Marine alkaloids from the cylindricine and lepadiformine families possess an interesting spirotricyclic skeleton. An intramolecular nitrone/olefin 1,3-dipolar cycloaddition has been used to form their spirocyclic 1-azaspiro[4.5]decane core in a regio- and stereoselective fashion. The cyclization precursor can be easily accessed using the asymmetric electrophilic hydroxyamination of enolate.