If the conversion of 6β {TAIL ~ hydroxy 6α,17α dimethylpregn 4 ene 3,20 dione} into Medrogestone is carded out with the Lewis acid, boron trifluoride etherate, rather than with the more conventional agents such as SOCl2 /pyridine, POCl3 /pyridine or {HEAD ~ 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 
If the conversion of 6β { TAIL ~ hydroxy 6α,17α dimethylpregn 4 ene 3,20 dione } into Medrogestone is carded out with the Lewis acid , boron trifluoride etherate , rather than with the more conventional agents such as SOCl2 /pyridine , POCl3 /pyridine or { HEAD ~ 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
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