Synthesis of S-(+)-methoprene

Article abstract of DOI:10.1007/BF00699984

An optically active juvenile hormone analogue, S-(+)-methoprene (1), is synthesized in six steps from technical grade S-(+)-3,7-dimethyl-1,6-octadiene (''(+)-dihydromyrcene'', e.e. ca. 50percent) by a novel procedure which begins with selective hydroalumination-oxidation to give S-(-)-citronellol.This alcohol is oxidized to give S-(-)-citronellal which on reaction with allylmagnesium chloride affords 6S,10-dimethyl-1,9-undecadien-4R/S-ol (5).Smidt-Moiseev oxygenation of 5 followed by dehydration leads to 6S,10-dimethyl-3E,9-undecadien-2-one.The latter on treatment with isopropoxyethynylmagnesium bromide is transformed into isopropyl 3,7S,11-trimethyl-2E/Z,4E,10-dodecatrienoate which upon Brown solvomercuration-reduction in MeOH gives 1 in 14percent overall yield.