Cyclic Depsipeptides

A cyclic depsipeptide, or a derivative thereof, having the structure of formula (I):

• wherein an ester bond is formed between the carboxy group of A7 and the hydroxy group of A2,
• wherein X and A1 are each independently optional,
• and wherein
• X is H or an amino group modifying moiety and may be typically selected from an aryl carbonyl residue or from an acyl residue,
• A1 is glutamine, ornithine, glutamic acid or a derivative thereof,
• A2 is threonine or serine,
• A3 is leucine,
• X is Ahp, 3-amino-piperidine-2-one, dehydro-AHP, Ahp-I, Ahp-II, proline, 5-hydroxy-proline or a derivative thereof, wherein the point of fusion (with A3 and A5) are at the nitrogen atom and the carboxyl oxygen (by virtue of the replacement of a hydrogen atom by a bond) of the proline, and 5-hydroxyproline,
• wherein Ahp, 3-amino-piperidine-2-one, dehydro-AUP, Ahp-I, and Ahp-II, are as defined below, and wherein the point of fusion (with A3 and A5) are at the nitrogen atoms of the said compounds (by virtue of the replacement of a hydrogen atom by a bond):
• wherein X is O or a bond, and R is an organic moiety or is a radical as defined in claim 3,
• A5 is isoleucine, phenylalanine or valine,
• A6 is tyrosine, N-Me-tyrosine or a derivative thereof,
• A7 is leucine, isoleucine or valine,
• or a pharmaceutically acceptable salt thereof.