Synthesis and biological activity of 19-azasqualene 2,3-epoxide as inhibitor of 2,3-oxidosqualene cyclase

19-Azasqualene 2,3-epoxide and its N-oxide, high-energy intermediate analogue inhibitors of 2,3-oxidosqualene (SO) cyclase, were obtained by total synthesis. These compounds were designed to mimic the C-20 carbonium ion precursor of lanosterol formed during SO cyclization. The synthesis involved the preparation of C₂₂ squalenoid aldehyde epoxide through a new procedure and the reconstruction of the squalenoid chain bearing a nitrogen at C-19 (pro C-20). 19-Azasqualene 2,3-epoxide was active on SO cyclase from rat and pig liver with an IC₅₀ of 1.5 μM in pig, while in SO cyclases of yeast (S cerevisiae and C albicans) microsomes it was 20-30-fold less active. It was inactive on squalene epoxidase from rat and pig liver at the highest concentrations tested (100 μM).