title: Organocatalytic Site-Selective Acylation of Avermectin B2a, a Unique Endectocidal Drug.
abstract: The organocatalytic site-selective monoacylation of avermectin B2a, an insecticidal and anti-parasitic drug, was accomplished. Although an acetylation of avermectin B2a using a 4-dimethylaminopyridine (DMAP) as a catalyst gave poor site-selectivity, use of our organocatalyst increased site-selectivity of the acylation at the C-5-OH as well as the yield of monoacetate. This catalyst was also effective in other acylations. Interestingly, trihaloacetylation under same conditions gave poor site-selectivity. However, the use of an enantiomer of our organocatalyst provided the C-4″-O-trihaloacetyl avermectin B2a with excellent site-selectivity. These results indicate that the site-selective acylation of avermectin B2a can be controlled by the combination of a suitable organocatalyst and an acid anhydride.
authors.affiliation: Kitasato Institute for Life Sciences, Kitasato University.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Koh
authors.initials: K
authors.lastname: Suzuki
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Hirose
authors.forename: Takumi
authors.initials: T
authors.lastname: Furuta
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ueda
authors.forename: Takeo
authors.initials: T
authors.lastname: Kawabata
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ōmura
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sunazuka
mesh_terms: D015761:4-Aminopyridine / Q000031:analogs & derivatives* / Q000737:chemistry; D000085:Acetates / Q000138:chemical synthesis / Q000737:chemistry; D000215:Acylation; D000977:Antiparasitic Agents / Q000737:chemistry*; D002384:Catalysis; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000737:chemistry; D008968:Molecular Conformation
chemical_list: D000085:Acetates; D000977:Antiparasitic Agents; C023882:avermectin B2a; D007559:Ivermectin; D015761:4-Aminopyridine; C003885:4-dimethylaminopyridine