Synthesis of 7-Deamidocephalosporin Lactone. Preliminary Communication

Condensation of azetidinone 1 with mercaptan 3 gave compound 5 . Bromination of 5 afforded two isomeric bromohydrins 11a and 11b which differ in the configuration at C(4). Acetylation and reduction with zinc and acetic acid of the above bromohydrins gave 7-deamidocephalosporin lactone ( 14 ).     

Synthese eines steroidischen 17 β-Pyrrolinons. Partialsynthetische Versuche in der Reihe der Herzgifte. 10.Mitteilung

Synthesis of a steroidal 17 β-pyrrolinone We describe the synthesis of 4′-(3 β-hydroxy-androst-5-ene-17 β-yl)-3′-pyrrolin-2′-one (6) starting from 3β-acetoxy-21-hydroxy-pregn-5-ene-20-one (1).     

Chemically Triggered Assembly of Chiral Triangular Metallomacrocycles

Self-assembly of chiral, half-sandwich complexes results in the formation of triangular metallomacrocycles under complete stereocontrol and in quantitative yields. The assembly-disassembly process can be triggered by the addition of acid or base (see scheme).     

Affine geometry over free unitary modules

In this paper we consider systems (P,L,,), where P is an arbitrary non-empty set, L a set of subsets of p and resp. a relation on PxP resp. LxL. In successive stages adding geometrical axioms, we characterize the class of those structures (P,L, ,), which coincides — up to isomorphisms — with the class of all Affine Barbilian-Spaces.     

Metal complexes with macrocyclic ligands. XIII. The complexation of Cu2+ with triazacycloalkanes

The potentiometric study of the complexation of Cu²⁺ with 1,4,7-triazacyclononane ( 1 ), 1,4,8-triazacyclodecane ( 2 ) 1,5,9-triazacyclododecane ( 3 ) has shown that CuL, CuL₂ and (CuLOH)₂ are the main species present in solution. Their stabilities (Table 1) and their absorption spectra (Table 2) indicate facial coordination of the cyclic triamines in a distorted octahedral geometry. The formation and dissociation kinetics have been measured by stopped-flow techniques. The formation in acetate buffer can be described by the reaction of Cu²⁺ and CuAcO⁺ with the monoprotonated species of the ligand. The bimolecular rate constants for these complexations (Table 3) decrease when the ring size increases. In contrast the dissociation induced by acid is only little affected by the ring size. Thus for these complexes the rate of formation and not that of the dissociation determines the overall stability.     

Combinatorial synthesis of bimetallic complexes with three halogeno bridges

Methods for the synthesis of bimetallic complexes in which two different metal fragments are connected by three chloro or bromo bridges are reported. The reactions are general, fast, and give rise to structurally defined products in quantitative yields. Therefore, they are ideally suited for generating a library of homo- and heterobimetallic complexes in a combinatorial fashion. This is of special interest for applications in homogeneous catalysis. Selected members of this library were synthesized and comprehensively characterized; single-crystal X-ray analyses were performed for 15 new bimetallic compounds.