FR-900848 (1) shows potent, selective activity against filamentous fungi such as Aspergillus niger, Mucor rouxianus, Aureobasidium pullulans, and various Trichophyton sp. etc. In contrast it is essentially inactive against non-filamentous fungi such as Candida albicans and Gram -positive and -negative bacteria. It shows activity in-vivo and is not appreciably toxic. Thus FR-900848 (1) represents a significant new lead for the design of nucleoside antifungal agents active against the major human pathogen Aspergillus fumigatus.
The stereochemistry and full structure of FR-900848 (1) has recently been established2 and a total synthesis completed.3 A series of model compounds were prepared using multiple asymmetric Simmons-Smith cyclopropanation reactions. Comparisons of spectroscopic data of synthetic 1,2-dicyclopropylethene, 1,12-quatercyclopropanedimethanol and 2-methylcyclopropanecarboxaldehyde derivatives of defined absolute stereochemistry with FR-900848 (1) and its degradation products were used to unequivocally establish the absolute stereochemistry of the natural product. A C2-symmetric 1,12-quatercyclopropanedimethanol was converted by desymmetrisation, selective monocyclopropanation and homologation into the fatty acid side chain of FR-900848. Coupling of this carboxylic acid with 5'-amino-5'-deoxydihydrouridine gave synthetic FR-900848. The unusual helical structure of FR-900848 is comparable with UC-11136, a cholesteryl ester transfer protein inhibitor from the fermentation broth of Streptomyces sp. UC 11136.4