In more detail, a compound having an S configuration selectively produces a compound having an S—R configuration, and a compound having an R configuration selectively produces {HEAD ~ a compound} having {TAIL ~ an R—S configuration} 
In more detail , a compound having an S configuration selectively produces a compound having an S — R configuration , and a compound having an R configuration selectively produces { HEAD ~ a compound } having { TAIL ~ an R — S configuration }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL