Naturstoffe mit Anti‐Bredt‐ und Brückenkopf‐Doppelbindung

Mak, Jeffrey Y. W.; Pouwer, Rebecca H.; Williams, Craig M.

doi:10.1002/ange.201400932

Cited by 24 publications

(10 citation statements)

References 273 publications

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“…Although, Bredt himself realized towards the end of his career that stable molecules could exist that violate his rule, [22] a philosophical perspective, based on the guidelines laid down by Fawcett, [9a] Prelog, [23] Wiseman, [9g] and Schleyer, [9h] could imply that natural products struggle to adhere to the rule. [24] Nevertheless, the bridging ring combination seen in EBC-219 (4) would be considered a stable system (e.g. Fawcett S value !…”

Section: Methodsmentioning

confidence: 99%

EBC‐219: A New Diterpene Skeleton, Crotinsulidane, from the Australian Rainforest Containing a Bridgehead Double Bond

Maslovskaya¹,

Savchenko²,

Krenske³

et al. 2014

Angew Chem Int Ed

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EBC-219 (4), isolated from Croton insularis (Baill), was established by spectroscopic and DFT methods as the first member of a new diterpene skeletal class, uniquely defined by the presence of a bicyclo[10.2.1] bridgehead olefin. The proposed biogenetic pathway to 4 from the co-isolated natural products EBC-131 (1), EBC-180 (2) and EBC-181 (3) is highly likely. EBC-180 (2) and EBC-181 (3) showed moderate to strong cytotoxic activity against various cancer cell lines.

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Section: Methodsmentioning

confidence: 99%

EBC‐219: A New Diterpene Skeleton, Crotinsulidane, from the Australian Rainforest Containing a Bridgehead Double Bond

Maslovskaya¹,

Savchenko²,

Krenske³

et al. 2014

Angew Chem Int Ed

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“…Tuscolid (1)a nd tuscorons Aa nd B( 2 and 3;F igure 1) [1] present structurally unique and stereochemically elaborate polyketides from Sorangium cellulosum,which hold aspecial place among myxobacterial natural products [2] and polyketides [3,4] as they originate from one joint biosynthesis.While tuscolid is characterized by a22-membered macrolactone ring with an uncommon chiral furan-3-one bearing ab ridgehead double bond, [5] thet uscorons are linear compounds with ar elated furan-3-one and polypropionate;h owever, the appending diene is connected to ad ifferent dihydropyran by an sp 2 -sp 3 fusion. While an interconversion has been tentatively proposed, [1] proof or details have remained elusive, [1] and further studies have been hampered by the lack of full stereochemical knowledge and amissing synthetic approach to resolve the supply issue of these scarce metabolites.Herein, we report the full stereochemical assignment of the tuscolid/tuscorons,the discovery of three novel tuscorons (4)(5)(6), and the total synthesis of tuscorons Da nd E, which unequivocally confirms our stereochemical proposal. In combination, these results provide detailed molecular insight into the unprecedented tuscolid/tuscoron rearrangement cascade.…”

mentioning

confidence: 99%

Stereochemical Determination of Tuscolid/Tuscorons and Total Synthesis of Tuscoron D and E: Insights into the Tuscolid/Tuscoron Rearrangement

et al. 2019

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The stereochemistry of the structurally unique myxobacterial polyketides tuscolid/tuscorons was determined by ac ombination of high-field NMR studies,m olecular modeling,a nd chemical derivatization and confirmed by am odular total synthesis of tuscorons Da nd E. Together with the discovery of three novel tuscorons,this study provides detailed insight into the chemically unprecedented tuscolid/ tuscoron rearrangement cascade.

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“…Ethylene can also convert 30 back into starting material 8 to avoid the formation of side products.I ntermediate 30 can then undergo intramolecular carbonyl olefination with the C4 carbonyl group to produce target product 27.I na ll cases, only desired product 27 was observed, andC 13 carbonyl olefination product 33 was not observed. This is probably due to the formation of ah ighly torsion-strained anti-Bredt bridge [20] double bond for 33.…”

Section: Retrosynthetic Analysismentioning

confidence: 99%

Divergent Total Syntheses of (−)‐Huperzine Q, (+)‐Lycopladine B, (+)‐Lycopladine C, and (−)‐4‐epi‐Lycopladine D

Hong

et al. 2017

Chemistry An Asian Journal

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We report herein our synthetic efforts towards the divergent syntheses of (À)-huperzine Q( 1), (+ +)-lycopladine B (2), (+ +)-lycopladine C( 3), and (À)-lycopladine D( 4). The 10-step total synthesis of (À)-huperzine Q( 1)a nd the first total syntheses of (+ +)-lycopladines B( 2)a nd C( 3)w ere accomplished through as eries of cascade reactions. Our approach involved aM ichael addition/aldol/intramolecular C-alkylation sequence to forge the 6/9 spirocycle ring, and this was followed by an ethylene-accelerated carbonyl-olefin metathesis to construct the common 6/5/9 ring system.F inally,l atestage enamine bromofunctionalization enabled us to access (À)-huperzine Q( 1), (+ +)-lycopladine B( 2), and (+ +)-lycopladine C( 3), and at andem C4-epimerization/retro-Claisenc ondensation furnished (À)-4-epi-lycopladine D( 63). IntroductionThe Lycopodium alkaloids are al arge family of complex natural products.N early 300 compounds have been isolated so far. [1] Owing to their intricate polycyclic skeletons andd iverse bioactivities, the total syntheses of these alkaloids have attracted broad attention from the synthetic community in recent years. [2] Among these compounds, (À)-huperzine Q( 1), (+ +)-lycopladine B( 2), (+ +)-lycopladine C( 3), and (À)-lycopladine D( 4) are four structurally relatedf awcettimine-type alkaloids (Figure 1). HuperzineQ (1)w as isolatedf rom Huperzia serrata by Zhu and co-workersi n2 002, and it possessesa nu nprecedented pentacyclic ring system and an aminal moiety. [3] The Takayama group [4] and the Zhao group [5] reported the total syntheseso f1 in 2011a nd 2015, respectively.( + +)-Lycopladine B (2), (+ +)-lycopladine C( 3), and (À)-lycopladine D( 4)w ere isolated from Lycopodium complanatum by Kobayashi and co-workers in 2006. [6] Whereasb oth (+ +)-lycopladines B( 2)a nd C( 3) contain au nique tetracyclic skeleton with ad ienamine moiety, (À)-lycopladine D( 4)c onsists of ap entacyclic core structure with ac arbinolamine lactone core. In 2013, Zhao and co-workers achievedt he first total synthesis of (À)-lycopladine D( 4). [7] Herein, we describe af ull account of our divergents yntheses of (À)-huperzine Q( 1), (+ +)-lycopladine B( 2), and (+ +)-lycopladine C( 3) [8] as wella so ur synthetic efforts towards (À)-lycopladine D( 4). Retrosynthetic analysisOur retrosynthetic analysisf or (À)-huperzine Q( 1), (+ +)-lycopladine B( 2), (+ +)-lycopladine C( 3), and (À)-lycopladine D( 4)i s outlined in Scheme 1. We envisioned that the aminal moietyi n 1 and the dienamine moieties in 2 and 3 could be derived from enamine intermediates 5 and 6,r espectively.W hereas both 5 and 6 could arise from 7 by aC 4-epimerization/cyclization sequence, diketone 7 could also potentially serve as ac ommon synthetic intermediate for the synthesis of (À)-lycopladine D( 4)t hrough aldehyde 10.T he cyclopentanone ring in 7 could be constructedf rom spirocyclic diketone 8,w hich could be readily accessed from enone 9 through our previously developed Michael addition/aldol/C-alkylation method.Initial synthe...

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Naturstoffe mit Anti‐Bredt‐ und Brückenkopf‐Doppelbindung

Cited by 24 publications

References 273 publications

EBC‐219: A New Diterpene Skeleton, Crotinsulidane, from the Australian Rainforest Containing a Bridgehead Double Bond

EBC‐219: A New Diterpene Skeleton, Crotinsulidane, from the Australian Rainforest Containing a Bridgehead Double Bond

Stereochemical Determination of Tuscolid/Tuscorons and Total Synthesis of Tuscoron D and E: Insights into the Tuscolid/Tuscoron Rearrangement

Divergent Total Syntheses of (−)‐Huperzine Q, (+)‐Lycopladine B, (+)‐Lycopladine C, and (−)‐4‐epi‐Lycopladine D

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