Synthesis of novel 6-alpha and 6-beta-alkylcarbonylmethyl substituted penems.

6-alpha and 6-beta Alkylcarbonylmethyl penems were synthesized from 6-alpha-bromo and 6-oxo penicillanates respectively and their in vitro antibacterial activity was studied. The compounds were generally active against Gram-positive but not against Gram-negative strains, the compounds of the 6-beta series being more active. Relatively to imipenem, taken as reference compound, the penems resulted more stable towards chemical hydrolysis in Tris-HCl buffered medium (pH 7.4) but more sensitive towards dehydropeptidase-I (DHP-I).

Synthesis and antimicrobial activity of DNA-gyrase inhibiting derivatives of 4-oxo-1,4-dihydro-3-pyridinecarboxylic acid.

A series of 6-substituted-1-aryl-4-oxo-1,4-dihydronicotinic acids were synthesised as monocyclic analogues of the quinolones. The 6-(2-aryl-1-methylethenyl)- and of the 6-(2-arylethenyl)-substituted compounds were shown to possess antibacterial properties that correlate with DNA gyrase inhibitory activity. Differently from the quinolones the antimicrobial activity of the compounds of this study is predominantly against Gram positive strains. The structure-activity relationships ascertained for these monocyclic compounds differ from those established for the quinolones.

Synthetic homo-oligomethionine chemoattractants. Conformation-activity study.

Using solution methods, we have synthesized several series of L-methionine homo-oligopeptides from the dipeptide to the hexapeptide with either a free alpha-carboxyl function or different C-blocking groups (methoxy, benzyloxy, benzylamino) and with N-blocking groups of either the amide type (formyl, pivaloyl) or the urethane type (tert.-butyloxycarbonyl). Compounds were compared to determine the combined effect of main-chain length and presence and nature of N- and C-blocking groups on conformation-activity relationship. Each peptide was tested for its ability to induce rabbit peritoneal polymorphonuclear leukocytes in the presence of cytochalasin B to secrete granule enzymes. In parallel, a conformational analysis was carried out in the solid state and in solution, using infrared absorption and circular dichroism. The biological and conformational data are discussed in relation to a recently proposed model of the chemotactic peptide receptor of rabbit neutrophils.