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

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

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