Hatching stimulation activity of steroidal glycoalkaloids toward the potato cyst nematode, Globodera rostochiensis.

Cyst nematodes (Globodera spp. and Heterodera spp.) are highly evolved sedentary endoparasites that are considered as harmful pests worldwide. The hatching of the dormant eggs of cyst nematodes occurs in response to hatching factors (HFs), which are compounds that are secreted from the roots of host plants. Solanoeclepin A (SEA), a triterpene compound, has been isolated as HF for potato cyst nematode (PCN) eggs, whereas other compounds, such as steroidal glycoalkaloids (SGAs), are also known to show weak hatching stimulation (HS) activity. However, the structures of both compounds are different and the HF-mediated hatching mechanism is still largely unknown. In the present study, we observed specific hatching of PCN eggs stimulated by the hairy root culture media of potato and tomato, revealing the biosynthesis and secretion of HFs. SGAs, such as α-solanine, α-chaconine, and α-tomatine, showed significant HS activity, despite being remarkably less activities than that of SEA. Then, we evaluated the contribution of SGAs on the HS activities of the hairy root culture media. The estimated SGAs content in the hairy root culture media were low and nonconcordant with the HS activity of those, suggesting that the HS activity of SGAs did not contribute much. The analysis of structure-activity relationship revealed that the structural requirements of the HS activity of SGAs are dependent on the sugar moieties attached at the C3-hydoroxyl group and the alkaloid property of their aglycones. The stereochemistry in the EF rings of their aglycone also affected the strength of the HS activity.

Progress toward the Total Synthesis of Goniodomin A: Stereocontrolled, Convergent Synthesis of the C12-C36 Fragment.

Goniodomin A is a marine polyether macrolide natural product isolated from the dinoflagellate Alexandrium hiranoi. In this paper, we report stereocontrolled, convergent synthesis of a fully functionalized C12-C36 fragment of goniodomin A. The synthesis of the C12-C25 vinylstannane involved a Wittig reaction and a reductive cycloetherification for the construction of the dihydropyran ring. The C26-C36 thioester was synthesized via a Nozaki-Hiyama-Kishi reaction of an aldehyde and an iodoalkyne, the former of which was easily prepared from (R)-malic acid as a chiral source by taking advantage of substrate-controlled diastereoselective reactions. Finally, a palladium-catalyzed coupling of the C12-C25 vinylstannane and the C26-C36 thioester completed the synthesis of the target compound.