Tetrahydropyran structure

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. 

The 2 1 copolymer, first reported in 1958 (1), was assumed to have the tetrahydropyran structure, I in Scheme 1 (2K Although this structure had been widely accepted ( 3), there was no convincing evidence for it. In fact, a number of reports in the literature suggested that the kinetically controlled route leading to a tetrahydrofuran ring, II in Scheme 1, would be more likely. Thus, it was shown by ESR that the 5-hexenyl radical, formed by photolysis of 6-heptenoyl peroxide, cyclizes... 

Typical carbon-oxygen bond distances m ethers are similar to those of alcohols (—142 pm) and are shorter than carbon-carbon bond distances m alkanes (—153 pm) An ether oxygen affects the conformation of a molecule m much the same way that a CH2 unit does The most stable conformation of diethyl ether is the all staggered anti conformation Tetrahydropyran is most stable m the chair conformation—a fact that has an important bearing on the structures of many carbohydrates... 

The structure of the antibiotic, 9, which has been variously named lacto-quinomycin-A and medermycin, was first reported by Okabe and coworkers in 1985.58 In early 2002,59 a communication was published reporting that the original structure, 9, was incorrect based on synthesis and that the substituted tetrahydropyran ring was attached to the 6-position to give 10, rather than the 8-position as originally reported. The authors based their conclusion on the fact that a key intermediate was identified as 6-bromo-3-hydroxybenzaldehyde rather than the 4-bromo-3-hydroxy benzaldehyde as previously reported.60... 

For instance, in structure 12-e, the C-X and C-0 dipole moments are additive, leading to a destabilization of the molecule by increasing the energy. In structure 12-a, offset of the C-X and C-0 dipole moments minimizes electrostatic interactions, thus leading to a more stable conformation. This electrostatic model was supported by the observed increase of the percentage of the equatorial conformation of 2-methoxy tetrahydropyran (14) when moving from a non-polar to a polar solvent (Table 3).12 In this model, the polar groups are not polarizable and lead to dipole/dipole (hard/hard) interactions. 

Acetals and ketals are very important protecting groups in solution-phase synthesis, but only a few constructs have been used as linkers in solid-phase synthesis (Tab. 3.3). The THP-linker (22) (tetrahydropyran) was introduced by Ellman [54] in order to provide a linker allowing the protection of alcohols, phenols and nitrogen functionalities in the presence of pyridinium toluene sulfonate, and the resulting structures are stable towards strong bases and nucleophiles. Other acetal-linkers have also been used for the attachment of alcohols [55, 56]. Formation of diastereomers caused by the chirality of these linkers is certainly a drawback. Other ketal tinkers tike... 

This article deals with the conformational analysis of substituted oxanes (tetrahydropyranes) and derivatives in which ring methylenes are replaced by further oxygen atoms (di-, tri-, tetroxanes, pentoxanes, and O ) or by carbonyl group(s) (oxanones, Meidrum s acid derivatives) and, if conforma-tionally of interest, systems incorporating these rings in polycyclic structures... 

Cross-cyclization of epoxides with homoallylic amines is an easy way to access tetrahydropyran moieties, which form the core structure of many biologically important natural products such as avermectins, aplysiatoxin, oscillatoxins, latrunculins, talaromycins, acutiphycins, and apicularens. Even though many methods are available for the synthesis of this moiety [14—24], its importance and wide applicability demands further methods. 

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