New isothiocyanatotolane liquid crystals with terminal but-3-enyl substitute

Four kinds of new but-3-enyl-based isothiocyanate liquid crystals composed of tolane core and but-3-enyl terminal group (A1–A4) were synthesised via seven step reactions based on 2-(4-bromophenethyl)-1,3-dioxolane, and four n-butyl analogues B1–B4 as comparison structures were also prepared. The mesomorphic properties and physical properties of the compounds were investigated. Single fluorinated compounds A2 and A3 exhibit monotropic nematic phase, and they have lower melting enthalpy and higher clearing points than those of the comparison compounds B2 and B3. The non-fluoro-substituted compound A1 and difluorinated compound A4 exhibit no nematic phase. Replacement of n-butyl chain by but-3-enyl as terminal group is enabled to increase birefringence (Δn ~ 0.394–0.430) and reduce rotational viscosity. These isothiocyanatotolanes with terminal but-3-enyl substitution have potential application for high birefringence mixtures.     

2‐Hydroxy‐1,2,3,6‐tetrahydro‐azulen‐6‐carboxylic Acid Ethyl Ester—A Novel Precursor for a New Class of Liquid Crystalline Materials

A novel approach for the syntheses of carbene adduct 4 is reported. A ring-enlargement strategy was employed for the synthesis of precursors 5 and 6 and established the mechanism of the formation of azulene derivative 6. Synthesis of target precursor 13, a novel precursor for the synthesis of new mesogenic materials, and its various halogenated derivatives (14–16) was carried out.     

Cholesteric star-shaped liquid crystals induced by a maltose core: synthesis and characteristics

Three esters of maltose (A1–A3) with 4–(4–(alkoxybenzoyloxy)phenoxy) –6–oxohexanoic acid (b1–b3) side-arms have been synthesised. All the maltose derivatives were laevo-rotationary, unlike their parent cores. The side arm b1 did not display liquid crystalline (LC) properties, and b2 and b3 displayed thermotropic nematic LC properties. The star-shaped compound (SSC) A1 with b1 side-arms did not display a mesomorphic phase. Unlike the nematic schlieren texture provided by side-arms b2 and b3, the star-shaped liquid crystals (SSLC) A2 and A3 displayed Grandjean and oily texture in the cholesteric phase. The results suggest that the LC properties of the side-arms have an important influence on the formation of LC properties in an SSC, and that the maltose core is important in determining the mesomorphic phase type. In other words, the SSC displayed LC properties only when the side-arms were also LC, and the maltose core induced a cholesteric phase in the SSLC with nematic side-arms. The mesomorphic regions for A2 and A3 were 39.1 and 53.7°C during the heating cycle and 63.8 and 107.0°C during the cooling cycle, respectively. The longer terminal chain rendered the mesomorphic region broader.     

Versicorin,a new lovastatin analogue from the fungus Aspergillus versicolor SC0156

A new lovastatin analogue versicorin (1), together with three related compounds, decumbenones A (2) and B (3) and versiol (4), were isolated from mycelial solid cultures of Aspergillus versicolor SC0156. Their structures were elucidated on the basis of MS data and NMR spectroscopic analysis. The new compound versicorin (1) possesses a hexahydro-2H-naphtho[1,8-bc]furan moiety, which is a rare type of the lovastatin-analogous compounds. A hypothetical biosynthetic pathway for compounds 1–4 was proposed.     

2,3-Seco-2,3-dioxo-lyngbyatoxin A from a Red Sea strain of the marine cyanobacterium Moorea producens

Chemical investigation of the organic extract of a Red Sea strain of the cyanobacterium Moorea producens has afforded 2,3-seco-2,3-dioxo-lyngbyatoxin A (1). Five known compounds including lyngbyatoxin A (2), majusculamides A and B (3 and 4), aplysiatoxin (5) and debromoaplysiatoxin (6) were also isolated. Their structures were elucidated by using HR-FAB-MS, 1D and 2D NMR analyses. The compounds were evaluated for antiproliferative activity against HeLa cancer cells. Lyngbyatoxin A (2) showed potent activity, with an IC₅₀ of 9.2 nM, while 5 and 6 displayed modest activity with IC₅₀ values of 13.3 and 3.03 μM, respectively. In contrast, compounds 1, 3 and 4 were inactive, with IC₅₀ values greater than 50 μM. The lack of cytotoxicity for 2,3-seco-2,3-dioxo-lyngbyatoxin A (1) demonstrates that the indole moiety in lyngbyatoxin (2) is essential for its cytotoxicity, and suggests that detoxification of 2 may be carried out by biological oxidation of the indole moiety to yield 1.     

Penicillilactone A,a novel antibacterial 7-membered lactone derivative from the sponge-associated fungus Penicillium sp. LS54

One novel 7-membered lactone derivative, penicillilactone A (1), together with two known compounds, rugulosin A (2) and rugulosin (3) were isolated from the sponge-derived fungus Penicillium sp. LS54. Their structures were elucidated on the basis of spectroscopic analysis and comparison with literature data. Remarkably, penicillilactone A (1) is the first natural product containing a 7-membered lactone ring fused with a furan core. Penicillilactone A (1) exhibited moderate antibacterial activity against aquatic pathogen Vibrio harveyi with an MIC value of 8 μg/mL.     

Synthesis of new boswellic acid derivatives as potential antiproliferative agents

Abstract

In the current investigation, a series of heterocyclic derivatives of boswellic acids were prepared along with new monomers of 3-O-acetyl-11-keto-β-boswellic acid (AKBA, 1) 11-keto-β-boswellic acid (KBA, 2) and several new bis-AKBA and KBA homodimers and AKBA-KBA heterodimers. The effects of these compounds on the proliferation of different human cancer cell lines, viz., FaDu (pharynx carcinoma), A2780 (ovarian carcinoma), HT29 (colon adenocarcinoma), and A375 (malignant melanoma), have been evaluated. Thus, KBA homodimer 21 effectively inhibited the growth of FaDu, A2780, HT29, and A375 cells with EC₅₀ values below 9?μM. In addition, compounds 7, 8, 11, 12, 15, 16, and 17 also exhibited cytotoxic effects for A2780, HT29, and A375 cancer cells. In particular, the pyrazine analog 8 was highly cytotoxic for A375 cancer cells with an EC₅₀ value of 2.1?μM.     

Phytochemical,cytotoxic and chemotaxonomic study on Ajuga forrestii Diels (Labiatae)

A phytochemical investigation of Ajuga forrestii Diels led to the isolation of 14 compounds, including eight neo-clerodane diterpenes (1–8), two phytoecdysteroids (9, 11), one stigmastane sterol (10) and three iridoid glycosides (12–14). The structures of these compounds were identified by spectroscopic methods and a comparison of their data with those reported in the literature. This is the first report of compounds 1–14 from A. forrestii. The cytotoxic activities of the aqueous extract of A. forrestii and several compounds have been studied and the chemotaxonomic significance of isolated compounds has also been summarised.     

A Convenient Synthesis of Protoanemonin

Abstract

A new convenient synthesis of protoanemonin (1) starting from 2-deoxy-d-ribose (3) is described. A key step in the sequence is the successive β- and δ-eliminations of 3,5-di-O-p-toluoyl-2-deoxy-d-ribono-1,4-lactone (6).     

PREPARATION OF 1,7-DISUBSTITUTED-1,2,3,4-TETRAHYDROISOQUINOLINES

ABSTRACT

A simple procedure for the preparation of 1,7-disubstituted-1,2,3,4-tetrahydroisoquinolines from 3,4-dihydroisoquinoline (2) is presented. This strategy overcomes the limitation of cyclisation approaches which generally require electron rich ring systems. A variety of 1-substituents has been incorporated using the appropriate organometallic or activated methylene nucleophile to prepare both electron rich (7a–f) and electron deficient 1,7-disubstituted-1,2,3,4-tetrahydroisoquinolines (16, 17).     

Activation and Facile Dealkylation of Monooxides of 1,8-Bis(alkylthio)naphthalene and 2,2′-Bis(alkylthio)biphenyl with Triflic Anhydride via Dithiadications

Abstract

Dithiadications bearing 1,8-bis(alkylthio)naphthalene 2A(a-e) and 2,2′-bis(alkylthio)biphenyl 2B(a-e) structure undergo either the facile deprotonation from the methyl group or dealkylation from the methylene groups by the triflate anion. Dications 2A(a) and 2B(a) having methyl groups were deprotonated readily to afford cyclic sulfonium salts 3A(a) and 3B(a). However, dithiadications 2A(b-e) and 2B(b-e) having ethyl, propyl, isopropyl and benzyl groups were readily dealkylated even at -45°C to give thiasulfonium salts 4A(b-e) and 4B(b-e) and alkyl triflates 5(a-e) in good yields. The intermediary formation of dithiadications 2A(a-e) and 2B(a-e) were confirmed by direct observation using NMR spectroscopy, D-labelled experiments and trapping experiments.     

Synthesis and Anticancer Activity of 1,2,3-Triazole Fused N-Arylpyrazole Derivatives

A novel series of triazole derivatives 11a–11j is synthesized. Structures of the products are confirmed by ¹H and ¹³C NMR, and mass spectral data. The anticancer activities of compounds 11a–11j are evaluated against three human cancer cell lines (MCF-7, A549, and A375) using the standard MTT assay in vitro, using doxorubicin as the positive control. All the compounds exhibit significant activity against cancer cell lines. The compounds 11a, 11d, 11e, 11g, and 11j demonstrate more potent activity than the positive control.

     

A Practical Synthesis of SDZ WAG 994 by Selective Methylation of N6-Cyclohexyladenosine

A selective 2′-O-methylation of N⁶-cyclohexyladenosine (2) under phase-transfer catalysis conditions and a preferential crystallization of N⁶-cyclohexyl-2′-O-methyladenosine (1, SDZ WAG 994) from a mixture of by-products is described. A plausible explanation for the selective crystallization of 1 as a hydrate is presented.     

SN2 Displacement of Carbohydrate Triflates by 9-Oximes of Erythromycin A and Of a Tylosin Derivative

ABSTRACT

The preparation of 9-O-glycosyloxime derivatives of erythromycin A (1) and tylosin (2) is reported. Access to this new class of macrolides was achieved from (E)-9-oxime of erythromycin A (3) and 9-oxime of tylosin 20-(1,3-dithiane) (4), by successful displacement of triflates of suitably protected carbohydrates.     

Novel amides and Schiff's bases derived from 1,3,4-oxadiazole derivatives: synthesis and mesomorphic behaviour

The synthesis and liquid crystalline properties of novel achiral amides (Ia–g, IIa–g and IVa,b), achiral Schiff's bases (IIIa–g and Va–g), chiral amides (VI, VII) and chiral Schiff's bases (VIII–XI) incorporating a 1,3,4-oxadiazole ring are reported. All amides of the series I and II display an enantiotropic smectic A phase. The amide IVa,b did not show mesomorphic properties. Amides of the series Ia–g and IIa–g contain a flexible n-tetradecylthio chain, the other terminal substituent is an n-alkoxy chain and n-alkyl chain, respectively (n?=?4–10) and the 1,3,4-oxadiazole is in the terminal rigid core. Amides Ia–g have broader mesomorphic range and higher thermal stability than the corresponding amides IIa–g. Amides IVa,d contain the 1,3,4-oxadiazole ring in the centre of the rigid core and two flexible alkoxy chains as flexible terminal substituents. Thus, the mesomorphic properties are favoured if 1,3,4-oxadiazole is shifted to a terminal position of the rigid core. Schiff's bases IIIa–g display an enantiotropic dimorphism smectic C–smectic A. Schiff's bases IIIa–g have a broader mesomorphic range than the analogous amides Ia–g. Schiff's bases Va–g exhibit a dimorphism smectic A–nematic, and in contrast to this the analogous amide IVa,b did not show mesomorphism. The chiral amides VI and VII and chiral Schiff's bases X and XI did not show mesomorphic properties and only the chiral Schiff's bases VIII and IX display a chiral smectic C phase in a short mesomorphic range. A density functional theory theoretical study at the B3LYP/6–311++G(d,p) level was performed in order to analyse the structural features that must be related with the mesomorphic behaviour of the reported compounds.     

Argininosecologanin,a secoiridoid-derived guanidine alkaloid from the roots of Lonicera insularis

A new secoiridoid-derived guanidine alkaloid, argininosecologanin (1), along with 12 known iridoids and secoiridoids (2–13), was isolated from the roots of Lonicera insularis. The structures of the isolated compounds were established by the spectroscopic analysis and comparison of their spectral data with previously reported data. Compound 1 was assigned as the first secoiridoid-derived guanidine alkaloid isolated as a natural product. A plausible biogenetic pathway for 1 is suggested based on its structural similarity to (E)-aldosecologanin (4).     

Secondary metabolites from the Colletotrichum gloeosporioides A12, an endophytic fungus derived from Aquilaria sinensis

Two new cyclohexene derivatives colletotricones A and B (1 and 2) and a new thiazole derivative colletotricole A (5), along with six known natural metabolites were isolated from the extract of Colletotrichum gloeosporioides A12, an endophytic fungus derived from Aquilaria sinensis. Among them, the colletotricones A and B possess a cyclohexenone skeleton, whereas the colletotricole A is a thiazole derivative. Their structures were fully assigned with the aid of extensive spectroscopic analysis and data from the literature. Moreover, cytotoxic activity in vitro of compounds 1 and 3–9 were evaluated against MCF-7, NCI-H460, HepG-2 and SF-268 tumour cell lines. The new compound 1 exhibited growth inhibitory activity against all the four tumour cell lines with IC₅₀ values ranging from 15.7 to 46.8 μM.     

Ester and Ketone Groups Substituted Mono- and Di- Azo-coupled Azocalix[4]arenes as Extractant for Hg+ and Hg2+, or Cr3+Cations

This article describes extraction properties of mono- (A1–A8) and di- (B1–B8) substituted azocalix[4]arene analogues. The ionophore solvent extractions of alkaline-earth (Sr²⁺), basic metal (Pb²⁺) and transition metal cations (Ag⁺, Hg⁺, Hg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cr³⁺) from aqueous phase to organic phase were carried out by azocalix[4]arene derivatives. It has been observed that they show a good extraction behavior toward selected heavy metal (Hg) and toxic metal (Cr), while A4 and B4 prefer Hg⁺, Hg²⁺ and Cr³⁺ among transition metal cations, respectively. The azocalix[4]arenes (A1–A8) and (B1–B8) are not efficient extractants for all of the selected metal cations, whereas A4 and B4 are selective only for Hg metal cation.     

Straightforward and Facile Synthesis of a Bioactive Component from Zingiber cassumunar Roxb.

Straightforward and facile synthesis of a bioactive component A from Zingiber cassumunarRoxb. is described. The phenylbutenoid dimer A was reported to possess anti-inflammatory and cytotoxic activities. The optically active cyclohexene ring fragment was obtained via the highly diastereo- and enantioselective Diels–Alder reaction of chiral acryloyloxazolidinones (1a and 1b) and 1-(4-hydroxy-3-methoxyphenyl)butadiene (2). The enantiomeric excess of Diels–Alder adducts 3a and 3bwere determined via high-performance liquid chromatotography of the corresponding bis-acetate (6). The greatest enantiomeric excess (99.9% ee) was obtained when the 4-phenyloxazolidin-2-one (1a) chiral auxiliary was used in combination with TiCl4. The optically pure bioactive compound A was prepared from the optically active Diels–Alder adduct (3a) in two additional steps.     

1,2-Propanediol-linked chiral symmetric and non-symmetric liquid crystal dimers containing trifluoromethyl

Four symmetric and non-symmetric chiral liquid crystal dimers containing trifluoromethyl groups, termed as TFBA-PD-TFBA, UEBBA-PD-TFBA, UEBA-PD-TFBA and UEA-PD-TFBA, respectively, have been synthesised and characterised. UEA-PD-TFBA exhibited chiral nematic phase, whereas the other three dimers displayed chiral smectic A phase. X-ray diffraction (XRD) has revealed the structure of the smectic A phase for TFBA-PD-TFBA to be intercalated, whereas that for UEBBA-PD-TFBA and UEBA-PD-TFBA to be monolayer and interdigitated, respectively. In addition, the weaker peak corresponding to a shorter layer spacing was observed for UEBBA-PD-TFBA and UEBA-PD-TFBA. Considering the results of XRD measurements and computer simulations, the structural model corresponding to the shorter layer spacing is assigned as horseshoe-like shape. The absence of smectic behaviour for UEA-PD-TFBA reveals that the weaker aromatic–aromatic interactions cannot stabilise the smectic A phase.