First total synthesis of (±)-oxerine

Aoyagi, Yutaka; Inariyama, Taku; Arai, Y.; Tsuchida, Sanae; Matuda, Yasuko; Kobayashi, Hiroyuki; Ohta, Akihiro; Kurihara, Teruo; Fujihira, Sumiyo

doi:10.1016/s0040-4020(01)85672-6

Cited by 28 publications

(11 citation statements)

References 14 publications

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“…The structure of plectrodorine was quite unprecedented, which slowed down the synthetic studies, while the first total synthesis of the slightly less complex (±)-oxerine was completed by Ohta and co-workers in 1994. 55 In 2006, Ohba and co-workers reported the total syntheses of (-)-plectrodorine and (+)-oxerine with an approach to the cyclopenta-[c]pyridine core of these target molecules that employed the IMDA of oxazole-olefins (Scheme 18). 56…”

Section: Syntheses Of (-)-Plectrodorine and (+)-Oxerinementioning

confidence: 99%

Intramolecular Diels–Alder Reactions of Oxazoles, Imidazoles, and Thiazoles

Nguyen

Wipf

2020

Synthesis

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The development of the intramolecular Diels–Alder cycloaddition of azole heterocycles, i.e. oxazoles (IMDAO), imidazoles (IMDAI), and thiazoles (IMDAT), has had a significant impact on the efficient preparation of heterocyclic intermediates and natural products. In particular, highly efficient and versatile IMDAO reactions have been utilized as a key step in several synthetic schemes to provide alkaloids and terpenoid target molecules. More limited studies have been performed on IMDAI and IMDAT cycloadditions. Some drawbacks, such as the occasionally challenging preparation of IMDA precursors, are also highlighted in this review. Perspectives are provided on how IMDAI and IMDAT transformations can be further expanded for target-directed syntheses.1 Introduction2 Oxazoles2.1 IMDAO Approaches to Furanosesquiterpenes and Furanosteroids2.1.1 Syntheses of Highly Oxygenated Sesquiterpenes2.1.2 Syntheses of (±)-Gnididione and (±)-Isognididione2.1.3 Synthesis of (±)-Stemoamide2.1.4 Synthesis of (±)-Paniculide A2.1.5 Syntheses of (+)- and (–)-Norsecurinine2.1.6 Synthesis of Evodone2.1.7 Syntheses of (±)-Ligularone and (±)-Petasalbine2.1.8 Syntheses of Imerubrine, Isoimerubrine, and Grandirubrine2.1.9 Syntheses of Furanosteroids2.1.10 Syntheses of Substituted Indolines and Tetrahydroquinolines2.2 IMDAO Approaches to Pyridines: the Kondrat’eva Reaction2.2.1 Syntheses of Suaveoline and Norsuaveoline2.2.2 Synthesis of Eupolauramine2.2.3 Syntheses of (–)-Plectrodorine and (+)-Oxerine2.2.4 Synthesis of Amphimedine2.2.5 Synthetic Approach to the Western Segment of Haplophytine2.2.6 Synthesis of Marinoquinoline A2.2.6.1 IMDAO Approach to Marinoquinoline A2.2.6.2 Scope of Allenyl IMDAO Cycloaddition2.3 Lewis Acid Catalysis in IMDAO Reactions2.3.1 Effects of Europium Catalysts on IMDAO Reactions2.3.2 Effects of Copper Catalysts on IMDAO Reactions3 Imidazoles 4 Thiazoles4.1 Syntheses of Menthane and Eremophilane4.2 Further Comments on the Intramolecular Cycloadditions of Thiocarbonyl Ylides5 Conclusions and Outlook

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Section: Syntheses Of (-)-Plectrodorine and (+)-Oxerinementioning

confidence: 99%

Intramolecular Diels–Alder Reactions of Oxazoles, Imidazoles, and Thiazoles

Nguyen

Wipf

2020

Synthesis

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“…[52][53][54][55][56][57][58][59][60] The reaction of 2,6-dimethylpyridine N-oxide hydrochloride (40) with phosphorus oxychloride in the presence of potassium carbonate led to the formation a mixture of 41 and 42. Treatment of the mixture with triethylamine converted the more reactive 41 to quaternary salt 43 which upon treatment with water gave 42 in (61%) yield.…”

Section: Reactions Of Pyridine N-oxides 21 Deoxygenationmentioning

confidence: 99%

Recent trends in the chemistry of pyridine N-oxide

Youssif¹

2001

Arkivoc

112

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This review describes the synthesis and reactions of pyridine N-oxides within the last ten years. The first part surveys the different synthetic methods which include ring transformation, classical oxidations using peracids, the use of metalloorganic oxidizing agents and cycloaddition reactions. The second part surveys the reactions of pyridine N-oxides including the deoxygenation, nucleophilic reaction and cycloaddition to N-O bond.

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“…26) We chose (5R,7S)-3 as the second target to demonstrate the versatility of our synthetic strategy, although racemic synthesis of oxerine has been accomplished by several research groups. [27][28][29][30] A brief account of the results reported here has been published in a preliminary form. 31) For the construction of the cyclopenta[c]pyridine skeleton via the intramolecular Diels-Alder reaction of oxazoles, we planned to employ the oxazole-olefin 4.…”

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confidence: 99%

Use of the Oxazole-Olefin Diels-Alder Reaction in the Total Synthesis of the Monoterpene Alkaloids (-)-Plectrodorine and (+)-Oxerine

2006

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Oxazoles have been shown to behave as dependable azadiene components in Diels-Alder reactions.1) Since Kondrat'eva reported the first example of a Diels-Alder reaction of an oxazole with an olefin to produce a pyridine in 1957, 2,3) this methodology has become a valuable tool for the preparation of highly substituted pyridines, such as pyridoxine and its analogues. Despite an early recognition of the practical value of the oxazole-olefin Diels-Alder reaction, there are few reports applying this cycloaddition intramolecularly to the synthesis of pyridine-containing natural products. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In the present study, we sought to explore the feasibility of intramolecular oxazole-olefin Diels-Alder reaction for an efficient construction of two monoterpene alkaloids possessing the cyclopenta[c]pyridine ring system. [20][21][22][23] Plectrodorine (1), selected as the first target for the monoterpene alkaloids, was isolated as a racemate together with isoplectrodorine (2) from the aerial parts of Plectronia odorata (Rubiaceae) by Koch and co-workers.24) The structure and relative stereochemistry of 1 were elucidated through a combination of spectral analysis and chemical transformation. The Koch group 25) then described the isolation of oxerine from the aerial parts of Oxera morieri (Verbenaceae) and proposed its absolute stereochemistry to be (5R,7S)-3 by partial synthesis of oxerine from harpagide of known absolute configuration. 26) We chose (5R,7S)-3 as the second target to demonstrate the versatility of our synthetic strategy, although racemic synthesis of oxerine has been accomplished by several research groups. [27][28][29][30] A brief account of the results reported here has been published in a preliminary form. 31)For the construction of the cyclopenta[c]pyridine skeleton via the intramolecular Diels-Alder reaction of oxazoles, we planned to employ the oxazole-olefin 4. The introduction of suitable olefinic dienophiles to the oxazole aldehyde 5 would provide 4, whereas the oxazole ring of 5 was envisaged to arise from the addition of a-lithiated methyl isocyanide to the g-butyrolactone 6 according to the procedure of Jacobi. 32,33) The requisite g-butyrolactone 6 was readily obtained from Seebach's dioxolanone 7. 34,35) Thus, reduction of 7 with BH 3 · Me 2 S followed by alkaline hydrolysis and acid-promoted lactone formation afforded 6 in 73% yield. The absolute configuration of 6 was further substantiated by the identity of specific rotation of the benzoate 8, derived from 6, with the data reported in the literature. 36) After protection of the tertiary hydroxy group in 6 with tert-butyldimethylsilyl triflate (TBDMSOTf) to afford the lactone 9, the formation of an oxazole ring was carried out by treatment of 9 with 2.5 eq of a-lithiated methyl isocyanide in THF at Ϫ78°C for 3 h followed by addition of AcOH, a slight modification of the Jacobi method, 32,33) giving the alcohol 10 in 66% yield. With a view to introducing an olefinic dienophile, the alcohol 10 was...

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First total synthesis of (±)-oxerine

Cited by 28 publications

References 14 publications

Intramolecular Diels–Alder Reactions of Oxazoles, Imidazoles, and Thiazoles

Intramolecular Diels–Alder Reactions of Oxazoles, Imidazoles, and Thiazoles

Recent trends in the chemistry of pyridine N-oxide

Use of the Oxazole-Olefin Diels-Alder Reaction in the Total Synthesis of the Monoterpene Alkaloids (-)-Plectrodorine and (+)-Oxerine

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