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