General access to polyhydroxylated nortropane derivatives through hetero diels-alder cycloaddition. Part II: Synthesis of (±) calystegine B2.

Abstract Calystegine B 2 was prepared by the intramolecular cyclisation of a polyhydroxylated 4-amino-cycloheptanone. This intermediate results from a heteroycloaddtion between an acylnitroso compound and a cyclohepta-1,3-diene. The diene is in turn obtained from iron-complexed tropone.