Concise Synthesis and Nematicidal Activity Evaluation of Waltherione S and its Derivatives against Meloidogyne incognita

The waltherione alkaloids are known for their diverse biological activities. This study reports the first total synthesis of waltherione S and explores the nematocidal potency of its derivatives.

The total synthesis of waltherione S was achieved in a five-step sequence starting from a commercially available pyridine derivative. A key step in the route was a reductive Heck reaction, which provided good regioselectivity for the coupling of compound 4 with terminal olefins. Derivatives of waltherione S were subsequently synthesized, and the structure of compound 5l was confirmed by X-ray crystallography. All compounds were then evaluated for their nematocidal activity.

The five-step synthetic sequence afforded waltherione S in an overall yield of 38.4%. A series of derivatives were successfully prepared. In biological assays, waltherione S and its synthesized derivatives demonstrated moderate nematocidal activity.

Although the synthesized compounds exhibited limited nematocidal potency, these findings are significant. They underscore the crucial role of the oxabicyclic octane and quinolone moieties present in waltherione A for its high nematocidal activity, providing valuable insight into the structure-activity relationship of this class of alkaloids.

This study successfully established the first total synthesis of waltherione S, offering an efficient route for accessing this natural product and its analogs. While the nematocidal activity of the target compounds was low, the results provide a critical understanding of the structural features necessary for activity, highlighting the oxabicyclic octane and quinolone moieties as the key pharmacophores for future design and optimization efforts.