Reaction of pentacyclo[5.4.0.02,6.03,10.05,9]undecan-8-one (1) with H2NOSO3H-HCO2H affords two pentacyclic lactams (2a) (15%) and (2b) (30%). Reaction of 1 with HN3-Tf2O results in the formation of a pentacyclic urea (3) (16%) and a tricyclic azidonitrile (4) (18%). The unusual "double Schmidt rearrangement" that results in the formation of 3 is rationalized via formation of an intermediate tetrazole (5) which undergoes subsequent acylation with concomitant Huisgen rearrangement. © 1995.