The aromatic amino acid constituent of echinocandin B: 3, 4-dihydroxyhomotyrosine (author's transl)]

The aromatic amino acid constituent of Echinocandin B: 3,4-Dihydroxyhomotyrosine. The antifungal antibiotic echinocandin B gave upon treatment of its tetrahydroderivative with anhydrous trifluoroacetic acid and subsequent methanolysis the tripeptide threonyl-(4-hydroxyprolyl)-(4-oxohomotyrosine) methyl ester ( 8 ), which could be hydrolysed to 4-oxohomotyrosine ( 11 ). These facts together with the earlier described hydrolysis of the antibiotic to 1-amino-3-p-hydroxyphenyl-2-propanone ( 6 ) and the reductive hydrolysis to homotyrosine suggested the presence of 3,4-dihydroxyhomotyrosine ( 14 ) as a constituent amino acid of echinocandin B. This was confirmed by a degradation of the intact tetrahydro-polypeptide with perjodate yielding p-hydroxybenzaldehyde and by the isolation of free 3,4-dihydroxyhomotyrosine upon mild acidic treatment of the tetrahydro-polypeptide.