Recent Development of the Cyclopropanol Methodology for the Preparation of Methyl or Methylene Branched Natural Compounds

Bekish, Andrei V.; Prokhorevich, Konstantin N.; Pritytskaya, T. S.; Kulinkovich, O. G.

doi:10.1002/chin.200628244

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“…After reduction of the double bond in the allylic alcohol 108 and separation of the diastereomers, threo-alcohol 104 was obtained in 14% overall yield (Scheme 37). [76] Scheme 37 The C2ϪC3 ring cleavage of the mesylate of 1-substituted cyclopropanol 109 has also been used as one of the key steps in the synthesis of alkaloids (S)-1-methylenepyrrolizidine (110) and (Ϫ)-heliotridane (111). The cyclopropanation of (S)-proline derivative 112 with titanacyclopropane 1, followed by protecting-group manipulations, mesylation of (S)-pyrrolidinyl-substituted cyclopropanol 113, and treatment of sulfonate 109 with magnesium bromide in boiling chloroform led to allyl bromide 114 in good yield (Scheme 38).…”

Section: Syntheses By C2؊c3 Ring Cleavagementioning

confidence: 99%

Synthetic Applications of Intermolecular Cyclopropanation of Carboxylic Esters with Dialkoxytitanacyclopropane Reagents

Kulinkovich

2004

Eur J Org Chem

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The reaction of carboxylic esters with ethylmagnesium bromide in the presence of titanium(iv) isopropoxide, which leads to the formation of substituted cyclopropanols, was disclosed in the late 1980Јs. The key organometallic intermediates in this transformation are diisopropoxytitanacyclopropane species, which act as 1,2-dicarbanionic equivalents. The intermolecular titanium-mediated cyclopropanation of carboxylic esters and subsequent transformation of the threemembered ring provides a convenient and flexible approach

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Section: Syntheses By C2؊c3 Ring Cleavagementioning

confidence: 99%

Synthetic Applications of Intermolecular Cyclopropanation of Carboxylic Esters with Dialkoxytitanacyclopropane Reagents

Kulinkovich

2004

Eur J Org Chem

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“…A convenient synthetic approach to cyclopropanols having chiral substituents is based on titanium(IV) alkoxide-catalyzed reactions of natural hydroxy-and aminocarboxylic acid esters with alkylmagnesium halides [2,3]. The key step in the stereoselective syntheses of branched carbon skeletons of pheromones of the pine sawfly (Diprion pini L.) [4], alkaloid Heliotridane [5], and C 13 -C 21 fragments of Epothilones [6] was cleavage of the three-membered carbon ring in chiral cyclopropanols.…”

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Synthesis of (+)-disparlure from diethyl (−)-malate via opening and fragmentation of the three-membered ring in tertiary cyclopropanols

2009

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+)-Disparlure [(7R,8S)-7,8-epoxy-2-methyloctadecane, pheromone of the gypsy moth Lymantria dispar L.] was synthesized starting from diethyl (-)-malate via cyclopropanation of the ester groups, selective protection of the 1,3-diol functionality, and successive opening and fragmentation of the three-membered rings in the corresponding tertiary cyclopropanols as key stages.THP is tetrahydropyran-2-yl. Cyclopropanols and their derivatives undergo opening of the three-membered ring with formation of aldehydes, ketones, carboxylic acids, allyl halides, and some other compounds [1]. These transformations often occur under mild conditions and with high selectivity, so that substituted cyclopropanols attract considerable interest as intermediate products in organic synthesis. A convenient synthetic approach to cyclopropanols having chiral substituents is based on titanium(IV) alkoxide-catalyzed reactions of natural hydroxy-and aminocarboxylic acid esters with alkylmagnesium halides [2,3]. The key step in the stereoselective syntheses of branched carbon skeletons of pheromones of the pine sawfly (Diprion pini L.) [4], alkaloid Heliotridane [5], and C 13 -C 21 fragments of Epothilones [6] was cleavage of the three-membered carbon ring in chiral cyclopropanols.In the present work we used the cyclopropanol strategy to synthesize (+)-disparlure [I, (7R,8S)-7,8-epoxy-2-methyloctadecane] which is sex attractant of the gypsy moth Lymantria dispar L., The stereogenic structural fragment in molecule I is oxirane ring [7,8].The key intermediate was THP-protected bis-cyclopropanol II; it was synthesized by titanium(IV) isopropoxide-catalyzed reaction of ethylmagnesium bromide with O-tetrahydropyranyl derivative of diethyl (S)-malate (III) [6], and the necessary carbon chain was built up via alkylation of products of successive oxidative cleavage and fragmentation of the threemembered rings (Scheme 1; for other synthetic approaches to (+)-disparlure (I) based on natural hydroxy carboxylic acids, see [9]).Differentiation of the cyclopropanol fragments in molecule II is readily attained via its selective transformation into 1,3-dioxane derivative IV [6] as shown in Scheme 2. Treatment of acetonide IV with sodium hypobromite in water-diethyl ether gave vinyl ketone V whose concentration in the products was more than 90% (according to the 1 H NMR data). The use of other brominating agents, such as Br 2 -MeOH, N-bromosuc-

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Recent Development of the Cyclopropanol Methodology for the Preparation of Methyl or Methylene Branched Natural Compounds

Abstract: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Cited by 2 publications

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Synthetic Applications of Intermolecular Cyclopropanation of Carboxylic Esters with Dialkoxytitanacyclopropane Reagents

Synthetic Applications of Intermolecular Cyclopropanation of Carboxylic Esters with Dialkoxytitanacyclopropane Reagents

Synthesis of (+)-disparlure from diethyl (−)-malate via opening and fragmentation of the three-membered ring in tertiary cyclopropanols

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