(+)-Septorine, a metabolite of Septoria nodorum, was synthesized via alanyl-isoleucyl anhydride (2) from L-isoleucine at the first time. Compound (2) was led to a pyrazine-carboxaldehyde (13), which was treated with p-methoxymethoxy-phenylmagnesium bromide to afford an alcohol (14) in a quantative yield. The alcohol (14) was oxidized to a ketone (16), which was subjected to the Pummerer reaction and the following hydrolysis to give (+)-septorine.