A novel stereo- and enantioselective synthesis of trans-9-alkyl-2-benzyl-5-methyl-6,7-benzomorphans

Abstract The first stereo- and enantioselective syntheses of trans-9-alkyl-2-benzyl-5-methyl-6,7-benzomorphans ( 12 ) are described. The addition of alkyl magnesium halides to ( R )-2-naphthyl-4-phenyl-1,3-oxazolidine ( 7 ) followed by treatment with iodomethane and quenching with acid gave (1 S ,2 S )-2-alkyl-1-methyl-1,2-dihydronaphthalenecarboxaldehyde ( 10 ). Homologation of 10 followed by reductive amination using benzylamine gave (1 S ,2 S )-trans-2-alkyl-1-benzylaminoethyl-1-methyl-1,2-dihydronaphthalene ( 11 ). Mercuric acetate-assisted cyclization of 11 followed by LAH reduction afforded (1 S ,5 S ,9 R )- 12 .