(7E,9E)-(2S,3aR,5R,6S,11R,12R,16R,17S,17aS)-12-Ethyl-6,16-dihydroxy-2-methoxy-5,9,17-trimethyl-11-trityloxymethyl-2,3,3a,4,5,6,11,12,15,16,17,17a-dodecahydro-1,13-dioxa-cyclopentacyclohexadecen-14-one

Tylonolide, cyclic 5,20-hemiacetal, (20S)-