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