abstract |
The present invention relates to novel antitumor depsipeptides produced by Micromonospora strain 39500, ATCC 55011, and having the structural formula wherein R1 is 2-methylpropanoyl, and R2 is 2-methylpropanoyl, propanoyl or acetyl; or R1 is 3-methylbutanoyl, and R2 is 2-methylpropanoyl or 3-methylbutanoyl; or R1 is propanoyl, and R2 is acetyl or propanoyl. |