Cyclopeptid‐Antibiotika aus <i>Aspergillus</i>‐Arten. Struktur der Echinocandine C und D

Abstract

Cyclopeptide antibiotics from Aspergillus species. Structure of echinocandins C and D The echinocandins B, C and D are antifungal antibiotics produced by a strain of Aspergillus rugulosus . All three metabolites are closely related representing cyclic oligopeptides composed of six amino acids and a linolic acid residue in an amide linkage. The complete structure of echinocandin B ( 1 ) has recently been established by X‐ray analysis. Structural assignments to the new minor metabolites C and D have now been made by hydrolytic and oxidative cleavage reactions, formation of N ‐acyl‐α‐aminoethers as well as by chemical correlations and extensive NMR. examinations. Echinocandin C ( 2 ), C 52 H 81 N 7 O 15 , contains 3‐hydroxyhomotyrosine in the place of 3, 4‐dihydroxyhomotyrosine present in 1 . Echinocandin D ( 3 ), C 52 H 81 N 7 O 13 , differs in two amino acids: 3, 4‐dihyroxyhomotyrosine and 4, 5‐dihydroxyornithine, unusual units of 1 being replaced by 3‐hydroxyhomotyrosine and ornithine.