Then {HEAD ~ the orthoester} is converted in high yields to {TAIL ~ the corresponding imidic ester} by condensation with an aniline while simultaneously removing alkanol from the reaction mixture to drive the equilibrium reaction to completion 
is converted to
Then { HEAD ~ the orthoester } is converted in high yields to { TAIL ~ the corresponding imidic ester } by condensation with an aniline while simultaneously removing alkanol from the reaction mixture to drive the equilibrium reaction to completion
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH REL 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 OTH OTH