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Chiral, C2-symmetric imidazolium and imidazolinium ions, as well as the corresponding copper or silver bound carbenoids, have been prepared. Structural study of these compounds by X-ray crystallography reveals a chiral pocket that surrounds the putative carbene site or the metal-carbene bond, at carbon 2, in three of the four ligands prepared. Preliminary investigation into the application of these complexes has shown one of them to be highly enantioselective in the hydrosilylation of acetophenone.

A series of lipopeptide compounds co-produced during the fermentation of pneumocandin Ao (L-671 ,329) and related semisynthetic compounds were evaluated in vivo against Pneumocystis carinii pneumonia and systemic candidiasis. In addition, they were tested in vitro against a panel ofpathogenic Candidaspecies and in a Candida membrane 1,3-jS-D-glucan synthesis assay. The results of these studies demonstrate that pneumocandin Ao and pneumocandin Bo (L-688,786) are the most potent compoundswhenconsidering both antipneumocystis and anticandida activity. Other compoundsin the series are selectively more potent against P. carinii or Candida albicans suggesting a diverging structure-activity relationship. Evaluation of these compoundsfor their ability to inhibit C. albicans l,3-/?-D-glucan synthesis in vitro demonstrates that they inhibit this process. A positive correlation between l,3-/?-D-glucan synthesis inhibition and in vitro antifungal activity was also demonstrated for some of the pneumocandins.

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