Studies of Australian soft corals. XXII. The structures of two novel sesquiterpenes and a nor sesquiterpene from Lemnalia africana, confirmed by a single-crystal X-ray study

Bowden, Bruce F.; Coll, JC; Mitchell, SJ; Skelton, Brian W.; White, AH

doi:10.1071/ch9802737

Cited by 23 publications

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“…17) The relative stereochemistry of 3 was deduced from a 2D NOESY experiment, which showed similar results as described for 1. The structure of elongatol C (3) was thus determined as lemnal-1(10)-en-2b,12a-diol.…”

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Nardosinane Sesquiterpenoids from the Formosan Soft Coral Nephthea elongata

Wang

Duh

2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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Soft corals of the genus Nephthea are rich in terpenoids and steroids. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] As part of our search for bioactive substances from marine organisms, the Formosan soft coral Nephthea elongata KÜKENTHAL (Nephtheidae) was studied because the CH 2 Cl 2 extracts showed significant cytotoxicity to P-388 (mouse lymphocytic leukemia) cell culture as determined by standard procedures.15,16) Bioassay-guided fractionation resulted in the isolation and chraracterization of seven new sesquiterpenoids, elongatols A-G (1-7).Elongatol A (1) gave a formula of C 15 H 24 O 3 , from the interpretatoion of its HR-FAB-MS, 13 C-NMR, and DEPT spectroscopic data. Thus, four degrees of unsaturation were determined for 1. 13) The a-configuration of hydroxy at C-2 was determined by comparison with J 1,2 of armatin D and its 2-epimeric analogues.17) The a-configuration of hydroxy at C-12 was determined by comparison with J 11,12 of its 12-epimeric analogues.17) The relative stereochemistry of 1 was deduced from a 2D NOESY experiment, which indicated that Me-13, Me-14, Me-15, H-6, H-7, and sesquiterpenoids, elongatols A-G (1-7) were isolated from the methylene chloride solubles of the Formosan soft coral Nephthea elongata. Their structures were elucidated by extensive spectroscopic analysis and their cytotoxicity against selected cancer cells was measured in vitro. Key words Nephthea elongata; nardosinane sesquiterpenoid; cytotoxicityChem. Pharm. Bull. 55(5) 762-765 (2007) © 2007 Pharmaceutical Society of Japan * To whom correspondence should be addressed. e-mail: yihduh@mail.nsysu.edu.tw

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“…17) The relative stereochemistry of 6 was deduced from a 2D NOESY experiment, which indicated that Me-13, Me-14, Me-15, H-6, and H-12 are on one side of the molecule, while H-4, H-7, and H-11 are on the opposite side of the molecule (Fig. 4).…”

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Nardosinane Sesquiterpenoids from the Formosan Soft Coral Nephthea elongata

Wang

Duh

2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…The R-configuration of the C-2 hydroxy group was determined by comparing the J 1,2 value of 3 with those of elongatol A (f), isolated from Nephthea elongata 10 ( Figure 2) and its 2-epimer analogue (0 Hz). 6,18 The second isolated compound from R. fulVum fulVum, nardosinanol D (4), was assigned with the elemental formula C 16 H 26 O 4 , as shown by its CIMS and 13 C NMR spectra. That the m/z 265 peak agrees with [M + H -H 2 O] + was clear from the required four oxygen atoms ( Table 1).…”

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

et al. 2008

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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.

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“…The absolute stereochemistries of several nardosinanoids isolated from the soft corals of the genera Paralemnalia and Lemnalia also had been determined. 1,4,[7][8][9][10][11][12][13] On the basis of the above results and biogenic consideration, the absolute configurations at C-1 and C-12 of neolemnanoids were considered to be identical as illustrated in formula 1-6. Thus, the absolute structures of 1-6 were established.…”

Section: Neolemnane-type Sesquiterpenoids From a Formosan Soft Coral mentioning

confidence: 99%

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13) Continuing study on searching new metabolites of this soft coral again afforded six new metabolites paralemnolins D-I (1-6) (neolemnanoids).

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Neolemnane-Type Sesquiterpenoids from a Formosan Soft Coral Paralemnalia thyrsoides

Huang

Chao

et al. 2007

Chem. Pharm. Bull.

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Soft corals belonging to the genera Paralemnalia [1][2][3][4] and Lemnalia [5][6][7][8][9][10][11][12] have been found to be a rich source of neolemnane and nardosinane sesquiterpenoids. Our previous investigation on the chemical constituents of a soft coral Paralemnalia thyrsoides has resulted in the isolation of three terpenoids, paralemnolins A-C.13) Continuing study on searching new metabolites of this soft coral again afforded six new metabolites paralemnolins D-I (1-6) (neolemnanoids). We describe herein the isolation, structure elucidation and biological activity of these compounds. Results and DiscussionParalemnolin H COSY spectrum was used to reveal the connectivity of H-4/H-5, H-5/H 2 -6, H 2 -6/H 2 -7, H-9/H 2 -10, and H 2 -10/H 2 -11 (Fig. 1). The vinyl methyl [d 1.57 (3H, d, Jϭ1.2 Hz)] attached at C-3 was confirmed by the HMBC correlations from H 3 -14 to C-2, C-3 and C-4. The methyl group attached at C-1 and the connectivities from C-7 to C-8 and C-8 to C-9 were deduced from the following HMBC correlations: H 3 -13/C-1, C-2, C-8, C-12 and H 2 -7/C-8, C-9. Moreover, a methyl [d 0.87 (3H, d, Jϭ6.6 Hz)] attached at C-12 was confirmed by the HMBC correlations from H 3 -15 to C-1, C-11, and C-12. The placement of the acetyl group at C-4 was confirmed by the HMBC correlation of H-4 (d 6.49) with C-3 and the carbonyl group of ester. Thus, the hydroxyl group should be positioned at C-5, and the planar structure of 1 was established. The relative stereochemistry and detailed 1 H-NMR data assignment of 1 were elucidated from the NOE correlations observed in a NOESY experiment (Fig. 2). The Z geometry of the 2,3-double bond was established by an NOE interaction between H-2 and H 3 -14. Also, H 3 -13 was found to show NOE interactions Six new sesquiterpenoids, paralemnolins D-I (1-6), have been isolated from the EtOAc extract of the soft coral Paralemnalia thyrsoides. The structures of these metabolites were determined by extensive spectroscopic analysis and by comparison of their spectral data with those of related metabolites. The absolute stereochemistry of these metabolites was established by application of the Mosher's method on 1 and on the basis of the absolute structures of other related compounds previously isolated from the soft corals of the genera Paralemnalia and Lemnalia. Cytotoxicity of these metabolites toward a limited panel of cancer cell lines also is reported.

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Studies of Australian soft corals. XXII. The structures of two novel sesquiterpenes and a nor sesquiterpene from Lemnalia africana, confirmed by a single-crystal X-ray study

Abstract: The isolation of two new sesquiterpenes (3) and (8) and a novel nor sesquiterpene (16) from Lemnalia africana is reported. In each case, the absolute stereochemistry was deduced chemically and spectroscopically, and confirmed by a single-crystal X-ray study on a suitable derivative (7).

Cited by 23 publications

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Nardosinane Sesquiterpenoids from the Formosan Soft Coral Nephthea elongata

Nardosinane Sesquiterpenoids from the Formosan Soft Coral Nephthea elongata

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

Neolemnane-Type Sesquiterpenoids from a Formosan Soft Coral Paralemnalia thyrsoides

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