Steric effects ih the reaction of di(bromomagnesio)alkanes with carboxylic esters

Largely different product distributions were observed on the action of various carboxylic esters with 1,4-di(bromomagnesio)butane and its homologue 1,5-di(bromomagnesio)pentane. The much larger yields of reduction product with the latter are the evidence for the structural geometric requirements for the annelation step.     

Heterodyne mixing experiments with NbN-based SIS junctions

Tests of niobium-nitride-based SIS junctions in our experimental receiver at ENS¹ have shown the remarkable stability in time and through thermal cycling of these high T_C material junctions; they were used to evaluate the real junction temperature in our vacuum cryogenerator. Results of heterodyne mixing experiments are presented at 100 GHz, showing that further progress in fabrication would be necessary. Detection experiments were performed at 460 GHz with encouraging results.     

Phototoxicity of Some Bromine-Substituted Rhodamine Dyes: Synthesis, Photophysical Properties and Application as Photosensitizers

Abstract— The synthesis of some bromine-substituted rhodamine derivatives viz. , 4,5-dibromorhodamine methyl ester (dye 2) and 4,5-dibromorhodamine n -butyl ester (dye 3) are reported. These dyes were synthesized to promote a more efficient cancer cell photosensitizer for potential use in in vitro bone marrow purging in preparation for autologous bone marrow transplantation. Spectroscopic and photo-physical characterization of these dyes together with rhodamine 123 (dye 1) are reported in water, methanol, eth-anol and also in a microheterogeneous system, sodium dodecyl sulfate. The possible mechanism of photosensi-tization is characterized in terms of singlet oxygen efficiency of these dyes. Singlet oxygen quantum yields for bromine-substituted dyes are in the range of 0.3-0.5 depending on the solvent. For dye 1 no singlet oxygen production is found. The photodynamic actions of these dyes in different cell lines are tested. It was found that dye 2 and dye 3 are efficient photosensitizers and mediate eradication of K562, EM2, myeloid cell lines (CML) and the SMF-AI rhabdomyosarcoma line.     

The symmetric traveling salesman polytope and its graphical relaxation: Composition of valid inequalities

The graphical relaxation of the Traveling Salesman Problem is the relaxation obtained by requiring that the salesman visit each city at least once instead of exactly once. This relaxation has already led to a better understanding of the Traveling Salesman polytope in Cornuéjols, Fonlupt and Naddef (1985). We show here how one can compose facet-inducing inequalities for the graphical traveling salesman polyhedron, and obtain other facet-inducing inequalities. This leads to new valid inequalities for the Symmetric Traveling Salesman polytope. This paper is the first of a series of three papers on the Symmetric Traveling Salesman polytope, the next one studies the strong relationship between that polytope and its graphical relaxation, and the last one applies all the theoretical developments of the two first papers to prove some new facet-inducing results.This work was initiated while the authors were visiting the Department of Statistics and Operations Research of New York University, and continued during several visits of the first author at IASI.     

Syntheses of Strychnos and Aspidospermatan-Type Alkaloids. 8. Selective Total Syntheses of Mossambine and 14-epi-Mossambine by a Radical Cyclization Reaction(1)

Mossambine (6) was obtained by a six-step reaction sequence from the indoloazepine ester 7. Radical cyclization of the tetracyclic vinyl iodide 12a provided a racemic pentacyclic ketone 16E, which could be converted to either enantiomer by condensation with (S or R)-N,S-dimethyl-S-phenylsulfoximine and selective pyrolysis of the resulting diastereomeric alcohols 18 and 19 or 20 and 21. Selective reductions of the resolved (or racemic) ketone 16E provided mossambine (6) and its hydroxy epimer 17.