Acetic acid (1R,4aS,8aS)-5,5,8a-trimethyl-1-{2-[(2R,3R)-2-methyl-3-(toluene-4-sulfonyloxymethyl)-oxiranyl]-ethyl}-1,4,4a,5,6,7,8,8a-octahydro-naphthalen-2-ylmethyl ester