122825-61-0 3,23,2'-Tri-O-acetyl-4''-isovaleryl-23-O-demycinosyltylosin Sch 37644 Sch-37644 Tylosin, 23-O-acetyl-23-O-de(6-deoxy-2,3-di-O-methyl-beta-D-allopyranosyl)-, 2A,3-diacetate 4B-(3-methylbutanoate)