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The synthesis and photoproperties of six new metal 1,4,8,11,15,18,22,25-octabutoxyphthalocyanines and photoproperties of the known, analogous Zn and metal-free phthalocyanines are described. The new compounds are AlPc(OBu){sub 8}OSiEt{sub 3}, GaPc(OBu){sub 8}OSiEt{sub 3}, GePc(OBu){sub 8}(OSiEt{sub 3}){sub 2}, SnPc(OBu){sub 8}(OSiEt{sub 3}){sub 2}, RuPc(OBu){sub 8}(py){sub 2}, and PdPc(OBu){sub 8} (where Pc(OBu){sub 8} represents the octabutoxyphthalocyanine ligand). Benzene-d{sub 6} solutions of all eight of the compounds give NMR spectra showing large ring-current effects. Benzene solutions of the compounds give visible spectra with absorption maxima in the 688-779-nm range having extinction coefficients between 1.0 {times} 10{sup 5} and 2.2 {times} 10{sup 5} M{sup {minus}1} cm{sup {minus}1}. The triplet-state properties of the phthalocyanines in benzene solutions have been measured by laser flash photolysis. The triplet states have absorption maxima in the 550-640-nm range, quantum yields in the 0.1-0.9 range, and lifetimes when the solutions are deaerated in the 0.5-150-{mu}s range. The rate constants for energy transfer from the triplet states of the compounds to O{sub 2} are between 1.3 {times} 10{sup 8} and 2.8 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}.

Clearly the photoinduced peroxy bond fission is much slower than that found for the 9-methylfluorenyl perester and is much more rapid than the same process in the fluorenone peresters. In all three molecules the peroxy bond is not conjugated with the chromophore and it is not unreasonable to assume that its bond-breaking rate is largely independent of the nature of the discrete chromophore. Thus we conclude that this large variance in observed rates reflects the rates at which energy can be transferred into the dissociable unit

The synthesis and characterization of 30 Al, Ga, Si, and Sn naphthalocyanines relevant to the search for improved photodynamic therapy agents are reported. The compounds that have been studied are AlNcCl, AlNcOH, AlNcOSi-(n-C 6 H 13 ) 3 ...

The transient phenomena in a laser flash photolysis study of a new series of xanthene dyes in ethanol solution at room temperature are described. The difference between the triplet- and ground-state absorption spectra of tetrabromohydrofluorescein (TBHF) or tetraiodohydrofluorescein (TIHF) shows peaks around 360 and 580 nm. Tetrabromohydrocyanofluorescein (TBHCF) and tetraiodohydrocyanofluorescein (TIHCF) demonstrate triplet-triplet absorption with peaks around 340 and 460 nm. The corresponding anion radicals D .- , which are produced by electron-transfer reactions from aromatic amina, have absorption maxima at 410 nm

The temperature dependence of the bimolecular rate constant for O 2 ( 3 Σ g ) quenching of a series of aromatic hydrocarbon triplet states, κ T ox , has been determined in toluene. Highly curved Arrhenius plots were obtained, indicating a change in rate-determining step over the available temperature range. At low temperatures, κ T ox of all hydrocarbons approached a common limiting slope that was consistent with 4 / 9 κ d . At higher temperatures, low positive or negative activation energies were observed, indicating the involvement of exciplex intermediacy in the overall quenching process

A series of 4- and 6-substituted derivatives of benzyl N-acetyl-β- D -glucosaminide were prepared and assessed as inhibitors of bovine β-1,4-galactosyl transferase. Of the azido, amino, and acetamido compounds tested, only the 4-amino compound (2) produced significant inhibition of this enzyme.

The synthesis of a series of bicyclic 2-hexulose derivatives (5), (6) and (7), which provide access to regiospecific carbohydrate-based ketone enolates, is described. The preparation of silyl enol ethers (21) and (22) from keto ether (5) and keto acetal (6), respectively, is also reported

Details are described of preliminary synthetic studies, based on Lewis acid-mediated alkylation of a silyl enol ether, that were directed towards the C11 glycoside of the herbicidin class of nucleosides. The chemistry presented focuses on limitations encountered with the reactivity of both the electrophilic and nucleophilic components designed to serve this longer term synthetic objective. α-Chloro sulfide 6 readily undergoes a Lewis acid-promoted internal redox reaction leading to sulfide 8; this is a consequence of the O-benzyl protecting group used at C-3 of chloro sulfide 6. This pathway is avoided by use of O-silyl protection, and reaction of the silyl-protected α-chloro sulfide 11 with the simple heterocyclic silyl enol ether 5 gives the herbicidin models 13a and 13b incorporating the required furano-pyrano-pyran skeleton. Further experiments showed that the nucleophilic component required for the herbicidins, the carbohydrate-based silyl enol ether 2, readily underwent Lewis acid-mediated rearrangement to give levoglucosenone 15.

Zirconocene η 2 -imine complexes formed by a CH activation route from a variety of amines are trapped by ω-halo-alkenes or -alkynes to afford 2,3-disubstituited pyrrolidines, piperidines and perhydroazepines on work up and cyclisation. In some cases it was necessary to use a protected hydroxyl group rather than the halide and cyclise in a separate step through selective formation of the O-mesylate.

The multigram synthesis of (2S)- and (2R)-2-(1-methylethyl)-5-oxo-2-phenylpentanenitriles 9a and 9b is described, using either (4R)-2,2-dimethyl-1,3-dioxolan-4-ylmethanol or (2R)-butane-1,2,4-triol as chiral auxiliary. The configuration of an intermediate dioxolane 10b is assigned by X-ray crystallography. The synthetic utility of the aldehydes is demonstrated by conversion to both enantiomers of the calcium antagonist noremopamil in >98% enantiomeric excess(ee). The enantiomeric purity of the final amines is assayed by 1H NMR spectroscopy in the presence of the chiral solvating agent (1R)-(–)-2,2,2-trifluoro-1-(9-anthryl)ethanol.

The three structural analogues of dec-9-enyl β-D-galactosyl-(1→4)-α-D-mannosyl phosphate, comprising thiophosphate, boranophosphate and methylphosphonate derivatives, were prepared via disaccharide H-phosphonate or trichloroacetimidate (for the methylphosphonate synthesis) intermediates.

A set of phosphodisaccharides, structural analogues of the β-D-galactosyl-(1→4)-α-D-mannosyl phosphate 1, are synthesized using the Koenigs–Knorr method for the glycosylation reactions and the glycosyl hydrogenphosphonate method for phosphorylation. The compounds were tested as acceptor substrates/putative inhibitors for the Leishmania α-D-mannosylphosphate transferase.

The protozoan parasite Trypanosoma cruzi is a causative agent of Chagas' disease, which affects millions of people in South and Central America. Throughout the life cycle, T. cruzi produce both common and stage-specific glycosylphosphatidylinositol(GPI)-anchored cell-surface macromolecules. The purified GPI fraction of T. cruzi trypomastigote mucins (tGPI) revealed extraordinary pro-inflammatory activity (comparable to those of bacterial lipopolysaccharide), which was allegedly associated with the presence of unsaturated fatty acids in the lipid moiety (structures 1 and 2). Two distinct novel synthetic strategies, both implicating the use of non-benzyl type protecting groups, were designed and applied for the chemical preparation of the tGPIs 1 and 2.

Novel inhibitors of Trypanosoma brucei and mammalian UDP-Glc 4'-epimerase were identified by screening a small library of natural products and commercially available drug-like molecules. The inhibitors possess low micromolar potency against the T. brucei and human enzymes in vitro, display a degree of selectivity between the two enzymes, and are cytotoxic to cultured T. brucei and mammalian cells.

The strengths of the SeCl2−Cl-, SeOCl2−Cl-, SeBr2−Br-, and TeCl2−Cl- bonds have been measured to be 133 ± 9, 150 ± 10, 110 ± 6, and 170 ± 7 kJ mol-1, respectively, by determining thresholds for collision-induced dissociation in a flowing afterglow-tandem mass spectrometer. These values are stronger than the previously measured D(SCl2−Cl-) and D(SOCl2−Cl-), both 85 ± 8 kJ mol-1. Bond energies and other properties for these molecules and TeOCl3- have also been computed by several high-level computational techniques, including B3LYP/aug-cc-pVTZ. There is excellent agreement between the experimental and computational energetics for SeCl3-, SeOCl3-, and TeCl3-. The bond strengths increase in the order S < Se < Te.

Deoxy and other analogues of d -glucosaminylphosphatidylinositol 1 have been synthesised and tested as substrates or inhibitors of a de- N -acetylase and mannosyltransferase (MT-1) involved in the biosynthesis of the glycosylphosphatidylinositol (GPI) membrane anchor of the parasite Trypanosoma brucei.

Appropriately protected deoxy and other analogues of 2-azido-2-deoxy- d -glucopyranosyl fluoride have been synthesised preparatory to inclusion into analogues of the d -glucosaminylphosphatidylinositol 1 .

The natural product (3) has been modified to provide the semi-synthetic nemadectins (15), (17), and (18).

Condensation of cyclic secondary α- amino esters with aryl aldehydes containing an ω-alkenyl group leads to intramolecular 1,3-dipolar cycloaddition, via an intermediate azomethine ylide, in good yield. The stereochemistry of the azomethine ylides is controlled by steric interactions developing during conversion of the intermediate carbinolamines to the iminium ion species and generally results in stereo specific dipole formation. There is no pronounced endo - exo selectivity in these cycloadditions and an intramolecular β-acrylate moiety is a more reactive dipolarophile than an intermolecular maleimide moiety.

The first macrocyclic diesters of (–)-platynecine (3) containing 10- and 11-membered rings have been prepared. (–)-Platynecine was obtained by catalytic hydrogenation of readily available (+)retronecine (1). Esterification of (+)-retronecine with different glutaric anhydride derivatives yielded mainly the 9-monoesters of (+)-retronecine. Lactonisation was carried out under high dilution conditions via the S-2-pyridyl thioesters to give the 11-membered macrocyclic diesters [(4)–(7)] of (–)-platynecine. Similar treatment of (–)-platynecine with succinic anhydride, and with cis- and trans-cyclohexane-1,2-dicarboxylic anhydride, produced the 10-membered pyrrolizidine alkaloid analogues (8), (9), and (10), respectively.