Synthesis of 2-Chloro-3-phthalimido-4-azetidinone and Related Derivatives from Penicillins

The current interest in new azetidinone antibiotics and their preparation has stimulated an intensive search for the synthesis of appropriately substituted monocyclic azetidinones.2- 5 Our initial efforts in this field resulted in the chlorinolysis of the carbon-sulfur bond in penicillin

Reactions of Penicillin Esters and Related Compounds with 1-Chlorobenzotriazole

Recently we reported chlorinolysis of the carbon-sulfur bond in penicillins1. Depending on the amount of halogen used, two kinds of products are .isolated. With 1 mole of chlorine, the reaction gives azetidinone sulfenyl chlorides III and with 2 moles of chlorine, olefinic azetidinone derivatives IV are formed

Thiazabicycloheptenones. Synthesis of Bicyclic Thiazoline Azetidinone Derivatives

Chlorinolysis of the S1-C5 bond in penicillin G and the subsequent cyclization of the obtained product to the thiazabicycloheptenone is described. The intermediate azetidinone imidoyl chloride III is prepared by treatment of the olefinic azetidinone II with phosphorous pentachloride. Cyclization of III is effected with thioacetate anion or hydrogen sulfide in the presence .of triethylamine. The structure and chirality of thiazabicycloheptenone IV were established by spectral data as well as by comparison with the sample prepared by an independent manner3 from penicillin G sulfoxide

Synthesis of 2-Chloro-3-phthalimido-4-azetidinone and Related Derivatives from Penicillins

The current interest in new azetidinone antibiotics and their preparation has stimulated an intensive search for the synthesis of appropriately substituted monocyclic azetidinones.2- 5 Our initial efforts in this field resulted in the chlorinolysis of the carbon-sulfur bond in penicillin

Reactions of Penicillin Esters and Related Compounds with 1-Chlorobenzotriazole

Recently we reported chlorinolysis of the carbon-sulfur bond in penicillins1. Depending on the amount of halogen used, two kinds of products are .isolated. With 1 mole of chlorine, the reaction gives azetidinone sulfenyl chlorides III and with 2 moles of chlorine, olefinic azetidinone derivatives IV are formed

Topological Phases in Graphitic Cones

The electronic structure of graphitic cones exhibits distinctive topological features associated with the apical disclinations. Aharonov-Bohm magnetoconductance oscillations (period Phi_0) are completely absent in rings fabricated from cones with a single pentagonal disclination. Close to the apex, the local density of states changes qualitatively, either developing a cusp which drops to zero at the Fermi energy, or forming a region of nonzero density across the Fermi energy, a local metalization of graphene.Comment: 4 pages, RevTeX 4, 3 PostScript figure

Thiazabicycloheptenones. Synthesis of Bicyclic Thiazoline Azetidinone Derivatives

Chlorinolysis of the S1-C5 bond in penicillin G and the subsequent cyclization of the obtained product to the thiazabicycloheptenone is described. The intermediate azetidinone imidoyl chloride III is prepared by treatment of the olefinic azetidinone II with phosphorous pentachloride. Cyclization of III is effected with thioacetate anion or hydrogen sulfide in the presence .of triethylamine. The structure and chirality of thiazabicycloheptenone IV were established by spectral data as well as by comparison with the sample prepared by an independent manner3 from penicillin G sulfoxide

A continuous isotropic-nematic liquid crystalline transition of F-actin solutions

The phase transition from the isotropic (I) to nematic (N) liquid crystalline suspension of F-actin of average length $3~\mu$m or above was studied by local measurements of optical birefringence and protein concentration. Both parameters were detected to be continuous in the transition region, suggesting that the I-N transition is higher than 1st order. This finding is consistent with a recent theory by Lammert, Rokhsar & Toner (PRL, 1993, 70:1650), predicting that the I-N transition may become continuous due to suppression of disclinations. Indeed, few line defects occur in the aligned phase of F-actin. Individual filaments in solutions of a few mg/ml F-actin undergo fast translational diffusion along the filament axis, whereas both lateral and rotational diffusions are suppressed.Comment: 4 pages with 4 figures. Submitted to Physical Review Letter

Nonperturbative approach to the Hubbard model in C60 cluster

We propose a computational scheme for the Hubbard model in the C60 cluster in which the interaction with the Fermi sea of charges added to the neutral molecule is switched on sequentially. This is applied to the calculation of the balance of charging energies, within a low-energy truncation of the space of states which produces moderate errors for an intermediate range of the interaction strength.Comment: 5 pages, Revtex, 2 figure

Dephthaloylation of Phthalimido-Containing Cephalosporins and Penicillins

Dephthaloylation of phthalimido functionalized cephalosporins and penicillins via the corresponding phthalisoimides was performed. Experimental procedures and mechanism of reaction are described