No description available.

Ring A of Ambruticin, in derivatized form (88), and a ring B derivative (93) were synthesized and used to determine the absolute stereochemistry of Ambruticin. The critical step that served to fix the stereochemistry in ring A could not be repeated on another system. Phosphonate 46 allowed the three-carbon homologation of aldehydes to conjugated ketene dithioacetals, but these could not be hydrolyzed. The resolution of 2-acetoxyaldehydes by 1-ephedrine was generalized, and an attempt was made to rationalize the behaviour of the intermediate oxazolidines, and to settle the controversy over their C(,2)-configurations.

No description available.

No description available.

A new method for the preparation of 1,5-disubstituted-1Z,4Z-pentadienes by the addition of alkenyl cuprates to vinyltriphenylphosphonium bromide followed by an aldehyde is described. This method is used for the syntheses of 6Z,9Z-heneicosadiene and 15,15-(diethyldithio)-13S-t-butyldiphenylsilyloxy-6Z,9Z,11E-pentadecatriene. Syntheses of $(-)$-(5R)-argentilactone and (+)-(5R)-goniothalamin are described. Model studies towards the synthesis of the novel antileukemic agent CI-920 were carried out.

The total synthesis of the biologically active, dextrorotatory enantiomer of 3-methyl-7(beta)-phenylacetamido-(DELTA)('3)-O-2-isocephem-4-carboxylic acid was accomplished. The key step involved the asymmetric cycloaddition of azidoacetyl chloride to the cinnamylidene Schiff base of protected D-threonine to generate the desired monocyclic cis (beta)-lactam diastereomer (9:1). The absolute configuration of the final product was confirmed by comparing its antimicrobial activity with that of the corresponding racemate. / The influence of (a) the (beta)-chiral center in the starting (alpha)-amino acid, (b) the bulk of the carboxylic acid and (c) the distribution of bulk throughout the imine on the stereochemical outcome of the reaction was studied. The absence of racemization during the cycloaddition was demonstrated by the use of deuterated precursors. The great potential of D-glucosamine derivatives as chiral templates in this reaction was clearly illustrated.

The syntheses of the cephalosporin analogs cis-N-(2'-hydroxyphenyl)-3-phenylacetamido-4-hydroxymethyl-2-azetidinone (37), cis-N-(2'-hydroxy-5'-nitrophenyl)-3-phenylacetamido-4-hydroxymethyl-2-azetidinone (59) and 7-(beta)-phenylacetamido-3'-hydroxybenzo{3,4}-0,2-isocephem (77) are described. Compounds 37 and 59 were devoid of antibacterial activity, while (beta)-lactam 77 showed weak activity against two micoorganisms. / Two new ring systems, 2-phenylcarbapenams 146 and 157 have been prepared. These are key intermediates in the syntheses of phosphonic acid carbapenam 148 and the carboxylic acid derivative 158, respectively. / The one carbon homologation of (beta)-trimethylsilyl-(alpha),(beta)-unsaturated esters with diazomethane was extended to the corresponding (beta)-trimethylsilyl or (beta)-t-butyldimethylsilyl aldehydes.

No description available.

No description available.

The use of Mitomycin C in the treatment of a wide range of neoplastic conditions is discussed. The mechanism of action of mitomycin anticancer antibiotics under reductive activation conditions using either enzymes, sodium dithionite, catalytic hydrogenation or chromium (Il) perchlorate is examined, as is the alkylation of DNA. An intramolecular [3+2] cycloaddition strategy has been employed to synthesise the pyrrolo[I,2-aJ]indole nucleus for a wide range of cyclopropamitosenes, whereas the key step in the synthesis of pyrrolo[I ,2-a]indoles without the cyclopropane ring was a modified Wittig reaction. From the onset of the work it was important to investigate the role of the 7 -methoxy group. Hence a variety of cyclopropamitosenes or related pyrrolo[I,2-a]indoles were subjected to C-7 exchange reactions with either (i) other alkoxides or (ii) cyclic / acyclic amines. In this way, structural modification at C-7 can be related to the biological results. Biological and electrochemical data were recorded for the cyclopropamitosenes and related pyrrolo[I,2-a]indoles and correlated with their structures.