Treatment of the lactal 2 with a nucleophile, such as {HEAD ~ a cyclic allylsilane} 6, in {TAIL ~ the presence} of a Lewis acid, such as BF3 OEt2, affords the final product 3 
in
Treatment of the lactal 2 with a nucleophile , such as { HEAD ~ a cyclic allylsilane } 6 , in { TAIL ~ the presence } of a Lewis acid , such as BF3 OEt2 , affords the final product 3
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH