In general {HEAD ~ the need} for such protecting groups will be apparent to those skilled in {TAIL ~ the art} of organic synthesis as well as the conditions necessary to attach and remove such groups 
In general { HEAD ~ the need } for such protecting groups will be apparent to those skilled in { TAIL ~ the art } of organic synthesis as well as the conditions necessary to attach and remove such groups
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH