Synthesis and biological evaluation of optically active 3-H-1-carbacephem compounds

3-H-1-Carbacephem nuclei with or without a 2 alpha- or 2 beta-methyl group were prepared via 2 + 2 cycloaddition followed by intramolecular Horner-Emmons cyclization. Optically active 3-H-1-carbacephem compounds were efficiently prepared by employing a penicillin acylase-producing microorganism in two ways. That is, the 7-phenylacetamide of a racemic carbacephem nucleus was hydrolyzed enantioselectively with the enzyme to afford the optically pure nucleus, which was then acylated to give antimicrobial compounds. Alternatively, a racemic carbacephem nucleus was directly and enantioselectively phenylglycylated with the enzyme. 3-H-1-Carbacephem nuclei appeared to be better substrates for penicillin acylase than penam or cephem nuclei of natural origin. 3-H-1-Carbacephem compounds showed potent antimicrobial activity; compound 32a exhibited activity comparable to that of ceftizoxime, a cephem analog with the same acyl group. It is of interest that the 3-H-1-carbacephem compound turned out to have more potent antimicrobial activity than its 3-substituted methyl analog.     

Novel synthesis of polyimide with pendant 1-phenylethyl ester using DBU and its thermal acid-catalyzed deesterification

A model reaction of o-(N-phenylcarbamoyl)benzoic acid (amic acid) with threefold amounts of 1-phenylethyl bromide (PEB) and 1,8-diazabicyclo-[5,4,0]-7-undecene (DBU) was carried out in NMP. The reaction gave N-[m-(1-phenylethoxycarbonyl)phenyl]phthalimide in almost quantitative yield at room temperature for 2 h. Polyimide containing pendant 1-phenylethyl ester (P-1a) was also prepared from polyamic acid with PEB using DBU according to the model reaction. The obtained polymer was exactly consistent with P-1a synthesized stepwise from the esterification of the corresponding polyimide containing pendant carboxylic acid with PEB. Therefore, the reaction of polyamic acid bearing pendant carboxylic acid with alkyl bromide proceeded quantitatively to give polyimide containing pendant ester in the presence of DBU. Also, this method was applied to the synthesis of polyimide containing 1-phenylethyl ether. However, the polyimide with quantitative etherification was not synthesized. The acid-catalyzed deesterification of P-1a film was carried out by heating the irradiated polymer film containing 10 wt % of p-nitrobenzyl 9,10-diethoxyanthracene-2-sulfonate, which produced sulfonic acid by irradiation, at various temperatures. Although thermal deesterification of P-1a started at 220°C without any acid catalyst, the deesterification occurred when the irradiated film was heated at the lower temperature. The degree of esterification can be determined from the disappearance of absorption at 700 cm⁻¹. The deesterification obeyed first-order kinetics. © 1996 John Wiley & Sons, Inc.     

Link Cobordism and the Intersection of Slice Discs

We work in the smooth category. An (oriented) (ordered) m-component n-(dimensional) link isa smooth oriented submanifold L = {K₁, ..., K_m} of Sⁿ⁺² whichis the ordered disjoint union of m manifolds, each PL-homeomorphicto the standard n-sphere. If m = 1, then L is called a knot. We say that m-component n-dimensional links L₀ and L₁ are (link-)concordantor (link-)cobordant if there is a smooth oriented submanifoldC = {C₁, ..., C_m} of Sⁿ⁺² x [0, 1] which meets the boundarytransversely in C, is PL-homeomorphic to L₀ x [0, 1], and meetsSⁿ⁺² x {l} in L_l (l = 0, 1). If m = 1, then we say that n-knotsL₀ and L_l are (knot-)concordant or (knot-)cobordant. Then wecall C a concordance-cylinder of the two n-knots L₀ and L_l. If an n-link L is concordant to the trivial link, then we callL a slice link. If an n-link L = {K₁, ..., K_m} Sⁿ⁺² = Bⁿ⁺³ Bⁿ⁺³ is slice,then there is a disjoint union of (n + 1)-discs in Bⁿ⁺³ such that is called a set of slice discs for L. If m = 1, then is called a slice disc for the knotL. 1991 Mathematics Subject Classification 57M25, 57Q45.     

Facile Synthesis of 1,4-Dihydropyridine Monocarboxylic Acids and Unsymmetric Dicarboxylates via Quaternary Ammonium Salts of 2-Aminoethyl 1,4-Dihydropyridine-3,5-dicarboxylates

Useful 1,4-dihydropyridine unsymmetric dicarboxylates [nitrendipine (1), nicardipine (2)] and monocarboxylic acid 4 were prepared from unsymmetric 2-aminoethyl methyl 1,4-dihydropyridine-3,5-dicarboxylates 2 and 3 via their corresponding quaternary ammonium salts 5–9.     

The intersection of three spheres in a sphere and a new application of the Sato-Levine invariant

Take transverse immersions such that (1) is an embedding, (2) and is connected, and (3) . Then we obtain three surface-links = (, ) in , where =(1,2,3), (2,3,1), (3,1,2). We prove that, we have the equality where is the Sato-Levine invariant of , if all are semi-boundary links.

     

Some properties of ordinary sense slice 1-links: some answers to problem (26) of Fox

We prove that, for any ordinary sense slice 1-link , we can define the Arf invariant, and Arf()=0. We prove that, for any -component 1-link , there exists a -component ordinary sense slice 1-link of which is a sublink.