Synthesis and properties of molecular probes for the rescue site on mutant cystic fibrosis transmembrane conductance regulator

Cystic fibrosis is a genetic disease caused by mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. In vitro experiments have demonstrated that 4-methyl-2-(5-phenyl-1H-pyrazol-3-yl)phenol (VRT-532, 1) is able to partially restore the function of mutant CFTR proteins. To help elucidate the nature of the interactions between 1 and mutant CFTR, molecular probes based on the structure of 1 have been prepared. These include a photoreactive aryl azide derivative 11 and a fluorescent dansyl sulfonamide 15. Additionally, a method for hydrogen isotope exchange on 1 has been developed, which could be used for the incorporation of radioactive tritium. Using iodide efflux assays, the probe molecules have been demonstrated to modulate the activity of mutant CFTR in the same manner as 1. These probe molecules enable a number of biochemical experiments aimed at understanding how 1 rescues the function of mutant CFTR. This understanding can in turn aid in the design and development of more efficacious compounds which may serve as therapeutic agents in the treatment of cystic fibrosis.

PNA HyBeacons for analysis of human mutations related to statin-induced myopathy

Aminoalkyl and alkyne-tagged PNA HyBeacons have been synthesized, labeled with fluorescein via conventional amide bond or triazole formation (click chemistry) and used to detect single nucleotide polymorphisms (SNPs) implicated in statin-induced myopathy. The PNA HyBeacons gave much better mismatch/mutant discrimination than conventional DNA HyBeacons but smaller fluorescence changes on melting.

3-(Tributylstannyl)allyl Alcohols: Useful Building Blocks for Solid-Phase Synthesis of Skipped Dienes and Trienes

Repeated Stille coupling of 3-substituted 3-(tributylstannyl)allyl alcohols 2 on a solid support was used to synthesize a 21 × 21 library of skipped dienes and a 21 × 21 × 21 library of skipped trienes. Starting 3-(tributylstannyl)allyl alcohols were prepared by Pd-catalyzed hydrostannation of substituted prop-2-yn-1-ols, by hydroalumination by LiAlH4 followed with transmetallation to tin using tributyltin methoxide, or by substitution of chlorine in (Z)-6-chloro-3-(tributylstannyl)hex-2-en-1-ol with appropriate nucleophile. Synthesized libraries were tested for the activity to endorphin receptors, but with negative results.

Syntheses of (-)-Isocitric Acid Lactone and (-)-Homoisocitric Acid. A New Method of Conversion of Alkynylsilanes into the Alkynyl Thioether and Corresponding Carboxylic Acids

A simple, stereoselective synthesis of natural isocitric and homoisocitric acids from a common alkynylsilane correlates the stereochemistry of these acids. Starting with dimethyl D-malate dianion, methyl 2-hydroxy-3-carbomethoxy-6-(trimethylsilyl)-5-hexynoate (6a) was prepared with a good stereoselectivity (threo/erythro 90/10). Oxidative cleavage of the triple bond provided isocitric acid lactone (8') in 15% overall yield starting from D-malic acid diester 1. The synthesis of homoisocitric acid relied on a new method of conversion of alkynylsilane to alkynyl thioether, which is converted to the carboxylic acid of the same chain length. Addition of benzenesulfenyl chloride to (trimethylsilyl)alkyne 6b and elimination of trimethylsilyl chloride gave the corresponding thioether 10, which by acid hydrolysis gave homoisocitric acid (11) in a 24% yield from D-malic acid ester. This novel method of conversion of alkynylsilane to the corresponding acid was illustrated with several other alkynyltrimethylsilanes.

Separation of the enantiomers of substituted putrescine and cadaverine analogues by gas chromatography on chiral and achiral stationary phases

Capillary gas chromatography (GC) on chiral stationary phases, i.e., Chirasil-Val [L-valine-tert.-(R)-alpha-butylamide] and XE-60-S-valine-(R)-alpha-phenylethylamide, has been applied to the resolution of various substituted analogues of putrescine as their N,N'-perfluoroacyl derivatives. The influence of the nature of the substituent on the retention behaviour and on the resolution of the enantiomers was studied. The results are discussed in terms of volatility and interaction with the chiral stationary phase. The 1,4-disubstituted putrescine analogues with two chiral centres were also clearly resolved into their corresponding stereoisomers. When the chain length between the two amino groups was increased, no clear resolution was obtained of the monosubstituted cadaverine analogues as their N,N'-perfluoroacyl derivatives. However, resolution was obtained after derivatization of the cadaverine analogues with (-)-alpha-methoxy-alpha-trifluoromethylphenylacetyl chloride, followed by GC analysis on an achiral phase.

A sensitive high-performance liquid chromatographic procedure with fluorometric detection for the analysis of decarboxylated S-adenosylmethionine and analogs in urine samples

A highly sensitive HPLC method for the determination of decarboxylated S-adenosylmethionine (dc-SAM) by fluorometric detection was developed. The reaction of dc-SAM and its analogs with chloroacetaldehyde leads to the corresponding 1,N6-etheno derivatives. These highly fluorescent derivatives were fully characterized through their proton nuclear magnetic resonance spectra and/or mass spectra. This derivatization procedure has been applied to the analysis of dc-SAM in rat and human urine. After a simple cation exchange column prepurification, the urine extracts were derivatized with chloroacetaldehyde and analyzed by reversed-phase HPLC with fluorometric detection. The method allowed the determination of subpicomole amounts of dc-SAM and was shown to be highly reproducible with the use of decarboxylated S-adenosylethionine as internal standard. The application of the method to the analysis of urine of rats treated with MDL 72175, a potent ornithine decarboxylase inhibitor, showed that the dc-SAM levels increased in a dose-related fashion.

Restoration of the polyamine contents in rat hepatoma tissue-culture cells after inhibition of polyamine biosynthesis. Relationship with cell proliferation

The restoration of the polyamine content in polyamine-deficient rat hepatoma tissue-culture (HTC) cells, after short duration of incubation in the presence of DL-alpha-difluoromethylornithine (F2MeOrn) or of (2R,5R)-6-heptyne-2,5-diamine [(2R,5R)MAP], two potent irreversible inhibitors of L-ornithine decarboxylase, has been studied in relation to cell proliferation. Both L-ornithine decarboxylase inhibitors deplete the cells of their putrescine and spermidine contents within one day after their addition to the culture medium. Thereafter, intracellular putrescine and spermidine concentrations are restored to near control values within one day when (2R,5R)MAP is removed from the medium, but remain at low levels at least for one day or longer after removal of F2MeOrn. In both conditions, spermine concentration stays at normal or above normal values and cell growth rates are unaffected. Thus, the total intracellular spermine content per culture parallels, in fact, the increase in cell number. The continuous presence of the drugs maintains the depletion of putrescine and spermidine and decreases the total intracellular spermine content of the culture to the same order of magnitude as it reduces the increase in cell numbers. These findings suggest that the antiproliferative effects of these L-ornithine decarboxylase inhibitors in HTC cells is primarily associated with the limitation of spermine biosynthesis rather than to the almost complete reduction of the putrescine and spermidine pools.