(1E,3R,4S,6R,7Z,9S,10R,11S,16R,17R,18S,19S,20Z)-10,16-bis((tert-butyldimethylsilyl)oxy)-1-iodo-3,9,11,17,19-pentamethyltricosa-1,7,20,22-tetraene-4,6,18-triol