Nardosinanols A−I and Lemnafricanol, Sesquiterpenes from Several Soft Corals, Lemnalia sp., Paralemnalia clavata, Lemnalia africana, and Rhytisma fulvum fulvum

Abstract

Ten new sesquiterpenes, nardosinanols A-I ( 1- 9) and lemnafricanol ( 10), have been isolated from several Kenyan soft corals, i.e., from Lemnalia sp., Paralemnalia clavata, Lemnalia africana, and Rhytisma fulvum fulvum. The structures and relative stereochemistry of these compounds were elucidated by interpretation of MS, COSY ( (1)H- (1)H correlations), HSQC, HMBC, and NOESY NMR spectroscopic experiments and in the case of 5 also by chemical transformation to compounds 11 and 12. Nine compounds ( 1- 9) are based on the nardosinane skeleton ( 1- 6 are nardosinanes and 7- 9 nornardosinanes). Lemnafricanol ( 10) possesses a novel tricyclic skeleton. Compounds 3, 7, and 10 were found to be toxic to brine shrimp with LC 50 values of 4.0, 0.35, and 0.32 microM, respectively.

Paralemnolins J-P, New Sesquiterpenoids from the Soft Coral Paralemnalia thyrsoide

“…[1][2][3][4][5][6][7][8] Our previous chemical investigation of the Formosan soft coral P. thyrsoides resulted in the isolation of twelve sesquiterpenoids, paralemnolins A-I, 2,3) paralemnanone, 4) isoparalemnanone, 4) and paralemnanol. 4) Our continuing search for bioactive compounds from this organism has further resulted in the isolation of seven paralemnolins J-P (1-7).…”

Sesquiterpenoids from the Formosan Soft Coral Lemnalia flava

“…IR spectra were recorded on a JASCO FT/IR-4100 infrared spectrophotometer. The NMR spectra were recorded on a Varian 400MR FT-NMR (or Varian Unity INOVA500 FT-NMR) instrument at 400 MHz (or 500 MHz) for 1 H and 100 MHz (or 125 MHz) for 13 C in CDCl 3 . Low resolution (LR)-MS and HR-MS were obtained by ESI on a Bruker APEX II mass spectrometer.…”

“…A molecular formula C 15 H 24 O 3 for 2 was suggested by ESI-MS, 13 C-and 1 H-NMR spectral data (Tables 1, 2), and the HR-ESI-MS of 15 (d 1.18, s) suggested the b-orientation of hydroxy group at C-2. From the above observations and further analysis of other NOE interactions (Fig.…”

“…The HR-ESI-MS of flavalin I (5) Tables 1, 2) with those of 11 13) showed that the structure of 5 should be very close to that of 11, with the exception of signals assigned to C-2, where a hydroxymethine in 11 was replaced by a keto group (d C 198.0) in 5. This was further supported by the planar structure established by 2D-NMR analysis of 5 (Fig.…”

“…12) Previous chemical investigations on soft corals of the genus Lemnalia have led to the isolation and identification of varieties of sesquiterpenoids. Some of these were found to possess several kinds of biological activities such as cytotoxic, 13,14) antimicrobial, 15) and anti-inflammatory properties. 16) In a previous paper, we reported the discovery of four new sesquiterpenoids with nardosinane-type skeleton from a Formosan soft coral Lemnalia flava.…”