Methyl 3-oxo-4-androstene-17β-carboxylate was prepared from pregnenolone acetate by bromoform reac-tion and esterification to give methyl 3β-hydroxy-5-androstene-17β-carboxylate, which subjected to Oppenauer oxidation in presence of aluminium isopropoxide using 2-nitrobenzaldehyde as hydrogen acceptor in toluene at 95℃ for 2h.

The Interspecific Competiton Between Woloszynskia sp. and Alexandrium tamarense:Influence of Phosphate Concentration and Initial Cell Density;