Abstract :
The structures of UCS1025A and related natural products are featured by a tricyclic furopyrrolizidine connected to a trans-decalin fragment. The genome of a thermophilic fungus is mined and the ucs gene cluster is activated to produce UCS1025A at a high titer. Oxidation of the 3S-methyl group to a carboxylate leads to an oxa-Michael cyclization and furnishes the furopyrrolizidine.