Tomato steroidal alkaloid glycosides, esculeosides A and B, from ripe fruits

Major novel steroidal alkaloid glycosides, named esculeoside A (1) and esculeoside B (2), have been isolated from the pink color-type and the red color-type, respectively, of the ripe tomato fruits of Lycopersicon esculentum MILL. for the first time. The structures of 1 and 2 have been characterized as 3-O-β-lycotetraosyl (5S,22S,23S,25S)-23-acetoxy-3β,27-dihydroxyspirosolane 27-O-β-d-glucopyranoside and 3-O-β-lycotetraosyl (5S,22S,23R,25S)-22,26-epimino-16β,23-epoxy-3β,23,27-trihydroxycholestane 27-O-β-d-glucopyranoside, respectively.     

Three novel pregnane glycosides from Epigynum auritum

Three novel pregnane glycosides with an unusual aglycone (Epigynumgenane), named Epigynosides A (1), B (2) and C (3), were isolated from the aerial part of Epiginum auritum. Their structures were elucidated by spectral means and confirmed by X-ray diffraction analysis.     

Cynanosides A-J, ten novel pregnane glycosides from Cynanchum atratum

Four novel 13,14:14,15-diseco-18-nor-pregnane-type steroidal glycosides, cynanosides A-D (1-4), and six novel 13,14:14,15-diseco-pregnane-type steroidal glycosides, cynanosides E-J (5-10) were isolated from the roots of Cynanchum atratum, together with one known compound, cynatratoside F (11). Their structures including the absolute stereochemistry were determined on the basis of spectroscopic analysis and chemical evidence, with combination of the modified Mosher method, the exciton chirality method and chemical transformations.     

Facile conversion of O-silyl protected sugars into their corresponding formates using POCl3·DMF complex

The direct O-formylation of two selectively protected sugar derivatives using the Vilsmeier-Haack (V-H) complex POCl₃·DMF was studied. Primary O-TBDMS and O-TBDPS ethers of sucrose, the most common disaccharide, underwent regio and chemoselective O-formylation with this formylating agent. This conversion was also studied with a monosaccharide analogue.     

Alkyl and dialkylammonium tetrafluoroborate catalyzed cis-trans isomerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane

Alkyl and dialkylammonium tetrafluoroborate promoted cis-trans isomerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane (1) in DMSO-d₆ were studied. The isomerization equilibrium constant K are within the range of 3.74-3.30 from 22 to 47 °C. Thermodynamic parameters of ΔH° and ΔS° for the isomerization were −0.95 kcal/mol and −0.59 cal/mol-K respectively. The isomerization rate is first order in [cis-1] and second order in [R_nNH_4−nBF₄]. Both components of R_nNH_4−n⁺ and BF₄⁻ are essential for the catalytic cis-trans isomerization. The catalytic strength follows the decreasing order of ⁺H₃N(CH₂)₆NH₃⁺>n-C₈H₁₇NH₃⁺>n-C₁₆H₃₃NH₃⁺>Me₃CNH₃⁺>PhCH₂NH₃⁺>Et₂NH₂⁺?Ph₂CHNH₃⁺, Et₃NH⁺. Inversion region was observed in the plot of ln(k_f/T) versus (1/T) with the ceiling located at around 38 °C. The positive activation enthalpy of 9 kcal/mol was estimated at 22-32 °C. The activation enthalpy turns to be slightly negative at T>38 °C.     

The biocatalytic conversion of 8-hydroxymanzamine A to manzamine A

The selective dehydroxylation of 8-hydroxymanzamine A (1) to form manzamine A (2) can be completed by fermentation with Fusarium solani or Streptomyces seokies. This unique biocatalytic conversion is important due to the fact that manzamine A has more desirable biological activity when assayed in a murine model against malaria.     

Synthesis of heliannane skeletons. Facile preparation of (±)-heliannuol D

Heliannuol D is a natural product with a 7,10-heliannane skeleton, isolated from Helianthus annuus. It has been synthesized in eight steps, in good yield, using a new biomimetic method. Key steps were a Fries rearrangement, a Grignard reaction and, finally, a base catalyzed cyclization.     

Suffruticosine, a novel octacyclic alkaloid with an unprecedented skeleton from Securinegasuffruticosa (Pall.) Rehd.

A novel securinega alkaloid, suffruticosine (1), was isolated from the leaves and barks of Securinegasuffruticosa. The structure of 1, characterized by a fused complex octacyclic system, was elucidated by combined spectroscopic techniques, especially 2D NMR and CD spectral analyses.     

Determination of quinolizidine alkaloids in Sophora medicinal plants by capillary electrophoresis

A new capillary electrophoresis (CE) method for the determination of quinolizidine alkaloids in Sophora medicinal plants was developed. A total of seven alkaloid components (cytisine, sophocarpine, matrine, lehmannine, sophoranol, oxymatrine and oxysophocarpine) were separated within 15 min. The running buffer was a 50 mM phosphate buffer containing 1%HP-β-CD and 3.3% isopropanol. The linear calibration ranges were 5.50-88.0 μg ml⁻¹ for cytisine and lehmannine, 5.00-88.0 μg ml⁻¹ for sophocarpine and sophoranol, 5.60-89.6 μg ml⁻¹ for matrine and oxysophocarpine, and 24.0-384 μg ml⁻¹ for oxymatrine. The recoveries of the seven alkaloids were 96.0-102.9% with relative standard deviations from 1.50 to 3.00% (n = 5). The method was successfully applied to different Sophora medicinal plants including Sophora flavescens, Sophora tonkinensis and Sophora alopecuroides.     

Mersinaline and mersirachine, novel quinolinic alkaloids of the mersinine group from Kopsia

Two quinolinic alkaloids belonging to the novel mersinine subclass were isolated from Kopsia singapurensis. The structures of these alkaloids were established by spectroscopic methods and possible biogenetic relationships between these and the mersinine alkaloids are presented.     

Conolutinine, a hexacyclic indole alkaloid with a novel ring system incorporating a diazaspiro center and fused oxadiazepine-tetrahydrofuran rings

A hexacyclic indole alkaloid possessing an unprecedented ring system incorporating a diazaspiro center and fused oxadiazepine-tetrahydrofuran rings has been isolated from the Malayan Tabernaemontana corymbosa. The structure was established by analysis of the spectroscopic data and a possible biogenetic pathway from a cleavamine-type precursor is presented.     

Two novel indole alkaloids, Kopsiyunnanines A and B, from a Yunnan Kopsia

Two novel indole alkaloids having unusual skeletons were isolated from the aerial part of Yunnan Kopsia arborea. Kopsiyunnanine A (1) is a new class of bisindole alkaloid composed of vallesiachotamine (modified Corynanthe-type) and Aspidospermatan-type alkaloids. Kopsiyunnanine B (2) is a new Corynanthe-type oxindole alkaloid rearranged by D ring rotation.     

New quinolizidine and diaza-adamantane alkaloids from Acosmium dasycarpum (Vog.) Yakovlev—Fabaceae

The phytochemical investigation of the methanol crude extract obtained from Acosmium dasycarpum (Vog.) Yakovlev root bark led to the isolation of the quinolizidine alkaloids lupanine, acosmine, acosminine and lupanacosmine, as well as the diaza-adamantane alkaloids panacosmine and dasycarpumine. Lupanacosmine (4) and dasycarpumine (6) have been described for the first time herein.     

Senepodines B-E, new C22N2 alkaloids from Lycopodium chinense

Four new C₂₂N₂Lycopodium alkaloids, senepodines B-E (2-5), consisting of an octahydroquinoline ring and a quinolizidine ring have been isolated together with senepodine A (1) from the club moss Lycopodium chinense. The relative and absolute stereochemistry of 2-5 were determined by combination of NOESY correlations and chemical transformation, while the absolute configuration of 1 was assigned by exciton chirality method.     

Leucolusine, a tetracyclic alkaloid with a novel ring system incorporating an oxindole moiety and fused piperidine-tetrahydrofuran rings

A tetracyclic ring-opened oxindole alkaloid, possessing an unprecedented ring system incorporating fused piperidine-tetrahydrofuran rings, has been isolated from the Malayan species, Leuconotis griffithii. The structure was established by analysis of the spectroscopic data and a possible biogenetic pathway from an Aspidosperma precursor is presented.     

Aminocadambines A and B, two novel indole alkaloids from Neolamarckia cadamba

Two novel monoterpenoid indole alkaloids, aminocadambines A (1) and B (2), characterized by tetrahydrofuran and 1,2,3,4-tetrahydropyridine rings, were isolated from the leaves of Neolamarckia cadamba. Their structures were elucidated on the basis of spectroscopic and computational methods. The absolute configuration of 1 was established by CD analysis. A plausible biosynthetic pathway for 1 and 2 is proposed.     

Direct conversion of polyconjugated compounds into their corresponding carboxylic acids by Acetobacter aceti

The conversion of polyconjugated aldehydes or alcohols into their corresponding acids was carried out using Acetobacter aceti. The analytical results were compared with those of the acids chemically obtained using a Horner-Wittig reaction.     

Facile synthesis of C-phosphanylformamidines via a carbene pathway

A direct synthetic approach to C-phosphanyl-N,N-dialkyl-N′-aryl(alkyl)-formamidines was developed. It was shown that phosphorylation of the formamidines proceeds at the nitrogen atom affording N-phosphanylformamidinium salts. Upon deprotonation, these salts gave C-phosphanylformamidines via formation of carbenes followed by a 1,2-phosphorus shift.     

Synthetic approaches towards an indole alkaloid isolated from the marine sponge Halichondria melanodocia

The exocyclic analogue of the indole alkaloid isolated from the marine sponge Halichondria melanodocia has been prepared via olefination of a phosphonoester derived from 3-(2-bromoacyl)indole. The formation of an unexpected indolylazepine is also discussed.     

Facile conversion of para-benzoquinones to para-alkoxyphenols with primary/secondary alcohols and amberlyst-15: a process showing novel reducing property of such alcohols

A new efficient methodology has been developed for the synthesis of para-alkoxyphenols, an important group of anti-melanoma compounds, by heating alcoholic solutions of para-benzoquinones in the presence of amberlyst-15. The most notable feature here is the behaviour of the used primary or secondary alcohol as an effective reducing agent.