relative stereochemistry of the β-keto carboxylic acid chain of the analogous alkaloid hirsutellomycin was determined in a stepwise manner. The C4′–C6′ syn relationships were predicted by comparing the NMR data of the corresponding ester fragments with that of hirsutellomycin. The relative stereochemistry of the whole molecule, including the epimerizable C2′ stereocenter, was determined by introduction
candidate biosynthetic gene cluster for a new cyclic depsipeptide of Chaetomium mollipilium. A heterologous reconstitution of the identified biosynthetic pathway predictably afforded a new cyclic depsipeptide composed of l-leucine, l-tryptophan, and a polyketide moiety. Interestingly, the 10-membered macrocycle structure generated equilibrium to an unprecedented cyclol structure. This study demonstrates
24- and 25-substituted avermectin and milbemycin derivatives
申请人:MERCK & CO. INC.
公开号:EP0428286A2
公开(公告)日:1991-05-22
Novel avermectin and milbemycin derivatives are disclosed, where the C-24 and C-25 carbon atoms are substituted by hydrogen, alkyl, alkenyl, substituted alkyl or substituted alkenyl groups. These compounds can be further substituted at the 4˝-, 5-, 13-, and 23-positions. The new C-24 and C-25 substituted avermectin and milbemycin derivatives are prepared by cleavage of known and suitably protected avermectin and milbemycin compounds. The new compounds are potent anti-parasitic agents, in particular, the compounds are anthelmintic, insecticidal and acaricidal agents.