Synthesis of the MN Ring of Caribbean Ciguatoxin C‑CTX‑1 via Desymmetrization by Acetal Formation

The MN ring of Caribbean ciguatoxin C-CTX-1 was synthesized from a meso-syn-2,7-dimethyloxepane derivative corresponding to the M ring via desymmetrization by acetal formation with a camphor derivative, followed by construction of the N ring via the Horner–Wadsworth–Emmons reaction and acetal formation. The meso-syn-2,7-dimethyloxepane derivative was synthesized via photoinduced electrocyclization of a conjugated exo-diene under flow conditions, giving a cyclobutene derivative, followed by ring expansion via oxidative cleavage and diastereoselective reduction of a β-hydroxy ketone

Synthesis and Complete Structure Determination of a Sperm-Activating and -Attracting Factor Isolated from the Ascidian <i>Ascidia sydneiensis</i>

For the complete structure elucidation of an endogenous sperm-activating and -attracting factor isolated from eggs of the ascidian <i>Ascidia sydneiensis</i> (<i>Assydn</i>-SAAF), its two possible diastereomers with respect to C-25 were synthesized. Starting from ergosterol, the characteristic steroid backbone was constructed by using an intramolecular pinacol coupling reaction and stereoselective reduction of a hydroxy ketone as key steps, and the side chain was introduced by Julia–Kocienski olefination. Comparison of the NMR data of the two diastereomers with those of the natural product led to the elucidation of the absolute configuration as 25<i>S</i>; thus the complete structure was determined and the first synthesis of <i>Assydn</i>-SAAF was achieved

Synthesis and Complete Structure Determination of a Sperm-Activating and -Attracting Factor Isolated from the Ascidian <i>Ascidia sydneiensis</i>

For the complete structure elucidation of an endogenous sperm-activating and -attracting factor isolated from eggs of the ascidian <i>Ascidia sydneiensis</i> (<i>Assydn</i>-SAAF), its two possible diastereomers with respect to C-25 were synthesized. Starting from ergosterol, the characteristic steroid backbone was constructed by using an intramolecular pinacol coupling reaction and stereoselective reduction of a hydroxy ketone as key steps, and the side chain was introduced by Julia–Kocienski olefination. Comparison of the NMR data of the two diastereomers with those of the natural product led to the elucidation of the absolute configuration as 25<i>S</i>; thus the complete structure was determined and the first synthesis of <i>Assydn</i>-SAAF was achieved