The method 1, wherein step is carried out by treating the compound of the formula in DMF in the presence of {HEAD ~ 20 to 40 molar equivalents} of {TAIL ~ POCl3} 
of
The method 1 , wherein step is carried out by treating the compound of the formula in DMF in the presence of { HEAD ~ 20 to 40 molar equivalents } of { TAIL ~ POCl3 }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL