2,2-dimethyl-propionic acid (2R,4R,6S,8R)-8-(2-acetoxy-butyl)-4-(tert-butyl-dimethyl-silanyloxy)-10-oxo-1,7-dioxa-spiro[5.5]undec-2-ylmethyl ester

2,2-dimethyl-propionic acid-(2R,4R,6R,8R,10S)-8-(2-acetoxy-butyl)-4-(tert-butyl-dimethyl-silanyloxy)-10-methoxy-1,7-dioxa-spiro[5.5]undec-2-ylmethyl ester

2,2-dimethy-propionic acid-(2R,4R,6R,8S,10S)-8-(2-acetoxy-buty)-4-(tert-butyl-dimethyl-silanyloxy)-10-hydroxy-1,7-dioxa-spiro[5.5]undec-2-ylmethyl ester