Cembranoids, Pseudopteranoids, and Cubitanoids of Natural Occurrence

Microbial Transformation of 5-Episinuleptolide

“…On the basis of its HR-ESI-MS at m/z 373.1534 [MϩNa] ϩ and 1 H-and 13 C-NMR spectroscopic data, the molecular formula of 2 was established as C 19 H 26 O 6 with seven degrees of unsaturation. The structure was determined mainly by comparison of its 13 C-NMR spectra with that of 5-episinuleptolide (1). Compound 2 lacked the carbonyl carbon at d 216.3 assigned to C-6 in 1 whilst it exhibited an extra oxygenated methine carbon at d 72.1 (Table 1).…”

“…10) Misinterpretation of the X-ray data and of the configuration at C-11 has led to confusion in the literature, and this error has been propagated in many of the later papers 11,12) and reviews. 13) Sato et al reported the C-11 epimer 14) and Shoji et al reported its C-5 epimer and named it sinuleptolide, 15) hence the name 5-episinuleptolide for compound 1. Recently, Tseng et al isolated and determined unambiguously the absolute configuration of 5-episinuleptolide (1) by a modified Mosher's method as 1R, 5S, 8R, 10S, 11R.…”

Navigating the Chiral Pool in the Total Synthesis of Complex Terpene Natural Products

“…197 (+)-Cubitene ( 157 ), 198 a member of a small family of diterpenes containing a twelve-membered ring (i.e. cubatinoids), 199 exemplifies these challenges (Scheme 14). In addition to its conformational flexibility, 157 is devoid of common functional groups, and a lack of such synthetic handles can complicate terpene syntheses.…”

New Cytotoxic Cembranes from the Sea Pen Gyrophyllum sibogae

“…The structural elucidation of this type of diterpenes has involved NMR spectroscopy with the help of X-ray crystallography in several cases. 2 In the course of our screening program for the search for new marine anticancer agents, we have focused our attention on the sea pen Gyrophyllum sibogae Hickson (1916) (family Pennatulidae, order Pennatulacea, subclass Octocorallia, class Anthozoa) because of the high cytotoxicity found in its organic extracts. Bioassay-guided isolation afforded two new diterpenes possessing a cembrane skeleton: 7,8-dihydroflabellatene A (1) and 7,8-dihydroflabellatene B (2).…”

“…2 In the course of our screening program for the search for new marine anticancer agents, we have focused our attention on the sea pen Gyrophyllum sibogae Hickson (1916) (family Pennatulidae, order Pennatulacea, subclass Octocorallia, class Anthozoa) because of the high cytotoxicity found in its organic extracts. Bioassay-guided isolation afforded two new diterpenes possessing a cembrane skeleton: 7,8-dihydroflabellatene A (1) and 7,8-dihydroflabellatene B (2). The isolation, structural determination, and bioactivity of these novel compounds are described below.…”