This in {HEAD ~ turn} is then ring closed by {TAIL ~ a stereospecific process} of inversion with pyridine in p toluenesulfonyl chloride to obtain dibenzofuran 
This in { HEAD ~ turn } is then ring closed by { TAIL ~ a stereospecific process } of inversion with pyridine in p toluenesulfonyl chloride to obtain dibenzofuran
OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH