TWO WATER-SOLUBLE FLUORESCENCE PROBES FOR CHEMIEXCITATION STUDIES: SODIUM 9,10-DIBROMO- AND 9, 10-DIPHENYLANTHRACENE-2-SULFONATE. SYNTHESIS, PROPERTIES AND APPLICATION TO TRIPLET ACETONE AND TETRAMETHYLDIOXETANE

The syntheses of sodium 9,10-dibromo- and 9,10-diphenylanthracene-2-sulfonate (DBAS and DPAS, respectively) are described and their photophysical properties determined. These two probes were used in aqueous solution studies of the kinetic parameters of tetramethyldioxetane thermolysis, which were found to be the same as in organic solvents. The yields of triplet and singlet acetone generated by the decomposition of this dioxetane in water are also comparable to the literature values in organic medium. The lifetime of triplet acetone in water was determined to be 13 ± 2 u.s by a method based on the measurement of the fluorescence decay of DBAS excited via energy transfer from triplet acetone, by the time-correlated single-photon counting technique. Sorbate ion quenches triplet acetone from tetramethyldioxetane with a rate constant smaller but close to the diffusion-controlled limit.     

Stereoselective association of binuclear metallacycles in coordination polymers

A series of structurally related binuclear metallacycles [Cd(NO(3))(2)L](2), where L is an angular exo-bidentate ligand, have been synthesized. Each metallacycle contains two coordinatively unsaturated, chiral metal centers within a single molecule, and the assembly of these metallacycles into polymeric framework structures has been studied systematically for the first time. Stereoselective homochiral association of [Cd(NO(3))(2)L](2) leads to the formation of helical coordination polymers, whereas meso type association results in nonhelical chain structures. The type of stereoselective aggregation depends on the conditions of self-assembly as well as on ligand functionality. Both helical and nonhelical polymeric complexes have been isolated for the metallacycle [Cd(NO(3))(2)(2,4'-pyacph)](2) (2,4'-pyacph = 2,4'-(4-ethynylphenyl)bipyridyl). Homochiral association results in the formation of helical [Cd(NO(3))]( infinity ) chains which link the binuclear [Cd(NO(3))(2)(2,4'-pyacph)](2) metallacycles into racemic two-dimensional sheets which contain both P and M [Cd(NO(3))]( infinity ) helices. In contrast, meso-association leads to the formation of nonhelical one-dimensional chains. It is shown that the product of homochiral association is predominately formed at room temperature and that of meso-association is generated at elevated temperatures. Thus, it may be concluded that the homochiral association appears to be energetically less favorable than the meso-association, a conclusion that has been confirmed by theoretical calculations of the crystal lattice energy. Several high-yield syntheses of bipyridyl-type ligands used for metallacyclic assembly are also reported.     

The chromatographic properties of a mixed-bed stationary phase combining reversed-phase and strong anion exchange properties

Summary The feasibility of using columns prepared by mixing together ion exchange and reversed-phase packing materials, for the simultaneous separation of ionised and unionised molecules, has been examined using a range of test solutes. Columns prepared in this way showed chromatographic properties which were intermediate between those of the individual phases. The dual nature of the retention mechanism allowed the retention of ionisable molecules to be adjusted using pH whilst that of uncharged compounds was unaffected. The simultaneous chromatography of model compounds and their glucuronide, sulphate and glycine conjugates, under a variety of conditions, was demonstrated.     

Synthesis,renal vasodilator and dopamine-sensitive adenylate cyclase activities of O-Methyl derivatives of 6-chloro-2,3,4,5-tetr ahydro-1-(4-hydroxyphenyl)-1H-3-benzazepin-7,8-diol (SK&F 82526)

The three possible mono-O-methyl derivatives of 6-chloro-2,3,4,5-tetrahydro-1-(4-hydroxyphenyl)-1H-3-benzazepin-7,8-diol (SK&F 82526) ( 1 ) have been synthesized to facilitate the isolation and characterization of metabolites of this compound and for biological testing. The syntheses generally involved preparation of appropriately substituted benzaldehydes, conversion of these to phenylacetic acids and use of these to N-acylate arylethanolamines. The phenylacetamides thus formed were reduced to amines and these were deprotected and cyclized to the desired final products. In one case deprotection followed cyclization. These compounds were tested as activators of dopamine-sensitive adenylate cyclase (a measure of DA-1 agonist activity) and as renal vasodilators. All three O-methyl derivatives were much less potent than 1 in cyclase activation and as renal vasodilators. Weak inhibition of adenyl cyclase was also observed for all three compounds and one showed weak renal vasoconstrictor activity. Preliminary investigation of the metabolism of 1 disclosed that two of the three monomethoxy compounds were formed in trace amounts in the rat and the dog. In a related investigation, the trimethoxy derivative of 1 was subjected to acid-catalyzed hydrolysis conditions. The relative ease of cleavage of methoxy groups was 7 > > 4′ > 8.     

The M gamma chain of human fetal hemoglobin; its identification and occurrence

High-performance liquid chromatographic procedures have been used in the detection and identification of a new gamma chain of human fetal hemoglobin (Hb). This M gamma chain is characterized by a Leu----Met replacement at position gamma 141; no other structural variations have been observed. The M gamma chain has been detected in red cell lysates of subjects with a heterozygosity for one of many types of so-called hereditary persistence of fetal hemoglobin conditions, which are characterized by an increased level of Hb F in adult life, in sickle cell anemia, and in a few cord blood samples. At present it is not possible to definitely identify the genetic cause of this newly discovered heterogeneity; an infidelity in translation or the existence of an unrecognized gamma globin gene should be considered.     

Stereoselective synthesis of the cyclic ether core of (+)-laurenyne

A concise enantioselective synthesis of the cyclic ether core of the marine natural product (+)-laurenyne has been accomplished using ring-closing metathesis for medium-ring construction.     

A biomimetic strategy for the synthesis of the tricyclic dibenzofuran-1,4-dione core of popolohuanone E

A concise synthesis of the complete tricyclic dibenzofuran-1,4-dione aromatic core of popolohuanone E has been demonstrated by mild base treatment of a biquinone intermediate, thus establishing a biomimetic route to this family of heterocyclic ring systems and the total synthesis of popolohuanone E.     

Macroreticular ion-exchange resins: some analytical applications to petroleum products

Extraction and subsequent recovery, in four separate fractions, of naphthenic acids, alkylphenols, pyrrollic compounds and nitrogen bases can be made from petroleum products using macroporous ion-exchange resins. Distinctive features of the technique are the use of dissolved gases in polar solvents as eluants and the application of the carbonate form of anion-exchange resins. The transition metal form of a macroreticular cation exchanger is shown to extract ligands from non-aqueous systems and a specific application to petroleum analysis is given.