| 摘要 |
This invention provides a process for preparing a compound of formula (I) : wherein R 1 is H or a hydroxyimino-protecting group; R 2 is H, C 1-4 alkyl or C 1-4 alkoxy; R 3 is C 1-8 alkyl, C 2-8 alkenyl or C 3-8 cycloalkyl; and R 4 is H, halo, C 1-4 alkyl or C 1-4 alkoxy, which process comprises the steps of: (a) reacting an avermectin B2 derivative with an oxidizing agent to form a 5-oxo compound; (b) allowing the 5-oxo compound to react with a compound of formula R 1 -O-NH 2 wherein R 1 is H or a hydroxyimino-protecting group, to form a 5-imino compound; (c) reacting the 5-imino compound with a thionocarbonizing agent to form a 4'', 23-bisthionocarbonyl ester; (d) reacting the 4'', 23- bisthionocarbonyl ester with a deoxygenation agent to form a 4'', 23- dideoxy compound; and (e) reacting the 4'', 23-dideoxy compound with an acid to form a compound of formula (I). |
