Synthetic studies on soft coral norcembranolides: total synthesis of (+)-10-epigyrosanolide E

Structural Elucidation and Structure–Anti-inflammatory Activity Relationships of Cembranoids from Cultured Soft Corals Sinularia sandensis and Sinularia flexibilis

“…The structure and absolute stereochemistry of 9 were also confirmed by single-crystal X-ray diffraction ( Figure 2) with Cu Kα irradiation [Flack parameter of 0.09 (3)] (CCDC 1044093). On the basis of the results presented above, compound 9 was established as (1R,4R,5R,13S,8E,11Z)-5-acetoxy-13-hydroxy-cembr-8(9),11 (12),15(17)-trien-16,4-olide In addition, the 11 known compounds obtained were identified as sinumaximol B (3), 17 pukalide (4), 21 10-epigyrosanoldie E (5), 14,15 diepoxycembrene A (7), 17 sinulaflexiolide K (10), 22 (−)-sandensolide (11), 23 11-dehydrosinulariolide (12), 24 sinulariolide (13), 25 3,4:8,11-bisepoxy-7-acetoxycembra-15(17)-en-1,12-olide (14), 26 dendronpholide F (15), 27 and dendronpholide G (16) 24 by comparison of spectroscopic data with published values. The absolute configurations of 4 and 15 were confirmed by single-crystal X-ray diffraction analysis with Cu Kα radiation [Flack parameters of 0.12(5) and 0.14(8), respectively] for the first time ( Figure 2).…”

Asymmetric, Stereodivergent Synthesis of (−)‐Clusianone Utilizing a Biomimetic Cationic Cyclization

“…Alkylative dearomatization of 9 with chiral triflate (−)-( R )- 10 [12] (Figure 3) led to the production of (−)-( S,S )- 8 and ( + )-( R,S ) -8 as a 1.3:1 mixture of diastereomers which were separated by preparative thin layer chromatography. When each was individually subjected to neat formic acid, diastereomer (−)-( S,S )- 8 converted in a stereodivergent manner to (−)-allyl clusianone (−)- 7 (72 %) and Cope product (−)-( S )- 13 (13 %), [20] while diastereomer ( + )-( R,S ) -8 exclusively afforded (−)-( S )- 13 (84 %, Scheme 4).…”

Rapid and scalable synthesis of chiral bromolactones as precursors to α-exo-methylene-γ-butyrolactone-containing sesquiterpene lactones

“…The secondary alcohol obtained in the course of the Barbier allylation should however readily undergo a Barton-McCombie deoxygenation. 60 Furthermore, it should be noted that sesquiterpene lactones exist at various stages of oxidation beyond the α-exo-methylene: accordingly, a wealth of further modifications of this motif are available in the literature, including epoxidation, 61 dihydroxylation, 62 conjugate reduction, 26,63 conjugate addition of C-nucleophiles, 64 ring-closing metathesis 65 or crossmetathesis, 66 to only name a few, to further extend the scope of natural products potentially reachable from these bromolactones.…”