Tetrahydrofuran structure

Figure 14-3. Transesterification reaction of the dinucleotide model where the nucleophile-containing ribose sugar is modelled by a tetrahydrofurane structure, whereas the cleaving sugar is further simplified and modelled as a simple primary alcohol (ethanol)...

To illustrate signal assignments in 13C NMR spectra of the benzotriazol-l-yl system, chemical shifts for five a-(benzotriazol-l-yl)tetrahydrofurans (structures 39-43) <2003JP0158> and three corresponding tetrahydropyrans (structures 27-29) <2001CJC1655> are listed in Table 5. Selected 13C NMR spectral data for triazolyl nucleoside analogs 44-50 <2003SPL461> are collected in Table 6. 

Milas and Golubovic42 used paper and column chromatography and spectroscopic methods to study the reaction of acetonylacetone with hydrogen peroxide. Beside compound 37, a peroxide (38) with the tetrahydrofuran structure is also reported to be formed.42 Seebach43 also obtained 37 from 2,5-dimethylfuran, 85% hydrogen peroxide, and a little 10% sulfuric acid (see Section II, A, 5). 37 forms a dibenzoate.43... 

Various linear and cyclic fully methylated polysilanes can be made by catalytic retyrangement of Si6(CH3)i4, and the cyclic compounds [Si(CH3)2] ( = 5-7) have been prepared by the action of Li on Si(CH3)2Cl2 in tetrahydrofuran. Structural data for some of these compounds are included in Table 21.1 (P-727). 

Examination by NMR of the polymers obtained from 2,7 1oxablcy-clo[2.2.Ijheptane at -78 C, showed that the polymer was exclusively composed of tetrahydrofuran structures. Cls and trans Isomers are... 

Lu, R, and Ralph, J. (2008) Novel tetrahydrofuran structures derived from 3- 3-coupling reactions involving sinapyl acetate in kenaf lignins. Org. Biomol. Chem. (6), 3681-3694. 

Muscarine 5, one of the active ingredients in the toadstool fly agaric Amanita muscaria), contains a 2,3,5-trisubstituted tetrahydrofuran structure. A number of stereocontrolled syntheses have been worked out for muscarine. One of these starts with methyl vinyl ketone [16] and cyclizes stereoselec-tively the appropriately substituted <5-unsaturated 2,6-dichlorobenzyl ether 3 with iodine ... 

The esterification of a liquid solution of sorbitol with fatty acids leads to a variety of mild tensioactive agents commonly known as sorbitan esters. Under esterification conditions and high temperature (>200°C), sorbitol undergoes an internal dehydration reaction to give a tetrahydrofuran structure (sorbitan) that is esterified by the fatty acid mainly on the primary hydroxyl group (see Figure 9.2.11). When an excess of fatty acid is used, di-esters and triesters are obtained. These sorbitan esters are commonly referred to as Span . They have low water solubility but are soluble in most cosmetic oils. They are typically used as water-in-oil (0/W) emulsifiers. 

The epoxide-opening reactions in the monensin synthetic pathway lead to the formation of tetrahydrofuran structures through nucleophilic addition to the proximal carbon. An alternative pathway would proceed through nucleophilic addition to the distal carbon, which would provide a tetrahy-dropyran structure. The formation of tetrahydrofurans is preferred over the formation of tetrahydropyrans under mildly acidic conditions, as will be discussed later in this chapter. Therefore questions arose as to whether enzymes are involved with the epoxide cascade reaction. Enzymatic involvement was demonstrated during studies on the biosynthesis of lasalocid A (8). The precursor of 8 should be diepoxide 9 in accord with the Cane-Cehner-Westley hypothesis. However, the formation of the tetrahydropyran in the... 

Xiong used an acid-mediated epoxide-opening cascade to prepare a penta-tetrahydrofuran structure for the synthesis of the tetra-tetrahydrofuran natural product omaezakianol (152 Scheme 4.31) [66]. This allowed for the synthesis of cyclization precursor 153 from squalene. Exposing 153 to CSA provided pentacycle 154 in a 21% yield that includes the formation of the epoxides. Reductive opening resulted in... 

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