Cubitane: a rare diterpenoid skeleton

Synthesis and biological analysis of truncated calyculone H

“…8 Toward this end we oxidized alcohol 24 with Py·SO 3 complex as before. Next, the intermediate aldehyde was subjected to zinc mediated allylation with allyl iodide 28 in THF to yield alcohol 29 with moderate diastereoselectivity (dr ≥ 7:3) in 46% yield over two steps.…”

“…8,9 Still, although a total synthesis of calyculone A ( 2 ) and its derivatives has remained elusive, thus far only one group has described an approach toward its core ring system. 10 Although calyculone A ( 2 ) has displayed substantial cytotoxicity, 6 as it happens with many marine natural products, the lack of an adequate supply of material has impeded research into the biological potential of the calyculones.…”

Cubitanoids and Cembranoids from the Soft Coral Sinularia nanolobata

“…Thus, the structure of 1 should contain an additional ring. The above data, in conjunction with a highly deshielded proton at δ H 4.21 (1H, d, J = 10.0 Hz, H-10) coupled by the olefinic H-9, were reminiscent of a cubitane skeleton [ 1 , 2 , 3 , 4 , 5 ].…”

“…Cubitane-type diterpenoids are a rare group of compounds that are isolated from termites, soft corals, and plants [ 1 ]. The first cubitanoid, (+)-cubitene, was discovered from the secretion gland of the termite Cubitermes umbratus [ 2 ].…”

“…In some plants, cubitene was detected by gas chromatography–mass spectrometry (GC/MS) from their volatile oils [ 6 ]. In the aforementioned three sources, cubitanoids were usually found in company with cembranoids [ 1 ], which represent a large group of compounds in soft coral [ 7 , 8 , 9 , 10 ]. The origin of cubitanoids was speculated to be associated with the co-occurring cembranoids based on a photochemical interconversion [ 4 ].…”