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