Cerebrosides from the Rhizomes of Gynura Japonica

Four new cerebrosides, gynuramides I?IV ( 1 ‐ 4 ), together with 37 known compounds were isolated from the rhizome of Gynura japonica. The structures of cerebrosides 1 ‐ 4 were determined by chemical and spectroscopic examination to be: (2S,3S,4R,8E)‐2‐[(R)‐2‐hydroxypentacosanoylamino]‐8‐en‐1,3,4‐octadecanetriol, (2S,3S,4R,8E)‐2‐[(R)‐2‐hydroxytetracosanoylamino]‐8‐en‐1,3,4‐octadecanetriol, (2S,3S,4R,8E)‐2‐[(R)‐2‐hydroxytricosanoylamino]‐8‐en‐1,3,4‐octadecanetriol, and (2S,3S,4R,8E)‐2‐[(R)‐2‐hydroxydocosanoylamino]‐8‐en‐1,3,4‐octadecanetriol.     

Dolabellane Diterpenoids from the Higher Plant Aglaia odorata

Two new dolabellane diterpenoids, (1R,3R,7E,11S,12R)‐dolabella‐4(16),7‐diene‐3,18‐diol ( 1 ) and (1R,3E,7R,11S,12R)‐dolabella‐3,8(17)‐diene‐7,18‐diol ( 2 ), and the known (1R,3E,7E,11S,12R)‐dolabella‐3,7‐dien‐18‐ol ( 3 ) were isolated from Aglaia odorata, along with twelve other known compounds. Their structures were elucidated on the basis of spectroscopic data. This is the first time that dolabellane‐type diterpenoids were detected in higher plants.     

Relativistic virial theorem for diatomic molecules. Application to H 2 +

Summary The virial theorem for a molecule in the relativistic clamped-nuclei approximation is derived. The individual energy contributionsA (momentum energy),B (mass energy),T=A+B (kinetic energy) andV (potential energy) are expressed in terms ofE, E/R (derivate w.r.t. the nuclear coordinates) and the relativistic correction E/² (derivative w.r.t. Sommerfield's fine-structure constant ). IfE and E/R are known as functions of , then all individual energy terms are also known as functions of . As an example, numerical results for H ₂ ⁺ are presented. The relativistic and nonrelativistic potential energy curves and the paradoxical behavior of their different contributions are analyzed and interpreted in both the largeR and shortR ranges.Dedicated to Professor W. Kutzelnigg on the occasion of his 60th birthday     

Convergence properties of Fock's expansion for S-state eigenfunctions of the helium atom

It is proved by functional analytic methods that for S-state solutions of Schrödinger's equation for the helium atom, Fock's expansion in powers of R ^1/2 and R ln R, where R is the hyperspherical radius r ₁ ² +r ₂ ² , converges pointwise for all R, thereby generalising a result of Macek that the expansion converges in the mean for all R<1/2. It is shown that for any value (even complex) of the energy E, Schrödinger's equation, considered as a partial differential equation with no boundary condition at R=, has infinitely many solutions representable by an expansion of the type proposed by Fock. Some of the open problems are discussed in determining whether for E in the point spectrum of the atomic Hamiltonian the physical eigenfunction _E, which has exponential decay as R , is representable by Fock's expansion.     

Total Synthesis,Stereochemical Assignment,and Field‐Testing of the Sex Pheromone of the Strepsipteran Xenos peckii

The sex pheromone of the endoparasitoid insect Xenos peckii (Strepsiptera: Xenidae) was recently identified as (7E,11E)‐3,5,9,11‐tetramethyl‐7,11‐tridecadienal. Herein we report the asymmetric synthesis of three candidate stereostructures for this pheromone using a synthetic strategy that relies on an sp³–sp² Suzuki–Miyaura coupling to construct the correctly configured C7‐alkene function. Comparison of ¹H NMR spectra derived from the candidate stereostructures to that of the natural sex pheromone indicated a relative configuration of (3R*,5S*,9R*). Chiral gas chromatographic (GC) analyses of these compounds supported an assignment of (3R,5S,9R) for the natural product. Furthermore, in a 16‐replicate field experiment, traps baited with the synthetic (3R,5S,9R)‐enantiomer alone or in combination with the (3S,5R,9S)‐enantiomer captured 23 and 18 X. peckii males, respectively (mean±SE: 1.4±0.33 and 1.1±0.39), whereas traps baited with the synthetic (3S,5R,9S)‐enantiomer or a solvent control yielded no captures of males. These strong field trapping data, in combination with spectroscopic and chiral GC data, unambiguously demonstrate that (3R,5S,9R,7E,11E)‐3,5,9,11‐tetramethyl‐7,11‐tridecadienal is the X. peckii sex pheromone.     

Neoclerodane Diterpenes from Amoora stellato‐squamosa

From the twigs of Amoora stellato‐squamosa, five new neoclerodane diterpenes have been isolated and characterized, methyl (13E)‐2‐oxoneocleroda‐3,13‐dien‐15‐oate (=methyl (2E)‐3‐methyl‐5‐[(1S,2R,4aR,8aR)‐1,2,3,4,4a,7,8,8a‐octahydro‐1,2,4a,5‐tetramethyl‐7‐oxo‐naphthalen‐1‐yl]pent‐2‐enoate; 1 ), (13E)‐2‐oxoneocleroda‐3,13‐dien‐15‐ol (=(4aR,7R,8S,8aR)‐1,2,4a,5,6,7,8,8a‐octahydro‐8‐[(E)‐5‐hydroxy‐3‐methylpent‐3‐enyl]‐4,4a,7,8‐tetramethylnaphthalen‐2(1H)‐one; 2 ), (3α,4β,13E)‐neoclerod‐13‐ene‐3,4,15‐triol (=(1R,2R,4aR, 5S,6R,8aR)‐decahydro‐5‐[(E)‐5‐hydroxy‐3‐methylpent‐3‐enyl]‐1,5,6,8a‐tetramethylnaphthalene‐1,2‐diol; 3 ), (3α,4β,13E)‐4‐ethoxyneoclerod‐13‐ene‐3,15‐diol (=(1R,2R,4aR,5S,6R,8aR)‐1‐ethoxydecahydro‐5‐[(E)‐5‐hydroxy‐3‐methylpent‐3‐enyl]‐1,5,6,8a‐tetramethylnaphthalen‐2‐ol; 4 ), and (3α,4β,14RS)‐neoclerod‐13(16)‐ ene‐3,4,14,15‐tetrol (=(1R,2R,4aR,5S,6R,8aR)‐decahydro‐5‐[3‐(1,2‐dihydroxyethyl)but‐3‐enyl]‐1,5,6,8a‐tetramethylnaphthalene‐1,2‐diol; 5 ), together with two known compounds, (13E)‐neocleroda‐3,13‐diene‐15,18‐diol ( 6 ) and (13S)‐2‐oxoneocleroda‐3,14‐dien‐13‐ol ( 7 ).     

New α‐Glucosidase Inhibitors from the Mongolian Medicinal Plant Ferula mongolica

The four new and four known sesquiterpenoid derivatives 1 – 4 and 5 – 8 , respectively, were isolated from the air‐dried roots of Ferula mongolica. The structures of these compounds were determined by spectroscopic methods and found to be rel‐(2R,3R)‐2‐[(3E)‐4,8‐dimethylnona‐3,7‐dienyl]‐3,4‐dihydro‐3,8‐dihydroxy‐2‐methyl‐2H,5H‐pyrano[2,3‐b][1]benzopyran‐5‐one ( 1 ), rel‐(2R,3R)‐2‐[(3E)‐4,8‐dimethylnona‐3,7‐dienyl]‐2,3‐dihydro‐7‐hydroxy‐2,3‐dimethyl‐4H‐furo[2,3‐b][1]benzopyran‐4‐one ( 2 ), rel‐(2R,3R)‐2‐[(3E)‐4,8‐dimethylnona‐3,7‐dienyl]‐2,3‐dihydro‐7‐hydroxy‐2,3‐dimethyl‐4H‐furo[3,2‐c][1]benzopyran‐4‐one ( 3 ), rel‐(2R,3R)‐2‐[(3E)‐4,8‐dimethylnona‐3,7‐dienyl]‐2,3‐dihydro‐7‐methoxy‐2,3‐dimethyl‐4H‐furo[3,2‐c][1]benzopyran‐4‐one ( 4 ), (4E,8E)‐1‐(2‐hydroxy‐4‐methoxyphenyl)‐5,9,13‐trimethyltetradeca‐4,8,12‐trien‐1‐one ( 5 ), the rel‐(2R,3S) diastereoisomer 6 of 2 , the rel‐(2R,3S) diastereoisomer 7 of 4 , and (4E,8E)‐1‐(2,4‐dihydroxyphenyl)‐5,9,13‐trimethyltetradeca‐4,8,12‐trien‐1‐one ( 8 ). These compounds were tested as inhibitors against the enzyme α‐glucosidase. The compounds 1 – 6 and 8 exhibited significant inhibitory activity and, therefore, represent a new class of α‐glucosidase inhibitors.     

Stable N‐Heterocyclic Germylenes of the Type [Fe{(η5‐C5H4)NR}2Ge] and Their Oxidation Reactions with Sulfur,Selenium, and Diphenyl Diselenide

Three new N‐heterocyclic germylenes of the type [Fe{(η⁵‐C₅H₄)NR}₂Ge] ( 1R Ge) containing particularly bulky alkyl [R = 2‐adamantyl (Ad), 1,1,2,2‐tetramethylpropyl (Pr*)] or aryl substituents [R = 2,6‐diisopropylphenyl (Dipp)] were prepared and structurally characterized, in two cases (R = Ad, Dipp), by single‐crystal X‐ray diffraction. Together with the previously described homologues with R = trimethylsilyl (TMS), tert‐butyl (tBu), and mesityl (Mes) their oxidative addition reactions with S₈ and Se₈ were studied, which afforded compounds of the type [ 1R Ge(μ‐E)]₂ (E = S, Se). The low solubility of most of these products severely hampered their purification and characterization. Nevertheless, their structural characterization by single‐crystal X‐ray diffraction was possible in six cases (E = S, R = Ad, Pr*; E = Se, R = Ad, Pr*, Mes, Dipp). No solubility problems were encountered in oxidative addition reactions with diphenyl diselenide, affording products of the type 1R Ge(SePh₂)₂, whose crystal structures could be determined in four cases (R = TMS, tBu, Mes, Dipp). Short intramolecular CH ··· Se contacts compatible with hydrogen bonds were observed for [ 1Ad Ge(μ‐Se)]₂, [ 1Pr* Ge(μ‐Se)]₂, and 1tBu Ge(SePh₂)₂.     

On The Steric Hindrance of Bulky Substituents – Determination of Their Cone Angles

A series of simple halogen compounds was studied with respect to steric hindrance by means of quantum mechanical methods utilizing the M062X/aug‐cc‐pvdz level of theory. The maximal cone angles of the halogen compounds R–E were computed for a series of different substituents (R carbon or silyl based substituents, E = halogen). Depending on the substitution pattern and the bulkiness of the substituent R a correlation between the cone angle and structural parameters is discussed. Estimates for the cone angles of any element attached to R are provided, that allows comparison of cone angles of different substituents at different distances, which can facilitate synthesis. Additionally, the bonding situation was assessed by natural bond orbital (NBO) analysis indicating that significant electronic effects should be considered when changing from silyl to carbon based substituents. Silyl based substituents display a considerably larger charge transfer to E compared to carbon based once.     

Two New 7‐Dehydrobrefeldin A Acids from Cylindrocarpon obtusisporum,an Endophytic Fungus of Trewia nudiflora

Two new 7‐dehydrobrefeldin A acids, (2E,4R*)‐4‐hydroxy‐4‐{(1R*,2S*)‐4‐oxo‐2‐[(1E)‐6‐oxohept‐1‐en‐1‐yl]cyclopentyl}but‐2‐enoic acid ( 3 ) and (2E,4R*)‐4‐hydroxy‐4‐{(1R*,2S*)‐2‐[(1E,6S*)‐6‐hydroxyhept‐1‐en‐1‐yl]‐4‐oxocyclopentyl}but‐2‐enoic acid ( 4 ), were isolated from the endophytic fungal strain Cylindrocarpon obtusisporum (Cooke & Harkness ) Wollenw . of Trewia nudiflora, together with two known compounds, 7‐dehydrobrefeldin A ( 2 ) and brefeldin A ( 1 ). Their structures were determined on the basis of extensive 1D‐ and 2D‐NMR‐spectral analysis.     

New Diarylheptanoids and Kavalactone from Alpinia katsumadai Hayata

Two new diarylheptanoids, katsumains A ( 1 ) and B ( 2 ), and one new kavalactone, katsumadain ( 3 ), together with the three known compounds (4E,6E)‐1,7‐diphenylhepta‐4,6‐dien‐3‐one ( 4 ), (5R,6E)‐1,7‐diphenyl‐5‐hydroxyhept‐6‐en‐3‐one ( 5 ), and cardamonin ( 6 ), were isolated from the seeds of Alpinia katsumadai Hayata . Their structures were elucidated mainly by spectroscopic methods (1D‐ and 2D‐NMR) and by mass spectrometry (HR‐ESI‐MS). Besides, the erroneous nomenclatures for (+)‐linderatin and (+)‐neolinderatin as given in [10] [11] were corrected to be 2′,4′,6′‐trihydroxy‐3′‐[(3R,4R)‐4‐isopropyl‐1‐methylcyclohex‐1‐en‐3‐yl]dihydrochalcone for (+)‐linderatin and 2′,4′,6′‐trihydroxy‐3′,5′‐bis[(3R,4R)‐4‐isopropyl‐1‐methylcyclohex‐1‐en‐3‐yl]dihydrochalcone for (+)‐neolinderatin, respectively.     

Sterols from the Stems of Momordica charantia

A new sterol, 5α,6α‐epoxy‐3β‐hydroxy‐(22E,24R)‐ergosta‐8,22‐dien‐7‐one ( 1 ), together with eight known sterols, 5α,6α‐epoxy‐(22E,24R)‐ergosta‐8,22‐diene‐3β,7α‐diol ( 2 ), 5α,6α‐epoxy‐(22E,24R)‐ergosta‐8,22‐diene‐3β,7β‐diol ( 3 ), 5α,6α‐epoxy‐(22E,24R)‐ergosta‐8(14),22‐diene‐3β,7α‐diol ( 4 ), 3β‐hydroxy‐(22E,24R)‐ergosta‐5,8,22‐trien‐7‐one ( 5 ), ergosterol peroxide ( 6 ), clerosterol ( 7 ), decortinol ( 8 ), and decortinone ( 9 ), were isolated from the stems of Momordica charantia. Their structures were elucidated by mean of extensive spectroscopic methods, including ¹H, ¹³C, 2D‐NMR and HR‐EI‐MS, as well as comparison with the literature data. Compounds 1 , 4 , 5 , 8 , and 91 were not cytotoxic against the SK‐Hep 1 cell line.     

Ceramides Isolated from Helianthus annuus L.

Three new compounds (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,10E)‐1,3,4‐trihydroxyicos‐10‐en‐2‐yl]docosanamide ( 1 ), (2R,3R)‐2,3‐dihydroxy‐N‐[(2S,3S,4R,10E)‐1,3,4‐trihydroxyicos‐10‐en‐2‐yl]docosanamide ( 2 ), N‐(2‐phenylethyl)tetracosanamide ( 3 ), together with a known ceramide, (2R)‐N‐[(2S,3S,4R,8E)‐1‐(β‐D ‐Glucopyranosyloxy)‐3,4‐dihydroxyoctadec‐8‐en‐2‐yl]‐2‐hydroxyhexadecanamide ( 4 ), were isolated from acetone extract of flower disc of Helianthus annuus L. The structures were identified on the basis of chemical and spectroscopic methods.     

Three New Indole Alkaloids from the Leaves of Alstonia scholaris

Three new akuamillan‐type indole alkaloids, i.e., 5‐methoxystrictamine (=methyl (5β,16R,19E)‐5‐methoxyakuammilan‐17‐oate; 1 ), methyl (16R,19E)‐1,2‐dihydro‐16‐(hydroxymethyl)‐5‐oxoakuammilan‐17‐oate ( 2 ), and methyl (2β,16R,19E)‐4,5‐didehydro‐1,2‐dihydro‐2‐hydroxy‐16‐(hydroxymethyl)akuammilan‐4‐ium‐17‐oate chloride ( 3 ), have been isolated from the leaves of Alstonia scholaris, together with ten known compounds. Their structures were determined by spectroscopic means. None of the constituents showed significant cytotoxic activity towards WT cells.     

A Rare New Cleistanthane Diterpene from the Pericarp of Trewia nudiflora

A minor, unprecedented diterpene, 3β,17‐dihydroxycleistantha‐12,15‐dien‐2‐one ( 1 ), was isolated from the CHCl₃‐soluble part of the EtOH extract of the pericarp of Trewia nudiflora. The structure of 1 was elucidated by means of 1D‐ and 2D‐NMR spectroscopic analyses as well as by HR‐MS. Also isolated were two known triterpenes, glutin‐5‐en‐3‐ol and olean‐18‐en‐3‐one (germanicone), as well as three known sterols, (22E,24R)‐5α,8α‐epidioxyergosta‐6,22‐dien‐3β‐ol, (22E,24R)‐5α,8α‐epidioxyergosta‐6,9(11),22‐trien‐3β‐ol, and (22E,24R)‐6‐methoxyergosta‐7,22‐dien‐3,5‐diol.     

Fine structure in the hydrogen atom boxed in a spherical impenetrable cavity

The spectrum of the hydrogen atom confined in a spherical impenetrable box of radius R_c has been investigated by many authors up to date, but not at the level of relativistic corrections. It is well known that, as R_c diminishes, all energy levels and the pressure increase very rapidly, whereas the polarizability goes to zero. In this report, we have computed the relativistic corrections that underlie the fine structure of the confined hydrogen atom, as a function of R_c. Such corrections correspond to relativistic kinetic energy, spin‐orbit coupling and the Darwin term, which are calculated in the frame of time‐independent perturbation theory, for which, use was made of the exact confined hydrogen atom wave functions. We show that for a confinement radius of 0.5 au the relativistic corrections increase up to three orders of magnitude with respect to those corresponding to the free atom. As R_c decreases, the kinetic energy correction and the spin‐orbit coupling for become negative whereas their absolute value and the Darwin term, which is positive, increase very rapidly.     

Diarylheptanoids from the Rhizomes of Alpinia officinarum

A novel dimeric diarylheptanoid, (5R,5′R)‐7,7′‐(6,6′‐dihydroxy‐5,5′‐dimethoxy[1,1′‐biphenyl]‐3,3′‐diyl)bis[5‐methoxy‐1‐phenylheptan‐3‐one] ( 1 ), and two new diarylheptanoids, (4E,6R)‐6‐hydroxy‐7‐(4‐hydroxy‐3‐methoxyphenyl)‐1‐phenylhept‐4‐en‐3‐one ( 2 ) and (4E,6R)‐6‐hydroxy‐1,7‐diphenylhept‐4‐en‐3‐one ( 3 ), together with seven known diarylheptanoids, were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by application of extensive spectroscopic analyses and the modified Mosher method.     

A Noncovalent Binding Strategy to Capture Noble Gases,Hydrogen and Nitrogen

A molecular design strategy to develop receptor systems for the entrapment of noble gases, H₂ and N₂ is described using M06L‐D3/6‐311++G(d,p)//M06L/6‐311++G(d,p) DFT method. These receptors made with two‐, three‐, four‐ and five‐fluorinated benzene cores, linked with methelene units viz. R_I, R_II, R_III and R_IV as well as the corresponding non‐fluorinated hydrocarbons viz. R_IH, R_IIH, R_IIIH and R_IVH show a steady and significant increase in binding energy (E_int) with increase in the number of aromatic rings in the receptor. A stabilizing “cage effect” is observed in the cyclophane type receptors R_IV and R_IVH which is 26–48% of total E_int for all except the larger sized Kr, Xe and N₂ complexes. E_int of R_IV…He, R_IV…Ne, R_IV…Ar, R_IV…Kr, R_IV…H₂ and R_IV…N₂ is 4.89, 7.03, 6.49, 6.19, 8.57 and 8.17 kcal/mol, respectively which is 5‐ to9‐fold higher than that of hexafluorobenzene. Similarly, compared to benzene, multiple fold increase in E_int is observed for R_IVH receptors with noble gases, H₂ and N₂. Fluorination of the aromatic core has no significant impact on E_int (∼ ±0.5 kcal/mol) for most of the systems with a notable exception of the cage receptor R_IV for N₂ where fluorination improves E_int by 1.61 kcal/mol. The E_int of the cage receptors may be projected as one of the highest interaction energy ranges reported for noble gases, H₂ and N₂ for a neutral carbon framework. Synthesis of such systems is promising in the study of molecules in confined environment. © 2018 Wiley Periodicals, Inc.     

Critical phenomena in isoelectronic diatomic sequences—the 14-electron sequence

A theory of isoelectronic molecules which describes stable and metastable members of a sequence has been developed. To achieve this synthesis, it has been necessary to require that the total electronic energy surface E(R,Z,Z') for the sequence contain critical points—that is, values of the nuclear charges Z and Z' at which energy minimum, maximum [at R_e(min) and R_e(max)], and horizontal inflection points occur. For ground state sequences a primary physical source of these extreme points is the screened, coulombic repulsion of like-charged atomic centers in the diatomics. With this realization, we can write analytical forms that have the correct scaling behavior and which properly model the screened, coulombic repulsion for E along certain straight-line trajectories in the (Z,Z') plane. This leads to the observation that R_e(max) values diverge logarithmically in λ-like transitions wherever the screened coulombic repulsion becomes small as the nuclear charges vary along those trajectories. At the horizontal inflection points the E surface contains A₂ folds, as required by Thom's theorem for analytical surfaces containing one control parameter. Within the isoelectronic sequence molecular subgroups have been noted and explained in terms of the underlying atomic shell structures of the molecules' constituent atoms. Using input data for seven stable molecules together with the analytical surface selected for study, we have estimated the equilibrium bond distances R_e(min), dissociation energies D_e(min), and harmonic force constants E⁽²⁾(min) for 18 other neutral and charged species.     

Enantioselective Access to (−)‐Ambrox® Starting from β‐Farnesene

Starting from inexpensive (E)‐β‐farnesene ( 1 ), an eight‐step enantioselective synthesis of the olfactively precious Ambrox^® ((?)‐ 2a ) has been performed. The crucial step is the catalytic asymmetric isomerization of (2E,6E)‐N,N‐diethylfarnesylamine ( 3 ) to the corresponding enamine (?)‐(R,E)‐ 4a , applying Takasago's well‐known industrial methodology. The resulting dihydrofarnesal ((+)‐(R)‐ 5 ) (90% yield, 96% ee), obtained after in situ hydrolysis (AcOH, H₂O), was then cyclized under catalytic SnCl₄ conditions, via its corresponding unreported enol acetate (?)‐(R)‐ 4b , to afford trans‐decalenic aldehyde (+)‐ 6a . Subsequent transformations furnished bicyclic ketone (?)‐ 8a and unsaturated nitrile (+)‐ 11 , both reported as intermediates to access to (?)‐ 2a .