Synthesis of Structural Analogues of Lyngbyatoxin A and Their Evaluation as Activators of Protein Kinase C

Syntheses of several new analogues of lyngbyatoxin A from a single common intermediate are described. These compounds bear a carbon chain at the 7-position of the indolactam V (ILV) nucleus which contains either a hydrophilic or a lipophilic group. The effect of these minor structural alterations on the ability of the ILV analogues to activate the enzyme protein kinase C (PKC) was determined by measuring the extent of phosphorylation of calf thymus histone (III-S). Introduction of a hydroxyl group on the C-7 appendage was found to dramatically decrease compound 3’s ability to activate PKC. This result is interpreted in terms of the decreased ability of 3 to associate with the membrane bilayer.