Fluorine analogs

Preparation of several fluorinated analogs of kanamycin A (673) were reported. 6"-Deoxy-6"-fluorokanamycin A (674) was prepared through... 

In the synthesis of fluorinated analogs of the acetylcholinesterase inhibitor, huperzine A, it was necessary to accomplish reductive elimination of the diol 15-D to 15-E. Of the methods for diol reduction, which seems most compatible with the other functional groups in this compound ... 

Hydrazinolysis of 148 provides quantitatively the corresponding azafagomine analog 149 (Equation 14). However, in some fluorinated analogs the fluorine atom acts as a leaving group to provide some hydrazino-substituted by-products. In the case of fluoromethyl derivative 150, compound 151 is isolated in 48% yield (Equation 15) <1997T9357>. 

Formation of the fluorinated analog was described by Dai and Lai and involved a Suzuki coupling [74] to produce compound 109 shown in Scheme 26. This compound is of interest as a known COX-2 inhibitor. 

A small number of fluorinated analogs has been prepared without prior protection of the hydroxyl groups, but, owing to the strongly basic conditions prevailing, such reactions as concurrent formation of the 3,6-anhydro derivative (7) may occur, as in the fluorination of methyl 6-O-p-tolylsulfonyl-a-D-glucopyranoside (6) with potassium fluoride in 1,2-ethanediol.77 A previous attempt to use this reaction, in... 

Although Parylene-N possesses an outstanding combination of physical, electrical, and chemical properties, the benzylic C—H bonds present are potential sites for thermal and oxidative degradation. It is well known that replacing a C— bond with a C—F bond not only enhances the thermal stability of the resulting polymer, but also reduces the dielectric constant. Because incorporation of fluorine is known to impart thermal and oxidative stability, it became of interest to prepare poly(a,a,a, a -tetrafluoro- p -xylylene), Parylene-F Joesten reported that the decomposition temperature of poly(tetrafluoro-j9-xylylene) is ca. 530°C. Thus, it seemed that the fluorinated analog would satisfy many of the exacting requirements for utility as an on-chip dielectric medium. 

Kutsuna, S., Chen, L., Abe, T., Mizukado, J., Uchimaru, T., Tokuhashi, K., and Sekiya, A. Henry s law constants of 2,2,2-tri-fluoromethyl formate, ethyl trifluoroacetate, and non-fluorinated analogous esters, Atmos. Environ., 39(32) 5884-5892,2005. 

FLUOROCARBONS. Compounds of carbon and fluorine-analogs of hydrocarbons in which the hydrogen has been replaced by fluorine. 

It is also believed that the triphosphorylated form of fluorinated analogs of pyrimidine can be included in RNA, and can have an effect on protein synthesis. 

P. Doze, P.H. Elsinga, E.F. deVries, A. van Waarde, W. Vaalburg, Mutagenic activity of a fluorinated analog of the /l-adrenoceptor ligand carazolol in the Ames test, Nucl. Med. Biol. 27 (2000) 315-319. 

The stability of peptides is generally increased when natural amino acids are substituted by fluorinated analogs (e.g., tri- or hexafluoroleucine, hexafluorova-line). Such stabilization augments with the number of hexafluoroleucine residues introduced [77]. Native-like structure was preserved, but the peptides had a more structured backbone and less fluid hydrophobic core. Substitution of four leucine residues by trifluoroleucines in the leucine zipper peptide GCN4-p1d led to a substantial gain in thermal stability and resistance to chemical denaturation of the... 

Remarkably, incorporation of fluorinated amino acids into proteins can also be accomplished in vivo. This supposes that the fluorinated amino acid analogs are recognized by the appropriate amino acyl-tRNA synthetase enzyme with efficiency similar to that of the natural amino acid. The proliferase response elicited by a fluorinated analog (a trifluoroisoleucine derivative) of murine interleukin-2 produced in an appropriate Escherichia coli strain was nearly as high as that of the authentic cytokine, indicating folding into an authentic, native structure [84],... 

Scheme 2. Structures of the native amino acid residues compared to their fluorinated analogs. Aminobutyric acid and its fluorinated analogs are referred to as substituted glycines (EGly).

As seen in Table 13.7, oxidation of HCFCs by OH generates a variety of halogenated aldehydes and ketones as well as phosgene (COCl2), its fluorine analog (COF2), C1C(0)F and HC(0)F, and the alcohol CF3OH. The ultimate atmospheric fate of these products depends on their structures, of course, which determines their absorption cross sections as well as reactivity with OH, and their solubility in aqueous solutions such as clouds, rainwater, and the oceans. 

Arce et al. also investigated the effect of anion fluorination in [CjCjIm] ILs on fhe exfracfion of efhanol from ETBE [36]. For this purpose, two anions, methanesulfonate and trifluoromethanesulfonate, were selected. The corresponding phase diagrams were plotted for both ternary ETBE + ethanol + IL systems. The solute distribution ratios for the IL with the nonfluorinated anion were higher, especially at low concentrations. As for the selectivities, better results were obtained for mefhanesulfonate IL at low solute concentrations, while at higher solute concentrations the selectivity was better for the fluorinated analog. 

It is very well known that polymers of high commercial value are obtained from formaldehyde by addition polymerization of its carbon-oxygen double bond. Not so well known is the addition polymerization capability of the carbon-sulfur double bond, probably because none of the polymers so obtained has yet become commercially acceptable. However, the polymerization chemistry of the carbon-sulfur double bond has been the subject of a number of studies and these have defined the preparation and properties of polythioformaldehyde, polythio-acetone, polymers from a small number of higher thioketones, and polymers from fluorine analogs of thioaldehydes and thioketones. The monomers have great reactivity beyond polymerization, and their general chemistry has been discussed in earlier reviews (/, 2). 

Inasmuch as there are such great differences between hydrogen and fluorine analogs, these classes will be discussed separately. Since hydrogen compounds are generally considered basic by most organic chemists, these will be discussed first, starting with thioformaldehyde. 

Similarly, the fluorinated analog of the codlemone phenomone has been synthesized by application of this coupling methodology13, as illustrated in equation 28. 

Except in the case of isobutyraldehyde, where the non-optimized poor yield may be due to the high volatility of the resulting product, the alcohols are formed in good yields. When the aldehyde is sterically hindered (entries 1-2), a-allylation is observed. Conversely, branched alcohols result from unhindered or aromatic aldehydes (entries 4 to 6). Starting from 3-methyl-2-butenal (entry 5), a fluorinated analog of Artemisia alcohol is formed in one step27. 

Emtricitabine (FTC) is a fluorinated analog of lamivudine with a long intracellular half-life (> 24 hours), allowing for once-daily dosing (Figure 49-2). Oral bioavailability of the capsules is 93% and is unaffected by food, but penetration into the cerebrospinal fluid is low. Elimination is by both glomerular filtration and active tubular secretion. 

Building blocks derived from microbial transformations are usually employed as the key units of fluorinated analogs of appropriate natural products or synthetic biologically active materials [42-45]. Among such useful compounds, trifluoromethylated carbohydrates constitute one of the most interesting fields for intensive study. Novel and efficient routes to access a variety of chiral... 

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