Hupermine A,a novel C16N2-type Lycopodium alkaloid from Huperzia phlegmaria

A novel C₁₆N₂-type Lycopodium alkaloid consisting of a quinolizidine with a 6-dimethylaminohexyl side chain, hupermine A (1), was isolated from the club moss of Huperzia phlegmaria, and the structure and relative stereochemistry were elucidated on the basis of spectroscopic data.     

Selective N-debenzylation of amides with p-TsOH

N-Benzylamides were debenzylated efficiently with 4 equiv. of p-TsOH in refluxing toluene. Good to quantitative yields of the desired primary amides were obtained within 2-4 h from a wide variety of N-2,4-dimethoxybenzylamides. N-4-Methoxylbenzyl amides and N-benzylamides were also debenzylated cleanly. In the case of N-2,4-dimethoxylbenzylamides, selective N-debenzylation was possible in the presence of N-Fmoc, N-t-BOC or N-trityl-protection. Protected amino acid amides survived these conditions without any detectable epimerization.     

Novel ent-kaurane dimers from Isodon rubescens var. rubescens

Three novel asymmetric ent-kaurane dimers xindongnins M-O (1-3) were isolated from Isodon rubescens var. rubescens. Their structures were elucidated by spectroscopic methods including 2D NMR analysis. The relative stereochemistry of 1 was determined by single crystal X-ray diffraction, which also confirmed the unique linkage of a single carbon-carbon bond between the two subunits of this dimer. A biogenetic pathway was proposed for the formation of these dimers.     

Lycobelines A-C, Novel C16N2-type Lycopodium alkaloids from Huperzia goebelii

Novel C₁₆N₂-type Lycopodium alkaloids consisting of a decahydroquinoline with an aminohexyl side chain, lycobelines A-C (1-3), were isolated from the club moss of Huperzia goebelii, and their structures and relative stereochemistry were elucidated on the basis of spectroscopic data and chemical correlations.     

Castanolide and epi-castanolide, two novel diterpenoids with a unique seco-norabietane skeleton from Salviacastanea Diels f. pubescens Stib.

Castanolide (1) and epi-castanolide (2), two novel diterpenoids possessing a unique seco-norabietane skeleton, were isolated from Salviacastanea Diels f. pubescens Stib. Their structures and relative stereochemistry were elucidated by extensive NMR analysis and confirmed by single-crystal X-ray diffraction study. A possible biosynthetic pathway of these two compounds was also proposed.     

E/Z Isomerization of 3,3-disubstituted allylic thioethers

Allylic thioethers of the general structure 1 underwent E/Z isomerization during both basic and acidic hydrolysis of the ester moiety at the remote end of the molecule. The isomerization was dependent on the substitution of the allylic moiety. The presence of a 5-membered heterocycle on the double bond supported the isomerization. However, analogous oxy-ethers were stable.     

Three new Lycopodium alkaloids from Huperzia carinata and Huperzia squarrosa

Eleven Lycopodium alkaloids with lycodine-type, lycopodine-type, and fawcettimine-related skeletons were isolated from the whole plants of Huperzia carinata (Desv. Ex. Poir.) Trevis and Huperzia squarrosa (G. Forst) Trevis (Huperziaceae). Among them, 8,15-dihydrohuperzine A (2), lycocarinatine A (3), and lycoposerramine U N-oxide (11) are new compounds. The structures of these new alkaloids were elucidated on the basis of 2D NMR correlations. Some of these isolated alkaloids were assayed for acetylcholinesterase (AChE) inhibitory activity.     

3,4-seco-Diterpenoids from Trigonostemon flavidus

Phytochemical investigation on the stems of Trigonostemon flavidus resulted in the isolation of five new 3,4-seco-diterpenoids, trigoflavidones A-E (1-5), structurally related to the main co-occurring known 3,4-seco-sonderianic acid (6) and 3,4-seco-sonderianol (7). Compound 4 possesses new 3,4-seco rearranged ent-pimarane skeletal type, characteristic of a vinyl group at C-8, while 5 features a unique five-membered ring (C₁) fused with a cyclopropane ring (C₂). The structures of the new compounds were established by a combination of spectroscopic data and computational methods. Compounds 1-7 were tested for their cytotoxicities on HL-60, SMMC-7721, A-549, MCF-7, and SW480 human tumor cell lines.     

6,7-Seco-ent-kaurane-type diterpenoids from Isodon eriocalyx var. laxiflora

Twenty nine 6,7-seco-ent-kaurane-type diterpenoids including 18 new ones, laxiflorolides C–T (1–18), along with 21 known ones were obtained from Isodon eriocalyx var. laxiflora. Laxiflorolides E–G (3–5) are the first identified naturally occurring 6,7-seco-ent-kauranoids that feature a 3,6-epoxy unit, and laxiflorolide M (11) is the first identified naturally occurring 6-nor-6,7-seco-ent-kauranoid. The absolute configurations of compounds 1, 3, 6, and 11 were determined by single-crystal X-ray diffraction analyses. The cytotoxic activity of the isolates was evaluated by an MTT assay.     

Characterization of CdS nanoparticles in solutions of P(TFE-co-PVDF-co-Prop)/N,N-dimethylformamide

We report in here the preparation of CdS nanoparticles (Q-CdS) in N,N-dimethylformamide (DMF) and poly(tetrafluoroethylene-co-vinylidenefluoride-co-propylene) (PTFE-co-PVDF-co-Prop) by reaction of cadmium acetate and thiourea at room temperature. The formation and size evolution of Q-CdS particles were followed by optical absorption spectroscopy as a function of the aging process of the solutions. The obtained results indicated that not only the Q-CdS particles were more stable in DMF than in aqueous solutions, probably due to the interaction with the CHNO group, but also they were formed in smaller sizes. The particle size obtained in DMF was estimated in 4-6 nm against 10-20 nm in aqueous solution. The results also showed that the velocity of Q-CdS formation is lower when the reaction was carried out in PTFE-co-PVDF-co-Prop dissolved in DMF. The Q-CdS particles formed in this system were also less stable than in pure DMF, probably due to the interaction of the CHNO fragment and CF₂ of polymer chain or phase segregation.     

An efficient synthesis of furano analogs of duocarmycin C1 and C2: seco-iso-cyclopropylfurano[e]indoline-trimethoxyindole and seco-cyclopropylfurano[f]quinoline-trimethoxyindole

seco-Iso-cyclopropylfurano[e]indoline-trimethoxyindole 1 and seco-cyclopropylfurano[f]quinoline-trimethoxyindole 2 are potent cytotoxic agents. Previous synthesis of these compounds was inefficient and the approach required separation of a mixture containing the isomeric indoline and quinoline intermediates 11 and 12, formed from radical cyclization of allylic bromide 10. Reported herein is an efficient and selective synthesis of either intermediate 11 or 12, thus product 1 or 2, as needed. The conditions of the Stobbe condensation, bromination, 5-exo-trig radical cyclization, amine-carboxylic acid coupling, and debenzylation were optimized for multi gram scale. As a result, the reaction times were shortened, the products were readily isolated, and the yields and purity improved.     

On the conformational characteristics of the O,O,O-trimethyl selenophosphate molecule

Spectroscopic and theoretical studies were carried out for O,O,O-trimethyl selenophosphate molecule. DFT structural and vibrational calculations were performed at 6-311++G^∗∗ level. Ar/matrix-FTIR spectra were recorded. A coexistence of different conformers with C₃ and C₁ symmetries was detected at different temperatures. Spectral evidence of a lower energy C_s conformer was found. These conclusions are consistent with the results from DFT calculations. A tentative assignment of the features observed in the Ar/matrix-FTIR spectra is proposed.     

Synthesis of N,N-dialkylaminobenzonitriles and halo-(N,N-dialkyl)benzamidines by reaction of halobenzonitriles with lithium amides

3- and 4-N,N-Dialkylaminobenzonitriles and 4-chloro-(N,N-dialkyl)benzamidines were isolated by reacting 4-chlorobenzonitrile with hindered lithium amides under thermodynamic (0 °C) and kinetic control conditions (−78 °C), respectively. As previously reported, a benzyne mechanism seems to be confirmed since N,N-dialkylaminobenzonitriles are formed. Only benzamidines were isolated in fair to high yields at both 0 °C and −78 °C with non-hindered lithium amides. Exploitation and mechanistic rationale of the reaction of different halobenzonitriles are also reported.     

Conformational analysis of bridgehead-substituted bicyclo[m.m.m]alkanes and bicyclo[8.8.n]alkanes

Conformational analyses of bicyclo[m.m.m]alkanes where m=1-10 and of bicyclo[8.8.n]alkanes where n=1-7 bearing methyl groups on the bridgeheads were carried out using a Monte Carlo search strategy. In the bicyclo[m.m.m]alkane series, greater variability was observed for the inter-bridgehead distance for larger values of m. This suggests that properly substituted bicyclo[8.8.8]hexacosanes or larger ring systems might serve as molecular springs.     

Suzuki-Miyaura monocouplings of p-dibromobiphenyl and substituted p-dibromo(penta-p-phenylenes)

The mono/bis ratio for the Suzuki-Miyaura cross coupling of p-dibromobiphenyl and p-dibromo(penta-p-phenylenes) with arylboronic acids and esters has been studied. The coupling reaction is demonstrated to be highly selective for monoarylation when the substrate is a p-dibromooligoarene, while selective biarylation is obtained for p-diiodoterphenyl. The mono/bis coupling-ratio for these compounds was highly sensitive to the nature of the halogen involved, however steric hindrance or electronic characteristics of the boronic derivative did not affect the selectivity of the reaction. The reaction yields observed were higher at room temperature and when arylboronic pinacol esters were used. These reactions also offer a useful method for the preparation of asymmetrically substituted terphenyls and hexa-p-phenylenes, giving good yields.     

Two novel tricyclic diterpenoids from Isodon rubescens var. taihangensis

Two novel tricyclic diterpenoids rubescensins U (1) and V (2) were isolated from the leaves of Isodon rubescens var. taihangensis. They were elucidated as a 8,15-seco-ent-kauranoid and an ent-abietanoid, respectively, by 1D and 2D NMR spectra, and single crystal X-ray analysis. Compound 1 is the first example of an 8,15-seco-ent-kaurane from the plants genus Isodon. A discussion of their biogenesis is described.     

2,6-Cyclo-xenicanes from the brown algae Dilophus fasciola and Dilophus spiralis

Seven new diterpenes, featuring the rare 2,6-cyclo-xenicane skeleton, along with eleven previously reported metabolites were isolated from the organic extracts of the brown algae Dilophus fasciola and Dilophus spiralis. The structure elucidation of the isolated natural products was based on detailed analyses of their spectroscopic data (NMR, MS, IR, UV), whereas the assignment of their relative configurations was assisted by molecular modelling studies.     

Cytotoxic ent-kauranoid derivatives from Isodon rubescens

An extensive study of the diterpenoids produced by the species of Isodon rubescens, has led to the isolation of 12 new ent-kaurane diterpenoids, hebeirubescensins A-L (1-12), and 19 known analogues. Their structures were determined on the basis of spectroscopic analysis. Selected compounds were assayed for their inhibitory ability against human A549, HT-29, and K562 cells. Among them, hebeirubescensins B and C exhibited significant cytotoxicity with IC₅₀ values of <2.0 μM. The structure-activity relationships were discussed.     

Radiation synthesis and characterization of poly(N,N-dimethylaminoethyl methacrylate-co-N-vinyl 2-pyrrolidone) hydrogels

In this study, radiation synthesis and characterization of swelling behavior and network structure of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), and poly(N,N-dimethylaminoethyl methacrylate-co-N-vinyl 2-pyrrolidone) (P(DMAEMA-co-VP)), hydrogels were investigated. PDMAEMA and P(DMAEMA-co-VP) hydrogels in the rod forms were prepared by irradiating the ternary mixtures of DMAEMA/VP/cross-linking agent, ethyleneglycol dimethacrylate (EGDMA), by gamma rays at ambient temperature. In composition ranges where the three components were completely miscible, water was also added to the ternary mixture to provide the formation of homogeneous polymerization and gelation. The influence of irradiation dose, comonomer, VP, and cross-linking agent, EGDMA, content on the total percentage gelation and monomer conversion were investigated. The effect of pH and temperature on the swelling behavior of hydrogels have also been examined. Hydrogels showed typical pH response and temperature responses, such as low-pH and low temperature swelling and high-pH and high temperature deswelling. Polymer-solvent interaction parameter (χ) and enthalpy and entropy changes appearing in the χ parameter for the P(DMAEMA-co-VP)-water system were determined by using Flory-Rehner theory of swelling equilibrium. The negative values for ΔH and ΔS indicate that prepared pure PDMAEMA and P(DMAEMA-co-VP) hydrogels have lower critical solution temperature (LCST) and Flory-Rehner theory of swelling equilibrium provides a satisfactory agreement to the experimental swelling data of the hydrogels.