A Convenient Method for Constructing Oxazolidine and Thiazolidine Rings in C₂₀-Diterpenoid Alkaloid Derivatives

Abstract

Recently we isolated and elucidated¹ the structures of two new C₂₀-diterpenoid alkaloids, lindheimerine (1) and ovatine (2), from Garrya ovata var. lindheimeri. To correlate lindheimerine with ovatine and to prepare some new oxazolidine and thiazolidine ring-containing analogs from the imine-containing derivatives for biological testing and spectral studies, we required a simple, high-yield method for constructing these rings. The earlier method reported² for constructing the oxazolidine ring from the imine derivative requires the use of a quaternization reaction involving ethylene chlorohydrine in dimethylformamide at 80°C.