approach to the total synthesis of natural antibiotic pamamycin621A is described, in which the stereogenic centers at the C-13 and C-15 were taken from a chiral building block derived from the inexpensive d-glucolactone while all others (except the C-10) were installed via chiral auxiliary-induced asymmetric Evans/Crimmins aldol reactions. In the synthesis of the smaller/lower fragment, an antiselective