An Exceptionally Short and Simple Enantioselective Total Synthesis of Pentacyclic Triterpenes of the β-Amyrin Family

Huang, Alan X.; Xiong, Zhaoming; Corey, E. J.

doi:10.1021/ja992411p

Cited by 82 publications

(31 citation statements)

References 13 publications

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“…[1,2] The allylic alcohol was synthesized according to a similar procedure. [3] To a solution of DMF (7.4 mL, 95.0 mmol, 3.0 equiv) in CHCl 3 (25 mL) was added PBr 3 (8.1 mL, 86.0 mmol, 2.7 equiv) dropwise at 0 °C. The mixture was stirred at 70 °C for 30 min, then cyclohexanone (8) (3.3 mL, 32.0 mmol, 1.0 equiv) was added dropwise over 30 min.…”

Section: Methodsmentioning

confidence: 99%

“…9 (1.01 g, 5.29 mmol, 1.0 equiv) in toluene (21 mL) was added 4-methoxybenzyl 2,2,2-trichloroacetimidate [4] (2.24 g, 7.93 mmol, 1.5 equiv) and La(OTf) 3 (164 mg, 0.28 mmol, 0.053 equiv). The mixture was stirred at 50 °C for 12 h. The reaction mixture was concentrated, and the crude residue was purified by flash chromatography (hexanes 99:1 98:2 hexanes/EtOAc) to give 10 as a colorless oil (1.60 g, 98% yield).…”

Section: -(((2-bromocyclohex-1-enyl)methoxy)methyl)-4-methoxybenzenementioning

confidence: 99%

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Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis

Baumgartner

Liu

et al. 2010

Org. Biomol. Chem.

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Section: Methodsmentioning

confidence: 99%

Section: -(((2-bromocyclohex-1-enyl)methoxy)methyl)-4-methoxybenzenementioning

confidence: 99%

Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis

Baumgartner

Liu

et al. 2010

Org. Biomol. Chem.

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“…Indeed, their importance has increased over the past three decades due to the development of new routes to polyolefinic precursors, methods of asymmetric synthesis, and different conditions for the key cyclization step [133][134][135][136][137][138][139].…”

Section: Syntheses By Biomimetic Approachesmentioning

confidence: 99%

Author Index To Volume 2

2007

CBC

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In this review we cover the structures, occurrence, biological activities and synthesis of all the spongianes and rearranged spongianes since their discovery in 1974. We have given special attention to structure revisions and biological properties of these polycyclic terpenoids of exclusive marine origin. However, an important part of the review describes the synthetic efforts in the field. Thus, this part has been subdivided into syntheses from other natural products, syntheses by biomimetic approaches and other approaches including enantioselective total syntheses. Marine terpenoids are typical constituents of the secondary metabolite composition of marine flora and fauna. These isoprenoid-derived compounds are common in almost all marine phyla and show a wide range of novel structures. Although most of them are also present in terrestrial organisms, the occurrence of a few skeletons is restricted to certain marine species. In this review we focus our attention to diterpenoids characterized by polycyclic structures having either the spongiane (I, C 20 ) (Fig. 1) carbon framework or several degraded or rearranged spongiane-derived skeletons.Spongiane diterpenoids are bioactive natural products isolated exclusively from sponges and marine shell-less mollusks (nudibranchs), which are believed to be able of sequestering the spongian-derived metabolites from the sponges, soft corals, hydroids and other sessile marine invertebrates on which they feed. Most of these compounds play a key role as eco-physiological mediators and are of interest for potential applications as therapeutic agents.Spongianes having the characteristic carbon skeleton I (Fig. 1) have been reviewed up to 1990 and listed in the Dictionary of terpenoids [1]. During the last two decades, many new members of this family of natural products have been isolated and described in specific reviews on naturally occurring diterpenoids by Professor Hanson [2], and the excellent reviewing work on marine natural products by Professor Faulkner [3,4], now continued by the team of Professor Blunt [5,6], all of which have mainly covered the isolation and structural aspects of spongianes. A recent review on the chemistry of diterpenes isolated from marine opisthobranchs, has also included articles on isolation and structure determination of spongianes up to 1999 [7]. The latter also covered some synthetic studies of this class of substances. To the best of our knowledge, there is only one more report dealing with the initial studies towards the synthesis of spongianes [8]. We now provide full coverage of recent advances in the field including a comprehensive description of the synthetic approaches and syntheses reported in the literature on spongianes up to march 2006. STRUCTURE, OCCURRENCE AND BIOLOGICAL ACTIVITYThe semisystematic naming of this family of diterpenoids was introduced in 1979 following the isolation of the first members of

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“…Enantioenriched epoxides obtained with this method were used by Corey in the total synthesis of several isoprenoids, like scalarenedial (16) [28], dammarendiol II [41], serratenediol [42], tetracyclic polyprenoids of sedimentary origin [43], and pentacyclic triterpenes of theamyrin family [44].…”

Section: Modifications Of Entities Involved In the Cyclization Mechanismmentioning

confidence: 99%

Biomimetic Cyclizations of Functionalized Isoprenoid Polyenes: A Cornucopia of Synthetic Opportunities

Brunoldi¹,

Luparia²,

Porta³

et al. 2006

COC

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The synthetic aspects of biomimetic cyclizations of isoprenoid polyenes, simulating one of the key steps in the biosynthesis of terpenoids in living organisms, have been reviewed, with emphasis on transformations carried out on carbocyclic systems. These reactions are made possible by a clever choice of initiating and terminating units of cyclization, and by introducing suitable functional groups on the acyclic precursor which can be manipulated after cyclization. Complex functionalized polycyclic structures are thus assembled with an efficiency paralleling or even superior that of purely biochemical processes. In particular, synthetic strategies towards alkyl and hydroxyl-substituted compounds have been examined in detail. The last part of the review has been dedicated to a thorough illustration of carbenium ion initiated polyene cyclizations, with their synthetic applications and a discussion of the different mechanisms proposed.

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An Exceptionally Short and Simple Enantioselective Total Synthesis of Pentacyclic Triterpenes of the β-Amyrin Family

Cited by 82 publications

References 13 publications

Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis

Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis

Author Index To Volume 2

Biomimetic Cyclizations of Functionalized Isoprenoid Polyenes: A Cornucopia of Synthetic Opportunities

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