Asymmetric synthesis of (−)-epi-blastmycinone and (2R,3S,4S)-3-hydroxy-4-methyl-2-(1′-n-tetradecyl)-butanolide via a tungsten-mediated cyclization reaction

Selective Synthesis of Chiral Dioxabicyclo[4.4.0]decane and Dioxabicyclo[5.3.0]decane from 3,4-Bisallyloxy-but-1-yne Derivatives via Ruthenium-Catalyzed En-yn-ene Metathesis

We prepared a series of chiral 3,4-bisallyloxy-but-1-ynes having syn and anti configurations. Treatment of these substrates with Grubbs catalyst Cl2(PCy3)2Ru=CHPh (3 mol %) preferably gave chiral dioxabicyclo[4.4.0]decane (yields > 55%) in addition to dioxabicyclo[5.3.0]decane in minor proportions. On substitution of the 4-allyloxy group of these substrates with a 4-but-2-enyloxy group, the metathesis reactions produced only dioxabicyclo[5.3.0]decane in the presence of Grubbs ruthenium-imidazolidene carbene catalyst.