Convergent total synthesis of epolactaene: application of bridgehead oxiranyl anion strategy

Kuramochi, Kouji; Nagata, Seigo; Itaya, Hideyoshi; Takao, Ken Ichi; Kobayashi, Susumu

doi:10.1016/s0040-4039(99)01512-9

Cited by 39 publications

(18 citation statements)

References 23 publications

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“…[2][3][4][5][6][7][14][15][16][17] Our group accomplished the total synthesis of epolactaene by a convergent approach utilizing a fluoride anion catalyzed aldol-type reaction of a silyl epoxylactone 3 with a tetraene aldehyde 4 (Scheme 1). [14][15][16] We established large-scale preparation of enantiomerically pure 3, starting from (S)-ethyl lactate (Scheme 2). The Z-selective Horner-Emmons reaction of ethyl diphenylphosphonoacetate 18) with (S)-2-(tertbutyldimethylsilyloxy)propanal (5) 19) afforded a 20:1 mixture of Z and E-,-unsaturated esters 6.…”

Section: Synthesis Of Epolactaenementioning

confidence: 99%

Synthetic and Structure-Activity Relationship Studies on Bioactive Natural Products

Kuramochi

2013

Bioscience, Biotechnology, and Biochemistry

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Section: Synthesis Of Epolactaenementioning

confidence: 99%

Synthetic and Structure-Activity Relationship Studies on Bioactive Natural Products

Kuramochi

2013

Bioscience, Biotechnology, and Biochemistry

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“…These α-cyano lithiooxiranes have been engaged in 1,2-metallate rearrangements with zirconium compounds. By contrast, deprotonation of the epoxylactone 194 was achieved 319 TMSCl as internal electrophile. Otherwise, only dimerization was observed.…”

Section: Carbalkoxy-stabilized Lithiooxiranes and Related Compoundsmentioning

confidence: 99%

Reactivity of Oxiranes with Organolithium Reagents

Chemla

Vrancken

2009

Patai's Chemistry of Functional Groups

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“…Halides, most notably iodides such as 11 [16] (Scheme 9), and stannanes such as 13 [17] (Scheme 10) are tolerated well. These examples also illustrate that double bonds, in particular trisubstituted double bonds, do not undergo E/Z-isomerization in the course of the reaction.…”

Section: Scheme 6 Oxidation Step In the Total Synthesis Of (+)-Cyclopmentioning

confidence: 99%

Sodium Chlorite-Hydrogen Peroxide — A Mild and Selective Reagent for the Oxidation of Aldehydes to Carboxylic Acids

Raach¹,

Reiser²

2000

J. prakt. Chem.

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605The oxidation of aldehydes to carboxylic acids is in principle easy to achieve. A number of reagents are known for this transformation [1], nevertheless, only few selective methods that reliably work with all types of aldehydes and also tolerate a broad range of other functional groups are available. Sodium chlorite had been discovered [2] to be effective for the conversion of aldehydes to carboxylic acids under mild conditions (equation 1), but side reactions could not always be avoided. RCHO + HClO 2 → RCOOH + HOCl(1) Problems arise due to the formation of hypochlorite, which is a more powerful oxidation reagent than chlorite and moreover, is able to oxidize the latter to chlorine dioxide. Consequently, to circumvent the complications described scavengers for hypochlorite were tested such as 2-methyl-2-butene [3], resorcinol [4] or sulfamic acids [5]. All these additives, although effective, display certain disadvantages. Eventually, hydrogen peroxide was introduced as trapping reagent by Dalcanale and Montanari [6], which subsequently had been adopted for many oxidations of aldehydes with sodium chlorite.A distinct advantage of the combination of hydrogen peroxide-sodium chlorite is the exclusive formation of inorganic by-products in the course of the oxidation. From an operational point of view the formation of oxygen, as depicted in equation 2, is a good indication for the progress of the reaction. Best reaction conditions have been achieved in aqueous acetonitrile buffered with NaH 2 PO 4 at pH 4.3, while with very sensitive substrates up to 5 equivalents of hydrogen peroxide at pH 2 are employed in order to accelerate the reduction of HOCl. Reactions are carried out at room temp. or even at 0 °C.Following these procedures, aliphatic, α,β-unsaturated and aromatic aldehydes can be converted to carboxylic acids with very few limitations. Moreover, this protocol has been proved so versatile that it had become also the method of choice as the final transformation for the two step conversion of alcohols to carboxylic acids which is initiated by the selective formation of aldehydes by periodinane [7], MnO 2 [8] or Swern-oxidation [9].Carboxylic acids are readily obtained from the corresponding aromatic and hetero aromatic aldehydes (Scheme 1 and 2). Electron rich substrates can be troublesome, giving rise to side products formed by chlorination or oxidation of the aromatic ring. The substitution of H 2 O 2 by DMSO as trapping reagent has been demonstrated to be a viable alternative to circumvent such problems. Oxidation of an electron donor has also to be considered as a possible obstacle. Unprotected aromatic amines and pyrrols are not tolerated as substrates resulting in no defined products, while thioethers are oxidized to sulfoxides and sulfones [6]. Ar H O Ar OH O R Me MeS S Me O S O O Me Ar = + R = H (93 %) R = OMe (86 %) R = OH (7 %) R = NH 2 (tars) R = NHCOMe (98 %) OH MeO (91 %) (chlorinated compounds only) 75 % 25 % Scheme 2 Oxidation of hetero aromatic aldehydes α,β-Unsaturated aldehydes can also be...

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Convergent total synthesis of epolactaene: application of bridgehead oxiranyl anion strategy

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 39 publications

References 23 publications

Synthetic and Structure-Activity Relationship Studies on Bioactive Natural Products

Synthetic and Structure-Activity Relationship Studies on Bioactive Natural Products

Reactivity of Oxiranes with Organolithium Reagents

Sodium Chlorite-Hydrogen Peroxide — A Mild and Selective Reagent for the Oxidation of Aldehydes to Carboxylic Acids

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