Tetrahydrofuran motif

In the total syntheses of squamocin A and squamocin D, acetogenins from Annonaceae, a double cyciization has been demonstrated to be feasible for the assembly of bis-tetrahydrofuran motifs (Equation 71) <2000EJ01889>. Intramolecular dehydration to afford tetrahydrofurans can efficiently be carried out by the Mitsunobu reaction <2003JOC4422> and a cationic platinum-catalyzed dehydration <2005SL152>. 

Fig. 2 Examples for natural products with tetrahydrofuran motif...

An asymmetric synthesis of tricyclic compounds through the desym-metrization of cyclohexadienones was developed to provide a wide variety of cyclohexadienones with tetrahydrofuran motifs via a [4 + 2] cycloaddition (14AGE8184). 

A novel Rh(I)-catalyzed one-pot carbocyclization and chlorosulfo-nylation of a 1,6-enyne with sulfonyl chloride can result in the formation of C-Cl, C-C, and C-S bonds of a tetrahydrofuran motif with high regioselectivity and stereoselectivity, in which sulfonyl chloride was proved to be an efficient linker in addition-carbocyclization reactions (13CC5014). 

The tetrahydrofuran motif is common across many natural product classes and important bioactive compounds. The formation of this important motif can be accessible through a number of synthetic pathways. Deska developed a four-step procedure converting the achiral ether 30 to the 2,5-tra 5-disubstituted dihydrofuran-3-one 33 in modest enantiomeric excess and diastereomeric ratio. Tanperature conditions for the cyclization were at room temperature or lower to... 

Marsden and coworkers have recently reported that the reaction of cyclic al-lylsiloxane (101) with aldehydes, in the presence of BF3 OEt2, gives access to a 2,3,4-substituted tetrahydrofuran motif (102) and (103) found in the furanolignan family of natural products (Equation 61) [60]. This reaction proceeds with complete trans selectivity at the 3 and 4 positions. 

Viewed (and drawn) in a terpene-like perspective, C-glycosyl compounds are in fact functionalized tetrahydrofurans and tetrahydropyrans. As such, they can be considered as versatile chirons for the synthesis of a variety of natural products containing cyclic ether motifs, such as in the ionophores. 

Phosphinocarbene or 2 -phosphaacetylene 4, which is in resonance with an ylide form and with a form containing phosphoms carbon triple bond, is a distillable red oil. Electronic and more importantly steric effects make these two compounds so stable. Carbene 4 adds to various electron-deficient olefins such as styrene and substituted styrenes. Bertrand et al. have made excellent use of the push-pull motif to produce the isolable carbenes 5 and 6, which are stable at low temperature in solutions of electron-donor solvents (THF (tetrahydrofuran), diethyl ether, toluene) but dimerizes in pentane solution. Some persistent carbenes are used as ancillary ligands in organometallic chemistry and in catalysis, for example, the ruthenium-based Grubbs catalyst and palladium-based catalysts for cross-coupling reactions. 

If a smaller amide such as lithium phenylamide (anilide) is used in this metathesis reaction tetrakis(tetrahydrofuran-0)lithium bis[tris(trimethylsilyl)methylzinc] tris([i-anilide) (7) is isolated according to Eq. 5. The central structural motif is a trigonal bipyramidal arrangement of the Zn2N3 moiety with the metal atoms in apical positions. Figure 2 shows the molecular structure of the zincate anion. 

On the basis of the chiral building block 105, a series of enantiopure helical macrocycles (110,112, and 114) containing tetraphenylene motifs were obtained. Platinum(II) complexes 110 and 112 were assembled in tetrahydrofuran (THF)... 

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