Macrocyclic 0x0-lactams containing an N-alkylamino side chain are stable natural products. Their electronimpact mass spectra are characterized by intensive [M-H20]+ signals, the molecular ion signal itself is missing. Under electrospray ionization conditions, on the other hand, the [M+ 1]+ ion is the only detected signal. The loss of water is explained in terms of an internal (thermal) Schtff-base formation, leading to a eg bicyclo [ll. 9.4]-system. The ...
