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The synthesis of a tricyclic N-nucleoside analogue in which an ethano bridge linked the urea NH group with the ring junction of the bicyclic tetrahydrofuropyran unit is described. Topological information observed from the structure led to the choice of an ethano bridge tethering the proximal urea nitrogen atom with [C.sub.3] at the junction of the perhydrofuropyran ring system.

An enantioselective synthesis of the antifungal natural product (+)-ambruticin S is achieved starting with the me thyl [alpha]-D-glucopyranoside, (R)-Roche ester, and (S)-glycidol as chirons, which has encompassed seven of the 10 stereogenic centers of the target molecule. The strategy for the construction of the dihydropyran subunit has involved a highly syn-selective Lewis acid catalyzed 6-endo-trig cyclization and other key steps in the synthesis has featured an epoxide opening with a dithiane anion, two efficient phosphonamide-anion based olefinations, and a late-stage C-glycosylation.

The importance of functional group orientations and the integrity of the bicyclic perhydrofuran core of malayamycin A and its N-nucleoside analogues as fungicides are examined. Molecular dynamics studies are performed in order to highlight the importance of properly orienting the urea and methyl ether groups.

A silver-mediated one-step procedure to 2,4-disubstituted and 2,4,5-trisubstituted oxazoles has been developed. The method is complementary to existing technologies, yet provides advantages with regard to simplicity, efficiency, and performance. The silver product can be readily recycled, thus minimizing waste. [ABSTRACT FROM AUTHOR]