Solid-Phase Combinatorial Synthesis and Biological Evaluation of Destruxin E Analogues

The solid‐phase combinatorial synthesis of cyclodepsipeptide destruxin E has been demonstrated. The combinatorial synthesis of cyclization precursors 8 was achieved by using a split and pool method on SynPhase Lanterns. The products were successfully macrolactonized in parallel in the solution phase by using 2‐methyl‐6‐nitrobenzoic anhydride and 4‐(dimethylamino)pyridine N‐oxide to afford macrolactones 9, and the subsequent formation of an epoxide in the side chain gave 18 member destruxin E analogues 6. Biological evaluation of analogues 6 indicated that the N‐MeAla residue was crucial to the induction of morphological changes in osteoclast‐like multinuclear cells (OCLs). Based on structure–activity relationships, azido‐containing analogues 15 were then designed for use as a molecular probe. The synthesis and biological evaluation of analogues 15 revealed that 15 b, in which the Ile residue was replaced with a Lys(N3) residue, induced morphological changes in OCLs at a sufficient concentration, and modification around the Ile residue would be tolerated for attachment of a chemical tag toward the target identification of destruxin E (1). Forced to change: The 18 member analogues of destruxin E (see scheme) were successfully synthesized. Biological evaluation of these analogues indicated that the N‐MeAla residue was crucial for inducing morphological changes in osteoclast‐like multinuclear cells (OCLs). Molecular probes were then prepared by replacing the Ile residue with a Lys(N3) residue for target identification in OCLs.