Diazonamide A analog

1. A compound of the formula

or a pharmaceutically acceptable salt or conjugate thereof.

2. The compound of claim 1 in the form of a pharmaceutically acceptable salt.

3. A pharmaceutical composition which comprises as active ingredient the compound of claim 1 or a salt thereof and further includes a pharmaceutically acceptable excipient.

4. A method to synthesize a compound of the formula:

which method comprises treating a compound of the formula:

or a protected form thereof having a protecting group in place of a hydrogen on at least one ring nitrogen,

with an activated ester of (S)-2-hydroxy-3-methylbutanoic acid or a protected form thereof having a protecting group on the 2-hydroxyl group;

followed by removal of any protecting groups that were present on the amine or the hydroxyl group.

5. The method of claim 4 , wherein the activated ester of (S)-2-hydroxy-3-methylbutanoic acid is the N-hydroxysuccinimide ester of (S)-2-hydroxy-3-methylbutanoic acid, which is treated with a compound of formula:

to provide the product of formula: