In summary, palladium-catalyzed cross-coupling reaction of 2-iodinated purines with organostannanes is a highly efficient approach to the synthesis of new and rare functionalized purine nucleosides. This approach may find wide application in purine and related heterocyclic chemistry. Biological studies assessing the antiviral activities of the target molecules against RNA viruses are currently under investigation. Mitomycins are potent antitumor antibiotics, and considerable research efforts have been made to rationalize the mechanism of action of mitomycins. As part of our approach, we have been screening the minor constituents from the fermentation broth of mitomycins since 1977. Fortuitously, we found two novel isomers of mitomycin A (1), designated as albomitomycin A (2) and isomitomycin A (3), from streptomyces caespitosus, and their tripartite interconversion (1 and 3 via 2), refered to as mitomycin rearrangement. We herein report the structure elucidation of 2 and 3 and their unique intramolecular reactions in Michael and retro-Michael modes. Fresh insights on the 1,4-diradical tetramethylene generated thermally from tetrahydropyridazine (TP) and from cyclobutane (CB) have been gained through studies of stereospecifically deuteriated substrates. At 380-420 OC, tetramethylene fragments to ethene about twice as fast as it closes to form CB; the two ends of the diradical appear to be stereochemically independent, with rotations about C-C bonds much more rapid than