Synthesis of bengamide E analogues and their cytotoxic activity

A series of bengamide E analogues were prepared from the corresponding polyketide chain and amino acids via amide coupling reactions. Opening of the polyketide chain lactone ring with α-aminolactams was successfully achieved under microwave irradiation in the presence of sodium 2-ethyl hexanoate. A cytotoxic activity evaluation against a panel of cancer cell lines (KB, HepG-2, Lu-1, MCF-7, HL-60 and Hela) indicated that the 2′R analogues were generally more cytotoxic than the 2′S analogues. Additionally, several analogues exhibited selective inhibition against various cancer cell lines: compounds 32a and 32b selectively inhibited MCF-7 cells, while 33b and 35b were more sensitive toward Lu-1 and HepG-2, respectively. Notably, some of the synthetic analogues possess cytotoxic activities with IC₅₀ values less than 1 µM.     

Semisynthesis of (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid

This paper describes the use of zamoranic acid in the first semisynthesis of the furolabdane (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid, which also establishes the absolute configuration of the natural product. Direct deconjugation of Δ⁷ in zamoranic acid and Bestmann methodology for the furan ring synthesis are the key steps.     

Semisynthesis of fuscoside B analogues and eunicosides, and analysis of anti-inflammatory activity

A small library of semisynthetic analogues of fuscol and eunicol have been prepared and evaluated for in vivo topical anti-inflammatory activity using the mouse-ear edema assay. The first glycosylation of fuscol and eunicol has been achieved using a modified Koenigs-Knorr glycosylation to synthesize new fuscosides and eunicosides, a novel structural class of diterpene glycosides. The availability of adequate glycosylation methods for this synthesis was limited owing to the instability of the glycosyl acceptors. Glycosyl donor protecting group type had a pronounced effect on overall glycosylation yields of a model glycosyl acceptor. This synthesis provided access to the unnatural β-glycosides allowing for an evaluation of the effect of differing anomeric stereochemistry on anti-inflammatory activity. The PEGylated derivatives of fuscol and eunicol were also synthesized by a convenient acid-promoted solvolysis of the natural product aglycones. This work highlights the importance of the glycan portion of fuscoside B, notably the stereochemical configuration of the glycosidic linkage, in the observed anti-inflammatory activity.     

Synthesis and cytotoxic activity of novel curcumin analogues

Five novel curcumin analogues bearing different substituents at 4-position of phenyl group were synthesized. Their structures were confirmed by NMR and HRMS spectrum. Their cytotoxic activities against six tumor cell lines were tested by the standard MTT assay in vitro. The results indicated that four analogues （1A-1C, 1E） with solubilizing moieties showed selective potent cytotoxicity against HepG2, HeLa and CT26 cell lines, and analogue 1A and 1C exhibited more potent cytotoxicity than curcumin against CT26 cell line. It was suggested that introduction of appropriate substituents to 4-position of phenyl group might be a potential option for structural modification of curcumin.     

Synthesis and cytotoxic activity of benzophenanthrolinone analogues of acronycine

Condensation of either 2-bromobenzoic acid (4) or 2-chloro-3-nitrobenzoic acid (5) with suitable aminoquinolines 6-8 afforded phenylquinolylamines 9-13. Acid mediated cyclization gave the corresponding 12H-benzo[b][1,7]phenanthrolin-7-ones 14 and 15, and 12H-benzo[b][1,10]phenanthrolin-7-ones 16-18. Compounds 14, 16, and 17 were subsequently N-methylated to 6-demethoxyacronycine and acronycine analogues 19-21, whereas reduction of the aromatic nitro group of 18 gave the amino derivative 22. Unsubstituted 12H-benzo[b][1,10]phenanthrolin-7-ones 16, 17, 20, and 21 were devoid of significant cytotoxic activity, whereas 18 and 22, bearing a nitrogen substituent at position 11, were significantly active. Unsubstituted 12H-benzo[b][1,7]phenanthrolin-7-ones 14 and 19, which include a pyridine nitrogen in the same 4-position as the pyran oxygen of acronycine exhibited cytotoxic activities within the same range of magnitude as acronycine itself.     

Synthesis and cytotoxic activity of benzopyranoxanthone analogues of benz.

Condensation of 3-hydroxy-2-naphthalenecarboxylic acid with phloroglucinol afforded 1,3-dihydroxy-12H-benzo[b]xanthen-12-one. Construction of an additional dimethylpyran ring onto this skeleton, by alkylation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement, gave access to a series of benzo[b]pyrano[2,3-i]xanthen-6-ones and benzo[b]pyrano[3,2-h]xanthen-7-ones related to psorospermine and benzo[b]acronycine. In contrast with what is observed in the pyridoacridone and benzopyridoacridone series, the linear benzo[b]-pyrano[2,3-i]xanthen-6-one derivatives were more potent than their angular benzo[b]pyrano[3,2-h]xanthen-7-one isomers. cis-3,4-Diacetoxy-5-methoxy-2,2-dimethyl-3,4-dihydro-2H,6H-benzo[b]pyrano[2,3-i]xanthen-6-one, the most active among the new compounds, was more potent than acronycine in inhibiting the proliferation of L1210 murine leukemia cells.     

Synthesis and cytotoxic activity of pyranocarbazole analogues of ellipticine and acronycine

Various 2,2,5,11-tetramethyl- and 2,2,5,6,11-pentamethyl-2,6-dihydropyrano[3,2-b]carbazole derivatives were synthesized by condensation of 3-methylbut-2-enal or 3-chloro-3-methylbut-1-yne with an appropriate hydroxycarbazole. These compounds associate the tricyclic system responsible for the intercalating properties of ellipticine related drugs, with the dimethylpyran pharmacophore of acronycine derivatives. The study of the biological properties of the new pyrano[3,2-b]carbazole derivatives was carried out in vitro on L1210 murine leukaemia cell line. The three (+/-)-cis-diol diesters 15, 16, and 18 were the most active compounds.     

Synthesis of tetracyclic dioxygenated isoquinolines and their cytotoxic activity

An efficient synthesis of new dioxygenated isoquinolines is reported. The novelty of this approach derives from its use of tricyclic-nitril (3) as a building block in a synthetic sequence of seven steps for the preparation of the tetracyclic isoquinoline (14) and its derivatives. The isoquinoline 16 was 10-fold more active against leukemia L₁₂₁₀ than the corresponding tetrahydroisoquinoline 14.     

Stolonidiol,a new marine diterpenoid with a strong cytotoxic activity from the Japanese soft coral

Structures of stolonidiol (1) and stolonidiol monoacetate (2), new marine diterpenoids with a strong cytotoxic activity from the Japanese soft coralClavularia sp., were established by means of spectroscopic analyses, chemical reactions, and X-ray crystallographic analysis.     

Synthesis of 13-amino telekin derivatives and their cytotoxic activity

Telekin is a eudesmane sesquiterpene-lactone naturally occurring in many medicinal plants with antitumour and anti-inflammatory activity. In this study, a series of 13-amino derivatives of telekin have been synthesised through Michael addition reaction, and their relative configurations were exemplified by the single crystal X-ray diffraction of the dimethylamine adduct. The in vitro cytotoxicity against three tumour cell lines of these amine derivatives was evaluated. The piperidine and 4-hydroxypiperidine adducts displayed stronger cytotoxic activity than telekin.     

Imines and lactones derived from friedelanes and their cytotoxic activity

Abstract

Friedelan-3-one (1) and friedelane-3,16-dione (2) isolated from leaves and branches of Maytenus robusta Reissek were subjected to structural modifications via nucleophilic addition to the carbonyl group and Baeyer-Villiger oxidation in order to synthesize potential cytotoxic compounds. The oximes friedelane-3-hydroxyimino (3) and 3-hydroxyiminofriedelan-16-one (4) together with the lactones friedelane-3,4-lactone (5) and 3,4-lactonefriedelan-16-one (6) were characterized by IR and NMR spectroscopic analyses. Compounds 4 and 6 are reported for the first time. Cytotoxic screening via MTT assay in human leukemia cell lines (THP-1 and K562) demonstrated no significant improvement of compounds 3-6 when compared to the starting materials. Only compounds 3 and 5 demonstrated an improvement against K562 cells. However, the same assay on ovarian and breast cancer cell lines (TOV-21G and MDA-MB-231) showed a reduction in the IC₅₀ for compounds 4-6, indicating that ring A modifications may enhance the biological potential.     

New neo-clerodane diterpenoid alkaloids from Scutellaria barbata with cytotoxic activities

Four new neo-clerodane diterpenoid alkaloids, named scutebarbatines I-L (1-4), were isolated from the whole plant of Scutellaria barbata D. DON. Their structures were established on the basis of detailed spectral analyses. In vitro, the four new compounds showed significant cytotoxic activities against three human cancer lines (HONE-1 nasopharyngeal, KB oral epidermoid carcinoma, and HT29 colorectal carcinoma cells), and gave IC(50) values in the range 3.2-8.3 microM.     

Synthesis of caprazamycin analogues and their structure--activity relationship for antibacterial activity

Synthesis of palmitoyl caprazol 7, which possesses a simple fatty acyl side chain at the 3' '-position of the diazepanone moiety, was carried out and their antibacterial activity was evaluated. The key elements of our approach include the improved synthesis of the key 5'-beta-O-aminoribosyl-glycyluridine derivative, installation of the palmitoyl side chain to the cyclization precursor, and the construction of the diazepanone by an intramolecular reductive amination. The second generation synthesis of (+)-caprazol was also established. Palmitoyl caprazol 7 exhibited antibacterial activity against Mycobacterium smegmatis ATCC607 (MIC = 6.25 microg/mL) with potency similar to that of the caprazamycins (CPZs). Palmitoyl caprazol 7 and N6'-desmethyl palmitoyl caprazol 28 also exhibited antibacterial activity against drug-resistant bacteria including methyciline-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) strains (MIC = 3.13-12.5 microg/mL).     

Toxicity and local anesthetic activity of diterpenoid alkaloids

The toxicity and local anesthetic activity of 74 diterpenoid alkaloids differing in the nature and position of functional groups in lycoctonine, heteratisine, napelline, hetisane, atisane, and denudatine skeletons and their synthetic derivatives were investigated. Compounds with local anesthetic activity and duration of action surpassing that of cocaine for surface anesthesia and that of novocaine and lidocaine for infiltration and trunk administration were identified. Structural factors affecting the toxicity and local anesthetic activity of the studied compounds were discussed. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 477–484, September–October, 2007.     

Surface activity and micellar properties of anionic gemini surfactants and their analogues

The properties of didodecyldiphenylether disulfonate gemini-type surfactants have been studied and compared to mono-alkylated and monosulfonated analogous surfactants. Dynamic and equilibrium surface tension measurements indicate that the gemini surfactants have a higher surface activity compared to that of the monoalkyl analogues. The gemini-type surfactants have much larger surface area per molecule, opposite effect of carbon number on CMC and considerable swelling of the micelles upon increasing surfactant concentration. Determination of aggregation numbers by fluorescence measurements reveals that the longer chain gemini surfactants form micelles having less than 10 molecules per micelle.     

Four new neo-clerodane diterpenoid alkaloids from Scutellaria barbata with cytotoxic activities

Four new neo-clerodane diterpenoid alkaloids, named scutebarbatines C-F (1-4), were isolated from the whole plants of Scutellaria barbata D. DON. Their structures were elucidated by spectral analyses (UV, IR, FAB-MS, 1D-NMR and 2D-NMR). In vitro, compounds 1-4 showed significant cytotoxic activities against three human cancer cell lines, namely, HONE-1 nasopharyngeal, KB oral epidermoid carcinoma, and HT29 colorectal carcinoma cells, and gave IC(50) values in the range 3.9-7.8 muM.