Total synthesis of pteridic acids A and B

A convergent synthesis of pteridic acids A and B, epimeric spiroacetal polyketides with potent plant growth promoter properties, is described. The use of boron aldol methodology efficiently achieved the stereocontrolled construction of advanced C1–C11 and C12–C16 subunits, which were coupled to generate a linear (Z)-enone precursor that underwent spiroacetalization with HF·pyridine, providing pteridic acids A and B after saponification.