Syntheses and absolute configurations of the marine sponge purines (+)-agelasimine-A and (+)-agelasimine-B

Ohba, Masashi; Iizuka, Kazuaki; Ishibashi, Hiroyuki; Fujii, Tozo

doi:10.1016/s0040-4020(97)10120-x

Cited by 27 publications

(14 citation statements)

References 44 publications

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“… [a] The reaction was carried out at 40 °C in an aqueous 1 M formate solution (20 mL) with a substrate (2 mmol) and 1 ‐SO 4 (0.5 μmol); F/S/C=40 000:4000:1; yields were determined by a GC analysis. [b] The reaction was carried out using a substrate (1 mmol) and 1 ‐SO 4 (1 μmol); F/S/C=20 000:1000:1; dihydrocarvone was isolated as a mixture ( trans / cis =1.7:1) 45…”

Section: Resultsmentioning

confidence: 99%

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pH‐Dependent Catalytic Activity and Chemoselectivity in Transfer Hydrogenation Catalyzed by Iridium Complex with 4,4′‐Dihydroxy‐2,2′‐bipyridine

Himeda¹,

Onozawa-Komatsuzaki²,

Miyazawa³

et al. 2008

Chemistry A European J

130

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Transfer hydrogenation catalyzed by an iridium catalyst with 4,4'-dihydroxy-2,2'-bipyridine (DHBP) in an aqueous formate solution exhibits highly pH-dependent catalytic activity and chemoselectivity. The substantial change in the activity is due to the electronic effect based on the acid-base equilibrium of the phenolic hydroxyl group of DHBP. Under basic conditions, high turnover frequency values of the DHBP complex, which can be more than 1000 times the value of the unsubstituted analogue, are obtained (up to 81 000 h(-1) at 80 degrees C). In addition, the DHBP catalyst exhibits pH-dependent chemoselectivity for alpha,beta-unsaturated carbonyl compounds. Selective reduction of the C=C bond of enone with high activity are observed under basic conditions. The ketone moieties can be reduced with satisfactory activity under acidic conditions. In particular, pH-selective chemoselectivity of the C=O versus C=C bond reduction was observed in the transfer hydrogenation of cinnamaldehyde.

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Section: Resultsmentioning

confidence: 99%

“…[b] The reaction was carried out using a substrate (1 mmol) and 1-SO 4 (1 mmol); F/S/C = 20 000:1000:1; dihydrocarvone was isolated as a mixture (trans/cis = 1.7:1). [45] Figure 3. Absorption spectra of 1 (0.1 mm) in an aqueous solution as a function of pH.…”

Section: Effect Of Acid-base Equilibrium Of Dhbpmentioning

confidence: 99%

pH‐Dependent Catalytic Activity and Chemoselectivity in Transfer Hydrogenation Catalyzed by Iridium Complex with 4,4′‐Dihydroxy‐2,2′‐bipyridine

Himeda¹,

Onozawa-Komatsuzaki²,

Miyazawa³

et al. 2008

Chemistry A European J

130

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“…(+)-Agelasimine A, 26, and (+)-Agelasimine B, 27, are two diterpene-adenine derivatives isolated from the orange sponge Agelas mauritiana (Figure 7). The synthesis of 26 and 27 was carried out by Ohba and co-workers [53], starting with (+)-trans-dihydrocarvone, 46, allowing them to establish the absolute configuration of both natural products. The authors previously developed a reaction sequence similar to that done for the racemic (±)-agelasimine A and (±)-agelasimine B [76,77].…”

Section: Synthesis Of (+)-Agelasimine a 26 And (+)-Agelasimine B 27mentioning

confidence: 99%

Antibacterial Natural Halimanes: Potential Source of Novel Antibiofilm Agents

et al. 2020

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The development of new agents against bacteria is an urgent necessity for human beings. The structured colony of bacterial cells, called the biofilm, is used to defend themselves from biocide attacks. For this reason, it is necessary to know their structures, develop new agents to eliminate them and to develop new procedures that allow an early diagnosis, by using biomarkers. Among natural products, some derivatives of diterpenes with halimane skeleton show antibacterial activity. Some halimanes have been isolated from marine organisms, structurally related with halimanes isolated from Mycobacterium tuberculosis. These halimanes are being evaluated as virulence factors and as tuberculosis biomarkers, this disease being one of the major causes of mortality and morbidity. In this work, the antibacterial halimanes will be reviewed, with their structural characteristics, activities, sources and the synthesis known until now.

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“…They have already been used for many syntheses of natural products, [1][2][3][4][5][6][7][8][9][10] especially labdanes. [11][12][13] The synthesis of 11-nordrim-7-ene-2,9-dione (7) (Scheme 2) and 11-nordrim-7-en-9-one (15) has previously been described by Gesson et al [14,15] We used the monoprotected dione 8 for the first synthesis of the 2,7-functionalized bisnorlabdane (11). The vinyl ketone 15 represents an appropriate starting material for the synthesis of hispanone (21) (Scheme 1), a fungicidal and bactericidal furolabdane, which was first obtained by the transformation of hispanolone, [16,17] and has also been isolated from the plants Ballota saxatilis [18] (Lamiaceae) and Galeopsis angustifolia [19] (Labiatae).…”

Section: Introductionmentioning

confidence: 99%