BC9 bc9 (1R,2R)-2-[(2S,6E,8R,9S,11R,13S,15S,16S)-7-cyano-8,16-dihydroxy-9,11,13,15-tetramethyl-18-oxooxacyclooctadec-6-en-2-yl]cyclobutanecarboxylic acid BC9