@-Alanine, an inexpensive a-amino acid, was converted into the 2-tert- butylperhydropyrimidin-4-one derivative 2, which can be alkylated with high diastereoselectivity via the corresponding enolate. The high stereoselectivity observed for the reaction of 2-Li with electrophiles seems to be due to steric hindrance generated by an axial disposition of the tert-butyl group at C (2), which directs addition from the enolate ...