On the exotherm of polyacrylonitrile. II. Examination of deuterated polymers

A series of α-, β,β-, and α,β,β-deuterium-labelled acrylonitrile monomers were prepared and polymerized. Secondary deuterium isotope effects on the polymerization and on the pyrolysis reactions that precede carbon fiber formation were observed. When deuterium is in the α-position, the polymerization rate is greater and the molecular weight is higher. It is proposed that either the propagation rate constant or both that constant and the termination rate constant are increased on deuterium substitution. In differential scanning calorimetry, the polyacrylonitrile exotherm occurs at higher temperatures and is narrower when deuterium is substituted at the α-position. On the other hand, the thermal gravimetric analysis activation energy for weight loss of polymer at temperatures below the acrylic exotherm is lower when deuterium is in the α-position, relative to the α-hydrogen polymers. As there is no correlation between the weight loss energy of activation and the various exotherm parameters, the weight loss energy of activation and the various exotherm parameters, the weight loss and exotherm are considered to be independent events. Examination of the distribution of deuterium substituted ammonia species evolved during 100–240°C thermal treatment of the α-and β, β-deuterated polyacrylonitriles provides a clear indication that both the α- and β-positions are directly involved in hydrogen migration to nitrogen, but the mechanism of ammonia generation remains unclear. © 1995 John Wiley & Sons, Inc.     

Stilbene Derivatives from Gnetum montanum Markgr. f. megalocarpum Markgr.

Three new stilbene derivatives, gnetumelin A ( 1 ), gnetumelin B ( 2 ), and gnetumelin C ( 3 ), along with the nine known stilbene derivatives 4 – 12 were isolated from Gnetum montanum Markgr . f. megalocarpum Markgr. Their structures were determined by spectroscopic analysis and comparison of the data with reported ones.     

Three New Phenol Compounds from Iris dichotoma Pall.

Three new phenolic compounds, irisdichototins D, E, and F ( 1 – 3 , resp.) were isolated from the stems of Iris dichotoma. The structures of the new compounds were elucidated by spectroscopic analyses, including 2D‐NMR techniques.     

Six New Cembranolides from the Hainan Soft Coral Lobophytum sp.

Six new cembrane diterpenes, lobophytolides A–F ( 1 – 6 , resp.), along with six known related cembranoids, 7 – 12 , were isolated from the Hainan soft coral Lobophytum sp. Their structures, including their relative configuration, were elucidated by extensive analyses of the spectroscopic data and by comparison with related known compounds.     

Three New Diterpenoids from Euphorbia sororia L.

Three new diterpenoids with jatrophane‐type skeleton, sororianolides A–C ( 1 – 3 , resp.), were isolated from Euphorbia sororia. The identification and structure elucidation of these compounds were based on 1D‐ and 2D‐NMR‐spectral data analysis. It was the first time to isolate diterpenoids in this species.     

Polyhydroxylated Steroids from the South China Sea Gorgonian Anthogorgia sp.

Four new polyhydroxylated steroids, namely anthogorgsteroids A–D ( 1 – 4 ), were isolated from the South China Sea gorgonian Anthogorgia sp. The structures of these compounds were elucidated by detailed spectroscopic analyses and comparison with reported data.     

Dammarane Triterpenes from Gardenia aubryi Vieill.

Three new dammarane triterpenoids, gardaubryones A–C ( 1 – 3 ), were isolated from the gum collected on the aerial parts of Gardenia aubryi Vieill ., together with the known compounds hydroxydammarenone II ( 4 ), ocotillone ( 5 ), cabraleone, and hollongdione. The structures of the novel compounds were established on the basis of mass spectrometry, NMR experiments, and chemical‐correlation reactions.     

Three New Phenylpropanoids from Inula nervosa Wall.

Three new phenylpropanoid compounds, named nervolans A–C ( 1 – 3 , resp.), together with two other known phenylpropanoids, coniferyl diangelate and sinapyl diangelate, were isolated from the aerial parts of Inula nervosa Wall . (Asteraceae), a traditional Chinese medicinal plant. The structures of 1 – 3 were elucidated by detailed spectroscopic analyses, including HR‐ESI‐MS data and 2D‐NMR spectroscopy. Compounds 1 – 5 exhibited mild inhibitory effects against NO production in LPS‐stimulated RAW264.7 cells.     

Three New Medicagenic Acid Saponins from Polygala micrantha Guill. & Perr.

Three new medicagenic acid saponins, micranthosides A–C ( 1 – 3 ), were isolated from the roots of Polygala micrantha Guill . & Perr ., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR experiments (¹H, ¹³C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3‐O‐β‐D ‐glucopyranosylmedicagenic acid 28‐[O‐β‐D ‐galactopyranosyl‐(1→4)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl] ester ( 1 ), 3‐O‐β‐D ‐glucopyranosylmedicagenic acid 28‐[O‐6‐O‐acetyl‐β‐D ‐galactopyranosyl‐(1→4)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl] ester ( 2 ), and 3‐O‐{O‐β‐D ‐glucopyranosyl‐(1→3)‐O‐[β‐D ‐glucopyranosyl‐(1→6)]‐β‐D ‐glucopyranosyl}medicagenic acid 28‐{O‐β‐D ‐apiofuranosyl‐(1→3)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐[β‐D ‐apiofuranosyl‐(1→3)]‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl} ester ( 3 ). Compounds 1 – 3 were evaluated against HCT 116 and HT‐29 human colon cancer cells, but they did not show any cytotoxicity.     

Trichodermates A–F,New Cytotoxic Trichothecenes from the Plant Pathogenic Fungus Trichoderma sp.

Trichodermates A – F ( 1 – 6 , resp.), six new trichothecene polyunsaturated octadioic acid esters, and (?)‐harzianum B ( 7 ) were isolated from the fermentation extract of Trichoderma sp., a plant pathogenic fungus isolated from stem rot of an unidentified tree in Thailand. The structures of 1 – 7 were elucidated by NMR experiments. The absolute configuration at C(12) in 3 was assigned by in situ dimolybdenum circular dichroism method, whereas that in 7 was deduced after hydrolysis of 7 to 8 via modified Mosher's method. Compounds 1 and 2 showed modest cytotoxic activities against the K562 (human myelogenous leukemia) cell line with IC₅₀ values of 12.12 and 13.08 μM , respectively.     

New Furostanol Glycosides from the Roots of Digitalis ciliata Trautv.

Three new furostanol glycosides, named ciliatasides A, B, and C ( 1 – 3 , resp.), have been isolated from the roots of Digitalis ciliata, along with two known furostanol glycosides. The structures of the new compounds were identified as (2α,3β,5α,14β,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐2‐hydroxyfurost‐20(22)‐en‐3‐yl β‐D ‐glucopyranosyl‐(1→2)‐[β‐D ‐glucopyranosyl‐(1→3)]‐β‐D ‐galactopyranoside ( 1 ), (2α,3β,5α,14β,22R)‐26‐(β‐D ‐glucopyranosyloxy)‐2‐hydroxy‐22‐methoxyfurost‐25(27)‐en‐3‐yl β‐D ‐galactopyranosyl‐(1→2)‐[β‐D ‐xylopyranosyl‐(1→3)]‐β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside ( 2 ), and (2α,3β,5α,14β,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐2,22‐dihydroxyfurostan‐3‐yl β‐D ‐glucopyranosyl‐(1→2)‐[β‐D ‐glucopyranosyl‐(1→3)]‐β‐D ‐galactopyranoside ( 3 ).     

Three New Xanthones from the Fungus Penicillium sp. NH‐7‐1

Three new xanthones, drimiopsins G–I ( 1 – 3 , resp.), and two known congeners, griseoxanthone C ( 4 ) and norlichexanthone ( 5 ), were isolated from a fungal isolate, Penicillium sp. NH‐7‐1. The structures of all compounds were determined on the basis of extensive spectroscopic analyses, as well as by comparison with literature reports, and the structure of compound 1 was further confirmed by single‐crystal X‐ray diffraction.     

Three New Hasubanan Alkaloids from Stephania hernandifolia (Willd.) Walp.

Three new hasubanan alkaloids, hernsubanines A–C ( 1 – 3 , resp.), were isolated from the whole plants of Stephania hernandifolia. Their structures were elucidated on the basis of physical and spectroscopic data. In in vitro tests for cytotoxic activity against two human cancer cell lines, A 549 and K 562, compound 1 did not exhibit any cytotoxicity.