Several sulfur-containing platensimycin (PTM) and platencin (PTN) analogues, with activities comparable to the parent natural products, have recently been discovered from microorganisms, implying a biomimetic route to diversify the PTM and PTN scaffolds for structure-activity relationship study. We present here a substrate-directed and scaleable semisynthetic strategy to make PTM and PTN sulfur analogues with excellent diasteroselectivity, without using any chiral catalysts. Most of the sulfur analogues showed strong activities against clinical Staphylococcus aureus isolates, with minimum inhibitory concentrations of 0.5-2 μg mL-1. Density functional theory calculations were in agreement with the observed selectivity for these analogues and suggest that the conformation restraints of the terpene cages of PTM and PTN on the transition states determine the si-face attack selectivity.