TRIUMF resonant ionization laser ion source

The range of isotopes available at the TRIUMF Isotope Separator Accelerator (ISAC) facility has been greatly enhanced by adding a Resonance Ionization Laser Ion Source (RILIS). A large wavelength range is accessible with the fundamental, second and third harmonic generation of titanium-sapphire laser light. In addition a dedicated laser is available for non-resonant laser ionization. The first on-line beam ⁶²Ga was delivered in Dec. 2004. In general RILIS improves the intensity, purity and emittance of ion beams. ⁶²Ga and ²⁶Al and Be beams have been delivered so far on-line. This work was financed by TRIUMF which is federally funded via a contribution agreement through the National Research Council of Canada.     

Synthesis and characterization of a semiflexible liquid crystalline polyester with a broad nematic region

In this paper, we report on the synthesis and detailed characterization of a new semiflexible nematic liquid crystalline polyester which could serve as a 'model' polyester for a variety of physical and physico-chemical investigations. The polymer is a nematic liquid over a wide temperature range-from the glass transition temperature at ∼95°C to the isotropic transition at ∼240°C. We expect this polyester to be particularly useful for studying the effect of flow on the orientation of liquid crystalline polymers, as well as the production and removal of disclinations.     

A practical synthesis of kifunensine analogues as inhibitors of endoplasmic reticulum alpha-mannosidase I

[reaction: see text] A practical synthesis of the potent class I alpha-mannosidase inhibitor kifunensine (1) beginning from the inexpensive and readily available starting material L-ascorbic acid (15) is described. The protected amino-alcohol ((2R,3R,4R,5R)-5-amino-2,3:4,6-diisopropylidenedioxyhexanol, 11) served as a key intermediate from which several N-1 substituted kifunensine analogues (including N-methyl, N-cyclohexyl, and N-bis(hydroxymethyl)methyl) and 2-desoxakifunensine analogues (including N-H and N-methyl) were prepared and screened for inhibition of human endoplasmic reticulum alpha-mannosidase I (ER Man I) and mouse Golgi alpha-mannosidase IA (Golgi Man IA). In addition, several pseudodisaccharide kifunensine analogues in which a mannose residue was tethered to N-1 of kifunensine via a two-, three-, or four-carbon linker and an affinity-bound kifunensine analogue were also prepared and evaluated for biological activity. While the synthesized N-1 kifunesine analogues were found to be less potent inhibitors of Class I alpha-mannosidases than kifuensine itself, the bis(hydroxymethyl)methylkifunensine analogue 6 was shown to selectively inhibit ER Man I over Golgi Man IA.     

The NMR spectra of porphyrins—19: 13C and proton NMR spectra of metal-free porphyrins with the Type-IX substituent orientation,and of their zinc(II) complexes

The ¹³C and proton NMR spectra of six porphyrins bearing the substituent orientation characteristic of the natural “Type-IX” arrangement are reported and assigned. Significant concentration effects in the spectra of the free base porphyrins, together with the broadening of the C_α (and occasionally C_β) carbon resonances due to NH tautomerism caused a significant loss of data in these spectra. However, the spectra of the corresponding zinc(II) porphyrins (with addition of excess pyrrolidine) show that both these extraneous effects are completely removed to give well-resolved spectra with accurately reproducible chemical shifts. These spectra are assigned and an analysis of the chemical shifts allows the deduction of substituent chemical shift (SCS) parameters for the peripheral substituents at the beta and meso carbons. There is no global effect of these beta substituents, the beta carbon SCS being confined to the immediate pyrrole ring, and the meso carbon SCS to the two adjacent pyrrole rings. The SCS parameters are analyzed and it is shown how they can be used to predict the peripheral and meso carbon chemical shifts of any porphyrin bearing the substituents discussed.     

Intramolecular azide-diene cycloadditions. An approach to fused bicyclic 3-pyrrolines based on a one-pot nitrene-diene cycloaddition equivalent.

Cyclization of heterosubstituted ω-azidodienes 11 provides fused bicyclic 3-pyrrolines 12 in one operation. These pyrrolines are potentially useful intermediates for natural products synthesis, as illustrated by further functionalization.     

Synthesis of benzo-fused 1-azabicyclo[m.n.0]alkanes via the Schmidt reaction: a formal synthesis of gephyrotoxin

The intramolecular capture of benzocyclobutyl, benzocyclopentyl, and benzocyclohexyl carbocations 7 by azides produces spirocyclic aminodiazonium ions 8, which undergo 1,2-C-to-N rearrangement with loss of dinitrogen to produce benzo-fused iminium ions resulting from either aryl (9) or alkyl (10) migration to the electron-deficient nitrogen atom. Reduction of the iminium ions affords regioisomeric benzo-fused 1-azabicyclo[m.n.0]alkanes, e.g., benzopyrrolizidines, benzoindolizidines, benzoquinolizidines, or perhydrobenzo[f]pyrrolo[1,2-a]azepines in two regioisomeric versions, anilines (e.g., 11-14) and benzylic amines (e.g., 15-18), the result of aryl and alkyl migrations, respectively. Generally, aryl migration is preferred, despite modeling that shows that the lowest energy aminodiazonium ions are those where the departing dinitrogen is preferentially antiperiplanar to the migrating alkyl group rather than the aryl group. The utility of this methodology was illustrated by a formal synthesis of the alkaloid gephyrotoxin 4. A dependence on the efficiency and regioselectivity of the Schmidt reaction upon subtle changes in the structure of the cation precursor was observed, necessitating the exploration of a variety of substrates. Fortunately, these materials were easily made. Ultimately, the azido-alkene 81 bearing a 2-bromoethyl side-chain was useful for the Schmidt reaction, producing the known benzo-fused indolizidine 49, which had been transformed by Ito et al. into gephyrotoxin 4. The synthesis of 49 required nine steps (five purifications) from commercially available 4-methoxy-1-indanone 60 and proceeded in 22% overall yield.