Fidaxomicin Impurity 20

(2R,3S,4S,5S,6R) -6- (((3E,5E,8S,9E,11S,12R,13E,15E,18S) -12- (((2R,3S,4R,5S) -3,4-dihydroxy-6,6-dimethyl-5- ((3-methylbutanoyl) oxy) tetrahydro-2H-pyran-2-yl) oxy) -11-ethyl-8-hydroxy-18- ((R) -1-hydroxyethyl) -9,13,15-trimethyl-2-oxooxacyclooctadeca-3,5,9,13,15-pentaen-3-yl) methoxy) -4-hydroxy-5-methoxy-2-methyltetrahydro-2H-pyran-3-yl 3,5-dichloro-2-ethyl-4,6-dihydroxybenzoate