If {HEAD ~ the conversion} of 6β hydroxy 6α,17α dimethylpregn 4 ene 3,20 dione into Medrogestone is carded out with {TAIL ~ the Lewis acid}, boron trifluoride etherate, rather than with the more conventional agents such as SOCl2 /pyridine, POCl3 /pyridine or MsCl/Et3 N/DMAP/CH2 Cl2, reaction temperatures below about 65° C. are feasible and isomerization to 6,17α dimethylpregna 6,8 diene 3,20 dione is largely avoided 
is carded out with
If { HEAD ~ the conversion } of 6β hydroxy 6α,17α dimethylpregn 4 ene 3,20 dione into Medrogestone is carded out with { TAIL ~ the Lewis acid } , boron trifluoride etherate , rather than with the more conventional agents such as SOCl2 /pyridine , POCl3 /pyridine or MsCl / Et3 N / DMAP / CH2 Cl2 , reaction temperatures below about 65 ° C. are feasible and isomerization to 6,17α dimethylpregna 6,8 diene 3,20 dione is largely avoided
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL REL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH