiterpene families, the germacrenes were identified as strategic key intermediates due to the following reasons: 1) germacrenes constitute a large class of cyclic terpenes, many of which have been shown to exhibit promising bioactivities and, in addition, are of growing importance in the perfumery industry; 2) germacrenes are known to be a biosynthetic linchpin en route to various related terpene congeners; and 3) most importantly, many studies have demonstrated that germacrenes can be transformed into mono-, di-, and tricyclic sesquiterpene subclasses (e.g., the elemenes, cadinanes, eudesmanes, guaianes, and bourbonanes) with the "Achilles heel" of these approaches being the accessibility of germacrene precursors in quantity. [3] Despite the industrial interest in terpene natural products, most of the naturally occurring germacrenes and their congeners are not easily available in bulk quantities due to a variety of challenges associated with their synthesis and/or isolation: germacrenes featuring a * pbaran@scripps.edu. † These authors contributed equally to the paper.Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Although the total synthesis of sesquiterpenes has been an area of intense research efforts for decades, [4] there is still no reliable synthetic pathway to rapidly forge the ten-membered germacrene carbocycle. The most effective synthetic approaches published to date (Scheme 1B) suffer from serious drawbacks such as low overall yield, poor step economy, and/or are impractical to perform on scale In addition, these syntheses either yield racemic products or start from chiral-pool starting materials. Whereas Nature's cyclase enzymes c...

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Scalable, Enantioselective Synthesis of Germacrenes and Related Sesquiterpenes Inspired by Terpene Cyclase Phase Logic

et al. 2012

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“…Chemoselective hydrogenation of the isopropylidene side chain in (+)‐ 1 using Crabtree’s catalyst17 afforded (+)‐shiromool18 ( 13 ) in good yield (65–84 %). It was found that the addition of 2,6‐di‐ tert ‐butylpyridine was crucial to suppress side‐product formation.…”

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Cost‐effectiveness and lung cancer clinical trials

Reeves

Gadgeel

et al. 2003

Cancer

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Terpen‐Zyklasenphase: Eine skalierbare und enantioselektive divergente Synthese von Germacran‐artigen Sesquiterpenen wurde entwickelt. Die besonderen Merkmale dieser Arbeit sind: 1) der direkte Ringschluss eines Farnesolderivats zu einem 10‐gliedrigen Carbocyclus 1 und 2) anschließende präparative Manipulationen an 1, um Zugang zu verschiedenen bicyclischen Gerüsten wie Guaianen, Cadinanen, Selinanen und Elemenen zu erlangen.

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“…Chemoselective hydrogenation of the isopropylidene side chain in (+)- 1 using Crabtree’s catalyst [17] afforded (+)-shiromool [18] ( 13 ) in good yield (65-84%). It was found that the addition of 2,6-di- tert -butylpyridine was crucial to suppress side product formation.…”

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