Controlled reduction of 5-alkyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium iodide: enantioselective synthesis of (−)-dihydropinidine and (+)-indolizidine 167B

Abstract A controlled reduction of (+)-(3 R ,5 S )-5-methyl- and (+)-(3 R ,5 S )-5- n -propyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2- a ]pyridin-4-ylium iodide 1 and 2 to generate (3 R ,5 S )-5-methyl- and (3 R ,5 S )-5- n -propyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2- a ]pyridine 3 and 4 , respectively, is reported. In addition, an enantioselective synthesis of (−)-(2 R ,6 S )-dihydropinidine and (+)-(2 S ,6 S )-indolizidine 167B starting from 3 and 4 , respectively, was achieved.