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.