An Efficient Biomimetic Synthesis of Some Marine Sponge Tyrosine Metabolites

Abstract

The oxidation of tyrosine ethyl ester and O-benzyl protected o-tyrosine methyl ester with either sodium tungstate/hydrogen peroxide or DMD gave the corresponding tyrosine oximes in high yields. Controlled bromination of the aromatic ring gave either the monobromo oxime, the dibromo oxime, or the spiroisoxazoline depending upon reaction conditions. The bromo tyrosine oximes were further transformed into the naturally occurring nitriles by base hydrolysis of the oximino esters and decarboxylation of the resulting oximino acids with trifluoroacetic acid in CP₂Cl₂.

Key Words:

• sponge metabolites
• tyrosine
• oximes
• oxidation
• bromination