[(2R,4S,6R,8R)-8-benzyloxymethyl-4-hydroxy-10-oxo-1,7-dioxaspiro[5.5]undec-2-yl]acetic acid tert-butyl ester

[(2R,4S,6R,8R,10S)-4-acetoxy-8-hydroxymethyl-10-methyl-10-triethylsilanyloxy-1,7-dioxaspiro[5.5]undec-2-yl]acetic acid tert-butyl ester

[(2R,4S,6S,8S,10S)-4-Acetoxy-10-methyl-8-((R)-3-methyl-2-methylene-4-oxo-butyl)-10-triethylsilanyloxy-1,7-dioxa-spiro[5.5]undec-2-yl]-acetic acid tert-butyl ester

[(2R,4S,6R,8R,10S)-4-acetoxy-8-{2-[2-((1S)-4-methoxybenzyloxy)-1-methylethyl]-allyl}-10-methyl-10-triethylsilanyloxy-1,7-dioxaspiro[5.5]undec-2-yl]acetic acid tert-butyl ester