Stereoselective synthesis of (+)-secosyrin 1

A Chiron approach for the synthesis of (+)-secosyrin 1 from d-mannitol has been described. The key steps are a stereoselective Wittig reaction and an intramolecular Michael addition on the disubstituted butenolide, leading to a highly stereoselective formation of the tertiary chiral centre of (+)-secosyrin 1.     

Simple route to 3-(2-indolyl)-1-propanones via a furan recyclization reaction

A simple route to 1-R-3-(2-indolyl)-1-propanones has been elaborated based on recyclization of 2-(2-aminobenzyl)furan derivatives. Being a modification of the Reissert indole synthesis, our approach employs the furan ring as a source of carbonyl function. This approach is general and allows varying of substituents in aromatic ring as well as in 3-position of indole nucleus.     

Synthesis of 1-(2-Ethoxyethyl)-4-hydroxy-4-[2-(1-hydroxycyclohexyl)ethynyl]piperidine and Heterocyclization under the Conditions of Hydration

The reaction of 1-(2-ethoxyethyl)piperidin-4-one with ethynylcyclohexanol led to the synthesis of a glycol, the hydration of which gave a mixture of spirocyclic compounds with a carbonyl group at various positions in the furan ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1649–1652, November, 2005.     

Total syntheses of (+/-)-montanin A and (+/-)-teuscorolide

The first total syntheses of (+/-)-montanin A and (+/-)-teuscorolide have been achieved from an advanced precursor previously developed via a Diels-Alder strategy; in the synthetic sequence, the synthesis of montanin A was first accomplished in 8 steps, from which teuscorolide was readily achieved in 2 steps by using a novel furan oxidative cyclization-retro-cyclization process as a key operation.     

Synthesis of (±)-(E,E)-2,7-Dimethylocta-2,4-dienedioic Acid

(±-(2E,4E)-2,7-Dimethylocta-2,4-dienedioic acid ( 1 ) was synthesized efficiently from furan, employing a rhodium-carbenoid-induced furan-ring-unravelling reaction followed by an unusual NaBH₄/CeCl₃⋅7 H₂O reduction, Wittig-Horner olefination, and diester hydrolysis.     

Palladium(II) chloride catalyzes the cross-coupling reaction of 2,5-bis-(butyltelluro)-furan and 1-alkynes

Palladium(II) chloride catalyzed the cross-coupling reaction of 2,5-bis-(butyltelluro) furan and terminal alkynes yielding both symmetrically and unsymmetrically substituted 2,5-bis-acetylenic furan derivatives. The methodology represents a general and efficient protocol for carrying out the synthesis of furan derivatives with potential biological activities.     

Enantioselective total synthesis of (-)-laurenditerpenol

A highly convergent total synthesis of (-)-laurenditerpenol has been accomplished through an organolithium to aldehyde nucleophilic addition. Preparation of the prerequisite key intermediates in optically pure form was based on an improved, short, and efficient synthesis of "wine lactone" from (S)-limonene and Corey's catalytic enantioselective Diels-Alder reaction of 2,5-dimethyl furan with diethyl fumarate.     

Synthesis of (-)-deoxypukalide, the enantiomer of a degradation product of the furanocembranolide pukalide.

A convergent stereoselective synthesis of (-)-deoxypukalide is described. This substance has not yet been found in Nature but is obtained through deoxygenation of pukalide, the first naturally occurring furanocembrane to be structurally elucidated. The route features a new intraannular furan synthesis that entails treatment of a 4-oxopropargylic beta-keto ester with silica gel. The product of this novel reaction, a 3-carboxy 2,5-bridged furan, is formed in 96% yield. The synthetic strategy was strongly directed by molecular mechanics calculations, which provided valuable insight into stereodefining steps including double bond stereochemistry and butenolide configuration.     

Total synthesis of (-)-nakadomarin A

A highly diastereoselective bifunctional organocatalyst controlled Michael addition, a nitro-Mannich/lactamization cascade, a furan N-acyliminium cyclisation, a sequential alkyne RCM/syn-reduction and an alkene RCM has allowed a 19 step, highly stereoselective synthesis of (-)-nakadomarin A.     

An efficient synthesis of 2-(guaiazulen-1-yl)furan derivatives via intramolecular Wittig reactions

An efficient and mild synthesis of 2-(guaiazulen-1-yl)furans,starting from easily accessible 1-(3-aryl-2-cyanopropenoyl) guaiazulenes,tributylphosphine and acyl chlorides,is described.The strategy employs the intramolecular Wittig protocol as a key step to append the crticial furan ring,leading to the highly functional furans in good yields.     

Synthesis and Some Transformations of 2-(3-Amino-1-Phenylpropyl)furan

A preparative method was developed for the synthesis of ethyl furfurylidenecyanoacetate. Its condensation with phenylmagnesium bromide gave ethyl α-cyano-β-(2-furyl)hydrocinnamate, the decarboxylation of which led to β-(2-furyl)hydrocinnamonitrile. Reduction of this nitrile with lithium aluminum hydride gave 2-(3-amino-1-phenylpropyl)furan. Some of its transformations were studied.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 517–521, April, 2005.     

Total synthesis of (−)-nakadomarin A: alkyne ring-closing metathesis

A 13-step, highly stereoselective synthesis of (−)-nakadomarin A has been achieved using the combination of a bifunctional organocatalyst controlled Michael addition, a nitro-Mannich/lactamization cascade, an alkyne ring-closing metathesis/syn-reduction, and furan/iminium ion cyclization/reduction as key steps.     

碳核苷类似物的合成与生物活性

利用杂环金属盐法,通过呋喃碳核苷中间体,合成了哒嗪、哒嗪酮等碳核苷,讨论了反应机理;提高了呋喃汞盐法合成碳核苷的收率及立体选择性.     

Synthesis of anti-HIV lithospermic acid by two diverse strategies

An efficient and convergent route for the synthesis of the natural product (+)-lithospermic acid, which possesses anti-HIV activity, was accomplished. The (±)-trans-dihydrobenzo[b]furan core therein was prepared by two different strategies. The first strategy involved the use of a palladium-catalyzed annulation to generate an appropriately substituted benzo[b]furan ester followed by a stereoselective reduction of a carbon-carbon double bond with Mg-HgCl(2)-MeOH. The second strategy relied on an aldol condensation between a suitably substituted methyl arylacetate and 3,4-dimethoxybenzaldehyde, followed by cyclization. Finally, a total synthesis of (+)-lithospermic acid was completed via coupling of a trans-dihydrobenzo[b]furan cinnamic acid with an enantiomerically pure methyl lactate.     

Synthesis and some transformations of 5-(N-tosylaminomethyl)furfuryl alcohols

Preparative methods were developed for the synthesis of 5-(N-tosylaminomethyl)furfuryl alcohols, and their behavior during the action of acidic catalysts was studied. It was established that the furan ring of these compounds is stable in the presence of orthophosphoric acid in glacial acetic acid and that their hydroxyl and N-tosylaminomethyl groups are involved in the transformations.     

Synthesis of isomeric bromo(diethoxyphosphorylmethyl)furans

Series of the previously unknown bromo(diethoxyphosphorylmethyl)furans including four of six possible regioisomers is synthesized. The target products were obtained by bromination of the corresponding (diethoxyphosphorylmethyl)furans or by a four-step synthesis including bromination of isomeric methyl-furancarboxylates, reduction of the products formed to the corresponding alcohols, substitution of hydroxy group with halogen and phosphorylation by the Michaelis-Becker reaction. It was established for the first fime that in the course of bromination of alkyl carboxylates and phosphonates of the furan series under the typical conditions of electrophilic reaction (Br₂ + 10% molar of AlCl₃, chloroform) the substituent enters not only into the heteroring, but also into the side chain. In the case of 5-methyl-2-(diethoxyphosphorylmethyl)furan only the last reaction pathway is observed. It is shown that bromo(chloromethyl)furans react with sodium diethyl phosphite not only according to the Michaelis-Becker scheme leading to phosphonates, but also by the pathway of debromination of the furan ring. The last unexpected reaction may acquire a practical use for removing a substituent protecting the α-position of the furan ring under mild conditions.     

The synthesis and transition temperatures of 5-(4-alkyl- and 4-alkoxy-phenyl)-2-cyanobenzo[b]furans and a 5-(4'-alkylbiphenyl-4-yl)-2-cyanobenzo[b]furan: a comparison with their biphenyl and terphenyl analogues

The synthesis and transition temperatures of a series of 5-(4-alkyl- and 4-alkoxy-phenyl)2-cyanobenzo[b]furans and a 5-(4'-alkylbiphenyl-4-yl)-2-cyanobenzo[b]furan are presented. The 2-cyanobenzo[b]furans show similar mesophase types to the analogous biphenyl and terphenyl compounds, which are obtained by replacing the benzo[b]furan unit with a phenyl ring. The transition temperatures for the 2-cyanobenzo[b]furan compounds are always higher than for their biphenyl and terphenyl counterparts, but they are much lower than for the corresponding phenylnaphthalenes. Five mesogenic benzo[b]furans without a cyano group were prepared as intermediates and these compounds have lower clearing points than their biphenyl analogues.     

Reaction of alkyl-3-nitro-and-3-bromo-3-nitroacrylates with 2-(2-nitroethenyl)furan

The diene condensation of β-nitro and β-bromo-β-nitroacrylates with 2-(2-nitroethenyl)furan as 1,3-diene leads to a mixture of regioisomeric tetrahydrobenzofurans transforming under the reaction conditions into benzofurancarboxylates due to the easy dehydrohalogenation, denitration, and dehydration. In the case of a gem-bromonitroacrylate reaction takes two routes: diene synthesis and alkylation of the furan ring, the latter process prevailing. The structure of products formed was established by spectral methods. The investigation of geometry of 2-(1-methoxycarbonyl-2-nitroethenyl)-5-(2-nitroethenyl)furan by XRD analysis showed that its vinyl fragments have the coplanar chelate-like structure with the cisoid orientation of the CO₂Me and NO₂ groups. The ester group deviates from the plane of the the carbon-carbon multiple bond.     

Transformation of 3-(Furan-2-yl)-1,3-di(het)arylpropan-1-ones to Prop-2-en-1-ones via Oxidative Furan Dearomatization/2-Ene-1,4,7-triones Cyclization

The approach to 3-(furan-2-yl)-1,3-di(het)arylprop-2-en-1-ones based on the oxidative dearomatization of 3-(furan-2-yl)-1,3-di(het)arylpropan-1-ones followed by an unusual cyclization of the formed di(het)aryl-substituted 2-ene-1,4,7-triones has been developed. The cyclization step is related to the Paal–Knorr synthesis, but the furan ring formation is accompanied in this case by a formal shift of the double bond through the formation of a fully conjugated 4,7-hydroxy-2,4,6-trien-1-one system or its surrogate.     

The synthesis and transition temperatures of 5-(4-alkyl- and 4-alkoxy-phenyl)-2-cyanobenzo[b]furans and a 5-(4'-alkylbiphenyl-4-yl)-2-cyanobenzo[b]furan: a comparison with their biphenyl and terphenyl analogues

The synthesis and transition temperatures of a series of 5-(4-alkyl- and 4-alkoxy-phenyl)2-cyanobenzo[b]furans and a 5-(4'-alkylbiphenyl-4-yl)-2-cyanobenzo[b]furan are presented. The 2-cyanobenzo[b]furans show similar mesophase types to the analogous biphenyl and terphenyl compounds, which are obtained by replacing the benzo[b]furan unit with a phenyl ring. The transition temperatures for the 2-cyanobenzo[b]furan compounds are always higher than for their biphenyl and terphenyl counterparts, but they are much lower than for the corresponding phenylnaphthalenes. Five mesogenic benzo[b]furans without a cyano group were prepared as intermediates and these compounds have lower clearing points than their biphenyl analogues.