Highly diastereoselective synthesis of trans-2,5-disubstituted tetrahydrofurans

trans-2,5-Disubstituted tetrahydrofurans were obtained as major diastereomers (trans/cis ratio 90:10-100:0) when acetylated gamma-lactols derived from (S)-glutamic acid were treated with titanium enolates of N-acetyl (R)-oxazolidin-2-thiones. A simple transesterification allowed us to obtain the corresponding methyl esters and recover the chiral auxiliary.     

Diastereoselective synthesis of 2,5-disubstituted tetrahydrofurans

This review focuses on synthetic methods allowing the preparation of 2,5-disubstituted tetrahydrofurans reported in the literature between 1993 and 2008.     

Stereoselective synthesis of 3-oxygenated-cis-dialkyl-2,5-substituted tetrahydrofurans from cyclohexadienediols

The 3-oxygenated-cis-dialkyl-2,5-substituted tetrahydrofuran system, present in several natural products, was prepared with good selectivity by acidic cyclization of 5-alkene-1,2,4-triol derivatives. The starting alkenol was obtained in few steps from a chiral cis-diol resulting from microbial oxidation of bromobenzene. The study of the cyclization allowed the rationalization of all experimental results by assuming a complete ionization at the allylic position and a model close to the one proposed by Labelle for homoallylic induction in five-membered ring closures.     

Efficient, stereoselective synthesis of trans-2,5-disubstituted morpholines

[reaction: see text] Enantio- and diastereoselective syntheses of trans-2,5-disubstituted morpholine derivatives are described. The routes are initiated by the reaction of enantiopure epoxides (2) with amino alcohols (3) and address the problem of regioselective hydroxyl activation-ring closure of the resulting amino diol adducts for (amino alcohol-derived) alkyl substituents of different steric demands.     

Synthesis of cis- and trans-2,5-disubstituted tetrahydrofurans by a tandem dihydroxylation-SN2 cyclization sequence

[reaction: see text] Dihydroxylation of delta- and epsilon-mesyloxy alpha,beta-unsaturated esters proceeds with in situ cyclization to afford 2,5-disubstituted and 2,3,5-trisubstituted tetrahydrofurans.     

Stereoselective synthesis of 3,4-disubstituted tetrahydrofurans and 2,3,4-trisubstituted tetrahydrofurans using an intramolecular allylation strategy employing allylsilanes

A Brønsted acid-mediated intramolecular allylation involving an allylsilane and an aldehyde has been used as the key step in a stereoselective synthesis of 3,4-disubstituted tetrahydrofurans and 2,3,4-trisubstituted tetrahydrofurans.     

Donor cyclopropanes in synthesis: utilising silylmethylcyclopropanes to prepare 2,5-disubstituted tetrahydrofurans

The use of donor-only silylmethylcyclopropanes in the Lewis acid promoted reaction with aldehydes to generate 2,5-disubstituted tetrahydrofurans is described. The diastereoselectivity obtained in the product is very much dependent upon the temperature of the reaction.     

The synthesis and development of 2,5-disubstituted tetrahydrofurans as potential scaffolds for diversity-oriented synthesis

The synthesis of 2,5-disubstituted tetrahydrofurans from donor silylmethylcyclopropanes (without bearing an acceptor function) is described. Their further elaboration via a wide range of synthetic transformations is presented to highlight the potential of this method and the resulting THFs as potential scaffolds for diversity-oriented synthesis.     

Stereoselective synthesis of hydroxy-substituted tetrahydrofurans

Iodocyclizations of 4-alkene-1,3-diol derivatives proceed with high stereocontrol to provide cis 2-iodomethyl-3-hydroxy(alkoxy)tetrahydrofurans. The effect of alkoxy substituents on the diastereoselectivity has also been assessed.     

Stereoselective synthesis of cis- or trans-2,4-disubstituted butyrolactones from Wynberg lactone

(R)-Wynberg lactone was used to prepare various asymmetric 2,4-disubstituted butyrolactones in three to four steps. Attainment of any possible stereoisomer, based upon commencement from (R)- or (S)-4-trichloromethyl-2-oxetanone, and the capacity to install disparate substituents at C₂ make this approach particularly versatile.     

Highly functionalized trans-2,5-disubstituted tetrahydrofurans from ribofuranoside templates: precursors to linked polycyclic ethers

Iodoetherification of C5 allylated ribo-furanosides leads to trans-2,5-disubstituted tetrahydrofurans with high selectivity. The application of this reaction to the synthesis of complex polycyclic ethers is illustrated in the preparation of a truncated, tricyclic analog of monensin A.     

Synthesis of 2,5-disubstituted tetrahydrofurans from organozinc halides and lactones

<正>2,5-Disubstituted tetrahydrofurans were obtained from lactones and organozinc halides in moderate to high yield in the presence of Lewis acids.     

Access to 2,5-disubstituted tetrahydrofurans from Grignard reagents and hemiacetal derivatives

The first diastereoselective addition of Grignard reagents onto cyclic oxocarbenium ions, obtained from glycosyl acetates, to afford 2,5-disubstituted tetrahydrofurans, is reported.     

Stereoselective synthesis of 2,4-disubstituted butanolides

A series of 2,4-disubstituted butanolides was prepared based on the trans-stereoselective electrophilic cyclization of substituted N-(pent-4-enoyl)pyrrolidines. The butanolides may be considered as synthons for this type of natural products. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 124–129, January, 2007.     

顺式-和反式-2,5-二取代四氢呋喃的立体选择性合成

内酯与有机锂试剂发生亲核加成反应,再在酸催化下用NaBH3CN还原,反应的立体选择性可能是由氢负离子在中间体氧鎓离子位阻最小的一侧进攻所引起.所得的三环化合物经热分解和加氢反应,制备顺式和反式-2,5-二取代四氢呋喃.     

Synthesis of 2,5-disubstituted tetrahydrofurans by stereospecific elimination-cyclization of 1-iodomethyl-1,5-bis-epoxides

[reaction: see text] Treatment of 1-iodomethyl-1,5-bis-epoxides with zinc in refluxing ethanol affords cis or trans 2-vinyl-5-(1-hydroxyethy)-substituted tetrahydrofurans stereospecifically in high yield.     

Stereoselective synthesis of functionalized pyroglutamates

Novel stereoselective synthesis of α-methylene-β-substituted pyroglutamates, and α-alkylidene-pyroglutamates has been achieved via substrate controlled asymmetric alkylation of l-threonine derived oxazole with Baylis-Hillman reaction based allyl bromides and acetates, respectively. The synthesized compounds were evaluated for their proteasome inhibition and cytotoxicity on multiple myeloma cells.     

An expedient synthesis of 2,5-disubstituted-3-oxygenated tetrahydrofurans

Single enantiomer 2,5-disubstituted-3-oxygenated tetrahydrofurans are synthesized in as little as four steps from a commercially available epoxide. The key steps are homoallylic alcohol epoxidation, palladium-catalysed alkoxy-carbonylation-lactonisation and Mitsunobu inversion. The protocol is applied to the formal total syntheses of (+)-kumausallene, (6S,7S,9R,10R)-6,9-epoxynonadec-18-ene-7,10-diol and the core of lytophilippine A.     

Stereoselective synthesis of 1,4-disubstituted 1,3-diene

New synthetic methods for the preparation of 1,3-dienes are described.