4-[4-acetoxy-6-methoxy-6-(4-methoxycarbonylmethylene-6-vinyl-tetrahydro-pyran-2-ylmethyl)-5,5-dimethyl-tetrahydro-pyran-2-yl]-3-hydroxy-butyric acid

4-[4-acetoxy-6-methoxy-6-(4-methoxycarbonylmethylene-6-vinyl-tetrahydro-pyran-2-ylmethyl)-5,5-dimethyl-tetrahydro-pyran-2-yl]-3-triethylsilanyloxy-butyric acid

4-[4-acetoxy-6-(4-bromomethylene-6-vinyl-tetrahydro-pyran-2-ylmethyl)-6-methoxy-5,5-dimethyl-tetrahydro-pyran-2-yl]-3-hydroxy-butyric acid methyl ester