An approach to the isoschizozygane alkaloid core using a 1,4-dipolar cycloaddition of a cross-conjugated heteroaromatic betaine.

[reaction: see text] A new strategy for the synthesis of the isoschizozygane alkaloid core has been developed that is based on a 1,4-dipolar cycloaddition reaction of a cross-conjugated heteroaromatic betaine. The resulting cycloadduct undergoes loss of COS, and further reduction delivers a 5a-aza-acenaphthylene intermediate that was transformed into the isoschizozygane skeleton upon treatment with acid.