Studies on the total synthesis of (2R, 4'R, 8'R)-.alpha.-tocopherol (vitamin E). Stereospecific cyclizations leading to optically active chromans

Cohen, Noal; Lopresti, Rocco J.; Neukom, Christian

doi:10.1021/jo00325a004

Cited by 67 publications

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“…The latter, proceeding via an oxidation–reduction pathway of the hydroquinone, had been discovered and studied in depth already by Cohen et al. and does not lead to erosion of ee ,21 as confirmed by subsequent studies 10c. 22 Based on these two key steps, a retrosynthesis was designed allowing full freedom both in the substitution pattern (α, β, γ, δ)‐ of the aromatic ring and in the chain leading to tocopherols and tocotrienols.…”

Section: Methodsmentioning

confidence: 90%

Total Synthesis of (R,R,R)‐γ‐Tocopherol through Cu‐Catalyzed Asymmetric 1,2‐Addition

Harutyunyan

Minnaard

2014

Chemistry A European J

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Section: Methodsmentioning

confidence: 90%

Total Synthesis of (R,R,R)‐γ‐Tocopherol through Cu‐Catalyzed Asymmetric 1,2‐Addition

Harutyunyan

Minnaard

2014

Chemistry A European J

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“…funktionelle Gruppe), an die nach Ringschluss (-C) das entsprechende Kettenstuck unter Bildung von 1 angefugt wird. In spateren Arbeiten [3] wurde von unseren Kollegen in Nutley gezeigt, dass bei geeigneten Bedingungen auch auf der Hydrochinon-Stufe A (R2 = H) stereospezifische Cyclisierung eintritt, welche sich analog via einen Redox-Cyclus uber Spuren des sich leicht bildenden Chinons formulieren lasst.…”

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Totalsynthese von natülichem α‐Tocopherol. 5. Mitteilung. Asymmetrische Alkylierung und asymmetrische Epoxidierung als Methoden zur Einführung der (R)‐Konfiguration an C(2) des Chroman‐Systems

Hübscher

Barrier

1990

Helvetica Chimica Acta

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Based on the reductive, stereospecific ring closure of (2R,4R,8'R)-a -'Tocopherylquinone' or corresponding analogues with a short, functionalized side chain (B, Scheme 1 ) to 1 resp. the chroman system of 1 (C), two different approaches for the introduction of the required tertiary methyl-substituted alcohol structure in the side chain of the aromatic precursors (A, Scheme 1 ) were developed. The first approach uses asymmetric alkylation in three different versions featuring a ) diastereoselective steering with chiral auxiliaries I-IV (Scheme 2) attached as esters to a-keto acids, b ) intermediate transfer of chirality in an ester enolate (from 18, Scheme 4 ) derived from an optically active a -hydroxyacid, c) enantioselective alkylation of phytenal (20) and subsequent ring closure with chirality transfer (Schemes 5-7). The second approach is based on the asymmetric epoxidation of ~-metallylalcohol (Sharpless epoxidation), the corresponding epoxyalcohol being converted in situ to the (S)-or (R)-chlorodiol (S)-and (R)-29, respectively, for isolation (Schemes 8 and 9 ) . Nucleophilic epoxide opening with a (3R,7R)-3,7,11-trimethyldodecyl (Cy;*) and an ArCH, unit in appropriate sequence is used to assemble the C-framework of the target molecule via corresponding epoxide intermediates from either chlorodiol. Combined with the use of the methoxymethyl-ether function for protection of the hydroquinone system, the epoxide approach provides a short route to 1 (Scheme 10). Einleitung

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“…For background to the chemistry of trolox, its substituted amides and their applications as antioxidants and anti-inflamatory agents, see: Ross et al (1995); Scott et al (1974); Cort et al (1975); Cohen et al (1981); Walther et al (1991); Silver et al (1992); Netscher & Gautschi (1992); Van Ginkel et al (1992); Moulin et al (1998); Vajragupta et al (2000); Koufaki et al (2010). For the use of trolox as an intermediate for the synthesis of natural tocols such as vitamin E and -tocotrienol, see: Cohen et al (1979); Hyatt & Skelton (1997); Sakito & Suzokamo (1982); Sugai et al (1991).…”

Section: Related Literaturementioning

confidence: 99%

rac-6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxamide from synchrotron data

et al. 2011

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The crystal structure of the title water-soluble analogue of vitamin E, trolox amide, C14H19NO3, solved and refined against synchrotron diffraction data, contains two molecules in the asymmetric unit. In both molecules, the heterocyclic ring is in a half-chair conformation. The crystal packing features a herring-bone pattern generated by N—H...O hydrogen bonds between the hydroxy and amide groups. O—H...O hydrogen bonds also occur

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Studies on the total synthesis of (2R, 4'R, 8'R)-.alpha.-tocopherol (vitamin E). Stereospecific cyclizations leading to optically active chromans

Cited by 67 publications

References 0 publications

Total Synthesis of (R,R,R)‐γ‐Tocopherol through Cu‐Catalyzed Asymmetric 1,2‐Addition

Total Synthesis of (R,R,R)‐γ‐Tocopherol through Cu‐Catalyzed Asymmetric 1,2‐Addition

Totalsynthese von natülichem α‐Tocopherol. 5. Mitteilung. Asymmetrische Alkylierung und asymmetrische Epoxidierung als Methoden zur Einführung der (R)‐Konfiguration an C(2) des Chroman‐Systems

rac-6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxamide from synchrotron data

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